A 5-year follow-up study of an atypical case of myotonic dystrophy

Abstract

This study presents 5-year follow-up data on NG, a woman with adult onset myotonic dystrophy and progressive cognitive decline who was first described by Wilson et al. The extent of the cognitive impairment is atypical of symptom-onset in adulthood and of paternal inheritance, both of which apply to this case. Together, the present and earlier studies report the results of regular neuropsychological assessments over a 16-year period. Severe impairment in executive functioning, episodic and semantic memory were apparent early in the history, while visuospatial skills and working memory were only mildly impaired after 16 years of follow-up. There was also a progressive dyslexia, initially characterized by the regularization errors typical of surface dyslexia, but subsequently dominated by visual/phonological reading errors. This pattern of impairment is not typical of myotonic dystrophy but resembles semantic dementia. Whilst the deficits may be attributable wholly to myotonic dystrophy pathology, the co-existence of a form of semantic dementia is also possible. It is noted that the aggregation of tau protein is a neuropathological feature common to both diseases.

Cognition in myotonic dystrophy type 1: a 5‐year follow‐up study

“…Interestingly, the difference in the vocabulary test became significant when controlling for age effects. An earlier single case study [14] provides information on possible memory decline in DM1 and the present study supports this finding in a larger group of patients. Modoni et al [16] proposed memory decline in patients with mild symptoms, small CTG repeat size and a late onset of the disease (mild/late onset DM1).…”

“…An earlier single case study provides information on possible memory decline in DM1 and the present study supports this finding in a larger group of patients. Modoni et al .…”

“…To our knowledge, this is the first study to show a decline in visuospatial construction ability, also correcting for the possible influence of visual impairment. Notably there was only a weak support for decline in executive functions as found in earlier studies .…”

“…Tuikka et al [13] reported no decline at follow-up. In contrast, one study has described major deterioration, involving executive functions, episodic and semantic memory [14]. More recently, studies have shown moderate decline within specific cognitive domains, such as executive and linguistic cognition [15,16].…”

Cognitive impairment in adult myotonic dystrophies: a longitudinal study

“…Regarding brain involvement, so far there has been no clear demonstration of the clinical relevance of the abnormal neuropsychological test scores and neuroimaging findings in patients with DM1. Longitudinal studies in cognitive function in adult DM1 are still limited [29,30,33] and controversial. The progressive decline in working capacity and physical activity in patients with DM1 has in general been attributed to the progression of muscular symptoms and respiratory insufficiency [34,35].…”