Association between cortical volume loss and cognitive impairments in essential tremor

Impairment of cognitive functions occurs in essential tremor (ET) although the mechanism is largely unknown. A possible association between cognitive performance and brain atrophy in ET patients was examined using neuropsychological tests and voxel-based morphometry (VBM).

Twenty-five patients with ET and 25 matched healthy controls were evaluated. ET was diagnosed using the National Institutes of Health collaborative genetic criteria. Severity of tremor was assessed using the Fahn-Tolosa-Marin (FTM) tremor rating scale. Subjects were assessed using a structured neuropsychological battery. Brain images were acquired using a 3T magnetic resonance imaging scanner. VBM analysis was performed using Statistical Parametric Mapping 8.

The age of the patients was 45.0 ± 10.7 years and of controls 45.4 ± 10.7 years. Tremor duration was 9.84 ± 6.63 years and total FTM score was 37.34 ± 17.67. Patients were divided into two groups: ETCI with cognitive impairment (three or more abnormal neuropsychological tests, 1.5 standard deviation criterion) and ETNCI without cognitive impairment. Compared with controls, the ETCI group had significantly impaired performance in neuropsychological tests. One-way analysis of variance was performed between the three groups (ETCI, ETNCI, controls) followed by the two-sample t test. Compared with controls, grey matter volume (GMV) loss was observed in ETCI in the cerebellum (anterior and posterior lobes) and medial frontal gyrus. GMV loss was observed in ETCI compared with ETNCI in the medial frontal gyrus, post central gyrus, anterior cingulate and insula. Impairment in neuropsychological tests significantly correlated with GMV of the medial frontal gyrus, superior parietal lobe, middle temporal gyrus, occipital lobe, lentiform nucleus, insular and cingulate cortices and cerebellum posterior lobe in ETCI.

A correlation between neurocognitive deficits in ETCI and GMV was observed suggesting that grey matter atrophy appears to be a correlate of cognitive impairment in ET.