Autonomic dysfunction in patients with episodic cluster headache during remission period

Autonomic dysfunction in patients with episodic cluster headache during remission period | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Autonomic dysfunction in patients with episodic cluster headache during remission period Alba López-Bravo, Elena Bellosta Diago, Marisa de la Rica Escuín, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6871540/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 13 Oct, 2025 Read the published version in Acta Neurologica Belgica → Version 1 posted You are reading this latest preprint version Abstract Background. The hypothalamus is involved in cluster headache (CH) pathophysiology and is a hub for autonomic control. While cranial autonomic symptoms are prominent during attacks, other autonomic manifestations may be present in CH. This study aims to explore the autonomic nervous system (ANS) in patients with CH during remission period. Methods. Cross-sectional study including 30 CH and 30 age- and sex-matched controls. We analysed time- and frequency-domain parameters of heart rate variability (HRV) and active orthostatic tests. To investigate the sympathetic nervous system, plasma norepinephrine (NE) levels were determined. All assessments were performed during remission period. Results. All HRV parameters were lower in CH; the percentage of adjacent R-R intervals that differ by more than 50 milliseconds (pNN50) and standard deviation of normal-to-normal R-R intervals in 24h (SDNN) were significantly lower in CH (pNN50, 31.0 [5.3–44.3] vs. 44.5 [25.8–58.5], p = 0.043; SDNN, 79.6 ± 42.6 vs. 99.6 ± 42.6, p = 0.004). All other time-domain parameters, including the root mean square of successive R-R differences (RMSSD) were lower in CH than in controls (RMSSD 59.5 ± 36.9 vs. 77.3 ± 39.4, p = 0.077). Compared to controls, mean HR was significantly higher in CH (64.2 [59.6–75.8] vs. 60.4 [57.3–62.7], p = 0.038). Supine and upright NE levels were significantly higher in CH, (supine 329.27 pg/ml ± 172.71 vs 224.91 pg/ml ± 99.03, p = 0.015; standing 489.93 pg/ml ± 206.82 vs 354.24 pg/ml ± 154.21, p = 0.019). Conclusions. The present study indicates a significant decrease in HRV and an upward trend of plasmatic NE levels in CH during remission periods, suggesting an imbalance of the ANS in this state. Autonomic dysfunction Autonomic Nervous System Cluster headache Headache Norepinephrine Parasympathetic Sympathetic Figures Figure 1 Figure 2 Figure 3 Figure 4 INTRODUCTION Cluster headache (CH) is a trigeminal autonomic primary headache characterized by unilateral pain attacks accompanied by cranial autonomic symptoms. Most patients with CH have bouts with daily headache attacks interspersed with symptom free periods (remission) that last for months to years at a time. This is the episodic CH phenotype (ECH), in contrast to chronic CH (CCH), which is defined by remission periods lasting less than three months per year [ 1 ]. The pathophysiology of CH is still not known, but findings from functional neuroimaging studies have suggested a central role of the posterior hypothalamus in the genesis of attacks [ 2 ]. However, other brain regions, known to be part of the pain processing brain network, are also thought to be involved in the pathogenesis of CH [ 3 ]. Cortical-hypothalamic-brainstem functional interconnections that can switch between out-of-bout and in-bout periods, igniting the trigeminovascular system and the consensual trigeminal autonomic reflexes, may represent the “neuronal background” of CH [ 3 ]. Trigeminal autonomic reflex activation is the basis for cranial autonomic symptoms (CAS) experienced during CH attacks [ 4 ]. In addition to CAS, systemic autonomic dysfunction may be present in CH [ 5 , 6 ], but studies have revealed inconsistent findings. A study assessed cardiovascular autonomic function at different stages of the disease (during and outside a cluster period) revealed no significant differences, except for resting diastolic blood pressure (BP), which was higher during the cluster period [ 5 ]. In this regard, increased BP and a blunted autonomic response to head-up tilt table test have been described in CH patients during the cluster period compared to healthy controls [ 6 ]. Less standardized studies have investigated autonomic function in the remission phase of episodic CH. Ofte et al ., studied cranial autonomic function during the remission phase in CH patients underwent dynamic pupillometry. They found a significant attenuation of pupillary light reflexes in both eyes compared to healthy controls, suggesting a reduction of cranial parasympathetic tone in the pain- free state of CH [ 7 ]. In addition, other authors have evaluated the potential role of different neurotransmitters and neuromodulators in the pathogenesis of ECH and CCH. As summarized in Table 1 , these studies have demonstrated an involvement of the hypothalamus in the genesis of CH and autonomic nervous system (ANS) dysregulation [ 8 – 14 ]. However, clear conclusions could not be made from data gathered and further studies with standardized tests are needed to elucidate the relationship of systemic autonomic function and CH. While CH are innately connected with the ANS, results of autonomic testing in previous studies have been variable in this disorder, especially, in the remission period. In this context, we hypothesized that patients with CH might experience ANS dysfunction, particularly during remission period. Accordingly, the overall aim of this study was to explore systemic autonomic function (sympathetic and parasympathetic) in ECH patients outside the cluster period compared to controls, using standardized autonomic assessment tests. METHODS Design and participants This cross-sectional study recruited thirty consecutive patients with ECH from the Headache Unit of the Hospital Clínico Universitario Lozano Blesa (Zaragoza, Spain) between September 2019 and May 2020. Inclusion criteria were 1) age 18–65 years 2) diagnosis of ECH according to the International Classification of Headache Disorders, 3rd edition (ICHD-3) [ 1 ] with the last cluster period at least 12 weeks before 3) without prophylactic headache medication at the time of recruitment 4) absence of pharmacological treatment of any kind in the month prior to the study, with the exception of non- steroidal anti-inflammatory drugs (free of symptomatic treatment in the previous 24 hours). Exclusion criteria All subjects with conditions known to affect ANS regulation were excluded, including: cardiac disorders, poorly-controlled hypertension or postural hypotension, chronic obstructive pulmonary disease, kidney and liver disease, endocrinological disorders and malnutrition, drug abuse (except for nicotine dependence) or chronic medications (potential effect on BP/HR. Subjects with signs of any other neurological disorder, particularly peripheral neuropathy, and serious psychiatric cognitive disorders, were also excluded. The control group was recruited during the same period and consisted of thirty subjects matched for age and sex with CH patients. All controls were interviewed to ensure they were healthy and free of neurological disorders, including other types of headache. The study was approved by the Regional Research Ethics Committee of Aragon (CEICA) and complied the scientific and ethical guidelines for human research established by the Helsinki Accord. All subjects provided written informed consent to participate in this study. Protocol All subjects were free of caffeine, alcohol, nicotine and medication from the previous evening. All procedures were performed in the morning (8–10 am), after 10 minutes of rest and avoiding previous physical activity. Subjects underwent a comprehensive medical history ( exclusion criteria , subjects with previous disorders were excluded) and a standardized battery of autonomic function tests, in a quiet, temperature-controlled room ( Fig. 1 ) . Three researchers (ALB, MRE, LDG) who were blinded to clinical data performed the battery of standardized autonomic test. Heart rate variability (HRV) and blood pressure(BP) Baroreflex-mediated withdrawal of cardiac parasympathetic activity and sympathetic activation maintain standing BP in healthy persons. Under normal circumstances, systolic BP (SBP) decreases by 10 mmHg, while diastolic BP (DBP) increases by 5 mmHg upon standing from a sitting or supine position. Similarly, HR increases by 5–20 beats per minute. Orthostatic hypotension is caused by a sustained fall in SBP or DBP after standing for 3 minutes. In contrast, some patients have a paradoxical increase in upright BP to hypertensive levels, presumably due to sympathetic activation overshoot. BP and HR were measured with a validated automated cuff sphygmomanometer over the brachial artery on the nondominant arm, using adequate cuffs according to arm circumference. After the subjects had rested for 10 minutes, three consecutive measures were taken after 1, 2 and 3 minutes of standing. HRV is the variation in consecutive heartbeats [R–R interval (RRI)] and is a marker of ANS activity in which increased HRV reflects parasympathetic predominance, whereas decreased HRV suggests sympathetic predominance. Time domain measures include standard deviation of normal to normal intervals (SDNN), root mean square of successive RRI differences (RMSSD) and percentage of successive RRI (pNN50). Frequency domain measures include low frequency (LF) and high frequency (HF). The following time domain parameters were measured [ 15 , 16 ]: Mean RR (ms): the mean of the RRI. SDNN (ms): the standard deviation of normal-to-normal RRI. SDNN reflects the parasympathetic component of the autonomic function. RMSSD (ms): the root means square of difference between successive normal intervals. It is an important indicator of parasympathetic activity. pNN50 (%): the percentage of differences greater than 50 ms between successive normal RRI. It predominantly reflects the parasympathetic activity. The following frequency domain parameters were measured [ 15 , 16 ]: LF (ms 2 ): it includes the absolute power of low-frequency band range between 0.04 Hz and 0.15 Hz and consists of a combination of sympathetic and parasympathetic effects. HF (ms 2 ): it includes the absolute power of high-frequency