Evaluation of cerebellar size in attention-deficit hyperactivity disorder.

Evidence from animal and human research suggests that the cerebellum may play a role in cognition. This includes domains of executive function that are normally attributed to the prefrontal cortex and are typically deficient in individuals with attention-deficit hyperactivity disorder (ADHD). To investigate cerebellar structure in ADHD, magnetic resonance imaging morphometry was used to measure the area of the cerebellar vermis in 12 males with ADHD and 23 male controls matched for age and Wechsler Full-Scale IQ. Analyses were conducted to evaluate group differences, as well as differences between matched pairs of subjects with ADHD and those without ADHD. All measurements were corrected for overall brain size. Both analyses revealed that the size of the posterior vermis was significantly decreased in males with ADHD (P < .05 in both analyses), and that within the posterior vermis, the inferior posterior lobe (lobules VIII-X) was involved in this reduction (P < .05 for group analysis, P < .005 for matched pair analysis), while the superior posterior lobe (lobules VI/VII) was not involved in the reduction. The finding of abnormal inferior posterior vermal size suggests that dysfunction within this region of the cerebellum may underlie clinical deficits seen in individuals with ADHD.