Brain Involvement in Myotonic Dystrophy Type 1: A Morphometric and Diffusion Tensor Imaging Study with Neuropsychological Correlation

Objective: Myotonic dystrophy type 1 (DM1), the most prevalent inherited neuromuscular disease in adults, is a genetic multisystem disorder with a well-established but not well-characterized cerebral involvement. The aim of this study was to evaluate the presence of white matter and gray matter abnormalities in DM1 patients and to investigate their relationship with neurocognitive dysfunction.

Methods: A total of 42 DM1 patients and 42 healthy controls were included in the study. Clinical, cognitive, and magnetic resonance imaging evaluations, including the use of structural and diffusion tensor imaging (DTI) techniques, were performed. White matter lesion (WML) load, volumetric analysis, and diffusivity changes were assessed and correlated with clinical and neuropsychological test findings.

Results: WMLs were significantly more frequent in DM1 patients (p < .001), and anterior temporal lobe lesions were only found in the patient group. Global and regional cortical volume loss and corpus callosum atrophy were found. Diffuse white matter DTI abnormalities, including fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity were observed with sparing of the internal capsule. Subcortical structures showed volume loss and increased median diffusivity. Neuropsychological evaluation showed significant impairment in several cognitive functions, but only visuospatial impairment was correlated with white matter abnormalities and cortical atrophy. Daytime sleepiness was associated with WML and ventral diencephalon and pallidum volume loss.

Conclusion: DM1 produces a widespread involvement of white matter and gray matter, including cortical and subcortical structures. These structural abnormalities are involved in the progressive neuropsychological functional impairment in these patients.