Juvenile myoclonic epilepsy (JME): symptoms, diagnosis and treatment

Juvenile myoclonic epilepsy is one of the genetic generalised epilepsies. Epilepsy Action describes it as a common epilepsy syndrome that usually begins in teenagers or young adults, with sudden muscle jerks as the main seizure type. It is also known as Janz syndrome. It belongs to a group that includes childhood absence epilepsy, juvenile absence epilepsy and epilepsy with generalised tonic-clonic seizures alone, with some overlap between them.

People who develop JME do not usually have any related health or development problems. Around 1 in 20 have a history of febrile seizures, and about one third have a family member with epilepsy. There is no link with problems before or during birth.

Epilepsy Action explains that there are three kinds of seizure in JME. Myoclonic seizures are sudden jerks of the muscles of the arms, legs or whole body, severe enough to make you drop things such as cups and plates or to fall over. Tonic-clonic seizures cause stiffening, loss of consciousness and then rhythmic jerks, and often follow a series or cluster of myoclonic jerks. People who have them usually have only about 1 or 2 a year. Absence seizures are when you switch off or stop responding, and are often the first type of seizure, sometimes months or years before the others.

Myoclonic jerks tend to happen soon after waking or later in the day when you are tired. Because they can be mistaken for clumsiness or a normal part of waking up, they are easily missed, and people often seek help only after a tonic-clonic seizure.

• Jerks of the arms or whole body, especially in the first hour after waking.

• Dropping or throwing things at breakfast or while brushing teeth.

• Brief blank spells that can be mistaken for daydreaming.

• A tonic-clonic seizure, often after a run of jerks, particularly after a late night or too little sleep.

• Seizures triggered by flickering lights in a minority.

Epilepsy Action says people with JME are much more likely to have seizures when they do not get enough sleep, that heavy alcohol use and being stressed or anxious can increase the risk, particularly of tonic-clonic seizures, and that over one third are photosensitive. It is uncommon for most people to be affected by flashing lights in their normal environment, but this is more likely if the person is tired.

The NHS also advises people with epilepsy to keep a diary to help identify triggers such as tiredness, stress, periods, flashing lights, food or drink.

Children and teenagers should see a paediatrician after a seizure, and adults should see an epilepsy specialist. Epilepsy Action says the specialist will want to know exactly what happens during a seizure and will often be able to recognise JME from your symptoms, asking about sudden jerks or jumps after waking.

An EEG (electroencephalogram), which records the brain's electrical activity, can help confirm the diagnosis. It is more likely to show abnormal activity after poor sleep or on waking, so a sleep-deprived EEG may be suggested, and photosensitivity may be tested with flickering lights, which can occasionally trigger a seizure. Epilepsy Action says other tests, such as brain scans or blood tests, are not usually needed to diagnose JME.

Most people with JME have seizures fully controlled with epilepsy medicines. Epilepsy Action says sodium valproate is often offered first as the most effective medicine for JME, usually controlling all three seizure types, but that it should not be taken if there is any possibility of getting pregnant because it can harm an unborn baby. Alternatives include levetiracetam, lamotrigine, clobazam, topiramate and zonisamide, sometimes in combination. The NHS says some types of epilepsy medicine can harm a baby if taken in pregnancy and that anyone who could get pregnant should discuss treatment with a specialist.

Because JME is usually lifelong, lifestyle matters. Epilepsy Action advises not drinking alcohol heavily and getting enough sleep. Regular bed and wake times, limiting late nights, taking tablets at the same time every day and not missing doses are the most useful habits. The NHS adds practical safety advice such as carrying medical ID, having showers rather than baths where possible and thinking about safety with activities like cooking, swimming or sport.

The NHS notes that when you can start driving again depends on the type of seizure and when it last happened, and that the DVLA's rules about epilepsy and driving apply. Epilepsy Action also says JME can sometimes be associated with difficulties in thinking, decision-making and behaviour, and that your doctor can advise on support.

The NHS says to call 999 if you think someone is having a seizure and it is the first time it has happened, it lasts longer than is usual for them or longer than 5 minutes if you do not know how long their seizures usually last, they do not recover as usual afterwards or have another seizure without recovering, or they have had 3 or more seizures in 24 hours. People with epilepsy do not always need to go to hospital after a seizure, and they usually have a care plan.

Epilepsy Action says some people with JME find their seizures get better as they get older, becoming less intense and less frequent, and a few may be able to stop medicines later in life. Most will need to take medicine for the rest of their lives, and it is common for seizures to return if medicine is stopped, so do not stop or change medicine without specialist advice.

Planning pregnancy needs an early conversation with a specialist, because medicine choice is important, and adult services can provide pre-conception counselling.

On the NHS the route is from the GP or emergency department to a paediatrician or epilepsy specialist, with EEG and long-term review in an epilepsy clinic or by an epilepsy specialist nurse. The NHS suggests checking whether you can get free prescriptions.

A private neurologist can offer a quicker appointment, an EEG or a second opinion on treatment. Given that JME is often lifelong, many people combine private opinions with ongoing NHS monitoring.