Abstract
The case is presented of a 60 years old man who developed sudden right hemiplegia without other accompanying neurological signs and later a spastic hemiparesis. Neuropathological studies indicated an ischaemic lesion of the left medullary pyramid which was accompanied by hypertrophy of the left inferior olivary nucleus. An additional lesion, demyelination of the right gracile tract, is poorly explained. This case represents the second reported instance of pure motor hemiplegia due to a circumscribed lesion in the medullary pyramid and possibly an unique instance of olivary hypertrophy without obvious damage to the central tegmental tract, ipsilateral superior cerebellar peduncle, or contralateral dentate nucleus. The olivary hypertrophy is thought to have arisen from local damage to the termination of the central tegmental fibres at the left inferior olivary nucleus. The question of the development of spasticity in a pure pyramidal tract lesion is discussed.