Cognitive deficits in patients with essential tremor.

Abstract

To assess cognitive and affective functioning in patients with essential tremor (ET). ET is traditionally thought to occur in isolation, without other neurologic abnormalities or cognitive changes. Recent evidence of gait disturbance and bradykinesia in these patients suggests that the neurologic abnormalities in ET may be more widespread than was once thought. Cognitive function in these patients has not been the subject of in-depth study. Cognitive performance and mood were assessed in 18 consecutive patients with ET and 18 consecutive patients with PD who visited the neurosurgical clinic for surgical treatment of their symptoms. The patients with ET were found to have deficits on tests of verbal fluency, naming, mental set-shifting, verbal memory, and working memory, as well as higher levels of depression. In contrast to these areas of deficit, their performance was better than that of the normative sample on several tests of verbal and nonverbal conceptualization and reasoning. Tremor severity was not correlated with cognitive deficits. Patients with PD had deficits on the same tests that were impaired in the ET group and on tests of visuospatial processes. Direct comparison of the ET and PD groups showed greater impairment in facial perception in the PD group and greater impairment in verbal fluency and working memory in the ET group. Patients with ET have deficits in specific aspects of neuropsychological functioning, particularly those thought to rely on the integrity of the prefrontal cortex, which suggests involvement of frontocerebellar circuits in this disease.