Bacterial Meningitis Caused by Posterior Fossa Pilonidal Sinus in a Pediatric Patient: A Case Report

Bacterial Meningitis Caused by Posterior Fossa Pilonidal Sinus in a Pediatric Patient: A Case Report | 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 Case Report Bacterial Meningitis Caused by Posterior Fossa Pilonidal Sinus in a Pediatric Patient: A Case Report Rong Zhuang, Chao Liang, Jia-Ping Jin, Bo Jin, Ming-ming Ni This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7522865/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Posterior fossa pilonidal sinus is a rare congenital defect characterized by a dermal sinus tract extending intracranially, potentially connecting with the dura mater or brain tissue. This abnormal passage facilitates bacterial entry into the central nervous system, increasing the risk of severe infections like pyogenic meningitis. We report a pediatric case of bacterial meningitis secondary to an occult posterior fossa pilonidal sinus. Despite receiving full-course, guideline-directed broad-spectrum antibiotic therapy, the patient exhibited persistent signs of infection. The diagnosis was achieved through multidisciplinary consultation combined with characteristic findings on magnetic resonance imaging (MRI). Surgical excision of the sinus tract resulted in complete resolution of the infection, with normalization of laboratory markers and neuroimaging findings. This case underscores the importance of considering occult anatomical defects when intracranial infections fail to respond to standard antimicrobial therapy. Early surgical intervention is crucial for definitive cure and prevention of recurrence. Posterior fossa pilonidal sinus bacterial meningitis next-generation gene sequencing case report Figures Figure 1 Figure 2 Introduction Bacterial meningitis is a severe central nervous system infection associated with high mortality, particularly in low-income countries, where the fatality rate can reach 54%. Even for survivors, long-term neurological sequelae are common( 1 ). Traditionally, bacterial meningitis is thought to arise from hematogenous spread following respiratory tract infections or direct extension from adjacent infections( 2 ). However, recurrent and refractory cases may not follow these conventional pathways, suggesting the presence of anatomical abnormalities that predispose patients to infection( 3 ). One such rare abnormality is the pilonidal sinus, a congenital defect typically located in the sacrococcygeal region, resulting from neural tube closure disorders( 4 ). While this condition is most found in the sacrococcygeal area, ectopic occurrences in other regions, particularly the posterior fossa, are exceptionally rare( 5 ). A posterior fossa pilonidal sinus forms an abnormal communication between the skin and the central nervous system, with the sinus tract extending from the skin surface, through the skull or spinal canal, and connecting directly with the dura mater or spinal cord and meninges( 4 ). This creates a pathway for bacterial invasion, which can lead to severe infections such as bacterial meningitis. The diagnosis of posterior fossa pilonidal sinus is challenging due to its insidious onset, non-specific symptoms, and limited detectability on routine imaging, which can result in delayed diagnosis, missed treatment opportunities, and poor outcomes( 6 ). This report presents a rare case of an infant with refractory bacterial meningitis caused by a posterior fossa pilonidal sinus. It emphasizes the importance of considering rare anatomical anomalies, such as pilonidal sinuses in atypical locations, when managing recurrent or treatment-resistant meningitis. Early recognition and targeted surgical intervention are essential to improve patient outcomes. Case presentation On hospital day 0, a one-year-old male infant was transferred from an outside hospital with a 13-day history of intermittent fever. Physical examination revealed subcutaneous nodules in the occipital region, which had shown repeated redness and swelling in the past. No sinus tract or fluid outflow was observed, and there were no signs of a buried sinus in the sacrococcygeal region. Both Kernig's and Brudzinski's signs were negative. Prior to admission, cerebrospinal fluid (CSF) analysis, performed at referring hospital, showed bacterial infection indicators, including a low glucose concentration of 2.27 mmol/L, elevated protein levels at 43.2 g/L, and a white blood