Myotonic dystrophy and progressive cognitive decline: a common condition or two separate problems?

We report the case of NG, a 43-year old woman with myotonic dystrophy (MYD) who has shown a slow decline in both motor and cognitive abilities since her referral to us at age 32. MYD is an autosomal dominant disorder characterised by weakening and wasting of the muscles together with impaired muscle relaxation. Cognitive abilities are usually little affected in the adult onset form, although there is a high risk of cognitive impairment in those with childhood onset. Cognitive decline is also typically associated with maternal inheritance. NG, who was diagnosed with MYD at the age of 18, inherited it from her father. We report the decline in NG's cognitive abilities over 11 years of longitudinal assessment, and consider whether she is an atypical MYD patient or whether the MYD and cognitive decline are attributable to two separate pathological processes.