Psychometric and cranial CT study in myotonic dystrophy.

Twenty-two adults with myotonic dystrophy were assessed for evidence of intellectual impairment and cranial CT abnormalities. Psychometric evaluation demonstrated significantly lower verbal and performance IQs in the MD subjects than in matched normal controls. The reduced performance IQ was not simply related to loss of fine motor skills. No significant differences were found in memory and personality assessments between the MD and control groups. Lateral ventricular surface area was measured on CT scans using a semiautomated image analysis technique and was found to have a positive correlation with age in a control group of 45 normal scans (r = 0.833, P less than 0.001). This correlation was lacking in the MD group of subjects (r = 0.345, P greater than 0.05), in eight of whom the ventricular surface area was above the upper limit for age found in the control group. Asymptomatic areas of focal atrophy were found in two subjects. There was no correlation between ventricular size and severity or duration of the disease or verbal or performance IQ.