Cerebellar ataxia · Grey Matter

Cerebellar ataxia is the loss of coordination that follows damage to the cerebellum: strength is normal, but movements become poorly aimed, poorly timed and unsteady, because the system that predicts and corrects them no longer works.

Cerebellar ataxia. Cerebellar ataxia is the loss of coordination that follows damage to the cerebellum: strength is normal, but movements become poorly aimed, poorly timed and unsteady, because the system that predicts and corrects them no longer works.

Its signs follow from losing the cerebellum's correction. The gait is wide-based and lurching. A finger brought to the nose overshoots or undershoots (dysmetria) and shakes more as it nears the target (intention tremor), rapid alternating movements become irregular (dysdiadochokinesia), speech becomes slurred and scanning, and the eyes may jerk (nystagmus). Damage to the midline vermis mainly affects balance and gait, damage to a hemisphere the limbs on the same side, because each half of the cerebellum serves its own side of the body.

Alcohol produces a temporary version of it. The unsteady walk and slurred speech of intoxication are largely cerebellar, and long-term heavy drinking can cause a lasting degeneration of the anterior vermis that leaves the gait broad and unsteady.

Its causes range widely: strokes, multiple sclerosis, tumours, toxins and drugs, vitamin deficiencies, and a large family of inherited spinocerebellar ataxias.

Cognitive and emotional changes can accompany it. Lesions of the posterior lobe impair planning, fluency and affect, the cerebellar cognitive affective syndrome.

Questions: Why does alcohol make walking unsteady and speech slurred? The cerebellum is especially sensitive to alcohol, which disturbs the signalling of its Purkinje cells and the circuits feeding them. With the predictive correction impaired, gait widens and sways, movements overshoot and speech loses its timing, the same signs a neurologist looks for in cerebellar disease (which is why the roadside test asks for walking heel to toe and touching the nose). Years of heavy drinking can make the change permanent by degenerating the front of the vermis, which leaves a broad, unsteady gait.