A COMPARISON OF CEREBRAL BLOOD-FLOW AND GLUCOSE-METABOLISM IN OLIVOPONTOCEREBELLAR ATROPHY USING PET

Objective: In sporadic cases of olivopontocerebellar atrophy (OPCA), to determine whether local cerebral blood flow (lCBF) is reduced, whether lCBF is coupled to local cerebral metabolic rate for glucose (lCMRglc), and whether lCBF measurements are potentially useful in diagnosing OPCA. Design: Positron emission tomography was used with [O-15]H2O to measure lCBF and with [F-18]fluorodeoxyglucose to measure lCMRglc in 17 patients with OPCA and 21 normal control subjects. Results: In OPCA patients, lCBF was significantly decreased in the cerebellum, but not in the cerebral cortex, basal ganglia, thalamus, or brainstem. In the same patients, lCMRglc was significantly decreased in the cerebellum and brainstem, where the largest changes were observed, and also in the cerebral cortex, basal ganglia, and thalamus. The ratio of lCBF to lCMRglc, an indicator of the coupling of blood flow to metabolism, was similar in OPCA patients and normal subjects for all regions except the brainstem, where the ratio was marginally decreased in OPCA patients. Using logistic discriminant analysis to assess the ability of lCBF and lCMRglc to differentiate OPCA patients from normal subjects, we found the cross-validated sensitivity of absolute lCMRglc as a predictor of OPCA was 82% with a corresponding specificity of 71%; the sensitivity of absolute lCBF was 71% and the specificity 76%. Conclusions: In sporadic cases of OPCA, lCBF is reduced in the cerebellum, CBF remains coupled to lCMRglc, and the lCBF pattern is a useful predictor of the diagnosis.