Progressive myoclonus epilepsy

Progressive myoclonus epilepsy
Classification and external resources
MeSH	D020191
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Progressive myoclonus epilepsy (PME) is a rare epilepsy syndrome caused by a variety of genetic disorders. The syndrome includes myoclonic seizures and tonic-clonic seizures together with progressive neurological decline.

Myoclonic seizures involve brief involuntary muscle twitching, and may become frequent enough to be disabling. Tonic-clonic seizures have two phases: the tonic phase may last a few seconds and involves the muscles tensing, and may lead to the person falling down; the clonic phase involves a convulsion of rapidly alternating muscle tensing and relaxing. Neurological dysfunction includes difficulty coordinating muscle movements (ataxia) and a decline in cognitive ability (dementia).

In the early stages, it can be difficult to distinguish progressive myoclonic epilepsy from benign idiopathic generalised epilepsies, such as juvenile myoclonic epilepsy. With PME, the initial effectiveness of anticonvulsant treatment diminishes as seizures become more frequent and neurological decline progresses. However, these can also be signs of anticonvulsant intoxication. The myoclonus in PME is usually severe and is the prominent seizure type.

Six specific disorders comprise the most common causes of progressive myoclonic epilepsy: Unverricht-Lundborg disease (Baltic myclonus); myoclonus epilepsy and ragged red fibres (MERRF syndrome); Lafora disease; neuronal ceroid lipofuscinoses; and type I sialidosis. Less common causes include dentatorubropallidoluysian atrophy (DRPLA); the noninfantile neuronopathic form of Gaucher disease; and atypical inclusion body disease. PME has also been reported in Niemann-Pick disease type C.

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