cell count (WBC) of 1820/µL. Based on these findings, the patient was diagnosed with purulent meningitis and continued the empirical antibiotic therapy that had been initiated at the referring hospital, which comprised meropenem and linezolid. Despite ongoing antibiotic therapy, the patient's fever persisted, reaching a peak of 40°C on hospital day 1, accompanied by a rise in the CSF nucleated cell count to 2447/µL. On hospital day 2, the next-generation sequencing (NGS) of the CSF identified Prevotella bivia (sequence number 180), corynebacterium diphtheriae (sequence number 5), and human herpesvirus 5 (sequence number 2702). Continuing the external treatment strategy, meropenem combined with linezolid was used for a total of 8 days spanning the pre- and post-admission period, no significant improvement was observed. As a result, linezolid was replaced with vancomycin to enhance the antimicrobial effect. On hospital day 8, the CSF nucleated cell count decreased to 316/µL, suggesting an initial response to treatment. Due to fluctuating body temperature and recurrent fever, naproxen was introduced on hospital day 12 for anti-inflammatory treatment. On hospital day 13, vancomycin was discontinued due to the development of a rash in the patient, with drug fever being considered as a possible cause. Antibiotic-induced fever is a potentially underrecognized complication that can be misdiagnosed as a new infection. Therefore, when recurrent infections manifest, the possibility of drug fever should also be considered. Despite adjustments, by hospital day 23, the patient’s body temperature continued to fluctuate, and CSF nucleated cell count increased to 760/µL. Given the poor efficacy of meropenem, treatment was adjusted to include linezolid and rifampicin. On hospital day 29, the CSF nucleated cell count remained elevated at 524/µL, indicating that the infection was not fully controlled. Despite ongoing treatment adjustments, the patient’s clinical response remained inadequate. This prompted a further investigation, and through a multidisciplinary consultation and MRI (Fig. 1 A), a posterior fossa pilonidal sinus was identified as a potential source of the recurrent infections. Consequently, surgical intervention was recommended to address the underlying anatomical defect. On hospital day 31, the patient underwent posterior cranial fossa lesion resection. The pathological report revealed pale yellow lipids in the cyst, with extensive acute and chronic inflammatory cell infiltration, consistent with a pilonidal cyst complicated by infection (Fig. 1 B). Postoperatively, the patient developed hydrocephalus, which required ventricular drainage surgeries on hospital days 33 and 39. Given that hydrocephalus can hinder the penetration of systemic antibiotics into the cerebrospinal fluid, intraventricular vancomycin was administered on hospital day 40, accompanied by dexamethasone, to deliver high local drug concentrations and achieve both antimicrobial and anti-inflammatory effects. By hospital day 44, the patient’s body temperature remained stable (Fig. 2 ), and the nucleated cell count in the CSF decreased significantly to 31/µL. Continued monitoring revealed normalization of both body temperature and CSF parameters. On hospital day 52, the external ventricular drainage device was successfully removed. A brief rise in body temperature, likely stress-related, was observed, but repeat lumbar puncture results ruled out infection recurrence. The patient was discharged in stable condition on hospital day 59, following a period of close monitoring and significant clinical improvement throughout the treatment course. Discussion While pilonidal sinuses are most located in the sacrococcygeal region, ectopic occurrences are exceptionally rarer( 7 ). While cases of pilonidal sinuses in atypical locations, such as the chin and lateral orbital regions( 8 , 9 ), have been reported, those in the posterior fossa are exceptionally uncommon. To date, only two such cases have been reported, and there is no established direct causal link to bacterial meningitis. In 1999, G. Borges reported a case in the skull region, where the patient exhibited symptoms of intermittent irritability, verbal and physical aggression, learning difficulties, phobias, and obsessive behaviors prior to surgery( 10 ). More recently, Hamzeh Yacoub et al. described a child with a posterior fossa pilonidal sinus who presented with generalized tonic-clonic