Tc-HMPAO-SPECT With Acetazolamide Challenge to Detect Hemodynamic Compromise in Occlusive Cerebrovascular Disease

Background and Purpose: Insufficiency of collateral supply may lead to low-flow infarcts in severe occlusive cerebrovascular disease. The aim of this study was to evaluate the feasibility of technetium99m-labeled hexamethylpropyleneamine oxime ("Tc-HMPAO) single-photon emission computed tomography (SPECT) to assess hemodynamic compromise in the anterior circulation. Methods: Cerebral blood flow before and after 1 g acetazolamide was analyzed by "Tc-HMPAO-SPECT in 21 symptomatic patients with documented extracranial obstructions. SPECT findings were correlated with the results of angiography, transcranial Doppler sonography, and computed tomographic scan. Results: The acetazolamide-induced increase of cerebral blood flow could be reliably monitored by increase of cerebral "Tc-HMPAO uptake, which varied between 11.4% and 47.6% in the less-affected hemisphere. Increment of hemispheric side-to-side asymmetry of tracer uptake after drug challenge revealed significant restriction of regional vasoreactivity in 11 patients. Agreement in assessing hemodynamic compromise was reached in 81% of patients with ophthalmic artery collaterals on angiography (p<0.001), in 76% with low-flow infarcts on computed tomographic scan (p<0.01), and in 91% with markedly reduced flow velocities on transcranial Doppler (p<0.0001). One patient developed a low-flow infarct in the area predicted by SPECT during follow up. Conclusions: We conclude that Tc-HMPAO-SPECT with acetazolamide challenge is a useful method for assessment of the adequacy of hemispheric collateral pathways in patients with severe occlusive cerebrovascular disease. (Stroke 1992;23:1733-1742)