Excessive daytime sleepiness in myotonic dystrophy

The aim of the present study was to assess whether or not there is any corr elation between magnetic resonance imaging (MRI) abnormalities and excessiv e daytime sleepiness (EDS) in a consecutive series of patients with myotoni c dystrophy (MD). The influences of nocturnal breathing abnormalities and s leep morphology on EDS were also evaluated. Ten MD patients were studied by means of an all-night polysomnographic recording, the multiple sleep laten cy test (MSLT) and MRI. Diagnosis of MD was established on the basis of the clinical and electrophysiological evidence of myotonia as well as of the c haracteristic genetic pattern. No patient had respiratory failure. Polysomn ography and MSLT were also evaluated in ten healthy age-matched controls un der the same environmental conditions. The mean MSLT value was significantl y low er in patients than in controls, Five of the ten patients were found to have pathological EDS. The quantitative sleep variables and the nocturna l apnoeas in these five patients were not significantly different from thos e of the patients without EDS. As two patients did not undergo MRI because of claustrophobia, the MRI data were considered in eight patients. Corpus c allosum (CC) atrophy was detected in four patients. whereas three patients showed hyperintense areas in the white matter. No correlation was found bet ween EDS and MRI indexes of subcortical atrophy as well as volume of the hy perintense areas. By contrast, a correlation was found between the MSLT val ue and the reduction in the anterior area of the CC. Our data suggest that CC atrophy might occur in MD patients, and that the size of the CC anterior area might be associated with EDS. (C) 1999 Elsevier Science B.V. All righ ts reserved.