Brain biochemistry in autopsied patients with essential tremor

The pathology of essential tremor is increasingly being studied; however, there are limited studies of biochemical changes in this condition. We studied several candidate biochemical/anatomical systems in the brain stem, striatum, and cerebellum of 23 essential tremor subjects who came to autopsy, comparing them with a control population. Striatal tyrosine hydroxylase, a marker of dopaminergic neurons, was 91.7 ± 113.2 versus 96.4 ± 102.7 ng/mg (not significant) in cases and controls, respectively. Locus coeruleus dopamine beta-hydroxylase, a marker of noradrenergic neurons, was not significantly different between the essential tremor and control groups. Parvalbumin, a marker of GABAergic neurons, was 199.3 ± 42.0 versus 251.4 ± 74.8 ng/mg (P = .025) in the pons in the region of the locus coeruleus of essential tremor subjects versus controls, whereas there was no difference in cerebellar parvalbumin. These results are supportive of a possible role for reduced GABAergic function in the locus coeruleus in essential tremor. The hypothesis that essential tremor represents early Parkinson's disease was not supported, as striatal dopaminergic markers were not reduced compared with control subjects.