Advanced Bilateral EEG Monitoring for Neuroprotection in High-Risk Cardiac Surgery: A Successful Case Report of Emergency Ascending Aortic Replacement

Advanced Bilateral EEG Monitoring for Neuroprotection in High-Risk Cardiac Surgery: A Successful Case Report of Emergency Ascending Aortic Replacement | 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 Advanced Bilateral EEG Monitoring for Neuroprotection in High-Risk Cardiac Surgery: A Successful Case Report of Emergency Ascending Aortic Replacement Lorenza DALLA MASSARA, Michele CARRON This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7700957/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 20 Jan, 2026 Read the published version in BMC Anesthesiology → Version 1 posted 15 You are reading this latest preprint version Abstract Background: Aortic surgery involving circulatory arrest and unilateral cerebral perfusion may lead to functional brain asymmetries undetected by standard monitoring. Frontal EEG, analyzed bilaterally, can provide deeper insights into cerebral physiology. Case Presentation: A 62-year-old female underwent emergency repair for type A aortic dissection with selective right-sided antegrade cerebral perfusion under deep hypothermia. Bilateral frontal EEG monitoring revealed a progressive suppression during circulatory arrest. Post-hoc spectral power analysis showed an early transient right-sided suppression during cooling, followed by delayed relative downregulation of the left hemisphere toward the end of surgery. Alpha/delta ratio (ADR) dropped below 0.2 bilaterally, with a peak ADR left versus right ratio of 2.3. These findings were not appreciable on raw EEG or cerebral oximetry alone. Post-hoc spectral analysis revealed functional hemispheric asymmetries possibly related to cooling techniques, asymmetric anesthetic redistribution and metabolic inactivation that are not appreciable on raw EEG or cerebral oximetry alone. Our observations support a multifactorial mechanism of EEG suppression and shed light on the potential diagnostic value of bilateral quantitative EEG monitoring. Conclusions: Quantitative bilateral EEG—particularly ADR and spectral power trends—may uncover functionally relevant cerebral asymmetries during aortic surgery, offering a complementary tool to guide neuroprotective strategies beyond standard oximetry. Electroencephalography Anesthesia General Brain Monitoring Alpha/Delta Ratio Aortic Surgery Hypothermia Cerebral Perfusion Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 20 Jan, 2026 Read the published version in BMC Anesthesiology → Version 1 posted Editorial decision: Revision requested 18 Dec, 2025 Reviews received at journal 17 Dec, 2025 Reviews received at journal 16 Dec, 2025 Reviewers agreed at journal 01 Dec, 2025 Reviewers agreed at journal 28 Nov, 2025 Reviewers agreed at journal 28 Nov, 2025 Reviewers agreed at journal 26 Nov, 2025 Reviewers agreed at journal 26 Nov, 2025 Reviews received at journal 18 Nov, 2025 Reviewers agreed at journal 05 Nov, 2025 Reviewers invited by journal 04 Nov, 2025 Editor assigned by journal 29 Oct, 2025 Editor invited by journal 28 Oct, 2025 Submission checks completed at journal 23 Oct, 2025 First submitted to journal 23 Oct, 2025 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. 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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-7700957","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":542204788,"identity":"5871c56e-777e-4c1f-9887-a37bcb85496f","order_by":0,"name":"Lorenza DALLA 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Frontal EEG, analyzed bilaterally, can provide deeper insights into cerebral physiology.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCase Presentation: A 62-year-old female underwent emergency repair for type A aortic dissection with selective right-sided antegrade cerebral perfusion under deep hypothermia. Bilateral frontal EEG monitoring revealed a progressive suppression during circulatory arrest. Post-hoc spectral power analysis showed an early transient right-sided suppression during cooling, followed by delayed relative downregulation of the left hemisphere toward the end of surgery. Alpha/delta ratio (ADR) dropped below 0.2 bilaterally, with a peak ADR left versus right ratio of 2.3. These findings were not appreciable on raw EEG or cerebral oximetry alone. 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