seizures and loss of consciousness. Notably, This child also had a history of recurrent meningitis, suggesting a possible link between the posterior fossa pilonidal sinus and the recurrent infections, though follow-up data is unavailable( 5 ). These rare cases underscore the unpredictable presentation and challenging diagnosis of posterior fossa pilonidal sinuses, which may remain undetected until they manifest as severe infections. Diagnosing pilonidal sinuses in unusual locations, especially the posterior fossa, is challenging due to their deep anatomical position and non-specific symptoms. This often leads to delayed diagnosis, allowing infections to persist and complicate with abscesses or neurological damage. In this case, the posterior fossa pilonidal sinus acted as a continuous pathway for bacterial entry into the central nervous system, causing a refractory infection despite standard antimicrobial therapy. This highlights the need for heightened suspicion when infections fail to respond to conventional treatment. Surgical excision, followed by targeted therapy, resulted in complete resolution of the infection, reinforcing the importance of addressing rare anatomical abnormalities in recurrent or persistent infections. More broadly, this case illustrates the value of personalized, anatomy-driven treatment strategies in managing complex infections that defy conventional therapeutic approaches. Abbreviations cerebrospinal fluid, CSF white blood cell count, WBC C-reactive protein, CRP next-generation gene sequencing, NGS magnetic resonance imaging, MRI Declarations Ethics approval and consent to participate This study was approved by the Ethics Committee of the Children’s Hospital of Nanjing Medical University. Clinical Trial Not applicable Consent for publication Written informed consent for publication of clinical details and clinical images was obtained from the parents of the patient. A copy of the written consent is available for review by the Editor of this journal. Availability of data and material The original contributions presented in the study are included in the article. Further inquiries can be directed to the corresponding author. Competing interests The authors declare no conflicts of interest. Funding This work was supported by Hospital Pharmacy Foundation of Jiangsu Pharmaceutical Association-Jiangsu Hengrui Pharmaceutical Industry Limited Company (H202103) Authors' contributions Chao Liang, Jia-Ping Jin, and Bo Jin oversaw patient care. Rong Zhuang and Ming-ming Ni drafted the manuscript. Bo Jin and Ming-ming Ni revised the manuscript. All authors reviewed and approved the final version of the manuscript. Acknowledgements None References Ait-Ali Y, Bourlon L, Jacobs FM. Review of Progress and Challenges in Bacterial Meningitis. JAMA (2023) 329(16):1406. doi: 10.1001/jama.2023.2545. Kim KS. Pathogenesis of Bacterial Meningitis: From Bacteraemia to Neuronal Injury. Nat Rev Neurosci (2003) 4(5):376-85. doi: 10.1038/nrn1103. Gutierrez M, Emmanuel PJ. Expanding Molecular Diagnostics for Central Nervous System Infections. Adv Pediatr (2018) 65(1):209-27. Epub 20180620. doi: 10.1016/j.yapd.2018.04.005. Wu P, Zhang Y, Zhang Y, Wang S, Fan Z. Progress in the Surgical Treatment of Sacrococcygeal Pilonidal Sinus: A Review. Int J Surg (2023) 109(8):2388-403. Epub 20230801. doi: 10.1097/JS9.0000000000000447. Yacoub H, Aqel A, Adas M, Hjouj Q, Yacoub Z, Yacoub R, et al. Extremely Rare Presentation of Pilonidal Sinus Disease in the Posterior Cranial Fossa of a 2-Year-Old Patient: A Case Report. J Neurol Surg Rep (2025) 86(3):e149-e52. Epub 20250711. doi: 10.1055/a-2641-6301. Mahmood F, Hussain A, Akingboye A. Pilonidal Sinus Disease: Review of Current Practice and Prospects for Endoscopic Treatment. Ann Med Surg (Lond) (2020) 57:212-7. Epub 20200801. doi: 10.1016/j.amsu.2020.07.050. Darnis B, Tedeschi L, Blanchet MC, Frering V, Crozet J, Gignoux B, et al. Management of Pilonidal Sinus and Recurrences in 2025. J Visc Surg (2025) 162(2):117-27. Epub 20250127. doi: 10.1016/j.jviscsurg.2024.12.005. Kucukkurt S, Ozle M, Rzayev S. Pilonidal Sinus of the Chin: Mistreated as a Dental Fistula. BMJ Case Rep (2016) 2016. Epub 20160128. doi: 10.1136/bcr-2015-213639. Karadag EC, Toy H, Tosun Z. Lateral Orbital Wall Destruction Due to Pilonidal Sinus. J Craniofac Surg (2016) 27(5):e461-2. doi: 10.1097/SCS.0000000000002778. Borges G, Maciel Junior JA, Carelli EF, Alvarenga M, De Castro R, Bonilha L. Pilonidal Cyst on the Vault. Case Report. Arq Neuropsiquiatr (1999) 57(2A):273-6. doi: 10.1590/s0004-282x1999000200017. Additional Declarations No competing interests reported. 