Lack of activation of human secondary somatosensory cortex in Unverricht-Lundborg type of progressive myoclonus epilepsy

Previous electroencephalographic and magnetoencephalographic studies have d emonstrated giant early somatosensory cortical responses in patients with c ortical myoclonus. We applied whole-scalp magnetoencephalography to study a ctivation sequences of the somatosensory cortical network in 7 patients wit h Unverricht-Lundborg-type progressive myoclonus epilepsy diagnostically ve rified by DNA analysis. Responses to electric median nerve stimuli displaye d 30-msec peaks at the contralateral primary somatosensory cortex that were four times stronger in patients than in control subjects. The amplitudes o f 20-msec responses did not significantly differ between the groups. In con trast to control subjects, 5 patients displayed ipsilateral primary somatos ensory cortex activity at 48 to 61 msec in response to both left- and right -sided median nerve stimuli. Furthermore, their secondary somatosensory cor tex was not significantly activated. These abnormalities indicate altered r esponsiveness of the entice somatosensory cortical network outside the cont ralateral primary somatosensory cortex in patients with Unverricht-Lundborg -type progressive myoclonus epilepsy. The deficient activation of the secon dary somatosensory cortex in Unverricht-Lundborg patients may reflect distu rbed sensorimotor integration, probably related to impaired movement coordi nation.