Almost half of epilepsy patients who have surgery find that it stops their seizures completely for at least 10 years, scientists said on Friday, suggesting an effective alternative to costly and difficult drug treatment.

In the first long-term study of post-surgery epilepsy patients, British researchers found that 82 percent of them were seizure-free after one year, 52 percent had no seizures after five years, and 47 had still had none after 10 years.

“If the seizures aren’t controlled with medication, that’s where surgery should be considered,” said John Duncan of the National Hospital for Neurosurgery at University College London, who led the study. “In those people, surgery has a good chance of stopping the seizures.”

Epilepsy is a brain disorder that affects around 50 million people worldwide, including many millions of young children and teenagers. It can cause recurring seizures, in which brain cells send out faulty signals, causing sometimes violent muscle spasms and loss of consciousness.

It can be focal epilepsy, where a specific part of the brain is affected, or generalized epilepsy, where the regions of the brain involved are much more spread out.

There is no cure for epilepsy, but medications can help prevent seizures in some patients. Common drugs include divalproex sodium, the generic version of Abbott Laboratories anti-seizure drug Depakote, and Trileptal sold by Swiss drugmaker Novartis AG.

According to the World Health Organization, recent studies in both developed and developing countries have shown that up to 70 percent of newly diagnosed children and adults with epilepsy can be successfully treated with anti-epileptic drugs.

After between two and five years of successful treatment, drugs can be withdrawn in about 70 percent of children and 60 percent of adults without relapses.

Around half of epilepsy cases are focal, and in Britain, where Duncan’s study was carried out surgery is generally only available for these patients - usually only when two or three types of medication have already failed.

The study, published in The Lancet medical journal, followed 615 patients for up to 19 years after their surgery.

The average duration of epilepsy before surgery was 20 years. Duncan and other experts said that in the light of their findings, it was important to improve pre-surgical assessments so that suitable patients could be offered surgery sooner.

Asked about the relative costs of the two approaches, Duncan said in a telephone interview that in Britain, such surgery has a one-off cost of around 13,000 pounds ($20,000). Drug therapy, in contrast, costs approximately 1,000 pounds ($1,500) a year plus ongoing costs of healthcare.

In a commentary on Duncan’s findings, Ahmed-Ramadan Sadek and William Peter Gray of the Wessex Neurological Center and Britain’s Southampton University said doctors should change current practice to refer patients who might benefit from surgery earlier.

“This study validates the long-term effectiveness of epilepsy surgery,” they wrote. “Clinical practice needs to change with the early referral of appropriate patients.”

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By Simon Roach and Kate Kelland