Changes in blood oxygen levels in the brain key to epilepsy surgery success

Researchers are moving a step closer to gaining a better understanding of why some people remain seizure free five years after brain surgery, while others don’t.

The team from the Epilepsy Society, led by Professor Louis Lemieux, hope that by mapping blood oxygen levels in key areas of the brain, they will be able to better predict those who are most likely to achieve long-term seizure freedom and those less likely to do well post-surgery.

Epilepsy surgery is used to treat people with drug-resistant temporal lobe epilepsy, but only where the epileptic zone can be accurately identified and where surgery would not damage other functions of the brain.

Now researchers have shown how using simultaneous EEG and fMRI (functional magnetic resonance imaging), they can map changes in blood oxygen levels associated with epileptic activity.

The researchers looked at a group of 30 patients at centres in London, Switzerland and Brazil. They were able to show that where surgery had been performed in areas of the brain that showed changes in the ratio of oxygenated and deoxygenated blood levels, 81 per cent of patients became seizure free. Where no change in the ratio was recorded, 78 per cent of cases continued to experience seizures.

Professor Lemieux said: “This is important information in helping potential surgery candidates and their neurologists and neurosurgeons decide whether epilepsy surgery is the best option for them.”

Meanwhile, a new study carried out by the University of Toronto, aimed to shed light on the impact of epilepsy surgery on children’s behaviour – an area in which previous research findings have been mixed.

Children with epilepsy are known to have elevated rates of behaviour problems, but while some studies have shown improvements in behaviour three to 18 months after surgery, others have demonstrated no change within this time interval.

For this study, behaviour was assessed using parent reports in 147 children who underwent epilepsy surgery and 40 children who did not.

According to results published in the medical journal Epilepsia, behavioural changes were not related to surgical status or seizure outcome.

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