Extranigral extension of structural midbrain lesions overshadows parkinsonism.

We report on a clinicoanatomical analysis of five patients with structural midbrain lesions who shared severe nigrostriatal dopaminergic denervation but presented different involuntary movements. The main clinical phenotype was parkinsonism in only one case; it was choreoballism in three cases and tremor and dystonia in one case. Structural midbrain lesions are likely to involve structures additional to nigral dopaminergic neurons. The extent of extranigral involvement may determine the diverse clinical manifestations associated with the structural midbrain lesions.