Intracranial Blood Flow Changes After Extracranial Carotid Artery Stenting

BACKGROUND: Carotid artery stenting is an endovascular treatment option for patients with extracranial carotid stenosis. However, intracranial blood flow changes following stenting have not been established. OBJECTIVE: To determine the effects of stenting on intracranial blood flow. METHODS: Records of patients who underwent stenting at our institution between 2004 and 2012 and had flow rates obtained pre- and poststenting by the use of quantitative magnetic resonance angiography were retrospectively reviewed. Percentage stenosis, stenosis length, and minimum vessel diameter were measured from cerebral angiography images. RESULTS: Eighteen patients were included. Mean age was 65 years with 67% presenting with symptomatic stenosis. Degree of stenosis ranged from 60% to 90%. Internal carotid artery (ICA) mean flow improved significantly poststenting from 174.9 ± 83.6 mL/min to 250.7 ± 91.2 mL/min (P = .011). Ipsilateral middle cerebral artery (MCA) flow, however, was not significantly altered poststenting (107.8 ± 41.6 mL/min vs 114.3 ± 36.3 mL/min; P = .28). Univariate analysis revealed that improved minimum vessel diameter after stenting, but not percentage stenosis (P = .18) or stenosis length (P = .45), is significantly associated with increased ICA flow (P = .02). However, improved percentage stenosis, stenosis length, minimum vessel diameter, and ICA flow poststenting were not significantly associated with increased MCA flow (P = .64, .38, .13, .37, respectively). CONCLUSION: ICA flow was compromised at baseline, improving 43% on average poststenting. Increased minimum vessel diameter was the factor most significantly associated with increased flow. Conversely, MCA flow was not significantly compromised at baseline nor altered after stenting, suggesting compensatory intracranial collateral supply prestenting that redistributes following ICA revascularization. ABBREVIATIONS: CAS, carotid angioplasty and stenting QMRA, quantitative magnetic resonance angiography SPECT, single-photon emission computed tomography