MRI of the brain in the Cohen syndrome: a relatively large corpus callosum in patients with mental retardation and microcephaly.

Our purpose was to perform the first systematic brain magnetic resonance imaging (MRI) study of a substantial number of Cohen syndrome (MIM n:o 216550) patients. 18 Cohen patients and 26 healthy volunteers were examined by MRI (1.0 T). All Cohen patients had essential features of this syndrome: typical facial and structural features, mental retardation, microcephaly, ophthalmologic symptoms, granulocytopenia and cheerful psychic disposition. All our patients belong to the recently published study of refined mapping of the Cohen syndrome gene by linkage disequilibrium. As visual analysis of MR images revealed an impression of a large corpus callosum (CC), quantitative analysis was performed. Sagittal diameter of the body of the CC was larger than that of controls (p = 0.02), whereas all sagittal diameters of the brain stem were markedly smaller (p < 0.0001), as was the midline internal skull surface (MISS) (p < 0.0001). The CC surface did not significantly differ from that of controls significantly. Our main finding, a relatively enlarged corpus callosum, has not previously been reported to associate with mental retardation. Though MRI alone can not confirm the diagnosis and no definite measurements can be recommended for clinical use, any clinical suspicion of this syndrome receives reinforcement through MRI: a relatively enlarged corpus callosum in a microcephalic head and normal signal intensities of the grey and white matters.