Spinocerebellar ataxia type 40 (SCA40) is a very rare subtype of autosomal dominant cerebellar ataxia type 1, characterized by the adult-onset of unsteady gait and dysarthria, followed by wide-based gait, gait ataxia, ocular dysmetria, intention tremor, scanning speech, hyperreflexia and dysdiadochokinesis.

A supranuclear gaze palsy is an inability to look in a vertical direction as a result of cerebral impairment. There is a loss of the voluntary aspect of eye movements, but, as the brainstem is still intact, all the reflex conjugate eye movements are normal.