An MRI volumetric analysis of frontal and nonfrontal gray and white matter was performed in 11 boys with Tourette syndrome (TS) only, 14 with TS + ADHD, 12 with ADHD only, and 26 healthy boys, at the Kennedy Krieger Institute, Baltimore, MD. Ages ranged from 7.0 to 15.5 years. Using 2 x 2 multivariate factorial analysis of variance (MANOVA), which characterized subjects for presence or absence of TS and ADHD, and various combinations, the effects of TS status, ADHD status, and the interaction of these two factors on frontal lobe white and gray matter volumes were determined. In subjects with TS, the right frontal lobe had a larger proportion of white matter, and the right frontal white matter volume was increased. ADHD was associated with a reduction in frontal lobe volumes that was attributable to decreased gray matter, especially in the left frontal lobe. The findings support a frontostriatal pathophysiology of Tourette syndrome. 
COMMENT. An increase in white matter in the right frontal lobe of patients with Tourette syndrome is in keeping with previous reports by the same authors of an enlarged rostrum of the corpus callosum associated with TS (see Progress in Pediatric Neurology III, PNB Publ, 1997;pp322-323) . In contrast, boys with ADHD were found to have a significant decrease in size of the corpus callosum rostral body. The effects of ADHD and TS on corpus callosum size were statistically independent.