RESUMO
PURPOSE: To report a method for determining absolute percentage change in cerebral blood flow (measurement of cerebrovascular reserve) before and after acetylazolamide (Diamox) administration in children with sickle cell anemia. MATERIALS AND METHODS: Thirty-six symptomatic sickle cell disease patients (48 studies) were evaluated. After the injection of either Tc-99m bicisate ethyl cysteinate dimer (ECD) or hexamethyl propylene amine oxime (HMPAO), both whole body scans (with geometric mean correction) and single photon emission computed tomography (CT) were performed pre- and post-Diamox administration with calculation of percentage brain uptake on the whole body images for both examinations and determination of cerebrovascular reserve (percentage change in brain uptake post-Diamox). Evaluation for regional cerebral perfusion change was also performed. RESULTS: The cerebrovascular reserve measurement was 17.6% +/- 43.5% (mean +/- 1 SD). Thirty-three of 48 studies (69%) showed an abnormal cerebrovascular reserve, while only 6 of 48 studies (12.5%) showed Diamox-induced regional perfusion changes in the brain. No statistically significant relationship was found between the occurrence of a regional perfusion abnormality versus loss of cerebrovascular reserve (P = 0.75, Fisher exact test), suggesting that these are independent variables. The cerebrovascular reserve was reproducible, with an average standard deviation of +/-0.54%. CONCLUSION: A new, simple method for calculation of cerebrovascular reserve is presented; this method is reproducible and appears to be an independent variable in the evaluation of cerebrovascular status in sickle cell anemia patients. It should allow further characterization of this complex patient population, and possibly assist in detection of patients at risk for developing "silent" or overt stroke.