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15:37:17","extension":"html","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":40155,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7522865/v1/986af2b59f3bc5d199e2406e.html"},{"id":92008404,"identity":"16560135-59c4-4d92-a3de-6d47b5f63038","added_by":"auto","created_at":"2025-09-23 15:29:17","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":4609365,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Preoperative MRI of the patient demonstrating the posterior fossa pilonidal sinus. (B) Histopathology of the resected lesion showing a pilonidal cyst with inflammatory cell infiltration.\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7522865/v1/68a1fd4199a1da652864e82b.jpg"},{"id":92009537,"identity":"37bcaaa8-2dbe-4d83-9585-af1ec09248f2","added_by":"auto","created_at":"2025-09-23 15:37:17","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":729863,"visible":true,"origin":"","legend":"\u003cp\u003eTemperature fluctuations during the treatment course and response to interventions\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7522865/v1/44baac6d69cf53f87558571d.jpg"},{"id":95030427,"identity":"3a38919a-5a79-43d8-a0d7-4f20b89e1705","added_by":"auto","created_at":"2025-11-03 14:09:06","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5682266,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7522865/v1/200556c4-b175-41e9-8768-ef2118ea3ce5.pdf"},{"id":92008399,"identity":"1ba561da-0ce2-4887-af32-f2845b856581","added_by":"auto","created_at":"2025-09-23 15:29:17","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":798122,"visible":true,"origin":"","legend":"","description":"","filename":"CAREchecklistEnglish2013.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7522865/v1/0c8e5a41d155effbb0133282.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Bacterial Meningitis Caused by Posterior Fossa Pilonidal Sinus in a Pediatric Patient: A Case Report","fulltext":[{"header":"Introduction","content":"\u003cp\u003eBacterial meningitis is a severe central nervous system infection associated with high mortality, particularly in low-income countries, where the fatality rate can reach 54%. Even for survivors, long-term neurological sequelae are common(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). Traditionally, bacterial meningitis is thought to arise from hematogenous spread following respiratory tract infections or direct extension from adjacent infections(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). However, recurrent and refractory cases may not follow these conventional pathways, suggesting the presence of anatomical abnormalities that predispose patients to infection(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). One such rare abnormality is the pilonidal sinus, a congenital defect typically located in the sacrococcygeal region, resulting from neural tube closure disorders(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). While this condition is most found in the sacrococcygeal area, ectopic occurrences in other regions, particularly the posterior fossa, are exceptionally rare(\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). A posterior fossa pilonidal sinus forms an abnormal communication between the skin and the central nervous system, with the sinus tract extending from the skin surface, through the skull or spinal canal, and connecting directly with the dura mater or spinal cord and meninges(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). This creates a pathway for bacterial invasion, which can lead to severe infections such as bacterial meningitis. The diagnosis of posterior fossa pilonidal sinus is challenging due to its insidious onset, non-specific symptoms, and limited detectability on routine imaging, which can result in delayed diagnosis, missed treatment opportunities, and poor outcomes(\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThis report presents a rare case of an infant with refractory bacterial meningitis caused by a posterior fossa pilonidal sinus. It emphasizes the importance of considering rare anatomical anomalies, such as pilonidal sinuses in atypical locations, when managing recurrent or treatment-resistant meningitis. Early recognition and targeted surgical intervention are essential to improve patient outcomes.