band range between 0.16 Hz and 0.4 Hz. It is considered that is modulated by the parasympathetic activity of ANS. LF/HF ratio: the ratio of LF-to-HF power. It reflects the sympathovagal balance and can be used to estimate HRV in general. HRV assessment was based on RRI records at rest and during during deep paced breathing, collected with a free smartphone app (Elite HRV Inc, version 5.5.6) for Apple via Bluetooth 4.0, and a wireless transmitter Polar H7 (Polar Electro Oy, Kempele, Finland) placed on the patient’s chest. The signals were transmitted to the computer for further analysis. The Polar H7 HR sensors have been validated both at rest and during exercise [ 17 ]. Subjects were trained to breathe at 6 cycles per minute, and respiratory sinus arrhythmia during deep-paced breathing was calculated from the mean of the 3 longest RRI during expiration divided by the mean of the 3 shortest RRI during inspiration (i.e., expiratory: inspiratory [E: I] ratio) [ 18 ]. The RRI series obtained were subjected to frequency and time domain analysis. Norepinephrine (NE) NE is the principal neurotransmitter of the sympathetic nervous system (SNS). NE in the bloodstream emanates mainly from networks of sympathetic nerves that enmesh blood vessels. Considering the sympathoneural origin of NE, plasma NE levels are used to indicate activity of the sympathetic noradrenergic system. For assessment of plasma NE levels, an intravenous catheter was inserted in the forearm into the antecubital vein. Venous blood samples were collected through the indwelling catheter after at least 15 minutes’ and after 10 minutes standing up for analysis of plasma NE levels by high-performance liquid chromatography. In addition, patients underwent a complete blood count and metabolic panel to rule out anemia, dehydration or electrolyte imbalances. Statistical Analysis First, the data were tested for normality using the Shapiro-Wilk and Kolmogorov-Smirnov tests. For parametric variables, data were expressed as means with standard deviations (SD), and for non-parametric variables, median and interquartile range (IQR). In bivariate analyses, Student's t-test, one-way ANOVA and Mann-Whitney tests were used to compare variables between groups. Repeated-measures ANOVA was performed to compare the effect of headache characteristics (case-control) and time on levels of NE. For all tests, a two-sided P-value of < 0.05 was used to determine statistical significance. All analyses were performed with R version 4.0.5 (R Foundation for Statistical Computing, Viena, Austria). RESULTS Thirty episodic CH patients and age- and sex-matched controls were included in the analysis. Baseline and clinical characteristics of participants are summarized in Table 2. Demographic characteristics including age, gender, smoking habits, and history of cardiovascular risk factors, were not significantly different between patients with CH and individuals in the control group. Attack and cluster period characteristics were recorded for all patients in the CH group. All included patients were out-of-bout, with a median since the last cluster period of 18.0 months [range, 3.0–48.0]. Orthostatic heart rate (HR) and blood pressure (BP) changes Adjusting for baseline values, we observed that absolute HR was higher in CH patients in all four states (supine, 1-2-3-min standing up). In turn, the orthostatic HR increase at each of the measurements was more pronounced in patients with CH compared to healthy controls ( Fig. 2 ) . There were no significant differences between groups in supine SBP and responses to 1-minute standing (131.93 ± 12.98 for CH vs 134.43 ± 14.05 for controls, p = 0.477). There was a non-significant increase in 2-minutes and 3-minutes standing up SBP in CH group (135.67 ± 14.49 and 133.53 ± 14.46, respectively), which was not observed in the headache-free group, which had a downward trend in SBP over time. DBP was higher in patients with CH in supine and 1 minute standing up, with similar absolute values at minute 3 ( Table 3 ). Table 3 Orthostatic heart rate and blood pressure changes in cluster headache patients and controls. Cluster headache (n = 30) Healthy controls (n = 30) Differences p SBP supine, mmHg 133.47 (16.85) 135.37 (16.69) 0.662 SBP 1-min standing up, mmHg 131.93 (12.98) 134.43 (14.05) 0.477 SBP 2-min standing up, mmHg 135.67 (14.49) 131.93 (13.77) 0.310 SBP 3-min standing up, mmHg 133.53 (14.46) 129.07 (14.53) 0.238 DBP supine, mmHg 83.40 (10.10) 81.83 (9.93) 0.547 DBP 1-min standing up, mmHg 91.33 (8.35) 89.03 (9.31) 0.318 DBP 2-min standing up, mmHg 90.63 (8.22) 90.70 (12.07) 0.980 DBP 3-min standing up, mmHg 88.90 (9.21) 89.33 (9.94) 0.862 HR supine, bpm 65.53 (13.72) 60.73 (9.49) 0.121 HR 1-min standing up, bpm 77.93 (14.68) 71.97 (10.96) 0.080 HR 2-min standing up, bpm 77.07 (13.20) 72.37 (10.21) 0.129 HR 3-min standing up, bpm 78.27 (14.19) 72.33 (11.17) 0.077 Notes: Values are presented as mean and standard deviation (SD). All participants were in normal sinus rhythm. Abbreviations: bpm, beats per minute; DBP, diastolic blood pressure; HR, heart rate; SBP, systolic blood pressure. Heart rate variability analysis (HRV) All HR parameters, including minimum, maximum and average HR, presented an upward trend in CH, highlighting a significantly higher average HR in the out-of-bout cluster period compared to controls (64.2 [59.6–75.8] vs. 60.4 [57.3-62.67], p = 0.038). Likewise, some time-domain and frequency-domain HRV parameters showed clinically relevant differences between groups. Compared to controls, CH patients had significantly lower pNN50 and SDNN values (pNN50, 31.0 [5.3–44.3] vs. 44.5 [25.8–58.5], p = 0.043; SDNN, 79.6 ± 42.6 vs. 99.6 ± 42.3, p = 0.004). Other HRV time-domain were also observed to decrease in the CH group, such as RMSSD (59.5 ± 36.9 vs. 77.3 ± 39.4, p = 0.077) ( Fig. 3 ) . Frequency-domain analysis in the remission period also showed a decreasing trend. However, there were no significant differences between the CH population and the control group ( Table 4 ). Table 4 Parameters of heart rate variability outside the cluster period. Cluster headache (n = 30) Healthy controls (n = 30) Differences p (95% CI) AV.HR (b/m), median (IQR) 64.2 (59.6–75.8) 60.4 (57.3–62.7) 0.038* Max.HR (b/m), median (IQR) 76.6 (70.4–85.9) 71.04 (66.1–79.5) 0.143 Min.HR (b/m), median (IQR) 54.0 (46.6–66.1) 49.7 (44.7–58.8) 0.169 E/I Ratio 1.4 (1.3–1.5) 1.5 (1.3–1.7) 0.249 SDNN (ms), mean (SD) 79.6 (42.6) 99.6 (42.6) 0.004* RMSSD (ms), mean (SD) 59.5 (36.9) 77.3 (39.4) 0.077 pNN50 (%), median (IQR) 31.0 (5.3–44.3) 44.5 (25.8–58.5) 0.043* LF power (ms 2 ), median (IQR) 4454.1 (1618.9-9451.3) 7657.3 (2636.4-12172.7) 0.121 HF power (ms 2 ), median (IQR) 614.3 (133.0-1645.7) 1262.2 (307.6-1931.4) 0.160 LF/HF ratio 7.6 (5.7–14.2) 6.3 (4.4–14.4) 0.492 Notes: Values are presented as mean and standard deviation (SD), median and interquartile range (IQR) Abbreviations: AV.HR, average heart rate; Max., maximum; Min., minimum; LF/HF, the ratio of low-frequency/high-frequency power; RMSSD, root mean square of the difference between successive normal intervals; pNN50, the percentage of the number of pairs of consecutive beat-to-beat intervals that differed by 50 ms; SDNN, the standard deviation of the normal-to-normal RR interval; LF, low frequency; HF, high frequency. * p < 0.05, significant differences between cluster headache and headache-free controls Plasma norepinephrine levels (NE) As shown in Fig. 4, supine and upright NE levels were significantly higher in CH group, 329.3 ± 172.7 pg/mL CH supine and 489.9 ± 206.8 pg/mL standing compared to healthy controls (224.9 ± 99.0 pg/mL and 354.2 ± 154.2 pg/mL, respectively). After standing, plasma NE levels rose by 44% of the resting value in the CH group and by 33% of the resting value in controls. DISCUSSION To the best of our knowledge, this is the first study to comprehensively and homogeneously assess different parameters of autonomic function outside the bout period in CH patients. One of the main findings of this cross-sectional study is that HRV parameters are significantly lower in CH. It looks like that pNN50, RMSSD and SDNN are particularly lower compared to headache-free controls, suggesting an autonomic dysfunction in the time-domain HRV parameters. HRV reveals the balance in ANS activity, in which an increase in HRV reflects parasympathetic predominance, whereas decreased HRV suggests sympathetic predominance [ 16 ]. Numerous studies have investigated HRV abnormalities in various painful conditions, including chronic migraine, in which investigations have consistently demonstrated an autonomic dysfunction as evaluated by HRV [ 19 ]. The mechanisms underlying the HRV change patterns in CH during spontaneous attacks confirmed the finding of increased parasympathetic tone [ 20 ]. In contrast, investigations of the remission period seem to differ [ 21 , 22 ]. We demonstrated that out-of-bout CH patients have lower time-domain parameters of HRV (pNN50, RMSSD, and SDNN), in addition to a higher mean HR compared to the control group. Although there were no significant differences between frequency-domain values, we also found a decreasing trend in all parameters evaluated. Our findings suggest a blunted parasympathetic system response in ECH during remission periods. Similar to our results, some studies revealed differences in time-domain and -frequency parameters in CH. In this regard, Tubani et al. , demonstrated severe sympathovagal imbalance during spontaneous attacks and mean LF and HF values during intercritic periods, suggesting ANS dysfunction [ 21 ]. Furthermore, an Italian study during spontaneous attacks in 8 CH patients revealed an increase in LF before attacks, followed by an increase in the HF component lasting until the attack subsided [ 22 ]. In opposition to these results, the study by van Vliet et al. , revealed no systematic cardiovascular autonomic functional changes in CH during a cluster period, outside the pain attack [ 5 ]. In contrast to our research, most of the studies focused on monitoring autonomic function during the cluster period. Furthermore, most of the investigations that have evaluated possible changes in remission periods are characterized by their methodological heterogeneity (simple sizes, patients on prophylactic medication, time since