Neurophysiological findings in the Rett syndrome, I: EMG, conduction velocity, EEG and somatosensory-evoked potential studies.

Nine girls, aged 10 to 22 years, with confirmed Rett syndrome--eight as stage IV and one at stage III--were investigated neurophysiologically. EMG and neurography studies were performed, and somatosensory-evoked responses (SER) were recorded as well as EEG with topographic mapping. Even in advanced clinical stages, no major motor root involvement or demyelinating motor peripheral neuropathy was detected on EMG or neurography, but an axonopathy, possibly of secondary origin, was observed. EEG showed slowing and dominance of low frequency activity of subcortical origin, with or without epileptic discharges. SER findings suggested involvement of the spinal cord and the spinothalamic system. Neurophysiological investigations can be used by the clinician in the differential diagnosis of the Rett syndrome.