Vestibulo-ocular arreflexia in families with spinocerebellar ataxia type 3 (Machado-Joseph disease).

OBJECTIVE To identify the presence of vestibulo-ocular arreflexia in patients with Machado-Joseph disease (MJD), which can easily be diagnosed at the bedside. METHODS Seven patients with MJD from five unrelated families and 11 patients with sporadic or hereditary cerebellar ataxia other than MJD underwent a detailed neuro-otological and oculomotor examination. Six MJD and five non-MJD patients also underwent electro-oculographic recordings and caloric tests. RESULTS Gaze evoked nystagmus, smooth pursuit, and saccade abnormalities were found in both MJD and non-MJD patients. However, in all seven MJD patients but in none of the non-MJD patients, sudden passively induced head thrust to both sides elicited pathological corrective catch-up saccades, indicating bilateral loss of the horizontal vestibulo-ocular reflex. This was further confirmed in six MJD patients who had absent vestibular response to both a standard caloric test and ice water ear irrigation. Nystagmus was induced by standard caloric irrigation in all non-MJD patients examined. There was no correlation between the loss of vestibular function and the severity of cerebellar impairment. CONCLUSIONS The presence of vestibulo-ocular arreflexia, as measured by the head thrust test in a patient with dominant cerebellar ataxia, strongly suggests the diagnosis of MJD.