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21 August 2015

Map of blood oxygen in brain could help predict epilepsy surgery outcomes

Researchers at Epilepsy Society 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 of researchers led by Professor Louis Lemieux (right), are hopeful that by mapping blood oxygen levels in key areas of the brain, they may be able to better predict those surgery candidates who are most likely to achieve long-term seizure freedom post surgery and those who are less likely to do well.

Epilepsy surgery

Epilepsy surgery is often considered as a treatment option for people with drug-resistant temporal lobe epilepsy. However surgery is only ever offered as an option where the epileptic zone can be accurately identified and where surgery would not damage other functions of the brain such as memory, language, vision and movement.

Detailed investigations to assess the risks and benefits of surgery are carried out by teams of epilepsy specialists using the most sophisticated diagnostic techniques. But in spite of this, almost 50 per cent of patients will not achieve seizure freedom five years after surgery.

Now researchers have shown how using simultaneous EEG (electroencephalography) and fMRI (functional magnetic resonance imaging), they can map changes in blood oxygen levels associated with epileptic activity. This can provide important information about where the epileptic zone lies.

Continuing seizures

The researchers looked retrospectively 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 Louis Lemieux explained: 'Our results demonstrate that changes in blood oxygen concentration  within or in the immediate vicinity of the surgical target is strongly related to a good surgical outcome in people with temporal lobe epilepsy.

'This is important information in helping potential surgery candidates and their neurologists and neurosurgeons decide whether epilepsy surgery is the best option for them.'

This research was first published in the Journal of Neurology, Neurosurgery and Psychiatry.

Find out more about epilepsy surgery.