last bout unspecified, etc.) [ 20 ]. BP and HR values with postural changes are determinant in the evaluation of ANS [ 23 ]. However, some patients have a paradoxical increase in upright BP, presumably due to sympathetic activation overshoot. Interestingly, our findings showed an increase at 2 and 3-minutes orthostatic SBP upon active standing in CH patients, compared to headache-free controls. At the same time, supine and 3-minutes supine DBP was higher in CH group. HR was also higher in all phases of the measurements, with a non-significant increasing trend over time, which was not present in healthy controls. Based on our findings, we speculate that there could be an evidence of reduced parasympathetic system and a trend toward increased sympathetic activity with standing during remission periods. Early observations of BP and HR changes in CH were made during provoked attacks and employing different methodologies in heterogeneous populations [ 24 ]. Thus, a Spanish study revealed a higher mean night-time systolic and diastolic BP and non-dipping pattern in CH population; however, the period of the included patients was not specified [ 25 ]. The same researchers demonstrated higher carotid intima-media thickness values during remission periods and hypothesized that CH out-of-bout have a higher risk of cardiovascular disease [ 26 ]. This is consistent with the orthostatic changes in HR and BP found in our study, in which we homogeneously evaluated patients with CH in the remission phase and without a previous diagnosis of cardiovascular disease. Plasma NE levels, taken together with the cardiovascular response to tilt and standing up may be a useful index of overall sympathetic function [ 27 ]. In our cohort, we observed significant differences in supine and standing plasmatic NE levels between groups. These findings could suggest a possible sympathetic nervous system hyperactivity during pain-free periods in CH. Some studies have attempted to explore the role of neurotransmitter changes in CH, but, most of them focused on the cluster period and the results are contradictory. Igarashi et al ., observed an increase in NE closely related to the pain attack. Conversely, they found no change in NE by 5 minutes standing during the remission period, but data for the last bout were not detailed [ 8 ]. Stritmatter et al. , examined twelve ECH during the cluster period and reported lower plasma and cerebrospinal fluid NE levels compared to controls [ 10 ]. Subsequently, a Swedish study observed an altered nocturnal growth hormone pattern in the remission phase, which could indicate a permanent hypothalamic disturbance; despite this, nocturnal secretion of NE, cortisol and insulin did not differ significantly between groups [ 12 ]. D’Andrea et al ., were the first to describe the involvement of alpha-agonists in CCH; they found high levels of NE and epinephrine in CCH patients and hypothesized an activation of endothelial receptors trace amine-associated, which may constitute a step in the physiopathology of cluster attacks [ 14 ]. The mechanisms underlying autonomic dysfunction in CH are yet to be fully explored, especially during remission periods. The central autonomic network is responsible for generating headache and CAS in CH. Additionally, more widespread systemic autonomic dysfunction may be present in this disorder [ 28 ]. Regarding CH pathophysiology, the hypothalamus role is undeniable in the genesis of attacks. Additional brainstem nuclei -locus coeruleus, raphe, periaqueductal grey- play a role in the regulation of pain input in CH and different cortical-hypothalamic-brainstem functional interconnections can switch between out-of-bout and in-bout periods, igniting the trigeminovascular system [ 29 , 30 ]. Based on this, some investigations have described the question of whether autonomic symptomatology is also of central origin in CH, and therefore not only present during pain attacks. Barloese et al. , performed a narrative review suggesting that interictal subclinical autonomic dysfunction may exist [ 20 ]. In this regard, Ofte et al. , found a bilateral reduction in cranial parasympathetic tone during remission [ 7 ]. These findings support evidence of reduced parasympathetic function in the pain- free state of CH. This is consistent with the results of our study, which suggest a reduction of parasympathetic system activity during remission periods of CH. Therefore, it could be plausible that the hypothalamus is involved in attacks, but the pathophysiology associated with in-bout/out-of-bout transitions may extend beyond the hypothalamus, and involve dynamic interactions with unidentified cortical and subcortical areas [ 29 ]. Recent voxel-based morphometric studies, mainly performed in the absence of pain attacks, have identified structural grey matter changes in mainly areas involved in the pain matrix [ 31 , 32 ]. These areas are part of the central autonomic network and functional abnormalities in this network could be related to autonomic dysfunction in the remission phase of our CH. Furthermore, white matter microstructural differences have been reported in frontal pain modulation areas during the cluster-bout period and these changes mostly persist during out‐of‐bout periods [ 33 ]. Finally, decreased functional co-activation of the hypothalamus and salience network areas has been observed, suggesting association with the defective central pain control pathway and dysregulation of the ANS [ 34 ]. Our study has some strengths. First, is the first study to report an integrated autonomic system evaluation in a homogeneous sample of out-bout CH patients. Some previous studies have performed HRV assessment during pain attacks or associated with in-bout/out-of-bout transitions in a heterogeneous sample. We conducted a cross-sectional study to assess sympathetic and parasympathetic activity during remission periods through an accurate and rigorous protocol in all patients. Second, the CH diagnoses of the patients included were well validated, and the recordings were made with standardized methods ensuring at least 12 weeks since the last cluster period and always carried out by the same researchers. At the same time, the present study has some limitations. First, it is a single-centre study that recruited patients; therefore, we cannot exclude a selection bias. The sample is small, and consequently conclusions should be drawn with caution. In addition, complete matching for smoking was not achieved; smoking is known to influence baroreflex sensitivity, but participants of our study were free of nicotine from the previous evening. Even though, we can not completely rule out that some changes we observed may be attributable to smoking and other lifestyles. Finally, although it is relatively well-established that time and frequency-domain are indexes of autonomic system-mediated HRV, spectral and nonlinear analysis are very sensitive and the conditions under which patients are investigated may be highly influential on the results. Thus, the results should be interpreted with caution and confirmed in a larger study in the future. CONCLUSION Patients with ECH have reduced time-domain HRV indices and increased plasma NE levels in supine and standing positions, which could reflect a decrease in parasympathetic activity with sympathetic hyperactivity during during pain-free periods. These findings could suggest an imbalance of the ANS and the involvement of different pain-related structures in the physiopathology of CH. Further studies involving more comprehensive and standardized tests of systemic autonomic function are needed in order to improve our knowledge related to dynamic transitioning between in-bout and out-of-bout periods in CH. Abbreviations ANS Autonomic nervous system BP Blood pressure CAS Cranial autonomic symptoms CH Cluster headache CCH Chronic cluster headache DBP Diastolic blood pressure ECH Episodic cluster headache HF High frequency HR Heart rate IQR Interquartile range HRV Heart rate variability LF Low frequency NE Norepinephrine pNN50 Percentage of successive RR intervals RMSSD Root mean square of successive RR intervals differences SDNN Standard deviation of normal-to-normal RR intervals SNS Sympathetic nervous system Declarations Author contributions Alba López-Bravo: study design, data collection, analysis and interpretation of data, statistical analysis, drafting and critical revision of the manuscript. Marisa de la Rica-Escuín: processed the samples and performed the experiments. Laura Díez Galán: processed the samples and performed the experiments. Elena Bellosta-Diago: study design, interpretation of data, drafting and critical revision of the manuscript, general supervision of the research group. Sonia Santos-Lasaosa: study design, interpretation of data, drafting and critical revision of the manuscript, general supervision of the research group. Data Availability Sharing data compromises ethical standards or legal requirements. Ethics approvals and consent to participate. This study was conducted in accordance with the declaration of Helsinki for research involving human subjects. All experiments were performed after obtaining ethical permit from the Regional Research Ethics Committee of Aragon (CEICA) Authority and after informed consent from all study participants. References Headache Classification Committee of the International Headache Society (IHS). The international classification of headache disorders, 3rd edition. 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Neurol Sci. 2017; 38(Suppl 1):37-43. https://doi.org/10.1007/s10072-017-2862-4 Yilmaz M, Kayancicek H, Cekici Y. Heart rate variability: highlights from hidden signals. J Integr Cardiol. 2018; 4:1-8. https://doi.org/10.15761/JIC.1000258 Katona PG, Jih F. Respiratory sinus arrhythmia: non-invasive measure of parasympathetic cardiac control. J Appl Physiol. 1975; 39:801-5. https://doi.org/10.1152/jappl.1975.39.5.801 Gambassi BB, Neves VR, Brito EZA, et al. A validation study of a smartphone application for heart rate variability assessment in asymptomatic adults. Am J Cardiovasc Dis. 2020; 10:219–29. Goldstein DS, Low PA. Clinical evaluation of the autonomic nervous system. Continuum (Minneap Minn), Autonomic Disorders. 