Cognitive function in myotonic dystrophy: a follow-up study.

Intellectual and cognitive function were studied in 35 patients with myotonic dystrophy (DM). All 5 patients with the congenital form showed moderate or mild mental retardation. The 30 adult-onset patients had normal intelligence and memory quotients. In this adult-onset group no differences in cognitive function were observed either with respect to sex or physical disability. The sex of the affected parent, mother vs. father, was also without effect in this group. A follow-up study was performed in 16 patients with a mean test interval of 12 years. There was no severe cognitive impairment over this time span or a significant correlation between the progression of physical and cognitive dysfunction.