Encephalopathy is a general term that means brain disease. Epileptic encephalopathies are a group of epilepsy syndromes in which seizures are associated with developmental delay or intellectual disability. In these conditions, the seizures are often frequent and difficult to control with medication. In some epileptic encephalopathies, there is a progressive decline in function.
Developmental and epileptic encephalopathy (DEE) refers to a group of severe epilepsy syndromes characterized by frequent seizures, often drug-resistant, and significant developmental delay or regression. These usually start in infancy or childhood. Common examples include infantile epileptic spasms syndrome and Lennox-Gastaut syndrome. Some of the others are discussed below.
Early infantile developmental and epileptic encephalopathy (EIDEE)
EIDEE begins when a baby is less than three months old. Affected infants can have different types of seizures, including tonic seizures, myoclonic seizures, spasms, focal seizures or sequential seizures. The EEG is very abnormal and may show a burst suppression pattern.
Causes include genetic abnormalities, brain malformations, acquired structural brain abnormalities and inherited metabolic disorders.
EIDEE has a poor prognosis. Children with this syndrome have severe psychomotor delays; they are unable to learn new psychomotor skills (skills that involve controlled movement) and may not make eye contact with others. Their seizures continue and are very difficult to control. Children with this syndrome may later develop infantile spasms, Lennox-Gastaut syndrome or drug-resistant focal epilepsy.
Progressive myoclonus epilepsies
The progressive myoclonus epilepsies (PMEs) are rare; no more than 1 per cent of people with epilepsy have one of these syndromes. The three characteristic symptoms are:
- myoclonic jerks
- progressive neurological deterioration with dementia, cerebellar ataxia (lack of muscle coordination due to disease of the cerebellum), neuropathy (nerve disease) and myopathy (muscle disease)
- epilepsy with generalized tonic-clonic seizures and possibly other seizure types as well
They are usually caused by autosomal recessive mutations. Examples of progressive myoclonus epilepsies are:
- Lafora’s disease
- myoclonus epilepsy with ragged red fibres (MERRF)
- neuronal ceroid lipofuscinoses
- type I sialidosis
- type 3 Gaucher’s disease
- Unverricht-Lundborg disease
The age of onset and the disease course of the different progressive myoclonus epilepsies vary. Some cause rapid degeneration and death. Others, such as Unverricht-Lundborg disease, progress more slowly, and with proper treatment, the person can live for a normal lifespan.
These syndromes are diagnosed with a thorough personal and family history and laboratory tests, which may include molecular genetic testing and muscle biopsies.
There is no cure at present for the progressive myoclonus epilepsies; people with these syndromes will be prescribed anti-epileptic drugs to control the seizures and myoclonic jerks.
Genetic counselling is possible for family members of people with most progressive myoclonus epilepsies because they have a clear inheritance pattern.
