Epilepsy Syndromes Juvenile Myoclonic

According to researchers at Toronto’s Hospital for Sick Children, juvenile myoclonic epilepsy is the most common idiopathic generalized epilepsy syndrome, and may account for up to 10 percent of all epilepsy cases. (“Generalized” means the seizure affects the entire brain, and “idiopathic” means the cause of the seizures is unknown).

Juvenile myoclonic seizures typically begin between 12 and 18 years of age. During myoclonic seizures, the arms, shoulders and sometimes also the legs will jerk suddenly. The individual may think that these muscle jerks are normal and won’t recognize them as seizures.

What Causes Juvenile Myoclonic Epilepsy?

Genetic inheritance seems to be an important causal factor in myoclonic seizures. Researchers have discovered that one-third to one-half of children with the disorder have a family history of epilepsy. As with all other epilepsy syndromes, inheritance is very complex, and the disorder has been linked to different genes in different individuals. In some cases, juvenile myoclonic epilepsy has also been associated with a prior history of febrile seizures and/or childhood absence epilepsy.

A number of factors may trigger myoclonic seizures. The most common of these include:

  • Alcohol use
  • Fatigue
  • Hunger
  • Illegal drug use
  • Intense emotion
  • Menstruation
  • Mentally challenging activities (i.e. decision-making, writing, math)
  • Photosensitivity (this is very common)
  • Stress.

Most teens with juvenile myoclonic epilepsy don’t have any neurological or developmental problems. The myoclonic seizures may, however, have a negative effect on learning capacity, reasoning and social development.

What Do Juvenile Myoclonic Seizures Look Like?

The defining characteristics of a myoclonic seizure are quick, jerky movements of the arms, shoulders and legs on one or both sides of the body. Sometimes the movements aren’t even perceptible, but will feel like an electrical current running through the body.

Myoclonic seizures typically occur first thing in the morning, and are often mistaken for sleepiness or clumsiness. Sometimes the disorder won’t even be diagnosed until the child experiences a generalized tonic-clonic seizure. These convulsive seizures tend to begin a few years after the onset of juvenile myoclonic epilepsy. It’s not uncommon for a myoclonic seizure to be followed up by a tonic-clonic seizure. Teens may also experience absence seizures, although these are not as common as convulsive seizures.

What’s the Prognosis for Juvenile Myoclonic Epilepsy?

Because there are so many risk factors that can trigger seizures, it may be necessary for individuals with juvenile myoclonic epilepsy to alter their lifestyles. This can be especially hard on teenagers who may feel as if their treatment regime is inhibiting their social life.

Myoclonic seizures usually respond extremely well to antiepileptic medication, but most individuals have to continue taking medication for their entire lives. Even if an individual has been seizure-free for many years, the likelihood that his seizures will begin again if he stops taking medication is extremely high.


Donner, E. J et al. (2006). Juvenile myoclonic epilepsy. Retrieved March 23, 2010, from http://www.aboutkidshealth.ca/Epilepsy/Juvenile-Myoclonic-Epilepsy.aspx?articleID=6985