The value of acetazolamide single photon emission computed tomography scans in the preoperative evaluation of asymptomatic critical carotid stenosis

Purpose: Acetazolamide (ACZ)-enhanced single photon emission computed tomog raphy (SPECT) scans can assess both cerebral perfusion and vascular reactiv ity. Patients with asymptomatic critical carotid artery stenosis were evalu ated for cerebral vascular reactivity to determine the effect of extracrani al occlusive disease and the effect of carotid endarterectomy (CEA) on intr acerebral reactivity. Methods: In 44 patients with asymptomatic critical carotid artery stenosis, cerebral per fusion and vascular reactivity were assessed before CEA with resting and ACZ-enhanced SPECT scans. All patients had a 70% or greater ips ilateral internal carotid artery stenosis. Preoperative ACZ-enhanced SPECT scans were obtained, usually 5 days before CEA. Postoperative ACZ-enhanced SPECT scans were obtained in 30 patients. Results: Preoperative SPECT scans were asymmetric, revealing focal (n = 19) or global (n = 15) decreased reactivity in 34 patients (77%). Ten patients had symmetric or normal reactivity. After CEA, 23 patients demonstrated an improvement in reactivity ipsilateral to the side of surgery. The remainin g seven patients failed to improve after surgery. Conclusion: Although all patients had a high-grade internal carotid stenosi s, nearly a quarter of the patients had excellent intracerebral collateral flow. Only 71% of patients demonstrated improved intracerebral vasoreactivi ty after CEA. The lack of improvement in the other patients may have result ed from intracerebral pathology or lack of improvement in the extracranial carotid hemodynamics.