This information is for people affected by or concerned about juvenile myoclonic epilepsy, including parents and carers. On this page we talk about how juvenile myoclonic epilepsy is diagnosed, what causes it, symptoms, treatment options and long-term outlook.
Use this page as a general guide and speak to a health professional for more information and support.
On this page
What is juvenile myoclonic epilepsy?
Juvenile myoclonic epilepsy is a common epilepsy syndrome that starts in children and young people, usually between the ages of 12 and 18 years. Between one to three people in every 10,000 people are believed to have this type of epilepsy. Juvenile myoclonic epilepsy is also sometimes called Janz syndrome.
Juvenile myoclonic epilepsy is part of a group of similar epilepsy syndromes called ‘idiopathic generalised epilepsies’ – ‘idiopathic’ means the cause is not known and ‘generalised’ means the seizure affects both sides of the brain. Other syndromes in this group include:
- Childhood absence epilepsy
- Juvenile absence epilepsy
- Epilepsy with generalised tonic-clonic seizures alone
All of these types of epilepsy have a strong genetic link. This means that families of people with juvenile myoclonic epilepsy are also likely to have had one of these syndromes.
At least one in 20 people who develop juvenile myoclonic epilepsy will have previously had childhood absence epilepsy.
What causes juvenile myoclonic epilepsy?
It is not completely understood what causes juvenile myoclonic epilepsy. More research is needed to know exactly why it happens in some people. However, genetic changes (mutations) in one of several genes are thought to cause or increase the chances of a person getting this type of epilepsy.
What are the different types of seizures?
People with juvenile myoclonic epilepsy have three types of seizures, these include:
- Myoclonic seizures – quick jerking of the arms or legs
- Tonic-clonic seizures – stiffing of the body, a loss of consciousness and jerking of the arms or legs
- Absence seizures – ‘switching off’ or ‘daydreaming’ (typical) or moving but with ‘floppy’ limbs (atypical)
People with juvenile myoclonic epilepsy are much more likely to have seizures when they do not get enough sleep. Drinking large amounts of alcohol, and being stressed or anxious can also increase the risk of seizures, particularly tonic-clonic seizures.
It is common for people with juvenile myoclonic epilepsy to be photosensitive. This means that flashing or flickering lights can trigger seizures.
How is juvenile myoclonic epilepsy diagnosed?
It’s easy for juvenile myoclonic epilepsy to be missed or mistaken for clumsiness. Usually, people only notice there’s a problem when they experience a tonic-clonic seizure.
If you think either yourself, or a child has epilepsy, including juvenile myoclonic epilepsy, contact a doctor. Children and young people may be referred to a paediatrician (a doctor who specialises in child health). Adults may be referred to a doctor who specialises in diagnosing and treating epilepsy.
Juvenile myoclonic epilepsy is usually diagnosed using a combination of:
- Your medical history and talking about your symptoms.
- An EEG (electroencephalogram) test – a painless test that uses small sensors attached to the scalp to pick up the electrical signals produced by the brain. An EEG test will shows spikes, mainly in the occipital lobe of the brain (the part involved in processing visual information).
- A test for photosensitivity during the EEG (intermittent photic stimulation), which uses flickering or flashing lights.
Treatment for juvenile myoclonic epilepsy
For certain people with juvenile myoclonic epilepsy, their doctor may suggest trying sodium valproate (also known as Epilim) as a first treatment option. People who may be offered sodium valproate include:
- boys and men
- girls aged under 10 years and who are unlikely to need treatment when they are old enough to have children
- women who are unable to have children.
However, sodium valproate is not suitable for everyone. Read more about the process for prescribing sodium valproate below.
If sodium valproate does not work, one of the following treatment options can be tried on its own:
- Lamotrigine (also known as Lamictal) – a medicine that comes as a tablet, that you swallow.
- Levetiracetam (also known as Keppra) – a medicine that comes as a tablet, liquid or granules, that you swallow or mix with water.
If one of these treatments does not work, and the diagnosis of epilepsy remains, then the other treatment may be tried. Lamotrigine can sometimes make myoclonic seizures worse. If this happens, your doctor may try the other treatment instead.
If neither of these treatments work, then the following anti-seizure medications may be tried on their own or as an add-on medication:
- Perampanel (also known as Fycompa) – a medicine that comes as a tablet, that you take by mouth.
- Topiramate (also known as Topamax) – a medicine that comes as a tablet or capsule, that you take by mouth.
Talk to your doctor about switching to a new treatment or adding a new treatment to your current routine. They will explain the reasons for changing treatments, the risks and benefits of each, and any possible treatment side effects.
Sodium valproate
In January 2024, new rules were introduced for prescribing sodium valproate.
Two specialists are now needed to approve:
- New or ongoing valproate treatments for girls and women.
- New valproate treatments for boys and men
The specialists must agree that your epilepsy does not respond to other treatments and the benefits of treatment outweigh the risks.
For girls and women, valproate can seriously harm an unborn baby when taken during pregnancy.
For boys and men, valproate may cause infertility. Some people’s fertility may return when their treatment is stopped or reduced. There is also some evidence that valproate can cause harm in the testicles of animals, but it’s unclear what this means for humans.
Never stop taking valproate before talking to your specialist first. Not taking medication as prescribed can increase the risk of a seizure.
Your epilepsy specialist will let you know when your treatment is due to be reviewed.
If you are planning a pregnancy it is important to speak to your healthcare professional as soon as possible about your treatment options.
If you have any questions or concerns about valproate, please speak to your healthcare professional.
Find out more about sodium valproate in the MHRA’s patient guide.
Find out more about Anti-seizure medications, contraception and pregnancy.
What’s the long-term outlook for people with juvenile myoclonic epilepsy?
For most people with juvenile myoclonic epilepsy, it is a lifelong condition which requires long-term treatment. This is because the chance of relapse is high if medicine is stopped.
However, although juvenile myoclonic epilepsy often continues into adulthood, it usually becomes less severe and can be managed well with the right treatment. For some people, they may be able to stop taking medicine altogether
Living with juvenile myoclonic epilepsy and getting support
Having a child with any form of epilepsy can be challenging and upsetting. Talk to the child’s doctor for help on how to support them well. And talk to your own doctor if you need support for yourself. If you’re caring for someone with juvenile myoclonic epilepsy, it’s important that you look after yourself and get the support you need.
You may find it helpful joining an in-person or online support group, where you can listen to or share experiences with other people who understand what you’re going through.
