Pathogenesis of Giant Somatosensory Evoked Potentials in Progressive Myoclonic Epilepsy

Abstract

Fifty-seven consecutive patients with myoclonus from various causes were studied by electrophysiological techniques. Giant somatosensory evoked potentials (SEPs) were observed almost exclusively in patients with progressive myoclonic epilepsy (PME) and diseases with similar clinical features that included lipidosis, neuronal ceroid lipofuscinosis and posthypoxic myoclonus. On the basis of combinations of the giant SEP and the myoclonus-related cortical spike demonstrated by jerk-locked averaging, myoclonus in these patients was classified into four types. In patients with 'cortical reflex' myoclonus (type I) who showed both the giant SEP and the myoclonus-related cortical spike, these two cortical activities were similar in terms of wave form, scalp topography, time relationship to either the long latency (C) reflex or myoclonus, the following cortical excitability, the effect of antimyoclonus drugs and alterations during slow wave sleep. It is therefore postulated that the giant SEP is generated, at least in part, by common physiological mechanisms to the myoclonus-related cortical spike, or that the latter may comprise a constituent of the former. In most patients with PME or allied diseases, both afferent and efferent components of the SEP are enhanced, but in some patients, only one of the two components seems to be predominantly enhanced.

Microglia-passaged simian immunodeficiency virus induces neurophysiological abnormalities in monkeys

“…The visually evoked N2 wave developed a significantly larger amplitude and was delayed compared with controls, similar to previously recognized so-called giant potentials observed in varied human clinical disease states (36). For example, the appearance of more waves in the entire evoked complex, shortening of latency, or giant potentials has been observed in progressive myoclonic, photosensitive, and petit mal epilepsy, as well as in subacute encephalopathies, including Creutzfeldt-Jakob disease and Lafora body disease (36)(37)(38). All these diseases have in common a theme of central hyperexcitability.…”

Potencial evocado somato-sensitivo em crianças com pontas evocadas por estímulo somato-sensitivo no eletrencefalograma

“…É bem conhecido que esses componentes com amplitude elevada são encontrados em pacientes com epilepsia mioclônica progressiva, mas, também ocorrem em outras afecções do SNC 4,[24][25][26][27][28][29][30] . Esse aumento de amplitude dos componentes corticais do PES pode representar uma hiperexcitabilidade do córtex somato-sensitivo correspondente ao possível local epileptogênico 29 .…”

“…Esse aumento de amplitude dos componentes corticais do PES pode representar uma hiperexcitabilidade do córtex somato-sensitivo correspondente ao possível local epileptogênico 29 . Assim, esse componente poderia estar relacionado à predisposição a crises epilépticas, nas epilepsias 452 Arq Neuropsiquiatr 2004;62 (2-B) parciais idiopáticas 1,4,13,16 .…”

Motor Excitability after the C Reflex in Cortical Reflex Myoclonus

“…Iong-loop reflex (C reflex), and premyoclonus spike detected by the jetk-locked ayeraging method [3][4][5]. This type of myoclonus has been thought to arise from pathological hyperactivity of long-latency transcranial reflexes.…”

“…Moreover, some patients with eortical reflex myoclonus show double C refiexes [4] or motor inhibition fbllowing C reflexes [8]. However, the mechanism ofthe second C reflex and the change ofmotor excitability after the C reflex or myoclonus has not been elucidated.…”