2007; 13:33-49. https://doi.org/10.1212/01.CON.0000299965.28266.ec Chuang CH, Li JY, King JT, Chen WT, Chen SP, Wang YF, et al. Abnormal heart rate variability and its application in predicting treatment efficacy in patients with chronic migraine: An exploratory study. Cephalalgia. 2023; 43:3331024231206781. https://doi.org/10.1177/03331024231206781 Barloese MC. A Review of Cardiovascular Autonomic Control in Cluster Headache. Headache. 2016; 56:225-39. https://doi.org/10.1111/head.12730 Tubani L, Baratta L, Giorgino F, Delfino M, Fiore G, Golluscio V, et al. Heart rate variability in cluster headache. Ann Ital Med Int. 2003; 18:42-6. De Marinis M, Strano S, Granata M, Urani C, Lino S, Calcagnini G, et al. Sympathetic-Parasympathetic Activation During Spontaneous Attacks of Cluster Headache: Evaluation by Spectral Analysis of Heart-Rate Fluctuations. Cephalalgia. 1995; 15:504-510. https://doi.org/10.1046/j.1468-2982.1995.1506504.x Jordan J, Biaggioni I, Grassi G, Fedorowski A, Kario K. When Blood Pressure Increases with Standing: Consensus Definition for Diagnosing Orthostatic Hypertension. Blood Press. 2023; 32:2161871. https://doi.org/10.1080/08037051.2022.2161871 Ekbom K. Heart rate, blood pressure, and electrocardiographic changes during provoked attacks of cluster headache. Acta Neurol Scand. 1970; 46: 215-224. https://doi.org/10.1111/j.1600-0404.1970.tb05617.x Santos Lasaosa S, Navarro Calzada J, Velázquez Benito A, Pérez Lázaro C. Nighttime blood pressure in cluster headache. Headache. 2011; 51:1445-9. https://doi.org/10.1111/j.1526-4610.2011.01991.x Lasaosa SS, Diago EB, Calzada JN, Benito AV. Cardiovascular Risk Factors in Cluster Headache. Pain Med. 2017; 18:1161-1167. https://doi.org/10.1093/pm/pnw305 Louis WJ, Doyle AE, Anavekar S. Plasma norepinephrine levels in essential hypertension. N Engl J Med. 1973; 288:599-601. https://doi.org/10.1056/NEJM197303222881203 Iser C, Arca K. Headache and Autonomic Dysfunction: a Review. Curr Neurol Neurosci Rep. 2022; 22:625-634. https://doi.org/10.1007/s11910-022-01225-3 Yang FC, Chou KH, Kuo CY, Lin YY, Lin CP, Wang SJ. The pathophysiology of episodic cluster headache: Insights from recent neuroimaging research. Cephalalgia. 2018; 38:970-983. https://doi.org/10.1177/0333102417716932 Silvestro M, Tessitore A, Orologio I, Battista G, Siciliano M, Tedeschi G, et al. Cluster headache pathophysiology: What we have learned from advanced neuroimaging. Headache. 2022; 62:436-452. https://doi.org/10.1111/head.14279 Matharu MS. Functional and structural neuroimaging in primary headache disorders. PhD Thesis, Institute of Neurology, University of London, London, UK, 2006. Absinta M, Rocca MA, Colombo B, et al. Selective decreased grey matter volume of the pain-matrix network in cluster headache. Cephalalgia 2012; 32: 109–115. https://doi.org/10.1177/0333102411431334 May A, Schwedt TJ, Magis D, Pozo-Rosich P, Evers S, Wang SJ. Cluster headache. Nat Rev Dis Primers. 2018; 4:18006. https://doi.org/10.1038/nrdp.2018.6 Qiu E, Tian L, Wang Y, Ma L, Yu S. Abnormal coactivation of the hypothalamus and salience network in patients with cluster headache. Neurology. 2015; 84(14):1402-8. https://doi.org/10.1212/WNL.0000000000001442 Table 1 and 2 Table 1 and 2 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Table1and2.docx floatimage1.jpeg Graphical Abstract Cite Share Download PDF Status: Published Journal Publication published 13 Oct, 2025 Read the published version in Acta Neurologica Belgica → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6871540","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":475504366,"identity":"5acedfea-18ac-4fc9-bcd6-d9f635ee74eb","order_by":0,"name":"Alba López-Bravo","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9UlEQVRIiWNgGAWjYDACdh4gUQBiMR8gUgszSIsBiMWWQLIWHgPidPA38x78wGBgk8fPf+abdEHNYXnz2YcfMHz4g1uLxGG+ZAkGg7RiyYaz26RnHDtsOOdcmgHjzDY81hzmMQBqOZy44WDvNmketjTGGTwMBsy8Dbh1yB/mMf4B0rL/MM8zaZ5/afYzeNg/MP/B4zCDwzxmEFvYeNikedtsEmfw8BgwM7Dh1mJ4mC/NIgHoF4kzbMbWvH02yUAtBQd78fhF7njv4RsfKoAh1n/44W2ebxK2QIdtfPADj8PAIAGMkMABAhpgukbBKBgFo2AU4AAA8WdH+NK1qooAAAAASUVORK5CYII=","orcid":"","institution":"Reina Sofía Hospital","correspondingAuthor":true,"prefix":"","firstName":"Alba","middleName":"","lastName":"López-Bravo","suffix":""},{"id":475504379,"identity":"917506bc-a444-4656-b747-47d753737d85","order_by":1,"name":"Elena Bellosta Diago","email":"","orcid":"","institution":"Clínico Universitario Lozano Blesa Hospital","correspondingAuthor":false,"prefix":"","firstName":"Elena","middleName":"Bellosta","lastName":"Diago","suffix":""},{"id":475504382,"identity":"83a98bf8-fc58-427e-b565-6e0895dd025d","order_by":2,"name":"Marisa de la Rica Escuín","email":"","orcid":"","institution":"Clínico Universitario Lozano Blesa Hospital","correspondingAuthor":false,"prefix":"","firstName":"Marisa","middleName":"de la Rica","lastName":"Escuín","suffix":""},{"id":475504393,"identity":"6aff2bb7-8698-4479-bb70-6cd5bd7cf1d4","order_by":3,"name":"Laura Díez Galán","email":"","orcid":"","institution":"Clínico Universitario Lozano Blesa Hospital","correspondingAuthor":false,"prefix":"","firstName":"Laura","middleName":"Díez","lastName":"Galán","suffix":""},{"id":475504395,"identity":"82afeb24-8753-4e55-82dd-579070121377","order_by":4,"name":"Sonia Santos Lasaosa","email":"","orcid":"","institution":"Clínico Universitario Lozano Blesa Hospital","correspondingAuthor":false,"prefix":"","firstName":"Sonia","middleName":"Santos","lastName":"Lasaosa","suffix":""}],"badges":[],"createdAt":"2025-06-11 11:53:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6871540/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6871540/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s13760-025-02915-8","type":"published","date":"2025-10-13T15:57:31+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":85644713,"identity":"298584d4-21ce-47ce-adb6-44099e9c02a5","added_by":"auto","created_at":"2025-06-30 08:17:10","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":329294,"visible":true,"origin":"","legend":"\u003cp\u003eStudy flow diagram and protocol.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6871540/v1/3ece300af44c4f9b46f29f5f.png"},{"id":85644714,"identity":"a4dd5bd6-6556-431f-8fc4-8c53d784a925","added_by":"auto","created_at":"2025-06-30 08:17:10","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":357787,"visible":true,"origin":"","legend":"\u003cp\u003eOrthostatic heart rate and blood pressure changes in cluster headache (CH) in remission and control group.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6871540/v1/25b95a9efa5e7923afa28422.png"},{"id":85644152,"identity":"7b2dbefd-eac8-4e64-9997-2f3afe07d8b8","added_by":"auto","created_at":"2025-06-30 08:09:08","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":137743,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of time-domain HRV parameters among cluster headache (CH) in remission and control group.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6871540/v1/ba1d257f32827c14d31c0c3b.png"},{"id":85644169,"identity":"514d71ee-3b99-4da2-a704-74a6047a9d56","added_by":"auto","created_at":"2025-06-30 08:09:11","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":214162,"visible":true,"origin":"","legend":"\u003cp\u003eSupine and standing up norepinephrine plasmatic levels in cluster headache (CH) in remission and control group.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6871540/v1/d714a4f7ed4707178a05f0df.png"},{"id":93956005,"identity":"1e13961d-47d7-4fc6-9695-d503c905f3de","added_by":"auto","created_at":"2025-10-20 16:09:10","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1719781,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6871540/v1/8e6c8fb4-dc9d-4185-9ae0-7f9c3658466f.pdf"},{"id":85644145,"identity":"9523abbd-fc44-42f9-a2f8-fbd1c4e0b4bd","added_by":"auto","created_at":"2025-06-30 08:09:07","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":23626,"visible":true,"origin":"","legend":"","description":"","filename":"Table1and2.docx","url":"https://assets-eu.researchsquare.com/files/rs-6871540/v1/5f5f30a109ba87589f26ba51.docx"},{"id":85644139,"identity":"892d3aea-a1f7-4a46-9b59-2afb9af35b68","added_by":"auto","created_at":"2025-06-30 08:09:07","extension":"jpeg","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":810975,"visible":true,"origin":"","legend":"\u003cp\u003eGraphical Abstract\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6871540/v1/fc858eac18cf50fe9db52439.jpeg"}],"financialInterests":"No competing interests reported.","formattedTitle":"Autonomic dysfunction in patients with episodic cluster headache during remission period","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eCluster headache (CH) is a trigeminal autonomic primary headache characterized by unilateral pain attacks accompanied by cranial autonomic symptoms. Most patients with CH have bouts with daily headache attacks interspersed with symptom free periods (remission) that last for months to years at a time. This is the episodic CH phenotype (ECH), in contrast to chronic CH (CCH), which is defined by remission periods lasting less than three months per year [\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eThe pathophysiology of CH is still not known, but findings from functional neuroimaging studies have suggested a central role of the posterior hypothalamus in the genesis of attacks [\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e]. However, other brain regions, known to be part of the pain processing brain network, are also thought to be involved in the pathogenesis of CH [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e]. Cortical-hypothalamic-brainstem functional interconnections that can switch between out-of-bout and in-bout periods, igniting the trigeminovascular system and the consensual trigeminal autonomic reflexes, may represent the \u0026ldquo;neuronal background\u0026rdquo; of CH [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eTrigeminal autonomic reflex activation is the basis for cranial autonomic symptoms (CAS) experienced during CH attacks [\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e]. In addition to CAS, systemic autonomic dysfunction may be present in CH [\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e], but studies have revealed inconsistent findings. A study assessed cardiovascular autonomic function at different stages of