How does an acetazolamide SPECT scan work to determine cerebrovascular disease?
Acetazolamide is utilized sometimes with SPECT imaging to uncover cerebrovascular disease that might potentially result in an eventual stroke. Acetazolamide is a potent vasodilator and can increase cerebral blood flow through vessels that are patent and without cerebrovascular disease. However, vessels with atherosclerotic disease are unable to dilate in response to acetazolamide resulting in a scan that demonstrates relatively reduced perfusion to the affected vascular territories. The typical plan for an acetazolamide challenge SPECT study is to administer acetazolamide intravenously about 1 hour prior to injection with a CBF radiotracer. If the scan does not show any CBF abnormalities, the implication is that there is no clinically significant cerebrovascular disease. If there is an asymmetry or some cortical area with reduced CBF, it is important to bring the patient back for a perfusion SPECT scan without acetazolamide. If the changes in CBF are observed both with and without acetazolamide, then the perfusional changes are permanent. However, if the acetazolamide scan is markedly different with specific areas of reduced perfusion, the implication is that these areas are at risk for a future cerebrovascular event.