Preliminary communication: neuroanatomical variations of the posterior fossa in men with the fragile X (Martin-Bell) syndrome.

Four men with fragile X (fra (X], or Martin-Bell, syndrome were studied by magnetic resonance imaging (MRI) to determine whether detectable abnormalities of the cerebellum were present. The cerebellum was chosen because of the apparently increased tendency for fra (X) patients to demonstrate autistic behavior and accumulating evidence implicating cerebellar abnormalities in autism. Compared with a control group of four normal men, fra (X) patients had a significantly decreased area of the cerebellar vermis, particularly the posterior portion, on planimetric analysis in the midsagittal plane. The pons and fourth ventricular areas also were decreased and increased, respectively, in the fra (X) men. Neuroanatomical and animal research increasingly implicates the cerebellar vermis as an important component in functional brain systems subserving sensory and motor integration, learning, and modulation of affect, motivation, and social behavior. Thus, vermis dysfunction could account for many of the behavioral and cognitive abnormalities observed in fra (X) males, particularly those which overlap with the behavioral syndrome of autism.