Hemiparkinsonism with infarction of the ipsilateral substantia nigra.

An elderly man suffering from dementia associated with hypertension developed right-sided parkinsonism marked by rigidity and flexion. At autopsy the brain showed generalized vascular changes chiefly in the white matter, diffuse plaque and neurofibrillary tangle formation in the temporal cortex, and a discrete gliotic scar in the right substantia nigra. Hemiparkinsonism with a strictly unilateral lesion confined to the substantia nigra has, to our knowledge, not been described before, and the fact that it was ipsilateral adds to its theoretical interest.