the disease (during and outside a cluster period) revealed no significant differences, except for resting diastolic blood pressure (BP), which was higher during the cluster period [\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e]. In this regard, increased BP and a blunted autonomic response to head-up tilt table test have been described in CH patients during the cluster period compared to healthy controls [\u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e]. Less standardized studies have investigated autonomic function in the remission phase of episodic CH. Ofte \u003cem\u003eet al\u003c/em\u003e., studied cranial autonomic function during the remission phase in CH patients underwent dynamic pupillometry. They found a significant attenuation of pupillary light reflexes in both eyes compared to healthy controls, suggesting a reduction of cranial parasympathetic tone in the pain- free state of CH [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eIn addition, other authors have evaluated the potential role of different neurotransmitters and neuromodulators in the pathogenesis of ECH and CCH. As summarized in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, these studies have demonstrated an involvement of the hypothalamus in the genesis of CH and autonomic nervous system (ANS) dysregulation [\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e]. However, clear conclusions could not be made from data gathered and further studies with standardized tests are needed to elucidate the relationship of systemic autonomic function and CH.\u003c/p\u003e\n\u003cp\u003eWhile CH are innately connected with the ANS, results of autonomic testing in previous studies have been variable in this disorder, especially, in the remission period. In this context, we hypothesized that patients with CH might experience ANS dysfunction, particularly during remission period. Accordingly, the overall aim of this study was to explore systemic autonomic function (sympathetic and parasympathetic) in ECH patients outside the cluster period compared to controls, using standardized autonomic assessment tests.\u003c/p\u003e"},{"header":"METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eDesign and participants\u003c/h2\u003e \u003cp\u003eThis cross-sectional study recruited thirty consecutive patients with ECH from the Headache Unit of the Hospital Cl\u0026iacute;nico Universitario Lozano Blesa (Zaragoza, Spain) between September 2019 and May 2020. Inclusion criteria were 1) age 18\u0026ndash;65 years 2) diagnosis of ECH according to the International Classification of Headache Disorders, 3rd edition (ICHD-3) [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] with the last cluster period at least 12 weeks before 3) without prophylactic headache medication at the time of recruitment 4) absence of pharmacological treatment of any kind in the month prior to the study, with the exception of non- steroidal anti-inflammatory drugs (free of symptomatic treatment in the previous 24 hours).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eExclusion criteria\u003c/h3\u003e\n\u003cp\u003eAll subjects with conditions known to affect ANS regulation were excluded, including: cardiac disorders, poorly-controlled hypertension or postural hypotension, chronic obstructive pulmonary disease, kidney and liver disease, endocrinological disorders and malnutrition, drug abuse (except for nicotine dependence) or chronic medications (potential effect on BP/HR. Subjects with signs of any other neurological disorder, particularly peripheral neuropathy, and serious psychiatric cognitive disorders, were also excluded. The control group was recruited during the same period and consisted of thirty subjects matched for age and sex with CH patients. All controls were interviewed to ensure they were healthy and free of neurological disorders, including other types of headache.\u003c/p\u003e \u003cp\u003e The study was approved by the Regional Research Ethics Committee of Aragon (CEICA) and complied the scientific and ethical guidelines for human research established by the Helsinki Accord. All subjects provided written informed consent to participate in this study.\u003c/p\u003e\n\u003ch3\u003eProtocol\u003c/h3\u003e\n\u003cp\u003eAll subjects were free of caffeine, alcohol, nicotine and medication from the previous evening. All procedures were performed in the morning (8\u0026ndash;10 am), after 10 minutes of rest and avoiding previous physical activity. Subjects underwent a comprehensive medical history (\u003cem\u003eexclusion criteria\u003c/em\u003e, subjects with previous disorders were excluded) and a standardized battery of autonomic function tests, in a quiet, temperature-controlled room \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. Three researchers (ALB, MRE, LDG) who were blinded to clinical data performed the battery of standardized autonomic test.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eHeart rate variability (HRV) and blood pressure(BP)\u003c/h3\u003e\n\u003cp\u003eBaroreflex-mediated withdrawal of cardiac parasympathetic activity and sympathetic activation maintain standing BP in healthy persons. Under normal circumstances, systolic BP (SBP) decreases by 10 mmHg, while diastolic BP (DBP) increases by 5 mmHg upon standing from a sitting or supine position. Similarly, HR increases by 5\u0026ndash;20 beats per minute. Orthostatic hypotension is caused by a sustained fall in SBP or DBP after standing for 3 minutes. In contrast, some patients have a paradoxical increase in upright BP to hypertensive levels, presumably due to sympathetic activation overshoot.\u003c/p\u003e \u003cp\u003eBP and HR were measured with a validated automated cuff sphygmomanometer over the brachial artery on the nondominant arm, using adequate cuffs according to arm circumference. After the subjects had rested for 10 minutes, three consecutive measures were taken after 1, 2 and 3 minutes of standing.\u003c/p\u003e \u003cp\u003eHRV is the variation in consecutive heartbeats [R\u0026ndash;R interval (RRI)] and is a marker of ANS activity in which increased HRV reflects parasympathetic predominance, whereas decreased HRV suggests sympathetic predominance. Time domain measures include standard deviation of normal to normal intervals (SDNN), root mean square of successive RRI differences (RMSSD) and percentage of successive RRI (pNN50). Frequency domain measures include low frequency (LF) and high frequency (HF).\u003c/p\u003e \u003cp\u003eThe following time domain parameters were measured [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eMean RR (ms): the mean of the RRI.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eSDNN (ms): the standard deviation of normal-to-normal RRI. SDNN reflects the parasympathetic component of the autonomic function.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eRMSSD (ms): the root means square of difference between successive normal intervals. It is an important indicator of parasympathetic activity.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003epNN50 (%): the percentage of differences greater than 50 ms between successive normal RRI. It predominantly reflects the parasympathetic activity.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eThe following frequency domain parameters were measured [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eLF (ms\u003csup\u003e2\u003c/sup\u003e): it includes the absolute power of low-frequency band range between 0.04 Hz and 0.15 Hz and consists of a combination of sympathetic and parasympathetic effects.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eHF (ms\u003csup\u003e2\u003c/sup\u003e): it includes the absolute power of high-frequency band range between 0.16 Hz and 0.4 Hz. It is considered that is modulated by the parasympathetic activity of ANS.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eLF/HF ratio: the ratio of LF-to-HF power. It reflects the sympathovagal balance and can be used to estimate HRV in general.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eHRV assessment was based on RRI records at rest and during during deep paced breathing, collected with a free smartphone app (Elite HRV Inc, version 5.5.6) for Apple via Bluetooth 4.0, and a wireless transmitter Polar H7 (Polar Electro Oy, Kempele, Finland) placed on the patient\u0026rsquo;s chest. The signals were transmitted to the computer for further analysis. The Polar H7 HR sensors have been validated both at rest and during exercise [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Subjects were trained to breathe at 6 cycles per minute, and respiratory sinus arrhythmia during deep-paced breathing was calculated from the mean of the 3 longest RRI during expiration divided by the mean of the 3 shortest RRI during inspiration (i.e., expiratory: inspiratory [E: I] ratio) [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The RRI series obtained were subjected to frequency and time domain analysis.\u003c/p\u003e\n\u003ch3\u003eNorepinephrine (NE)\u003c/h3\u003e\n\u003cp\u003eNE is the principal neurotransmitter of the sympathetic nervous system (SNS). NE in the bloodstream emanates mainly from networks of sympathetic nerves that enmesh blood vessels. Considering the sympathoneural origin of NE, plasma NE levels are used to indicate activity of the sympathetic noradrenergic system.\u003c/p\u003e \u003cp\u003eFor assessment of plasma NE levels, an intravenous catheter was inserted in the forearm into the antecubital vein. Venous blood samples were collected through the indwelling catheter after at least 15 minutes\u0026rsquo; and after 10 minutes standing up for analysis of plasma NE levels by high-performance liquid chromatography. In addition, patients underwent a complete blood count and metabolic panel to rule out anemia, dehydration or electrolyte imbalances.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eFirst, the data were tested for normality using the Shapiro-Wilk and Kolmogorov-Smirnov tests. For parametric variables, data were expressed as means with standard deviations (SD), and for non-parametric variables, median and interquartile range (IQR). In bivariate analyses, Student's t-test, one-way ANOVA and Mann-Whitney tests were used to compare variables between groups. Repeated-measures ANOVA was performed to compare the effect of headache characteristics (case-control) and time on levels of NE. For all tests, a two-sided P-value of \u0026lt;\u0026thinsp;0.05 was used to determine statistical significance. All analyses were performed with R version 4.0.5 (R Foundation for Statistical Computing, Viena, Austria).