A type of brain surgery conducted in childhood for medication-resistant epilepsy not only reduces chronic seizures but can protect memory development, a study by a team from Great Ormond Street Hospital and its research partner the UCL Institute of Child Health has found.

Epilepsy surgery is associated with a risk of memory damage, so the findings, published in Brain, represent an important breakthrough.

Around 30% of children with epilepsy have medication-resistant seizures. Surgery to remove brain tissue which causes seizures can be an effective alternative epilepsy treatment, but there have been concerns that removing important tissue could damage a child's memory. This is particularly relevant where surgery is carried out on one of the temporal lobes, which are known to be important for supporting memory. In adults temporal lobe surgery has been shown to lead to memory loss. However, the GOSH and ICH team's research, the first to examine children's memory development in the long-term, suggests that a child's brain responds differently to the surgery.

The research team looked at 42 patients who had temporal lobe surgery in childhood and were re-examined as young adults, on average nine years after the procedure. Seizures had completely stopped in 86% and more than half were no longer taking epilepsy medication. They were compared against 11 patients with epilepsy who did not have surgery. Those who had the surgery demonstrated significantly improved recollection of events and factual information.

The research also shed light on how memory function adapts in children with epilepsy. Verbal memory noticeably improved after right temporal lobe surgery, and visual memory improved after left temporal lobe operations. This suggests that uncontrolled seizures obstruct memory development, and that function in the healthy temporal lobe may be restored and improved after surgery.

The best memory outcomes were seen in children with the least brain tissue removed. Aiming to eliminate seizures as effectively as possible, surgeons have historically removed brain tissue surrounding the affected area causing epileptic fits. The research at GOSH and ICH suggests that less extensive surgery can effectively stop seizures, and that to give children the best possible memory outcome, it is important to leave as much unaffected brain tissue as possible in place.

The findings follow a previous study showing that these children also experience long-term improvements in measures of intelligence (IQ).

Torsten Baldeweg, Professor of Cognitive Neuroscience at the UCL Institute of Child Health and lead author of the study, said: "Prior to this research we had little understanding of what kind of impact the surgery has on long-term memory outcome when the procedure takes place in childhood. Our findings show that surgery can make an important difference, but also that careful identification of the area of the temporal lobe to be operated on is vitally important.

"In the future, better pre-operative diagnostics through improved imaging will hold the key to reducing seizures and maximising memory outcome for children who have this surgery."