Neuropsychological Assessment Should Always be Considered in Myotonic Dystrophy Type 2

Myotonic dystrophies (DMs) are hereditary, multisystem, slowly progressive myopathies. One of the systems they affect is the CNS. In contrast to the well-established cognitive profile of myotonic dystrophy type 1 (DM1), only a few studies have investigated cognitive dysfunction in individuals with myotonic dystrophy type 2 (DM2), and their findings have been inconsistent. To identify the most commonly affected cognitive domains in individuals with DM2, we performed a formal comprehensive review of published DM2 studies. Using the terms "myotonic dystrophy type 2" AND "cognitive deficits," "cognitive," "cognition," "neuropsychological," "neurocognitive," and "neurobehavioral" in all fields, we conducted an advanced search on PubMed. We read and evaluated all of the available original research articles (13) and one case study, 14 in total, and included them in our review. Most of the research studies of DM2 reported primary cognitive deficits in executive functions (dysexecutive syndrome), memory (short-term nonverbal, verbal episodic memory), visuospatial/constructive-motor functions, and attention and processing speed; language was rarely reported to be affected. Based on the few neuroimaging and/or multimodal DM2 studies we could find, the cognitive profile of DM2 is associated with brain abnormalities in several secondary and high-order cortical and subcortical regions and associative white matter tracts. The limited sample size of individuals with DM2 was the most prominent limitation of these studies. The multifaceted profile of cognitive deficits found in individuals with DM2 highlights the need for routine neuropsychological assessment at both baseline and follow-up, which could unveil these individuals' cognitive strengths and deficits.