The key gene, Atp1a3, regulates levels of chemicals such as sodium and potassium in brain cells.

It has long been suspected that an imbalance of these chemicals may cause some cases of epilepsy.

The University of Leeds study, which appears in Proceedings of the National Academy of Sciences, raises hopes of new treatments for the condition.

Lead researcher Dr Steve Clapcote said: “An imbalance of sodium and potassium levels has long been suspected to lead to epileptic seizures, but our study is the first to show beyond any doubt that a defect in this gene is responsible.”

Much work is needed to determine whether the same mechanism is in play in humans.

But the human ATP1a3 gene is more than 99% the same as the mouse version.

Epilepsy is a common neurological condition that affects almost one in every 200 people.

However, the causes are unknown in the majority of cases.

Current drug treatments are ineffective in around one third of epilepsy patients.

The Leeds team worked on Myshkin mice, which have a tendency to develop seizures.

They showed that those animals who did develop seizures carried a specific defective version of Atp1a3.

These mice responded when treated with the common anti-epileptic medication valproic acid – proving that they did indeed have a form of epilepsy.

To try to counter this, the researchers bred the epileptic mice with animals that carried an extra copy of the normal Atp1a3 gene.

The addition of the normal gene counteracted the faulty gene in the resulting offspring – which were completely free from epilepsy.

Scan showing epilepsy activity in a mouse brain

Very promising

Dr Clapcote said: “Our study has identified a new way in which epilepsy can be caused and prevented in mice, and therefore it may provide clues to potential causes, therapies and preventive measures in human epilepsy.”

“Our results are very promising, but there’s a long way to go before this research could yield new antiepileptic therapies.”

Dr Clapcote said his team had started to screen DNA samples from epilepsy patients to investigate whether Atp13a gene defects were involved in the human condition.

Delphine van der Pauw, of the charity Epilepsy Research UK, said: “These results are promising.

“If the findings can be repeated in human studies, new avenues for the prevention and treatment of inherited epilepsy will be opened.”

Simon Wigglesworth, of Epilepsy Action, stressed the research was at an early stage – but agreed that it was encouraging.

He said: “At the moment there is no treatment to cure epilepsy, other than surgery, which is only effective for small numbers.”

One in 133 people in the UK has epilepsy, and at any one time 300,000 have an active form of the condition.

What causes epilepsy?

An epileptic seizure is caused by over-activity of the brain cells, which produces a surge of electricity.

This may be due to a variety of factors, such as brain damage from birth injuries, head injury, stroke, brain tumours and alcoholism.

There is some evidence to suggest the condition sometimes has a genetic basis – although it is rare for it to run in families.

In many instances, the cause of the condition is a mystery.

Epilepsy is caused by surges of electrical activity

Are there different types of seizure?

Yes. Essentially, there are two types.

A partial seizure begins in one specific part of the brain, and may spread to other areas.

A generalised seizure can start in both sides of the brain at once.

Partial seizures:

• Simple partial seizure – Confined to one particular area of the brain. The person retains consciousness, but may be fearful, and experience a strong sense of deja vu. Symptoms include jerking of an arm and an unpleasant taste in the mouth.
• Complex partial seizure – The electrical disturbance spreads, disrupting consciousness. The person may interact with the surroundings, but be unaware of what they are doing and have no recollection of the event.Symptoms may include repeatedly chewing, swallowing or scratching. Afterwards the person is likely to be confused for some minutes.

Generalised seizures:

• Tonic clonic seizure – This leads to ‘grand mal’ convulsions in which the person loses consciousness, falls to the ground, becomes stiff and shakes.In some instances a tonic clonic seizure may occur after an initial partial seizure – in which case the person may have some warning of what is about to occur.
• Absence attack – A blank spell lasting a matter of seconds from which recovery is almost immediate.
• Myoclonic seizures – Jerks caused by a sudden contraction of the muscles. Can affect the whole body usually restricted to one or both arms and sometimes the head.
• Tonic seizures – All the muscles contract. The body stiffens and the person will fall over if unsupported.
• Atonic seizures – All muscle tone is lost and the person simply drops to the ground.

How is epilepsy treated?

There are a wide range of anti-epileptic drugs to prevent seizures.

Which drug is prescribed will depend on the individual patient, and their particular form of epilepsy.

The drugs are effective, but can have side effects, including drowsiness and dizziness.

Some drugs may produce longer term side effects, such as acne and weight gain.

Anti-epileptic drugs should not be taken in tandem with some other medications. They may also slightly increase the risk of malformations if taken during pregnancy.

Is surgery an option?

Yes, for people who do not respond to drug treatment.

The most common form of surgical treatment is to remove the hippocampus – a part of the brain involved in memory which is particularly vulnerable to damage.

Other forms of surgery which may be considered include:

• Temporal lobectomy – a larger part of the temporal lobe is removed.
• Sub-pial resection – fine cuts are made in the motor areas of the brain.
• Hemispherectomy – the removal of the whole of one side of the brain
• Corpus callosotomy – cutting the fibres that connect the two halves of the brain.

An alternative to neurosurgery is a treatment called vagal nerve stimulation in which a pacemaker device is placed under the skin to stimulate the vagus nerve in the neck.

This form of treatment does not usually cure the epilepsy, but can reduce seizure frequency and severity.