Signal change of the substantia nigra on diffusion-weighted imaging following striatal infarction.

Diffusion-weighted imaging can depict secondary signal changes of the substantia nigra in patients with ipsilateral striatal infarction. We report four patients who demonstrated obvious signal changes of the substantia nigra in the subacute phase of stroke. Embolic stroke was diagnosed in all of the cases, and none of the patients presented clinical deterioration in their course. Embolic mechanism might be more closely related to the secondary change of the substantia nigra than thrombosis. The relationship between secondary nigral degeneration and stroke etiology or between the nigral lesions and recanalization of the middle cerebral artery remains unclear.