Cortical reflex negative myoclonus

Abstract

Three patients with progressive myoclonic epilepsy (PME), two of them clinically manifesting only negative myoclonus and the other manifesting both positive and negative myoclonus, were electrophysiologically investigated, and compared with two other patients with PME presenting with only positive myoclonus. Electric stimulation of the median nerve during sustained active wrist extension in the three patients with negative myoclonus often elicited a short lapse of the posture in the stimulated hand associated with a silent period in the muscle discharge with or without being preceded by an abrupt increase in the muscle discharge (C reflex). The occurrence of the stimulus-induced silent period was significantly correlated with that of the giant somatosensory evoked potentials (SEPs), and in two patients the silent period was elicited also in the opposite (non-stimulated) hand when the giant SEP was recorded at the hemisphere ipsilateral to the stimulus as well. In one patient, the duration of the silent period was positively correlated with the amplitude of the cortical SEP. Furthermore, the duration of the induced silent period was closely related to the recovery function of SEP in each individual case. In contrast, in the two patients manifesting only positive myoclonus, the silent period was not elicited by the peripheral stimulation, and the somatosensory cortex was hyperexcitable immediately after the peripheral stimulus. Thus, this stimulus-sensitive negative myoclonus is mediated by a transcortical reflex mechanism, and corresponds to the negative form of the cortical reflex myoclonus ('cortical reflex negative myoclonus').

Nonconvulsive focal inhibitory seizure: Subdural recording from motor cortex

“…Recent studies using transcranial magnetic stimulation 1 have established the presence of cortical inhibitory motor system in humans, which seems to be involved in a variety of clinical conditions such as focal dystonia, 2 cortical reflex negative myoclonus, 3 and ictal negative phenomena in epilepsy. Nonconvulsive focal inhibitory seizure-ictal paralysis-is a poorly recognized, rare phenomenon that manifests paresis or paralysis of a body part unassociated with convulsion.…”

Propriospinal Negative Myoclonus

“…Moreover, it is also possible that two or more mechanisms contribute to EMG suppression. Cortical reflex negative myoclonus [10] was less likely because there was no evidence of hyperexcitability of the cerebral cortex.…”

“…Propriospinal myoclonus should be considered as a cause of negative myoclonus, in addition to the wellknown cortical or subcortical negative myoclonus [10].…”

Epileptische Anfälle im Kindesalter

“…Fokale und "generalisierte" negative Myoklonien wie auch eine epilepsia partialis continua sind pathophysiologisch den Reflexanfällen verwandt [15]:Somatosensible Potenziale (SEPs) infolge erhöhter Muskelspannungen (z. B. bei der Rumpfaufrichtung oder Anhebung einer Extremität gegen die Schwerkraft), triggern epileptische kortikale Entladungen, die ihrerseits wiederum zu Änderungen der Muskelspannungen oder der Gelenkstellungen führen,sodass sich solche Anfälle über den Mechanismus eines gestörten Regelkreises selbst unterhalten können.Deshalb ist es auch nicht verwunder- …”