Cognitive phenotype of childhood myotonic dystrophy type 1: A multicenter pooled analysis

There is clear evidence for brain involvement in childhood myotonic dystrophy type 1 (DM1) from imaging studies and the prevalence of intellectual impairment and neurodevelopmental disorders. The cognitive profile of children with DM1 however is poorly understood. The aim of this study was to assess the cognitive profile of children with DM1.

Neuropsychological examination reports of 45 children aged 2-17 y were analyzed. All cognitive subtests used in this cohort were pooled in 10 cognitive domains. For every patient a composite z-score was calculated for every assessed domain. Composite scores were classified as average (z > -1), mild cognitive impairment (-1 ≥ z > -2), or major cognitive impairment (z ≤ -2).

The nature and extent of neuropsychological examinations differed between centers and patients. The domains with the highest frequency of major cognitive impairment were social cognition (4/9 children tested; 44%), attention (13/32; 41%), and fine motor skills (3/10; 30%). Combining mild and major cognitive impairment, working memory (20/28; 71%), attention (21/32; 66%), and visuospatial functions (16/28; 57%) were the most frequently affected domains. Long-term memory was least affected, with mild impairment only in 5/29 (17%).

Children with DM1 may have specific cognitive deficits, most frequently affecting working memory, attention, and visuospatial functions, in addition to the previously described global intellectual impairments. We recommend including a standardized neuropsychological examination in the standards of care for DM1 children. Early recognition of cognitive deficits and behavioral disorders in children with DM1 can improve their management.