Essential tremor (ET) is classified as a pure motor system disease. It has been previously reported that impairments in cognitive functions can be associated with ET. The authors assessed cognitive functions in a relatively young patient group with ET and comparison subjects. Correlations between tremor severity and regional cerebral blood flow (rCBF) and neuropsychological test performances of ET patients and comparison subjects were investigated. Sixteen patients with ET and 16 comparison subjects were assessed by a comprehensive neuropsychological test battery designed to assess global attention, language, memory, visuospatial functions, and executive functions. In 11 of 16 patients and in nine of 16 comparison subjects, rCBF was measured by technetium-99m-hexamethyl propylene amine oxime single photon emission computed tomography (technetium-99m-HMPAO SPECT). The tremor severity was quantified using the Clinical Rating Scale for Tremor (CRST). Findings revealed that ET patients differed significantly from comparison subjects on tests assessing visuospatial functions and verbal memory, whereas differences in other tests did not reach statistical significance. There was no significant difference between the rCBF of ET patients and comparison subjects. There were statistically significant inverse correlations between tremor severity and executive functions. Tremor severity was inversely correlated with bilateral frontal blood flow by technetium-99m-HMPAO SPECT. Conclusions suggest that the subclinical cognitive deficits characterized by visuospatial and verbal memory impairments and executive dysfunction may be a clinical feature of ET, and the cerebello-thalamo-frontal network may play a role in the pathophysiology of this disorder.

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