Type 3 GM1 gangliosidosis: characteristic MRI findings correlated with dystonia.

We describe three brothers with type 3 GM1 gangliosidosis presenting as dystonia. The ages of the patients when examined were 28, 31, and 33. They had developed dysarthria with facial grimacing since early childhood. The common neurological sign was generalized dystonia. Both dystonic postures and dystonic movements resulting from varying degrees of fixed rigidity of each muscle involved did not disappear when the patients were lying or sitting relaxed. There was no correlation between the severity of dystonia and the residual activities of acid beta-galactosidase. Magnetic resonance imaging (MRI) showed bilaterally symmetric high intensity lesions only in the putamen on T2-weighted and proton density images. Selective putaminal changes on MRI may be the lesions most responsible for symptomatic dystonia in this disorder.