{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T12:26:28Z","timestamp":1786969588579,"version":"build-2736575974"},"reference-count":29,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T00:00:00Z","timestamp":1786924800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Neurol. Int.","Neurology International"],"abstract":"<jats:p>Background: Flow diverters (FDs) are widely used to treat intracranial aneurysms. Although effective, FD-related thrombosis or progressive stenosis may lead to acute or delayed cerebral hypoperfusion with significant neurological morbidity. Management options are limited when medical or endovascular rescue strategies fail. This study aims to evaluate the role of extracranial\u2013intracranial bypass (EC-IC bypass) as a rescue strategy across the spectrum of FD-related cerebral hypoperfusion. Methods: We retrospectively reviewed all patients who underwent EC-IC bypass for FD-related cerebral hypoperfusion over a 10-year period in our institution. Both acute and chronic presentations were included. Clinical status was assessed using the modified Rankin Scale (mRS). Imaging evaluation included digital subtraction angiography (DSA), computed tomography angiography (CTA), magnetic resonance angiography (MRA) and quantitative magnetic resonance imaging for bypass flow assessment. Surgical technique, antiplatelet therapy, timing of intervention and clinical outcomes were analysed. Results: Five patients with FD-related cerebral hypoperfusion who underwent superficial temporal artery\u2013middle cerebral artery bypass (STA-MCA bypass) were identified. Two distinct patterns emerged. Three patients developed early hypoperfusion within the first month of FD placement, presenting with acute neurological deficits and treated by emergent or urgent bypass under dual antiplatelet therapy. Two patients developed late hypoperfusion years after the procedure, presenting with progressive haemodynamic symptoms and treated by elective flow-augmentation bypass under aspirin monotherapy. At discharge, only one patient had an mRS \u2265 3. At one-year follow-up, a favourable outcome (mRS \u2264 2) was observed in all patients with available data. Follow-up data were missing for one patient. Conclusions: EC-IC bypass represents a feasible rescue strategy for FD-related cerebral hypoperfusion when medical or endovascular treatments fail. In our experience, though limited, STA-MCA bypass can provide sufficient cerebral reperfusion, even in urgent settings and under dual antiplatelet therapy, leading to favourable neurological outcomes.<\/jats:p>","DOI":"10.3390\/neurolint18080151","type":"journal-article","created":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T11:00:05Z","timestamp":1786964405000},"page":"151","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Acute and Chronic Cerebral Hypoperfusion After Flow-Diverter Placement: Is There a Role for Extra\u2013Intracranial Bypass? A Case Series and Narrative Literature Review"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0009-0005-6608-3253","authenticated-orcid":false,"given":"Alessandro","family":"Tozzi","sequence":"first","affiliation":[{"name":"Interventional Neuroradiology Unit, Neurosurgery Department, Fondazione IRCCS Istituto Neurologico \u201cCarlo Besta\u201d, 20133 Milan, Italy"},{"name":"Department of Clinical Sciences and Community Health, University of Milan, 20122 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Valentina","family":"Caldiera","sequence":"additional","affiliation":[{"name":"Interventional Neuroradiology Unit, Neurosurgery Department, Fondazione IRCCS Istituto Neurologico \u201cCarlo Besta\u201d, 20133 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Giuseppe","family":"Ganci","sequence":"additional","affiliation":[{"name":"Interventional Neuroradiology Unit, Neurosurgery Department, Fondazione IRCCS Istituto Neurologico \u201cCarlo Besta\u201d, 20133 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Paolo","family":"Ferroli","sequence":"additional","affiliation":[{"name":"Unit of Neurosurgery, Neurosurgery Department, Fondazione IRCCS Istituto Neurologico \u201cCarlo Besta\u201d, 20133 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5494-8292","authenticated-orcid":false,"given":"Marco","family":"Schiariti","sequence":"additional","affiliation":[{"name":"Unit of Neurosurgery, Neurosurgery Department, Fondazione IRCCS Istituto Neurologico \u201cCarlo Besta\u201d, 20133 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0003-8206-2810","authenticated-orcid":false,"given":"Matteo","family":"Milani","sequence":"additional","affiliation":[{"name":"Interventional Neuroradiology Unit, Neurosurgery Department, Fondazione IRCCS Istituto Neurologico \u201cCarlo Besta\u201d, 20133 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0141-0437","authenticated-orcid":false,"given":"Isabella","family":"Canavero","sequence":"additional","affiliation":[{"name":"Cerebrovascular Unit, Department of Clinical Neurosciences, Fondazione IRCCS Istituto Neurologico \u201cCarlo Besta\u201d, 20133 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7836-2122","authenticated-orcid":false,"given":"Benedetta","family":"Storti","sequence":"additional","affiliation":[{"name":"Cerebrovascular Unit, Department of Clinical Neurosciences, Fondazione IRCCS Istituto Neurologico \u201cCarlo Besta\u201d, 20133 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2493-628X","authenticated-orcid":false,"given":"Anna","family":"Bersano","sequence":"additional","affiliation":[{"name":"Cerebrovascular Unit, Department of Clinical Neurosciences, Fondazione IRCCS Istituto Neurologico \u201cCarlo Besta\u201d, 20133 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Francesco","family":"Acerbi","sequence":"additional","affiliation":[{"name":"Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, 56124 Pisa, Italy"},{"name":"Unit of Neurosurgery, University Hospital of Pisa, 56124 Pisa, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6716-2923","authenticated-orcid":false,"given":"Elisa Francesca Maria","family":"Ciceri","sequence":"additional","affiliation":[{"name":"Interventional Neuroradiology Unit, Neurosurgery Department, Fondazione IRCCS Istituto Neurologico \u201cCarlo Besta\u201d, 20133 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"193","DOI":"10.1227\/01.neu.0000430297.17961.f1","article-title":"Flow-diverter devices for intracranial aneurysms: Systematic review and meta-analysis","volume":"73","author":"Arrese","year":"2013","journal-title":"Neurosurgery"},{"key":"ref_2","first-page":"1764","article-title":"In-Stent Stenosis as a Delayed Complication of Neuroform Stent-Supported Coil Embolization of an Incidental Carotid Terminus Aneurysm","volume":"25","author":"Fiorella","year":"2004","journal-title":"Am. 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