\u003c/p\u003e \u003c/div\u003e"},{"header":"RESULTS","content":"\u003cp\u003eThirty episodic CH patients and age- and sex-matched controls were included in the analysis. Baseline and clinical characteristics of participants are summarized in Table 2. Demographic characteristics including age, gender, smoking habits, and history of cardiovascular risk factors, were not significantly different between patients with CH and individuals in the control group. Attack and cluster period characteristics were recorded for all patients in the CH group. All included patients were out-of-bout, with a median since the last cluster period of 18.0 months [range, 3.0\u0026ndash;48.0].\u003c/p\u003e\n\u003ch3\u003eOrthostatic heart rate (HR) and blood pressure (BP) changes\u003c/h3\u003e\n\u003cp\u003eAdjusting for baseline values, we observed that absolute HR was higher in CH patients in all four states (supine, 1-2-3-min standing up). In turn, the orthostatic HR increase at each of the measurements was more pronounced in patients with CH compared to healthy controls \u003cstrong\u003e(\u003c/strong\u003eFig. 2\u003cstrong\u003e)\u003c/strong\u003e. There were no significant differences between groups in supine SBP and responses to 1-minute standing (131.93\u0026thinsp;\u0026plusmn;\u0026thinsp;12.98 for CH vs 134.43\u0026thinsp;\u0026plusmn;\u0026thinsp;14.05 for controls, p\u0026thinsp;=\u0026thinsp;0.477). There was a non-significant increase in 2-minutes and 3-minutes standing up SBP in CH group (135.67\u0026thinsp;\u0026plusmn;\u0026thinsp;14.49 and 133.53\u0026thinsp;\u0026plusmn;\u0026thinsp;14.46, respectively), which was not observed in the headache-free group, which had a downward trend in SBP over time. DBP was higher in patients with CH in supine and 1 minute standing up, with similar absolute values at minute 3 \u003cstrong\u003e(\u003c/strong\u003eTable 3\u003cstrong\u003e).\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 3\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eOrthostatic heart rate and blood pressure changes in cluster headache patients and controls.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCluster headache (n\u0026thinsp;=\u0026thinsp;30)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eHealthy controls (n\u0026thinsp;=\u0026thinsp;30)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDifferences\u003c/p\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSBP supine, mmHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e133.47 (16.85)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e135.37 (16.69)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.662\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSBP 1-min standing up, mmHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e131.93 (12.98)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e134.43 (14.05)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.477\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSBP 2-min standing up, mmHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e135.67 (14.49)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e131.93 (13.77)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.310\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSBP 3-min standing up, mmHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e133.53 (14.46)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e129.07 (14.53)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.238\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDBP supine, mmHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e83.40 (10.10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e81.83 (9.93)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.547\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDBP 1-min standing up, mmHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e91.33 (8.35)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e89.03 (9.31)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.318\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDBP 2-min standing up, mmHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e90.63 (8.22)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e90.70 (12.07)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.980\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDBP 3-min standing up, mmHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e88.90 (9.21)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e89.33 (9.94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.862\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHR supine, bpm\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e65.53 (13.72)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e60.73 (9.49)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.121\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHR 1-min standing up, bpm\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e77.93 (14.68)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e71.97 (10.96)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.080\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHR 2-min standing up, bpm\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e77.07 (13.20)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e72.37 (10.21)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.129\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHR 3-min standing up, bpm\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e78.27 (14.19)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e72.33 (11.17)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eNotes:\u003c/strong\u003e Values are presented as mean and standard deviation (SD). All participants were in normal sinus rhythm.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAbbreviations:\u003c/strong\u003e bpm, beats per minute; DBP, diastolic blood pressure; HR, heart rate; SBP, systolic blood pressure. \u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eHeart rate variability analysis (HRV)\u003c/h2\u003e\n\u003cp\u003eAll HR parameters, including minimum, maximum and average HR, presented an upward trend in CH, highlighting a significantly higher average HR in the out-of-bout cluster period compared to controls (64.2 [59.6\u0026ndash;75.8] vs. 60.4 [57.3-62.67], p\u0026thinsp;=\u0026thinsp;0.038).\u003c/p\u003e\n\u003cp\u003eLikewise, some time-domain and frequency-domain HRV parameters showed clinically relevant differences between groups. Compared to controls, CH patients had significantly lower pNN50 and SDNN values (pNN50, 31.0 [5.3\u0026ndash;44.3] vs. 44.5 [25.8\u0026ndash;58.5], p\u0026thinsp;=\u0026thinsp;0.043; SDNN, 79.6\u0026thinsp;\u0026plusmn;\u0026thinsp;42.6 vs. 99.6\u0026thinsp;\u0026plusmn;\u0026thinsp;42.3, p\u0026thinsp;=\u0026thinsp;0.004). Other HRV time-domain were also observed to decrease in the CH group, such as RMSSD (59.5\u0026thinsp;\u0026plusmn;\u0026thinsp;36.9 vs. 77.3\u0026thinsp;\u0026plusmn;\u0026thinsp;39.4, p\u0026thinsp;=\u0026thinsp;0.077) \u003cstrong\u003e(\u003c/strong\u003eFig. 3\u003cstrong\u003e)\u003c/strong\u003e. Frequency-domain analysis in the remission period also showed a decreasing trend. However, there were no significant differences between the CH population and the control group \u003cstrong\u003e(\u003c/strong\u003eTable 4\u003cstrong\u003e).\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003ctable id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 4\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eParameters of heart rate variability outside the cluster period.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCluster headache\u003c/p\u003e\n \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;30)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eHealthy controls\u003c/p\u003e\n \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;30)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDifferences \u003cem\u003ep\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e(95% CI)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAV.HR (b/m), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e64.2 (59.6\u0026ndash;75.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e60.4 (57.3\u0026ndash;62.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.038*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMax.HR (b/m), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e76.6 (70.4\u0026ndash;85.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e71.04 (66.1\u0026ndash;79.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.143\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMin.HR (b/m), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e54.0 (46.6\u0026ndash;66.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e49.7 (44.7\u0026ndash;58.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.169\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eE/I Ratio\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.4 (1.3\u0026ndash;1.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.5 (1.3\u0026ndash;1.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.249\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSDNN (ms), mean (SD)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e79.6 (42.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e99.6 (42.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.004*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRMSSD (ms), mean (SD)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e59.5 (36.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e77.3 (39.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003epNN50 (%), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e31.0 (5.3\u0026ndash;44.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e44.5 (25.8\u0026ndash;58.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.043*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLF power (ms\u003csup\u003e2\u003c/sup\u003e), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4454.1 (1618.9-9451.