Changes in regional brain glucose metabolism measured with F-18-FDG-PET in essential tremor

Background There is growing evidence that essential tremor (ET) is a multiple-system disorder. Previous PET studies in ET typically have measured brain oxygen consumption and cerebral blood flow. Purpose To compare ET patients with control subjects to investigate any regional change in cerebral glucose metabolism through statistical parametric mapping (SPM) analysis of F-18-fluorodeoxyglucose positron emission tomography (F-18-FDG-PET). Material and Methods We studied 17 patients with ET (17 men; mean age, 67.3 ± 4.8 years) and age-sex matched normal subjects. All subjects underwent FDG-PET imaging, and evaluated severity of tremor symptoms was measured as score on the Fahn-Tolosa-Marin rating scale (FTM). We also evaluated detailed the medical history and neurological examinations in all patients. Results The mean age of tremor onset was 57.6 ± 12.9 years and the mean FTM score was 15.1 ± 4.9. Brain FDG-PET analysis demonstrated hypometabolism in the medial frontal lobe, medial temporal lobe, and the precuneus of parietal lobe. However, there was no significant difference of glucose metabolism in the cerebellum. Conclusion We propose that motor symptom of ET are caused by electrophysiological disturbances within cortical-cerebellar networks, rather than degenerative process of cerebellum, because the metabolism of the cerebellum was normal at rest. Furthermore, the abnormal glucose metabolism in the cerebral regions that do not mainly participate in motor function suggest that these regions may play a role as early markers of non-motor manifestations.