Motor network disruption in essential tremor: a functional and effective connectivity study.
UNLABELLED The pathophysiology of essential tremor (ET) is unknown but recent studies report that the majority of ET cases has cerebellar Purkinje cell (PC) degeneration and its sequelae. OBJECTIVE To perform PC counts in ET, and normal and Parkinson's disease (PD) controls to determine the relationship of PC loss to ET. METHODS All ET cases and PD controls were followed at our clinic. Normal controls had no history of neurological disease and had normal standard neuropathological studies. The PC counts were done by a neuropathologist who was blinded to the clinical diagnosis. Three different methods were used for counting PC; section through any part of the PC, through any part of the PC nucleus, and through any part of PC nucleolus. The counts were done in five non-contiguous microscopic fields. RESULTS 59 brains were studied. These included 12 ET, 41 PD controls, and six normal controls. The mean age at death was 82.7 in ET, 79.1 in PD, and 75.7 years in the normal controls. The mean duration of symptoms was 34 years in ET and 15.7 years in the PD cases. The mean PC counts through any part of the neuron were 64.8 in ET, 56.2 in PD, and 58.0 in normal controls. Differences were not significant. CONCLUSION Cerebellar PC loss does not distinguish ET from controls. It is concluded that PC loss is neither a pathological basis for, nor the distinctive feature of ET.