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7657.3 (2636.4-12172.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.121\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHF power (ms\u003csup\u003e2\u003c/sup\u003e), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e614.3 (133.0-1645.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1262.2 (307.6-1931.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.160\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLF/HF ratio\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.6 (5.7\u0026ndash;14.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.3 (4.4\u0026ndash;14.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.492\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eNotes:\u003c/strong\u003e Values are presented as mean and standard deviation (SD), median and interquartile range (IQR)\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAbbreviations:\u003c/strong\u003e AV.HR, average heart rate; Max., maximum; Min., minimum; LF/HF, the ratio of low-frequency/high-frequency power; RMSSD, root mean square of the difference between successive normal intervals; pNN50, the percentage of the number of pairs of consecutive beat-to-beat intervals that differed by 50 ms; SDNN, the standard deviation of the normal-to-normal RR interval; LF, low frequency; HF, high frequency.\u003c/p\u003e\n\u003cp\u003e* p \u0026lt; 0.05, significant differences between cluster headache and headache-free controls\u003c/p\u003e\n\u003cdiv id=\"Sec12\"\u003e\n \u003ch2\u003ePlasma norepinephrine levels (NE)\u003c/h2\u003e\n \u003cp\u003eAs shown in Fig.\u0026nbsp;4, supine and upright NE levels were significantly higher in CH group, 329.3\u0026thinsp;\u0026plusmn;\u0026thinsp;172.7 pg/mL CH supine and 489.9\u0026thinsp;\u0026plusmn;\u0026thinsp;206.8 pg/mL standing compared to healthy controls (224.9\u0026thinsp;\u0026plusmn;\u0026thinsp;99.0 pg/mL and 354.2\u0026thinsp;\u0026plusmn;\u0026thinsp;154.2 pg/mL, respectively). After standing, plasma NE levels rose by 44% of the resting value in the CH group and by 33% of the resting value in controls.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eTo the best of our knowledge, this is the first study to comprehensively and homogeneously assess different parameters of autonomic function outside the bout period in CH patients. One of the main findings of this cross-sectional study is that HRV parameters are significantly lower in CH. It looks like that pNN50, RMSSD and SDNN are particularly lower compared to headache-free controls, suggesting an autonomic dysfunction in the time-domain HRV parameters.\u003c/p\u003e \u003cp\u003eHRV reveals the balance in ANS activity, in which an increase in HRV reflects parasympathetic predominance, whereas decreased HRV suggests sympathetic predominance [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Numerous studies have investigated HRV abnormalities in various painful conditions, including chronic migraine, in which investigations have consistently demonstrated an autonomic dysfunction as evaluated by HRV [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The mechanisms underlying the HRV change patterns in CH during spontaneous attacks confirmed the finding of increased parasympathetic tone [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. In contrast, investigations of the remission period seem to differ [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWe demonstrated that out-of-bout CH patients have lower time-domain parameters of HRV (pNN50, RMSSD, and SDNN), in addition to a higher mean HR compared to the control group. Although there were no significant differences between frequency-domain values, we also found a decreasing trend in all parameters evaluated. Our findings suggest a blunted parasympathetic system response in ECH during remission periods.\u003c/p\u003e \u003cp\u003eSimilar to our results, some studies revealed differences in time-domain and -frequency parameters in CH. In this regard, Tubani \u003cem\u003eet al.\u003c/em\u003e, demonstrated severe sympathovagal imbalance during spontaneous attacks and mean LF and HF values during intercritic periods, suggesting ANS dysfunction [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Furthermore, an Italian study during spontaneous attacks in 8 CH patients revealed an increase in LF before attacks, followed by an increase in the HF component lasting until the attack subsided [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. In opposition to these results, the study by van Vliet \u003cem\u003eet al.\u003c/em\u003e, revealed no systematic cardiovascular autonomic functional changes in CH during a cluster period, outside the pain attack [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In contrast to our research, most of the studies focused on monitoring autonomic function during the cluster period. Furthermore, most of the investigations that have evaluated possible changes in remission periods are characterized by their methodological heterogeneity (simple sizes, patients on prophylactic medication, time since last bout unspecified, etc.) [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eBP and HR values with postural changes are determinant in the evaluation of ANS [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. However, some patients have a paradoxical increase in upright BP, presumably due to sympathetic activation overshoot. Interestingly, our findings showed an increase at 2 and 3-minutes orthostatic SBP upon active standing in CH patients, compared to headache-free controls. At the same time, supine and 3-minutes supine DBP was higher in CH group. HR was also higher in all phases of the measurements, with a non-significant increasing trend over time, which was not present in healthy controls. Based on our findings, we speculate that there could be an evidence of reduced parasympathetic system and a trend toward increased sympathetic activity with standing during remission periods.\u003c/p\u003e \u003cp\u003eEarly observations of BP and HR changes in CH were made during provoked attacks and employing different methodologies in heterogeneous populations [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Thus, a Spanish study revealed a higher mean night-time systolic and diastolic BP and non-dipping pattern in CH population; however, the period of the included patients was not specified [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. The same researchers demonstrated higher carotid intima-media thickness values during remission periods and hypothesized that CH out-of-bout have a higher risk of cardiovascular disease [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. This is consistent with the orthostatic changes in HR and BP found in our study, in which we homogeneously evaluated patients with CH in the remission phase and without a previous diagnosis of cardiovascular disease.\u003c/p\u003e \u003cp\u003ePlasma NE levels, taken together with the cardiovascular response to tilt and standing up may be a useful index of overall sympathetic function [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. In our cohort, we observed significant differences in supine and standing plasmatic NE levels between groups. These findings could suggest a possible sympathetic nervous system hyperactivity during pain-free periods in CH.\u003c/p\u003e \u003cp\u003eSome studies have attempted to explore the role of neurotransmitter changes in CH, but, most of them focused on the cluster period and the results are contradictory. Igarashi \u003cem\u003eet al\u003c/em\u003e., observed an increase in NE closely related to the pain attack. Conversely, they found no change in NE by 5 minutes standing during the remission period, but data for the last bout were not detailed [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Stritmatter \u003cem\u003eet al.\u003c/em\u003e, examined twelve ECH during the cluster period and reported lower plasma and cerebrospinal fluid NE levels compared to controls [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Subsequently, a Swedish study observed an altered nocturnal growth hormone pattern in the remission phase, which could indicate a permanent hypothalamic disturbance; despite this, nocturnal secretion of NE, cortisol and insulin did not differ significantly between groups [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. D\u0026rsquo;Andrea \u003cem\u003eet al\u003c/em\u003e., were the first to describe the involvement of alpha-agonists in CCH; they found high levels of NE and epinephrine in CCH patients and hypothesized an activation of endothelial receptors trace amine-associated, which may constitute a step in the physiopathology of cluster attacks [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe mechanisms underlying autonomic dysfunction in CH are yet to be fully explored, especially during remission periods. The central autonomic network is responsible for generating headache and CAS in CH. Additionally, more widespread systemic autonomic dysfunction may be present in this disorder [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Regarding CH pathophysiology, the hypothalamus role is undeniable in the genesis of attacks. Additional brainstem nuclei -locus coeruleus, raphe, periaqueductal grey- play a role in the regulation of pain input in CH and different cortical-hypothalamic-brainstem functional interconnections can switch between out-of-bout and in-bout periods, igniting the trigeminovascular system [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eBased on this, some investigations have described the question of whether autonomic symptomatology is also of central origin in CH, and therefore not only present during pain attacks. Barloese \u003cem\u003eet al.\u003c/em\u003e, performed a narrative review suggesting that interictal subclinical autonomic dysfunction may exist [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. In this regard, Ofte \u003cem\u003eet al.\u003c/em\u003e, found a bilateral reduction in cranial parasympathetic tone during remission [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. These findings support evidence of reduced parasympathetic function in the pain- free state of CH. This is consistent with the results of our study, which suggest a reduction of parasympathetic system activity during remission periods of CH.