What do you know about epilepsy? Genetic epilepsies and progressive myoclonic epilepsies

Dr. Beatriz González Giráldez is, since 2010, attending physician at the Epilepsy Unit of the Hospital Universitario Fundación Jiménez Díaz. She has published several articles and chapters in national and international books, mainly on progressive myoclonic epilepsies and genetic epilepsies.

Causes of genetic epilepsies

It is now known that some types of epilepsy are due to a genetic disorder, and that this can occur even in patients with no previous family history of epilepsy.

Diagnosis of genetic epilepsies

Diagnosis is based on the physician’s clinical suspicion that a genetic cause underlies a particular type of epilepsy, and then on the confirmation of this cause through the application of specific studies or tests. A negative (or normal) result does not exclude a genetic disorder if the test performed is not appropriate for detecting the specific type of disorder that a given patient presents.

In turn, a positive finding does not imply that this is the definitive cause of the epilepsy suffered by the patient. The physician interpreting the test must be familiar with the various forms of genetic epilepsy in order to put the result in an appropriate clinical context and for it to acquire relevant meaning. Genetic diagnosis is therefore useful to confirm the diagnosis, but also to avoid the need for additional tests, to provide genetic counseling to prevent the development of epilepsy in offspring and in some cases to select the best possible treatment.

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What is video-EEG monitoring?

Video-electroencephalographic monitoring (video-EEG) is the simultaneous and continuous recording of brain activity and clinical behavior of patients over a prolonged period of time. It is performed in a video-EEG monitoring unit.

It is one of the most useful tests in the diagnosis and management of patients with epileptic seizures, from neonates to the elderly:

  • Prolonged duration and sleep recording increase the possibility of detecting paroxysmal brain abnormalities (epileptiform or not) since conventional EEG is often normal in patients with epilepsy.
  • Prolonged recording offers the possibility of recording the clinical episodes suffered by the patient, being able to establish whether or not they are epileptic seizures, and if they are, to determine in which area of the brain they originate and whether the patient could be a candidate for surgical treatment.

Types of video-EEG monitoring

1) Short video-EEG monitoring (1 day)

  • It is useful for quantification of epileptiform activity and recording of episodes in patients with very frequent seizures and/or who may be provoked during monitoring.
  • Changes in medication are not usually performed.

2) Prolonged monitoring (2 or more days)

  • The objective is to record the episodes suffered by the patient in order to establish a diagnosis of epilepsy or of non-epileptic paroxysmal events, for example syncope, paroxysmal sleep disorders or episodes of psychological origin.
  • The duration generally depends on clinical-medical criteria and it may be necessary to reduce or even withdraw the medication under the strict supervision of health personnel.

What are progressive myoclonic epilepsies?

Progressive myoclonic epilepsies (PME) are a heterogeneous group of rare diseases usually with onset in childhood or adolescence and characterized by the association of myoclonus, epilepsy and some degree of progressive neurological deterioration (motor and/or cognitive). The most frequent and therefore best recognized forms are Unverricht-Lundborg disease, Lafora disease, myoclonic epilepsy with torn red fibers, neuronal ceroid lipofuscinosis and type I sialidosis. The prognosis of these diseases is equally variable, depending on the particular entity, but in general they carry a high degree of disability as a consequence of seizures and/or associated neurological impairment.

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Causes of progressive myoclonic epilepsy

They are genetic diseases (currently more than 30 genes related to these diseases are known). In many of them the genetic alteration conditions an enzymatic deficit and/or accumulation of deposit material. Most of them are inherited in an autosomal recessive manner (the parents are healthy but each one carries a genetic alteration which, when coinciding in the patient, causes the disease).

Diagnosis of progressive myoclonic epilepsy

Accurate diagnosis of each clinical entity is challenging and relies primarily on clinical aspects (age of onset, association of signs and symptoms, clinical course, and inheritance pattern). Neurophysiological studies such as electroencephalogram and evoked potentials can be helpful, but ultimately it is molecular diagnostic techniques (special biochemical tests and genetic testing) that now make it possible to reach a specific diagnosis in many patients presenting with progressive myoclonic epilepsy.

Treatment of progressive myoclonic epilepsy

Treatment of PME is often difficult and usually focuses on pharmacological treatment of symptoms such as myoclonus, seizures, or intercurrent complications. In addition there are antiepileptic drugs that should be avoided because they may worsen these symptoms. Although for most MPD there is no specific treatment, in some specific entity there is the possibility of enzyme replacement and in others the possibility of a specific genetic treatment in the immediate future is encouraging. Once the diagnosis is confirmed it is equally important to perform genetic counseling with the parents because of the risk of recurrence of the disease in future offspring.