Abstract
Convergence nystagmus was obserbed in a 54-year old man with familial spinocerebellar degeneration. Neurological findings showed cerebellar ataxia including dysmetria with scanning speech, gait disturbance and horizontal diplopia. The mother, 4 of the 7 siblings and her maternal grandmother had a similar history. NMR-CT revealed significant atrophy of the brainstem and cerebellum. Convergence nystagmus was present in the primary position and was accentuated by convergence on ENG. Other neurotological findings showed bilateral horizontal gaze nystagmus, which was marked in adducent eyes, direction-changing positional nystagmus to the lower ear on the upper eye only, impaired OKN in the horizontal planes which was marked in abducent eyes during quick phase and saccadic pursuit. Cold caloric stimulations elicited tonic eye deviation in the direction of the slow phase on each side. Neurotological findings suggested impairment of the bilateral eye movement system in the midbrain, pons and vestibulocereberum. There was no case of spinocerebellar degeneration among the 74 cases of convergence nystagmus reported in the literature.
