This is a common epilepsy syndrome that begins between the ages of 6 and 26 years. However, it usually starts between the ages of 12 and 16. It is slightly more common in girls than in boys.
It is a type of epilepsy called a ‘genetic generalised epilepsy’, which is the same as an ‘idiopathic generalised epilepsy’.
Other names for juvenile myoclonic epilepsy (JME)
• Janz syndrome
All people with JME will have myoclonic seizures. That is why the epilepsy syndrome is called juvenile myoclonic epilepsy.
Myoclonic seizures cause sudden jerks of the muscles, either in the arms, legs, face or the whole body. These seizures usually happen soon after waking up and sometimes when getting dressed or having breakfast. They may also happen in the evening or when the person is tired. The jerks may cause the person to drop things such as cutlery, cups and plates.
About two thirds of people with JME also have tonic-clonic seizures. They usually happen in the morning, within an hour or two of waking up. These are more likely to happen if the person with JME has been to bed late the night before or has woken up earlier than usual, or if both have happened.
About one third to one half of children and young people with JME also have absence seizures. These can happen at any time of the day, but are most likely in the morning. The absences are very similar to the absences that occur in juvenile absence epilepsy.
Photosensitivity affects between 4 and 5 out of every 10 people with JME. This means that the myoclonic or tonic-clonic seizures are triggered by flickering or flashing light at certain frequencies. This is tested for by doing a flickering or flashing light test during an electroencephalogram (EEG), called ‘intermittent photic stimulation’. Photosensitivity will usually show up on the EEG if the person has JME. Very occasionally, a person with JME who is photosensitive and has not started any treatment with an epilepsy medicine will have one or two short myoclonic seizures during intermittent photic stimulation. Very rarely, a person may have a tonic-clonic seizure during intermittent photic stimulation. Specific advice will be given if your child is photosensitive.
It is important that the doctor making a diagnosis has a full account and description of what happens during the seizures. This is particularly important if the person with JME has myoclonic or ‘jerk’ seizures, which can be easily missed. It is quite common for someone who has jerks soon after waking up or at breakfast time to think these are part of waking up so does not mention them. The doctor who is taking the account from the person should always ask if the young person or teenager has jerks or jumps in the morning and if they drop things at this time.
The EEG is usually abnormal, and shows abnormal activity or discharges that come from both sides of the brain at the same time. These are called generalised spike and wave or polyspike and slow wave discharges. This activity is more often seen when the person is drowsy or falls asleep as the EEG is being done. The EEG will show evidence of photosensitivity in between 4 and 5 out of every 10 people with JME.
The seizures in JME are usually fully controlled with epilepsy medicines, particularly sodium valproate (Epilim). However, doctors should not prescribe sodium valproate to girls unless other medicines are unsuitable. This is because, if taken during pregnancy, sodium valproate can harm the unborn baby. If sodium valproate is prescribed to a girl under the age of puberty, she and her parents should be told to contact her doctor as soon as she starts her periods to have her treatment reviewed. Girls who have started their periods and are taking sodium valproate will need to use effective contraception. They will also need to sign a form each year to show that they understand the risks of getting pregnant.
Lamotrigine may also be helpful. However, this medicine is not as good as sodium valproate at stopping the absence or myoclonic seizures. Other medicines, including levetiracetam (Keppra), clobazam, topiramate (Topamax) and zonisamide (Zonegran), may also be helpful. Sometimes a combination of 2 of these medicines may be required.
There may be research studies open that are relevant to this epilepsy syndrome. Your child’s doctor will be able to discuss this with you.
Information about treatments for children can be found on the Medicines for Children website.
Between 7 and 8 out of every 10 people with JME will need to take epilepsy medicines for the rest of their lives. If the medicine is stopped, it is common for seizures to return.
A number of people with JME will show some attention and learning difficulties, usually during the middle and late teenage years. These are usually only mild in degree. They seem to occur as part of the syndrome and are not always associated with poor seizure control.
Living with juvenile myoclonic epilepsy
What is a syndrome?
A syndrome is a group of signs and symptoms that, added together, suggest a particular medical condition. In epilepsy, examples of these signs and symptoms would be things like the age at which seizures begin, the type of seizures, whether the child is male or female and whether they have physical or learning disabilities, or both. The results of an electroencephalogram (EEG) are also used to help identify epilepsy syndromes.
If you would like to know more about an epilepsy syndrome, please speak to your doctor. If you would like to know more about epilepsy in general, please contact the Epilepsy Action Helpline.
Epilepsy Action would like to thank Dr Richard Appleton, consultant paediatric neurologist and honorary professor in paediatric neurology at Alder Hey Children’s Hospital, Liverpool, UK for preparing this information.