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The Effect of Extracranial‐to‐Intracranial Bypass on Cerebral Vasoreactivity: A 4D Flow MRI Pilot Study
Author(s) -
Callen Andrew L.,
Caton Michael T.,
Rutledge Caleb,
Raper Daniel,
Narvid Jared,
VillanuevaMeyer Javier E.,
Abla Adib
Publication year - 2020
Publication title -
journal of neuroimaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.822
H-Index - 64
eISSN - 1552-6569
pISSN - 1051-2284
DOI - 10.1111/jon.12776
Subject(s) - medicine , digital subtraction angiography , bypass surgery , cerebral blood flow , occlusion , superficial temporal artery , magnetic resonance imaging , surgery , middle cerebral artery , artery , angiography , radiology , anesthesia , cardiology , ischemia
BACKGROUND AND PURPOSE Extracranial‐to‐intracranial (EC‐IC) surgical bypass improves cerebral blood flow (CBF) and cerebrovascular vasoreactivity (CVR) for patients with carotid occlusion. Bypass graft patency and contribution of the graft to the postoperative increase in CVR are challenging to assess. To assess the effectiveness of 4D flow magnetic resonance imaging (MRI) to evaluate bypass graft patency and flow augmentation through the superficial temporal artery (STA) before and after EC‐IC bypass. METHODS Three consecutive patients undergoing EC‐IC bypass for carotid occlusion were evaluated pre‐ and postoperatively using CVR testing with pre‐ and poststimulus 4D flow‐MRI for assessment of the bypass graft and intracranial vasculature. RESULTS Preoperatively, 2 patients (patients 1 and 3) did not augment flow through either native STA. The third, who had evidence of extensive native EC‐IC collateralization on digital subtraction angiography (DSA), did augment flow through the STA preoperatively (CVR = 1). Postoperatively, all patients demonstrated CVR > 1 on the side of bypass. The patient who had CVR > 1 preoperatively demonstrated the greatest increase in resting postoperative graft flow (from 40 to 130 mL/minute), but the smallest CVR, with a poststimulus graft flow of 160 mL/minute (CVR = 1.2). The 2 patients who did not demonstrate augmentation of graft flow preoperatively augmented postoperatively from 10 to 20 mL/minute (CVR = 2.0) and 10‐80 mL/minute (CVR = 8.0), respectively. Intracranial flow was simultaneously interrogated. Two patients demonstrated mild reductions in resting flow velocities in all interrogated vessels immediately following bypass. The patient who underwent CVR testing on postoperative day 48 demonstrated a stable or increased flow rate in most intracranial vessels. CONCLUSION Four‐dimensional flow MRI allows for noninvasive, simultaneous interrogation of the intra‐ and extracranial arterial vasculature during CVR testing, and reveals unique paradigms in cerebrovascular physiology. Observing these flow patterns may aid in improved patient selection and more detailed postoperative evaluation for patients undergoing EC‐IC bypass.