The Acetazolamide Challenge: Techniques and Applications in the Evaluation of Chronic Cerebral Ischemia

A 34-year-old man with severe headache and blurry vision was diagnosed with Moyamoya disease. CT perfusion maps. A, Baseline. B, After ACZ administration. CBF (measured in mL/100 g/min) is diminished in bilateral ACA, ACA-MCA watershed, and the MCA territories (depicted as blue to green). These areas show a very suboptimal increase in CBF after ACZ administration and thus exhibit limited CVR. Note the increased CBF secondary to vasodilatory capacity in the PCA and MCA-PCA distribution after ACZ administration.

SPECT perfusion study of a 64-year-old man with high-grade right M1 and A1 segment stenosis. A, Baseline. B, After ACZ administration. There is decreased uptake and perfusion (arrows) involving the right frontal, parietal, and temporal lobes on the ACZ study (B), which resolve during baseline conditions (arrowheads).

CTP. Chronic left internal carotid artery occlusion. A, Baseline. B, After ACZ administration. There is significant hypoperfusion in the left hemisphere at baseline with decreased CBF and increased TTP (A, short arrows). After administration of ACZ (B), CBF decreases throughout the left hemisphere, resulting in negative calculated CVR percentages. The left-sided TTP increases even further in post-ACZ flow maps as seen by the accentuated asymmetry (B, long arrows). Note the normal increase in the right-sided CBF after the vasodilatory stimulus of ACZ (B, arrowheads).

CT perfusion maps in a 51-year-old patient presenting with right-sided hemiparesis who was diagnosed with Moyamoya disease, demonstrating bilateral supraclinoid internal carotid occlusion. A, Baseline. B, After ACZ administration. The baseline pre-ACZ PCT (A) demonstrates the typical pattern of Moyamoya disease with decreased CBF and increased MTT and TTP in the bilateral anterior and middle cerebral distributions (arrows). After ACZ challenge (B), the CBF in the anterior circulation decreases consistent with steal phenomenon (B, CBF, arrows). The CBF map demonstrates a normal expected increase in the PCA territories. There is further prolongation of the MTT and TTP in both ACA and MCA distributions (arrowheads, B), consistent with worsening of cerebral hemodynamics after ACZ, and type III physiology. The patient successfully underwent left-sided ECIC bypass surgery.