Abstract 157: Validation Of Quantitative Eeg In The Assessment Of Cerebral Vasodilatory Reserve In Patients With Severe Stenosis Of Intracranial Internal Carotid Or Middle Cerebral Artery

Abstract

Background and aim: Estimation of cerebral vasodilatory reserve (CVR) provides important information about the adequacy of autoregulatory mechanisms in patients with severe steno-occlusive disease of intracranial internal carotid (ICA) or middle cerebral artery (MCA). Acetazolamide-challenged HMPAO-SPECT (Az-SPECT) is an established method of assessing CVR. Owing to the high cost and some radiation exposure, it cannot serve as the primary screening tool to select high-risk patients. Transcranial Doppler (TCD), often used as a screening tool, may be limited by insufficient temporal acoustic windows in a considerable proportion of patients. Quantitative electroencephalography (QEEG) monitors electrical brain activity with excellent temporal resolution. This pilot study aimed to study the feasibility of QEEG in assessing CVR in our cohort of ICA or MCA stenosis and its correlation with Az-SPECT. Methods: Consecutive symptomatic patients with severe steno-occlusive disease of ICA/MCA and impaired CVR on Az-SPECT were evaluated with QEEG. QEEG was recorded during breath-holding and hyperventilation, with 5minutes rest in between. The composite alpha index (CAI), which unifies fluctuations in alpha band power and its variablility, was calculated. An inter-hemispheric difference of more than 50% was deemed significant, with lower CAI indicating impaired CVR. Each modality was independently evaluated, with each cerebral hemispheres graded as having either impaired or preserved CVR. Results: 14 patients (10 males, mean age 59yrs, range 42-73years) were included. There was good correlation between the grades assigned to each hemisphere based on QEEG and SPECT. (Spearman’s correlation, r=0.67, p=0.008). Conclusion: Our preliminary data suggests that QEEG reliably detects impaired CVR in patients with severe intracranial stenosis. It may be used as a primary screening tool in patients unsuitable for TCD evaluations or as a complementary test in identifying patients at high-risk for cerebral ischemia and candidates for possible revascularization procedures.