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

Abstract

Previous electroencephalographic and magnetoencephalographic studies have demonstrated giant early somatosensory cortical responses in patients with cortical myoclonus. We applied whole-scalp magnetoencephalography to study activation sequences of the somatosensory cortical network in 7 patients with Unverricht-Lundborg-type progressive myoclonus epilepsy diagnostically verified by DNA analysis. Responses to electric median nerve stimuli displayed 30-msec peaks at the contralateral primary somatosensory cortex that were four times stronger in patients than in control subjects. The amplitudes of 20-msec responses did not significantly differ between the groups. In contrast to control subjects, 5 patients displayed ipsilateral primary somatosensory cortex activity at 48 to 61 msec in response to both left- and right-sided median nerve stimuli. Furthermore, their secondary somatosensory cortex was not significantly activated. These abnormalities indicate altered responsiveness of the entire somatosensory cortical network outside the contralateral primary somatosensory cortex in patients with Unverricht-Lundborg-type progressive myoclonus epilepsy. The deficient activation of the secondary somatosensory cortex in Unverricht-Lundborg patients may reflect disturbed sensorimotor integration, probably related to impaired movement coordination.

Sensorimotor, Visual, and Auditory Cortical Atrophy in Unverricht-Lundborg Disease Mapped with Cortical Thickness Analysis

“…[29][30][31][32] Transcranial magnetic stimulation 33,34 and MEG 35 studies have pointed to impaired sensorimotor cortical inhibition in EPM1. An absence of activation of the SII has been reported in patients who exhibited more severe motor symptoms, 36 and the authors speculated that deficient activation of the SII could account for the disturbed sensorimotor integration, contributing to impaired movement coordination. The same phenomenon may be reflected in our finding that the "Myoclonus with Action" score correlated negatively with CTH in the sensory areas, including the SII area.…”

Bilateral alterations in somatosensory cortical processing in hemiplegic cerebral palsy

“…It should be noted, however, that our results generally support the earlier results of normal contralateral representation of somatosensory functions as most of these ipsilateral responses in our participants were evoked by stimulation of the normal hand and had longer latencies than the contralateral responses. Ipsilateral SI responses have been reported to be enhanced in Unverricht–Lundborg‐type progressive myoclonus epilepsy 24 and in an individual with complex regional pain syndrome 25 . The presence of ipsilateral SI responses may reflect reduced inhibition of commissural fibres 25 .…”

Magnetoencephalographic Findings in Two Cases of Juvenile Myoclonus Epilepsy

“…Only a few articles in the literature refer to MEG findings in patients with progressive myoclonic epilepsy (Lafora disease and Unverricht-Lundborg type) and some researchers suggest that MEG allows increased spatial resolution and a more precise localization of pre-myoclonic spikes (Verrotti et al 2003;Forss et al 2001;Uesaka et al 1996). In general, differences between MEG and EEG findings may be related with the MEG exhibiting greater sensitivity in the different conductivities and superiority of the MEG channels.…”