[Conventional and quantitative electroencephalography in patients with Steinert's myotonic dystrophy]. / Electroencefalografía convencional y cuantitativa en pacientes con distrofia miotónica de Steinert.

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.

[Spectral analysis of EEG coherence in Alzheimer's disease]. / Analisis espectral de la coherencia cerebral en la enfermedad de Alzheimer.

INTRODUCTION: In analysis of the electrical activity of the brain, coherence is a measure of the degree of synchrony between two or more regions of the brain with regard to their frequency values over a unit of time. AIMS: To explore the functional alterations caused by Alzheimer's disease (AD), by evaluating the behaviour of coherence over the whole spectrum of EEG frequencies. PATIENTS AND METHODS: We studied a group of 42 patients with AD, according to criteria of the NINCDS ADRDA group. Partial coherence (e.g. between two derivations each time) was calculated within and between hemispheres, during a state of mental rest; the Z statistic was also determined by comparing the coherence values with the standard data for age, sex and functional state of the brain. RESULTS: Significantly low coherence values were obtained for the frontal central regions of the left hemisphere (LH) and for the occipital parietal regions of the right hemisphere (RH) in the delta band. The same localisations were carried out for the theta band, in addition to the centrotemporal and temporal regions of the LH. The highest incoherence values were observed for the alpha and beta bands, more specifically in frontal central and occipital parietal derivations of the RH, and temporal derivations of the LH. CONCLUSIONS: Non activated partial coherence acts as an indicator of the degree of functional disconnection between brain regions in AD. Studying activated coherence in these patients could contribute new elements to our knowledge about the functional disorders observed in this disease.