Juvenile myoclonic epilepsy (JME) is the most common of the generalized epilepsy syndromes to emerge in mid-to-late childhood. It is characterized by the presence of absence (formerly called petit mal) seizures, myoclonic seizures and generalized tonic-clonic (formerly called grand mal) seizures. Typically, the first seizure type to present are absence seizures - these start anywhere between the ages of 5 and 16 years of age. Myoclonic jerks are seen about 1 to 9 years later, with an average age of 14 or 15 years. Generalized tonic-clonic seizures appear a few months later after that, although they can appear earlier. Both males and females are affected equally.
What does juvenile myoclonic epilepsy look like?
- The hallmark characteristics of juvenile myoclonic epilepsy are the presence of myoclonic jerks that occur on awakening from sleep either in the morning or from a nap. They are typically described as shock-like, irregular and arrhythmic movements of both arms. Sometimes these movements are restricted only to the fingers making the patient or individual look clumsy or prone to dropping things.
- In almost 20% of individuals, these myoclonic jerks occur primarily on one side as opposed to both sides of the body.
- Some types of myoclonus are normal and do not imply epilepsy. The most common of these is so-called hypnic jerks, which most of us have just as we are falling asleep.
- Generalized tonic-clonic seizures are reported in nearly all patients and absence seizures are seen in 1 out of 3 people with JME. A small percentage of patients may never develop a generalized tonic-clonic seizure.
- When the patient develops myoclonic jerks, they typically occur in clusters and may be the warning sign prior to the generalized tonic-clonic seizure.
- The most concerning aspect of juvenile myoclonic epilepsy is the presence of a condition known as myoclonic status epilepticus. This occurs primarily when an individual awakens and has multiple myoclonic seizures that do not readily stop. It is precipitated by sleep deprivation or missing medications.
- All seizures, especially the myoclonic jerks, occur within 30 minutes to an hour of awakening. Myoclonic jerks rarely occur at any other time unless the individual is quite tired.
What can trigger seizures in persons with JME?
One of the most interesting aspects of juvenile myoclonic epilepsy is the fact that there are two very common seizure-precipitating factors - sleep deprivation and stress. Sleep deprivation and fatigue, primarily after excessive alcohol intake, are the most powerful precipitants of myoclonic jerks and generalized tonic-clonic seizures in JME. Other common precipitating factors include mental stress, emotion, and in particular excitement or frustration. Some people with JME experience seizures that are triggered by flickering light, such as strobe lights at dances, TV, video games, or light shining through trees or reflecting off ocean waves or snow. These are called photosensitive seizures. Occasionally, myoclonic seizures are also provoked by factors such as decision-making or calculations.
Is JME inherited?
Juvenile myoclonic epilepsy is a genetically determined syndrome. About 50-60% of families with juvenile myoclonic seizures report seizures in either a direct relative or a cousin. The inheritance is of a complex type, although there are certain subtypes that have distinct genetic patterns associated with it.
How is JME diagnosed?
The EEG is the most important test in making a diagnosis of juvenile myoclonic epilepsy. The EEG in untreated individuals is typically abnormal with what is known as a 3-6 Hz generalized polyspike and wave discharge. An example of this condition is reflected in the figure below.
MRIs are typically normal. 30% of patients may show a photoparoxysmal response or an abnormal EEG in response to flickering lights. It is important when someone has a question of juvenile myoclonic epilepsy that if a normal EEG is obtained, that an EEG capturing sleep and wakefulness is performed in order to make certain that the diagnosis has been accurately assessed.
How is JME treated?
- The treatment of juvenile myoclonic epilepsy starts with advice regarding lifestyle and avoidance of precipitating factors. It is essential that one avoids drinking alcohol.
- Avoiding sleep deprivation is essential too. People with JME should make sure they get adequate rest and appropriate outlets for emotions and stress in order to lessen the potential for seizures.
- Valproic acid is the most effective anti-epileptic drug in the treatment of juvenile myoclonic epilepsy; however, it is not the appropriate first choice to treat women of childbearing years.
- Levetiracetam is another possible drug choice; however, it has not been well studied for all of the seizure types that occur within this syndrome. Levetiracetam is approved for use in the treatment of myoclonic seizures in juvenile myoclonic epilepsy.
- Lamotrigine is widely used for juvenile myoclonic epilepsy. However, it may lead to worsening of the myoclonic jerks even though it may be helpful for the generalized convulsions and absence seizures.
- Clonazepam given in small doses could be effective for myoclonic jerk. Phenobarbital is another option. Lastly, topiramate and zonisamide can be helpful, particularly in women of childbearing years.
- Medications that should be avoided include: vigabatrin, tiagabine, gabapentin, pregabalin, phenytoin, oxcarbazepine, and carbamazepine. Carbamazepine, in particular, is not effective for myoclonic jerks and may actually worsen myoclonic and absence seizures. Yet, carbamazepine and phenytoin may be useful for generalized convulsions.
What is the outlook for persons with JME?
- It appears that seizures in people with JME tend to improve after the fourth decade of life.
- Seizures are generally well controlled with medications in up to 90% of patients.
- People who have multiple seizure types may require more medications in order to control them.
- It is likely that lifelong treatment with a seizure drug is usually necessary, even in people with well-controlled JME. Withdrawal could result in a relapse of seizures, even in patients who have been seizure free for many years with appropriate drugs.
- In some individuals with mild forms of the condition, the dose of seizure medication may be reduced slowly over months, particularly in older aged individuals. If myoclonic seizures come back or persist, medications need to be restarted.