Somatosensory evoked potential recovery in myotonic dystrophy

Objective: To evaluate recovery functions of the sensory cortex using somat osensory evoked potentials (SEPs) elicited by paired stimuli of the median nerve in patients with myotonic dystrophy (MD). Subjects/methods: Twelve MD patients were enrolled in the present investiga tion. Five patients with facioscapulohumeral muscular dystrophy (FSH) and 1 2 healthy volunteers were studied as control groups. SEP was recorded from the hand sensory area contralateral to the median nerve stimulated at the w rist. Single pulse or paired-pulse stimuli at various interstimulus interva ls (ISIs) (10, 20, 40, 60, 80, 100, 150, 300 and 300 ms) were given. Recove ry functions of N9, N20onset-N20peak, N20-P25 and P25-N33 components were s tudied. Results: Conventional SEPs to a single stimulus were normal in the latency and amplitude in all the patients. Recovery functions of both N9 and N20o-N 20p components were normal in the patients. In contrast, in MD patients, di sinhibited or hyperexcitable recovery pattern was observed in recovery curv es of the N20-P25 or P25-N33 components, whereas those were normal in FSH p atients. Conclusions: Disinhibited cortical excitability (or hyperexcitability) is p resent in the sensory cortex in patients with myotonic dystrophy. This may reflect cortical pathology or functional alteration of the sensory cortex i n MD. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.