Acetazolamide SPECT Scans in the Evaluation of Symptomatic and Asymptomatic Patients with Carotid Occlusive Disease

Abstract

Acetazolamide (ACZ)-enhanced Single Photon Emission Computer Tomography (SPECT) scans can assess both cerebral perfusion and vascular reactivity. Patients with poor reactivity lack perfusion reserve, and are at risk for stroke should perfusion diminish further. This study compared the preoperative ACZ-enhanced SPECT scans of 60 symptomatic to 40 asymptomatic patients with internal carotid artery stenosis (ICAS) in an effort to better define the cause of their symptoms and effects of carotid endarterectomy (CEA) on cerebral perfusion and reactivity in these two groups of patients. Symptomatic patients had at least a 60% (x=84%) ICAS. Asymptomatic patients had at least an 80% (x=90%) ICAS. Preoperative ACZ SPECT scans were obtained usually one week before CEA. All patients underwent CEA. Postoperative ACZ SPECT scans were obtained in 78 of the patients, usually at the first postoperative (-30 days) visit.

	PRE-OP SPECT SCAN					PRE-OP SPECT SCAN
	Ipsilateral Perfusion			Ipsilateral Reactivity		Ipsilateral Reactivity
	n	decreased	nl	decreased	nl	n	improved
Symptomatic	60	30(50%)	30(50%)	51(85%)	9(15%)	50	40(91%)
Asymptomatic	40	29(72.5%)	11(27.5%)	31(77.5%)	9(22.5%)	28	19(73%)
Total	100	59	41	82	18	78	59
*These percentages are based on a denominator of 44 symptomtic and 26 asymptomatic patients. These are the patients who had decreased preoperative reactivity and underwent a postoperative ACZ scan.

Asymptomatic patients demonstrated poorer perfusion than symptomatic patients, which tends to support the premise that most strokes and carotid symptoms are secondary to emboli rather than hypoperfusion. Interestingly, cerebral reactivity was poor in both symptomatic and asymptomatic patients before CEA, suggesting inadequate collaterals and dependency on the ipsilateral carotid. Carotid endarterectomy improved vasoreactivity in 84% of the patients. ACZ SPECT scans provided evidence of the return of cerebral perfusion and reactivity following endarterectomy.