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. Ann Neurol 2001;49:90–97

Investigations of the Somatosensory System with Magnetoencephalography

“…These findings suggested that the SI cortex encodes details about somatosensory stimuli, while responses at SII cortices and PCC are less sensitive to stimulus type and have more integrative features (Forss et al, 1994b). Similar observations have been made in patients with progressive myoclonic epilepsy, in whom "giant" SEFs have been observed in bilateral SI cortex but with normal responses at bilateral SII cortices (Forss et al, 2001).…”

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 .…”

Magnetoencephalography in pediatric neuroimaging

“…Most MEG studies have been conducted with adult subjects, but some MEG data already exist on children. Pediatric MEG studies have mainly focused on epilepsy surgery (Paetau, Hämäläinen, Hari, Kajola, Karhu, Larsen, Lindahl & Salonen, 1994; Chuang, Otsubo, Hwang, Orrison & Lewine, 1995; Minassian, Otsubo, Weiss, Elliott, Rutka & Snead, 1999), on rolandic epilepsy (Kubota, Oka, Kin & Sakakihara, 1996; Minami, Gondo, Yamamoto, Yanai, Tasaki & Ueda, 1996; Kamada, Moller, Saguer, Kassubek, Kaltenhauser, Kober, Uberall, Lauffer, Wenzel & Vieth, 1998; Kubota, Takeshita, Sakakihara & Yangisawa, 2000), on the Landau‐Kleffner syndrome and related disorders (Paetau, Kajola, Korkman, Hämäläinen, Granström & Hari, 1991; Paetau, 1994; Lewine, Andrews, Chez, Patil, Devinsky, Smith, Kanner, Davis, Funke, Jones, Chong, Provencal, Weisend, Lee & Orrison, 1999; Paetau, Granström, Blomstedt, Jousmäki, Korkman & Liukkonen, 1999; Sobel, Aung, Otsubo & Smith, 2000), on sensory cortex properties in progressive myoclonus epilepsies (Karhu, Hari, Paetau, Kajola & Mervaala, 1994; Lauronen, 2001; Forss, Silen & Karjalainen, 2001), and on dyslexia (Heim, Eulitz, Kaufmann, Fuchter, Pantev, Lamprecht‐Dinnesen, Matulat, Scheer, Borstel & Elbert, 2000; Simos, Breier, Fletcher, Bergman & Papanicolaou, 2000). This article will briefly review the basic principles of MEG and give some examples of the present use of MEG in children.…”