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  • Updated 12.31.2023
  • Released 11.21.2011
  • Expires For CME 12.31.2026

Progressive myoclonus epilepsies



The progressive myoclonus epilepsies are a group of rare genetic disorders clinically characterized by the presence of myoclonic and generalized tonic-clonic seizures, myoclonic jerks, and progressive neurologic deterioration. In this article, the authors give a general overview of the main types of progressive myoclonus epilepsies and the advances in the understanding of their pathophysiology and management.

Key points

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

• Myoclonic jerks may be cortical or subcortical in origin.

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

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

• Newer antiseizure medications like perampanel have been found to be useful in the management of myoclonus.

• Disease modifying treatments like enzyme replacement and gene therapies have shown promise leading to a much better trajectory of the disease course.

Historical note and terminology

Progressive myoclonus epilepsy was first recognized as a clinical entity following original descriptions by Unverricht (74), Lundborg (44), and Lafora (42). Progressive myoclonus epilepsies were classically defined as progressive disorders presenting primarily with the association of epileptic generalized tonic-clonic seizures and multifocal, segmental, 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. However, cerebellar involvement is not always present in all the types of progressive myoclonus epilepsy. During the last century, many conditions were gradually added to the list of diseases that present as progressive myoclonus epilepsy. Most of them have clearly been clinically and genetically defined in the last 20 years.

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ISSN: 2831-9125