DECREASED CEREBELLAR POSTERIOR VERMIS SIZE IN FRAGILE-X-SYNDROME - CORRELATION WITH NEUROCOGNITIVE PERFORMANCE

We examined whether posterior vermis size is smaller in individuals wi th fragile X syndrome (fra X) than in control subjects and whether thi s decreased size is associated with cognitive performance. Cognitive a nd behavioral dysfunctions have been identified in fra X; however, und erlying neuropathogenic mechanisms remain unclear. MRI was used to inv estigate the posterior fossa in 32 males with fra X, 28 males with oth er causes of cognitive disability (CD), and 38 males with normal devel opment (ND) as well as and in 37 females with fra X and 53 female cont rol subjects. Among females with fra X, neurocognitive correlates of p osterior vermis size were examined. Posterior vermis size (cross-secti onal area) in males with fra X was significantly smaller compared with CD and ND groups, particularly when corrected for intracranial area. Posterior vermis size corrected for intracranial area was significantl y smaller in females with fra X compared with control subjects. Compar ed with males with fra X and non-fra X control subjects, posterior ver mis size in females with fra X was intermediate. After statistically r emoving the effect of mean parental IQ, posterior vermis size predicte d a significant proportion of the variance (10 to 23%) of performance on full-scale, verbal, and performance IQ; block design; categories ac hieved on the Wisconsin Card Sorting Test; and the Rey inventory score . The size of the posterior vermis is significantly decreased in fra X , more so in males than in females. In females with fra X, posterior v ermis size predicts performance on selected cognitive measures.