Juvenile myoclonic epilepsy (JME)

also known as Janz syndrome

This is a fairly common type of epilepsy which can develop between eight and 26 years of age, but usually starts between the ages of 12 and 16. It usually affects girls more commonly than boys.

Symptoms

There are three different types of seizure which can occur in this sort of epilepsy.

Myoclonic seizures

These cause the person to have sudden jerks of the muscles, either in the arms, legs, face or in the whole body. These seizures usually happen soon after waking up and may happen when getting dressed or having breakfast. They may also happen in the evenings if the person is tired.

Tonic clonic seizures

Two thirds of all people with juvenile myoclonic epilepsy will also have this type of seizure. These usually happen in the morning within one or two hours of waking up. This type of seizure is more likely to happen if the person has been to bed late the night before, or has woken up earlier than usual.

Absence seizures

About one third to one half of children and teenagers will also have absence seizures. These episodes can happen at any time of the day, but they most frequently occur in the morning. The absences last from 10 – 40 seconds.

Photosensitivity (which means that the myoclonic or tonic-clonic seizures are triggered by flickering or flashing light) is common in people with JME. Photosensitivity can usually be seen in the electroencephalogram (EEG) of people with JME.

Diagnosis

A full and accurate history is very important in diagnosing this type of epilepsy. It is important to tell the doctor who is making the diagnosis about any myoclonic or 'jerk' seizures – even if the doctor forgets to ask about this type of seizure.

An EEG test will also be very helpful in making a diagnosis, as this type of epilepsy is associated with some specific EEG patterns. The EEG will usually show whether the person is also photosensitive.

Treatment

Many people with JME respond well to anti-epileptic drugs (AEDs), particularly sodium valproate (Epilim). Sometimes lamotrigine (Lamictal) may be taken. Other drugs including levetiracetam (Keppra) and clonazepam (Rivotril) may also be helpful.

Prognosis (outlook)

Most people (about eight out of every 10 people with JME) need to take AEDs for the rest of their life, as it is common for seizures to return if the medication is withdrawn.

As seizures are more likely to happen if a person does not get enough sleep or drinks too much alcohol, it is advisable for people with this syndrome to maintain regular sleeping habits and think carefully about the amount of alcohol they consume.

Support organisation

Contact a Family, 209-211 City Road, London, EC1V 1JN, telephone 0808 808 3555, http://www.cafamily.org.uk/

Epilepsy Action is indebted to Dr Richard Appleton, a Consultant Paediatric Neurologist who specialises in children’s epilepsy, and to Dr Rachel Kneen, Consultant Paediatric Neurologist and Dr Stewart Macleod, Specialist Registrar in paediatric neurology, at Alder Hey at Alder Hey Children’s Hospital, Liverpool, who have kindly prepared the information on this page.

Because this page is written by an epilepsy healthcare professional and not by Epilepsy Action, it falls outside the requirements of the Information Standard. This is why the Information Standard logo is not shown on this page.