\u003c/p\u003e \u003cp\u003eTherefore, it could be plausible that the hypothalamus is involved in attacks, but the pathophysiology associated with in-bout/out-of-bout transitions may extend beyond the hypothalamus, and involve dynamic interactions with unidentified cortical and subcortical areas [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Recent voxel-based morphometric studies, mainly performed in the absence of pain attacks, have identified structural grey matter changes in mainly areas involved in the pain matrix [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. These areas are part of the central autonomic network and functional abnormalities in this network could be related to autonomic dysfunction in the remission phase of our CH. Furthermore, white matter microstructural differences have been reported in frontal pain modulation areas during the cluster-bout period and these changes mostly persist during out‐of‐bout periods [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Finally, decreased functional co-activation of the hypothalamus and salience network areas has been observed, suggesting association with the defective central pain control pathway and dysregulation of the ANS [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOur study has some strengths. First, is the first study to report an integrated autonomic system evaluation in a homogeneous sample of out-bout CH patients. Some previous studies have performed HRV assessment during pain attacks or associated with in-bout/out-of-bout transitions in a heterogeneous sample. We conducted a cross-sectional study to assess sympathetic and parasympathetic activity during remission periods through an accurate and rigorous protocol in all patients. Second, the CH diagnoses of the patients included were well validated, and the recordings were made with standardized methods ensuring at least 12 weeks since the last cluster period and always carried out by the same researchers.\u003c/p\u003e \u003cp\u003eAt the same time, the present study has some limitations. First, it is a single-centre study that recruited patients; therefore, we cannot exclude a selection bias. The sample is small, and consequently conclusions should be drawn with caution. In addition, complete matching for smoking was not achieved; smoking is known to influence baroreflex sensitivity, but participants of our study were free of nicotine from the previous evening. Even though, we can not completely rule out that some changes we observed may be attributable to smoking and other lifestyles. Finally, although it is relatively well-established that time and frequency-domain are indexes of autonomic system-mediated HRV, spectral and nonlinear analysis are very sensitive and the conditions under which patients are investigated may be highly influential on the results. Thus, the results should be interpreted with caution and confirmed in a larger study in the future.\u003c/p\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003ePatients with ECH have reduced time-domain HRV indices and increased plasma NE levels in supine and standing positions, which could reflect a decrease in parasympathetic activity with sympathetic hyperactivity during during pain-free periods. These findings could suggest an imbalance of the ANS and the involvement of different pain-related structures in the physiopathology of CH. Further studies involving more comprehensive and standardized tests of systemic autonomic function are needed in order to improve our knowledge related to dynamic transitioning between in-bout and out-of-bout periods in CH.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eANS Autonomic nervous system\u003c/p\u003e\n\u003cp\u003eBP Blood pressure\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCAS Cranial autonomic symptoms\u003c/p\u003e\n\u003cp\u003eCH Cluster headache\u003c/p\u003e\n\u003cp\u003eCCH Chronic cluster headache\u003c/p\u003e\n\u003cp\u003eDBP Diastolic blood pressure\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eECH Episodic cluster headache\u003c/p\u003e\n\u003cp\u003eHF High frequency\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eHR Heart rate\u003c/p\u003e\n\u003cp\u003eIQR Interquartile range\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eHRV Heart rate variability\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eLF Low frequency\u003c/p\u003e\n\u003cp\u003eNE Norepinephrine\u0026nbsp;\u003c/p\u003e\n\u003cp\u003epNN50 Percentage of successive RR intervals\u003c/p\u003e\n\u003cp\u003eRMSSD Root mean square of successive RR intervals differences\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSDNN Standard deviation of normal-to-normal RR intervals\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSNS Sympathetic nervous system\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAlba L\u0026oacute;pez-Bravo: study design, data collection, analysis and interpretation of data, statistical analysis, drafting and critical revision of the manuscript.\u003c/p\u003e\n\u003cp\u003eMarisa de la Rica-Escu\u0026iacute;n: processed the samples and performed the experiments.\u003c/p\u003e\n\u003cp\u003eLaura D\u0026iacute;ez Gal\u0026aacute;n: processed the samples and performed the experiments.\u003c/p\u003e\n\u003cp\u003eElena Bellosta-Diago: study design, interpretation of data, drafting and critical revision of the manuscript, general supervision of the research group.\u003c/p\u003e\n\u003cp\u003eSonia Santos-Lasaosa: study design, interpretation of data, drafting and critical revision of the manuscript, general supervision of the research group.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSharing data compromises ethical standards or legal requirements.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEthics approvals and consent to participate. This study was conducted in accordance with the declaration of Helsinki for research involving human subjects. All experiments were performed after obtaining ethical permit from the Regional Research Ethics Committee of Aragon (CEICA) Authority and after informed consent from all study participants.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eHeadache Classification Committee of the International Headache Society (IHS). The international classification of headache disorders, 3rd edition. Cephalalgia. 2018; 38:1-211. https://doi.org/10.1177/0333102417738202 \u003c/li\u003e\n\u003cli\u003eMay A, Bahra A, Büchel C, Frackowiak RS, Goadsby PJ. Hypothalamic activation in cluster headache attacks. Lancet. 1998; :275-8.https://doi.org/10.1111/jdi.14094 \u003c/li\u003e\n\u003cli\u003eSilvestro M, Tessitore A, Orologio I, Battista G, Siciliano M, Tedeschi G, et al. Cluster headache pathophysiology: What we have learned from advanced neuroimaging. 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Neurology. 2015; 84(14):1402-8. https://doi.org/10.1212/WNL.0000000000001442\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table 1 and 2","content":"\u003cp\u003eTable 1 and 2 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Autonomic dysfunction, Autonomic Nervous System, Cluster headache, Headache, Norepinephrine, Parasympathetic, Sympathetic","lastPublishedDoi":"10.21203/rs.3.rs-6871540/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6871540/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe hypothalamus is involved in cluster headache (CH) pathophysiology and is a hub for autonomic control. While cranial autonomic symptoms are prominent during attacks, other autonomic manifestations may be present in CH. This study aims to explore the autonomic nervous system (ANS) in patients with CH during remission period.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCross-sectional study including 30 CH and 30 age- and sex-matched controls. We analysed time- and frequency-domain parameters of heart rate variability (HRV) and active orthostatic tests. To investigate the sympathetic nervous system, plasma norepinephrine (NE) levels were determined. All assessments were performed during remission period.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll HRV parameters were lower in CH; the percentage of adjacent R-R intervals that differ by more than 50 milliseconds (pNN50) and standard deviation of normal-to-normal R-R intervals in 24h (SDNN) were significantly lower in CH (pNN50, 31.0 [5.3–44.3] vs. 44.5 [25.8–58.5], p = 0.043; SDNN, 79.6 ± 42.6 vs. 99.6 ± 42.6, p = 0.004). All other time-domain parameters, including the root mean square of successive R-R differences (RMSSD) were lower in CH than in controls (RMSSD 59.5 ± 36.9 vs. 77.3 ± 39.4, p = 0.077). Compared to controls, mean HR was significantly higher in CH (64.2 [59.6–75.8] vs. 60.4 [57.3–62.7], p = 0.038). Supine and upright NE levels were significantly higher in CH, (supine 329.27 pg/ml ± 172.71 vs 224.91 pg/ml ± 99.03, p = 0.015; standing 489.93 pg/ml ± 206.82 vs 354.24 pg/ml ± 154.21, p = 0.019).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe present study indicates a significant decrease in HRV and an upward trend of plasmatic NE levels in CH during remission periods, suggesting an imbalance of the ANS in this state.\u003c/p\u003e","manuscriptTitle":"Autonomic dysfunction in patients with episodic cluster headache during remission period","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-30 08:08:31","doi":"10.21203/rs.3.rs-6871540/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"eb8681e3-fccf-44c9-bf90-82eb05042a94","owner":[],"postedDate":"June 30th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-10-20T16:01:26+00:00","versionOfRecord":{"articleIdentity":"rs-6871540","link":"https://doi.org/10.1007/s13760-025-02915-8","journal":{"identity":"acta-neurologica-belgica","isVorOnly":false,"title":"Acta Neurologica Belgica"},"publishedOn":"2025-10-13 15:57:31","publishedOnDateReadable":"October 13th, 2025"},"versionCreatedAt":"2025-06-30 08:08:31","video":"","vorDoi":"10.1007/s13760-025-02915-8","vorDoiUrl":"https://doi.org/10.1007/s13760-025-02915-8","workflowStages":[]},"version":"v1","identity":"rs-6871540","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6871540","identity":"rs-6871540","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}