\u003c/p\u003e"},{"header":"Case presentation","content":"\u003cp\u003eOn hospital day 0, a one-year-old male infant was transferred from an outside hospital with a 13-day history of intermittent fever. Physical examination revealed subcutaneous nodules in the occipital region, which had shown repeated redness and swelling in the past. No sinus tract or fluid outflow was observed, and there were no signs of a buried sinus in the sacrococcygeal region. Both Kernig's and Brudzinski's signs were negative. Prior to admission, cerebrospinal fluid (CSF) analysis, performed at referring hospital, showed bacterial infection indicators, including a low glucose concentration of 2.27 mmol/L, elevated protein levels at 43.2 g/L, and a white blood cell count (WBC) of 1820/\u0026micro;L. Based on these findings, the patient was diagnosed with purulent meningitis and continued the empirical antibiotic therapy that had been initiated at the referring hospital, which comprised meropenem and linezolid. Despite ongoing antibiotic therapy, the patient's fever persisted, reaching a peak of 40\u0026deg;C on hospital day 1, accompanied by a rise in the CSF nucleated cell count to 2447/\u0026micro;L. On hospital day 2, the next-generation sequencing (NGS) of the CSF identified \u003cem\u003ePrevotella bivia\u003c/em\u003e (sequence number 180), \u003cem\u003ecorynebacterium diphtheriae\u003c/em\u003e (sequence number 5), and human herpesvirus 5 (sequence number 2702). Continuing the external treatment strategy, meropenem combined with linezolid was used for a total of 8 days spanning the pre- and post-admission period, no significant improvement was observed. As a result, linezolid was replaced with vancomycin to enhance the antimicrobial effect. On hospital day 8, the CSF nucleated cell count decreased to 316/\u0026micro;L, suggesting an initial response to treatment. Due to fluctuating body temperature and recurrent fever, naproxen was introduced on hospital day 12 for anti-inflammatory treatment. On hospital day 13, vancomycin was discontinued due to the development of a rash in the patient, with drug fever being considered as a possible cause. Antibiotic-induced fever is a potentially underrecognized complication that can be misdiagnosed as a new infection. Therefore, when recurrent infections manifest, the possibility of drug fever should also be considered. Despite adjustments, by hospital day 23, the patient\u0026rsquo;s body temperature continued to fluctuate, and CSF nucleated cell count increased to 760/\u0026micro;L. Given the poor efficacy of meropenem, treatment was adjusted to include linezolid and rifampicin. On hospital day 29, the CSF nucleated cell count remained elevated at 524/\u0026micro;L, indicating that the infection was not fully controlled. Despite ongoing treatment adjustments, the patient\u0026rsquo;s clinical response remained inadequate. This prompted a further investigation, and through a multidisciplinary consultation and MRI (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA), a posterior fossa pilonidal sinus was identified as a potential source of the recurrent infections. Consequently, surgical intervention was recommended to address the underlying anatomical defect. On hospital day 31, the patient underwent posterior cranial fossa lesion resection. The pathological report revealed pale yellow lipids in the cyst, with extensive acute and chronic inflammatory cell infiltration, consistent with a pilonidal cyst complicated by infection (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB). Postoperatively, the patient developed hydrocephalus, which required ventricular drainage surgeries on hospital days 33 and 39. Given that hydrocephalus can hinder the penetration of systemic antibiotics into the cerebrospinal fluid, intraventricular vancomycin was administered on hospital day 40, accompanied by dexamethasone, to deliver high local drug concentrations and achieve both antimicrobial and anti-inflammatory effects. By hospital day 44, the patient\u0026rsquo;s body temperature remained stable (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), and the nucleated cell count in the CSF decreased significantly to 31/\u0026micro;L. Continued monitoring revealed normalization of both body temperature and CSF parameters. On hospital day 52, the external ventricular drainage device was successfully removed. A brief rise in body temperature, likely stress-related, was observed, but repeat lumbar puncture results ruled out infection recurrence. The patient was discharged in stable condition on hospital day 59, following a period of close monitoring and significant clinical improvement throughout the treatment course.