Leigh disease (subacute necrotizing encephalomyelopathy): MR documentation of the evolution of an acute attack.

The radiologic evolution of Leigh disease is documented with sequential brain MR in the acute phase of the illness, at 3 weeks, and at 3 months. High-signal-intensity lesions seen on T2-weighted images in the first week resolved by 3 months, whereas new lesions appear during the chronic stage. Putamenal involvement is not a pathognomonic radiologic finding. Brain stem tegmentum, particularly the mesencephalon, is characteristically involved on MR in the early and late phases of the illness.