Eye movement abnormalities in essential tremor may indicate cerebellar dysfunction

Experimental and clinical data indicate that the cerebel-lum is involved in the pathophysiology of advanced stages of essential tremor (ET). The aim of this study was to determine whether a dysfunction also affects cerebellar structures involved in eye movement control. Eye movements of 14 patients with ET and 11 age-matched control subjects were recorded using the scleral search-coil technique. Vestibular function was assessed by electro-oculography. Eight ET patients had clinical evidence of intention tremor (ETIT); six had a predominantly postural tremor (ETPT) without inten-tion tremor. ET patients showed two major de®cits that may indicate cerebellar dysfunction: (i) an impaired smooth pursuit initiation; and (ii) pathological suppres-sion of the vestibulo-ocular re¯ex (VOR) time constan