Review on progressive myoclonus epilepsies (PMEs) and related disorders: Recent advances in clinical, genetic and neurophysiological aspects

Abstract

PMEs are a genetic disorders which previously had a nosological confusion. The characteristics of PMEs are action or intentional myoclonus, ataxia and mental decline. There are considerable geographic and ethnic variability, DRPLA and PME-related disorder, benign adult familial myoclonus epilepsy (BAFME), are relatively popular in Japan whereas they are extremely rare in the other countries. The major PME disorders such as Lafora disease, Neuronal Ceroid Lipofuscinosis, Sialidosis, Unverricht-Lundborg disease, Mitochondrial disease, DRPLA, and BAFME were described along with case reports. Special attention is given to the BAFME which are adult onset photosensitive epilepsy with various degree of action and postural myoclonus and occasional GTCs and has a dominant hereditary pattern and benign course. Recent advances in genetic studies provided a new aspects of the basic mechanism of PMEs, and now DNA diagnosis became possible in many cases. The locus of BAFME was recently found in chromosome 8 q 23.3-24.1. Neurophysiological aspects of all of these PMEs and BAFME had a high amplitude somatosensory evoked potentials (SEPs) except for DRPLA where SEP and the auditory brainstem potential (ABP) were suppressed. The myoclonus of DRPLA, clinically indistinguishable from those of the other PMEs, may have different mechanism such as subcortical origin.