Progressive myoclonus epilepsies

Beatriz G Giráldez MD (Dr. Giráldez of Hospital Universitario Fundación Jiménez received honorariums from Eisai.)
Jose M Serratosa MD PhD (Dr. Serratosa of Fundación Jiménez Díaz received honorariums from Bial, Eisai, and UCB Pharma for speaking engagements and consultation fees from Eisai and UCB Pharma.)
Jerome Engel Jr MD PhD, editor. (Dr. Engel of the David Geffen School of Medicine at the University of California, Los Angeles, has no relevant financial relationships to disclose.)
Originally released November 21, 2011; last updated June 7, 2016; expires June 7, 2019

This article includes discussion of progressive myoclonus epilepsies, progressive myoclonic epilepsy, PME, and neuronal ceroid lipofuscinosis. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

The progressive myoclonus epilepsies are a group of genetic and rare disorders clinically characterized by the presence of myoclonic and tonic-clonic seizures, myoclonus, and progressive neurologic deterioration. In this article, the authors give a general overview of the main types of progressive myoclonus epilepsy.

Key points

 

• The progressive myoclonus epilepsies are a group of genetic and rare disorders clinically characterized by the presence of typically refractory myoclonic seizures, tonic-clonic seizures, and progressive neurologic deterioration.

 

• Onset of symptoms is usually during childhood or adolescence.

 

• Most progressive myoclonus epilepsies are caused by a pathogenic mutation in a gene inherited as an autosomal recessive trait. Less common progressive myoclonus epilepsies are inherited as an autosomal dominant trait or through mitochondrial inheritance.

 

• Most of the known causative progressive myoclonus epilepsy genes encode lysosomal proteins, with few exceptions (ion channels). Despite increasing knowledge of the etiology of most progressive myoclonus epilepsy disorders, the pathogenic mechanisms leading to neurodegeneration and epilepsy remain largely unknown.

 

• Histological and/or genetic studies are frequently required to confirm the diagnosis.

 

• Treatment is essentially symptomatic, limited to management of the epileptic seizures, myoclonus, and intercurrent complications. Genetic counselling is mandatory.

Historical note and terminology

Progressive myoclonus epilepsy was first recognized as a clinical entity following original descriptions by Unverricht (Unverricht 1891), Lundborg (Lundborg 1903), and Lafora (Lafora and Glueck 1911). Progressive myoclonus epilepsies are classically defined as progressive disorders presenting primarily with the association of epileptic generalized tonic-clonic seizures and multifocal, segmental, often intention, sometimes massive myoclonic jerks, with dementia being a less constant component. Cerebellar symptoms were reported in the original description of dyssynergia cerebellaris myoclonica, a mixup of forms of progressive myoclonus epilepsy described by Ramsay Hunt in 1921, but they are not always present in progressive myoclonus epilepsy. During the 20th century, many conditions were gradually added to the list of diseases that present as progressive myoclonus epilepsy, and most have been clearly clinically and genetically defined in the last 20 years.

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