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eWhile pilonidal sinuses are most located in the sacrococcygeal region, ectopic occurrences are exceptionally rarer(\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). While cases of pilonidal sinuses in atypical locations, such as the chin and lateral orbital regions(\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e), have been reported, those in the posterior fossa are exceptionally uncommon. To date, only two such cases have been reported, and there is no established direct causal link to bacterial meningitis. In 1999, G. Borges reported a case in the skull region, where the patient exhibited symptoms of intermittent irritability, verbal and physical aggression, learning difficulties, phobias, and obsessive behaviors prior to surgery(\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). More recently, Hamzeh Yacoub et al. described a child with a posterior fossa pilonidal sinus who presented with generalized tonic-clonic seizures and loss of consciousness. Notably, This child also had a history of recurrent meningitis, suggesting a possible link between the posterior fossa pilonidal sinus and the recurrent infections, though follow-up data is unavailable(\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). These rare cases underscore the unpredictable presentation and challenging diagnosis of posterior fossa pilonidal sinuses, which may remain undetected until they manifest as severe infections.\u003c/p\u003e\u003cp\u003eDiagnosing pilonidal sinuses in unusual locations, especially the posterior fossa, is challenging due to their deep anatomical position and non-specific symptoms. This often leads to delayed diagnosis, allowing infections to persist and complicate with abscesses or neurological damage. In this case, the posterior fossa pilonidal sinus acted as a continuous pathway for bacterial entry into the central nervous system, causing a refractory infection despite standard antimicrobial therapy. This highlights the need for heightened suspicion when infections fail to respond to conventional treatment. Surgical excision, followed by targeted therapy, resulted in complete resolution of the infection, reinforcing the importance of addressing rare anatomical abnormalities in recurrent or persistent infections. More broadly, this case illustrates the value of personalized, anatomy-driven treatment strategies in managing complex infections that defy conventional therapeutic approaches.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003ecerebrospinal fluid, CSF\u003c/p\u003e\n\u003cp\u003ewhite blood cell count, WBC\u003c/p\u003e\n\u003cp\u003eC-reactive protein, CRP\u003c/p\u003e\n\u003cp\u003enext-generation gene sequencing, NGS\u003c/p\u003e\n\u003cp\u003emagnetic resonance imaging, MRI\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Ethics Committee of the Children\u0026rsquo;s Hospital of Nanjing Medical University.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Trial\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWritten informed consent for publication of clinical details and clinical images was obtained from the parents of the patient.\u0026nbsp;A copy of the written consent is available for review by the Editor of this journal.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and material\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe original contributions presented in the study are included in the article. Further inquiries can be directed to the corresponding author.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by Hospital Pharmacy Foundation of Jiangsu Pharmaceutical Association-Jiangsu Hengrui Pharmaceutical Industry Limited Company (H202103) \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eChao Liang, Jia-Ping Jin, and Bo Jin oversaw patient care. Rong Zhuang and Ming-ming Ni drafted the manuscript. Bo Jin and Ming-ming Ni revised the manuscript. All authors reviewed and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAit-Ali Y, Bourlon L, Jacobs FM. Review of Progress and Challenges in Bacterial Meningitis. \u003cem\u003eJAMA\u003c/em\u003e (2023) 329(16):1406. doi: 10.1001/jama.2023.2545.