Cerebellar volume and cerebellar metabolic characteristics in adults with dyslexia.

Developmental dyslexia is associated with problems in a range of linguistic and non-linguistic skills. Some of those problems have been attributed to dysfunction of the cerebellum and its associated neural systems. Two studies of cerebellar structure were undertaken by our group. In Study 1, white and grey matter volumes in the cerebellum were investigated in 10 dyslexic and 11 control adult male, right-handed participants using whole-brain volumetric MRI (3D-T1-weighted data sets with a spatial resolution of 0.8 x 0.8 x 0.8 mm(3)). The key finding was that the dyslexic group had a larger volume of white matter in both cerebellar hemispheres, differences that remained significant even when adjusting for total cerebellar volume. In Study 2, with the same participants, long-echo-time proton spectroscopy was used to investigate the ratios of the metabolites choline (Cho), N-acetylaspartate (NAA), and creatine (Cr) in the cerebellar hemispheres and vermis. Two significant differences were found: The dyslexic group had a lower ratio of NAA/Cho in the right cerebellar hemisphere together with a higher ratio of Cho/Cr in the left cerebellar hemisphere. Although it is difficult to interpret the volumetric and spectroscopic results unambiguously, taken together they suggest two possible interpretations: excessive connectivity or abnormal myelination.