Juvenile myoclonic epilepsy (JME)

Other names for juvenile myoclonic epilepsy (JME)

• Janz syndrome

Who gets juvenile myoclonic epilepsy (JME)?

JME is one of the most common epilepsy syndromes that starts in children and young people. Around 1 in 10 people with epilepsy have this syndrome. It usually starts between the ages of 12 and 18, although it can sometimes begin at a younger or older age than this. It’s slightly more common in girls than in boys.

People who develop JME don’t usually have any related health or development problems, although around 1 in 20 have a history of febrile seizures. There isn’t any link with problems during or before birth. About one third of children who develop JME may have a family member who has epilepsy.

JME is part of a group of related epilepsy syndromes called ‘idiopathic generalised epilepsies (IGE)’ or ‘genetic generalised epilepsies (GGE)’, which all have a strong genetic link. The other syndromes in this group include:

• Childhood absence epilepsy (CAE)
• Juvenile absence epilepsy (JAE)
• Epilepsy with generalised tonic-clonic seizures alone (GTCA)

There is some overlap between these syndromes. At least 1 in 20 people who develop JME have previously had CAE.

Symptoms of Juvenile myoclonic epilepsy

There are 3 different types of seizures that people with JME may get. These are called myoclonic, tonic-clonic and absence seizures.

All people with JME have myoclonic seizures. Myoclonic seizures cause sudden jerks of the muscles in the arms, legs, or whole body. The jerks can be severe enough to make you drop things – like cups and plates – or to fall over.

About 9 in 10 people with JME also have tonic-clonic seizures. These cause you to stiffen (the tonic part), fall unconscious and then immediately have a number of rhythmic jerks (the clonic part). Tonic-clonic seizures often come on following a series or cluster of myoclonic seizures. If you do get tonic-clonic seizures, you’ll usually only have about 1 or 2 a year. Although sometimes, you may get a cluster of a few of these seizures over a few weeks.

About one third of people with JME also have absence seizures. These are when you ‘switch off’ or stop responding. They’re often the first type of seizure people with JME get, sometimes months or years before myoclonic and tonic-clonic seizures start. For this reason, many children are diagnosed with JAE first.

People with JME are much more likely to have seizures when they don’t get enough sleep. Seizures often happen soon after waking up, or later in the day if you’re tired. Drinking large amounts of alcohol, and being stressed or anxious can also increase the risk of seizures, particularly tonic-clonic seizures.

Over one third of people with JME are photosensitive. This means that the myoclonic or tonic-clonic seizures are triggered by flickering or flashing lights. This is also more likely to happen if the person is tired or has had less sleep. It is uncommon for most people to be affected by this in their normal day-to-day environment.

Diagnosis of Juvenile myoclonic epilepsy

Often, people with JME only notice a problem and seek a diagnosis when they have had a tonic-clonic seizure. Myoclonic seizures can be easily missed and mistaken for clumsiness, or a normal part of waking up.

Children and teenagers should see a specialist doctor called a paediatrician for an assessment after having a seizure. As an adult, you’ll see a specialist in diagnosing and treating epilepsy. The specialist will want to know exactly what happens when you or your child have a seizure.

The specialist will often be able to recognise JME by talking to you about your symptoms. They will ask you if you have any sudden jerks or jumps after you have woken up. A test called an EEG (electroencephalogram) can help confirm a diagnosis. An EEG looks at electrical activity in the brain. In someone with JME, the EEG will usually show abnormal activity. This is more often seen when the person has not had much sleep, or as they’re waking up. Because of this, the doctor may suggest doing a sleep-deprived EEG test .

Your doctor may also test for photosensitivity during the EEG, with flickering or flashing lights. This technique is called ‘intermittent photic stimulation’. It’s possible that this may trigger a seizure in some people.

You don’t usually need other tests, such as brain scans or blood tests to diagnose JME.

Treatment of Juvenile myoclonic epilepsy

Most people with JME have their seizures fully controlled with epilepsy medicines.

Sodium valproate is often offered first, as this is the most effective medicine for JME. It usually controls all three types of seizure that happen in JME. But you shouldn’t have this medicine if there is any possibility that you could get pregnant. This is because, if it is taken during pregnancy, sodium valproate can harm an unborn baby. Because of this, your specialist may prescribe a different medicine if there is any possibility of pregnancy. If they do recommend treatment with sodium valproate, they will discuss the risks and benefits first.

If you are taking sodium valproate and are able to get pregnant, your doctor should review your treatment every year and make sure that you’re taking effective contraception.

Other medicines your doctor may prescribe include:

• levetiracetam
• lamotrigine
• clobazam
• topiramate
• zonisamide

Sometimes your doctor may prescribe a combination of 2 of these medicines.

Information about treatments for children can be found on the Medicines for Children website.

Outlook for Juvenile myoclonic epilepsy

Some people with JME find their seizures get better as they get older, becoming less intense and happening less often. A few people may be able to stop taking medicines later in life. But most people with JME will need to take epilepsy medicines for the rest of their lives. If the medicine is stopped, it’s common for seizures to return.

As JME is usually something that you’ll have for life, your doctor will give you advice about lifestyle changes you can make to reduce the risk of seizures. This includes not drinking alcohol heavily, and making sure you get enough sleep.

JME can sometimes be associated with difficulties in thinking, decision-making and behaviour. Your doctor can advise on support available in these areas if needed.

Support

Contact – for families with disabled children

Freephone helpline: 0808 808 3555
Email: helpline@contact.org.uk