\u003c/li\u003e\n\u003cli\u003eKim KS. Pathogenesis of Bacterial Meningitis: From Bacteraemia to Neuronal Injury. \u003cem\u003eNat Rev Neurosci\u003c/em\u003e (2003) 4(5):376-85. doi: 10.1038/nrn1103.\u003c/li\u003e\n\u003cli\u003eGutierrez M, Emmanuel PJ. Expanding Molecular Diagnostics for Central Nervous System Infections. \u003cem\u003eAdv Pediatr\u003c/em\u003e (2018) 65(1):209-27. Epub 20180620. doi: 10.1016/j.yapd.2018.04.005.\u003c/li\u003e\n\u003cli\u003eWu P, Zhang Y, Zhang Y, Wang S, Fan Z. Progress in the Surgical Treatment of Sacrococcygeal Pilonidal Sinus: A Review. \u003cem\u003eInt J Surg\u003c/em\u003e (2023) 109(8):2388-403. Epub 20230801. doi: 10.1097/JS9.0000000000000447.\u003c/li\u003e\n\u003cli\u003eYacoub H, Aqel A, Adas M, Hjouj Q, Yacoub Z, Yacoub R, et al. Extremely Rare Presentation of Pilonidal Sinus Disease in the Posterior Cranial Fossa of a 2-Year-Old Patient: A Case Report. \u003cem\u003eJ Neurol Surg Rep\u003c/em\u003e (2025) 86(3):e149-e52. Epub 20250711. doi: 10.1055/a-2641-6301.\u003c/li\u003e\n\u003cli\u003eMahmood F, Hussain A, Akingboye A. Pilonidal Sinus Disease: Review of Current Practice and Prospects for Endoscopic Treatment. \u003cem\u003eAnn Med Surg (Lond)\u003c/em\u003e (2020) 57:212-7. Epub 20200801. doi: 10.1016/j.amsu.2020.07.050.\u003c/li\u003e\n\u003cli\u003eDarnis B, Tedeschi L, Blanchet MC, Frering V, Crozet J, Gignoux B, et al. Management of Pilonidal Sinus and Recurrences in 2025. \u003cem\u003eJ Visc Surg\u003c/em\u003e (2025) 162(2):117-27. Epub 20250127. doi: 10.1016/j.jviscsurg.2024.12.005.\u003c/li\u003e\n\u003cli\u003eKucukkurt S, Ozle M, Rzayev S. Pilonidal Sinus of the Chin: Mistreated as a Dental Fistula. \u003cem\u003eBMJ Case Rep\u003c/em\u003e (2016) 2016. Epub 20160128. doi: 10.1136/bcr-2015-213639.\u003c/li\u003e\n\u003cli\u003eKaradag EC, Toy H, Tosun Z. Lateral Orbital Wall Destruction Due to Pilonidal Sinus. \u003cem\u003eJ Craniofac Surg\u003c/em\u003e (2016) 27(5):e461-2. doi: 10.1097/SCS.0000000000002778.\u003c/li\u003e\n\u003cli\u003eBorges G, Maciel Junior JA, Carelli EF, Alvarenga M, De Castro R, Bonilha L. Pilonidal Cyst on the Vault. Case Report. \u003cem\u003eArq Neuropsiquiatr\u003c/em\u003e (1999) 57(2A):273-6. doi: 10.1590/s0004-282x1999000200017.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"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":"Posterior fossa pilonidal sinus, bacterial meningitis, next-generation gene sequencing; case report","lastPublishedDoi":"10.21203/rs.3.rs-7522865/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7522865/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePosterior fossa pilonidal sinus is a rare congenital defect characterized by a dermal sinus tract extending intracranially, potentially connecting with the dura mater or brain tissue. This abnormal passage facilitates bacterial entry into the central nervous system, increasing the risk of severe infections like pyogenic meningitis. We report a pediatric case of bacterial meningitis secondary to an occult posterior fossa pilonidal sinus. Despite receiving full-course, guideline-directed broad-spectrum antibiotic therapy, the patient exhibited persistent signs of infection. The diagnosis was achieved through multidisciplinary consultation combined with characteristic findings on magnetic resonance imaging (MRI). Surgical excision of the sinus tract resulted in complete resolution of the infection, with normalization of laboratory markers and neuroimaging findings. This case underscores the importance of considering occult anatomical defects when intracranial infections fail to respond to standard antimicrobial therapy. Early surgical intervention is crucial for definitive cure and prevention of recurrence.\u003c/p\u003e","manuscriptTitle":"Bacterial Meningitis Caused by Posterior Fossa Pilonidal Sinus in a Pediatric Patient: A Case Report","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-23 15:29:12","doi":"10.21203/rs.3.rs-7522865/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":"57e55093-be54-49e2-a553-790679845f22","owner":[],"postedDate":"September 23rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-03T14:08:21+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-23 15:29:12","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7522865","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7522865","identity":"rs-7522865","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}