Abstract TP150: Intracranial steal phenomenon in Patients with Severe Steno-occlusive Disease of Intracranial Carotid or Middle Cerebral Artery

Background: Intracranial stenosis is a strong risk factor for stroke recurrence. In severe stenosis, perfusion is maintained by collaterals and cerebral autoregulation (CA). CA may be impaired due to inadequate cerebral vasodilatory reserve (CVR) & intracranial steal phenomenon, so called ‘reversed-Robin Hood syndrome (RRHS)’. Identification of patients with inadequate CVR and RRHS may help in selecting high-risk patients. Methods: We prospectively included patients with symptomatic and severe stenosis of intracranial carotid (ICA) & middle cerebral artery (MCA). CVR was evaluated with TCD & breath-holding index (BHI) Results: TCD detected inadequate CVR in 112 patients (79 males, mean age 57yrs; range 23-79yrs) with severe intracranial stenosis of ICA or MCA. RRHS with a median steal magnitude of 17% (inter-quartile range, IQR 10) was seen in 35 (31%) patients. HMPAO-SPECT demonstrated perfusion deficit (median 8%; IQR 13%) in 33 out of these 35 cases (sensitivity 78%, specificity 96% with positive predictive value 96%). A strong relationship between RRH on TCD and SPECT was noted on ROC curve analysis (area under curve 0.93; 95% confidence interval 0.88-0.98;p Conclusions: Intracranial steal phenomenon in patients with severe intracranial stenosis is associated with high risk of cerebral ischemic events. Acetazolamide-challenged HMPAO-SPECT is reliable in the diagnosis of reversed Robin Hood syndrome in patients with severe steno-occlusive disease of intracranial carotid and middle cerebral artery. Identification of RRHS might help in identifying a target group of patients for possible revascularization