Hemichorea--a late sequel of an extradural haematoma.

Hemichorea developed several weeks after evacuation of a traumatic extradural haematoma. The abnormal movements were confined to arm and leg on the side opposite the surgery. No other causes of chorea were found. The connection between the extradural haematoma and the late onset hemichorea is not well understood; mechanical pressure on basal ganglia structures, vascular disturbances of the anterior choroidal artery as well as biochemical alterations are all possible mechanisms.