Conventional and quantitative electroencephalography in patients with Steinert's myotonic dystrophy

Introduction. Steinert's myotonic dystrophy (SMD) is a systemic-type dominant autosomal disease, with variable clinical expression. Recent magnetic resonance studies conducted in patients with this disease have described the presence of lesions in the white matter of the brain and there have also been reports of a correlation between these and the presence of cognitive disorders. Nevertheless, very little work has been published about the electroencephalographic (EEG) findings in this disease. Patients and methods. In this study both conventional and quantitative EEG were performed on 10 patients with SMD aged between 17 and 50 years. Results. 90% of the patients showed a posterior alpha rhythm that was disorganised but which reacted on opening and closing the eyes, as well as the presence of continuous theta activity over the base activity that was bilaterally more pronounced towards the frontal-central regions. In the quantitative analysis we observed an increase in the absolute energies for the slow bands and a decrease for the fast bands on the frequency spectrum. In most patients (80%) spectral peaks were found within the theta range of frequencies as a correlate of the slow activity observed in the conventional analysis. Conclusions. It can be concluded that a quantitative EEG could be useful in the study of what, for many years, has been considered to be a 'neuromuscular' disease and that the use of other more precise methods, such as cerebral coherence and brain electrical tomography, could shed new light on the functional management of these patients.