Improving pre-surgery assessment
Grant round winners 2010
£90,923 over 36 months
Professor Matthew Walker
Institute of Neurology, University, College, London
In refractory epilepsy (RE), seizures are unresponsive to anti-epileptic drug treatment and this is the case for approximately a third of people with epilepsy. RE is notoriously difficult to treat and surgery to remove the affected part of the brain is often the best hope for seizure control.
Before surgery can proceed, doctors must find out the region of the brain in which the seizures begin (the seizure origin) – i.e. the correct part of the brain to remove. For many, this requires electrodes to be placed onto and into the brain to record the underlying electrical activity (via EEG), and this is an invasive and uncomfortable process. Prolonged recording with these electrodes also carries the risk of infection. Current data show that only half of people who undergo epilepsy surgery achieve seizure freedom, which indicates that current methods to locate the seizure origin are far from perfect.
Two advanced methods of brain investigation have recently been developed; one that detects abnormally fast rhythms of activity in groups of neurons (called high frequency oscillations – HFOs) in invasive EEG recordings; and another that analyses the brain’s response to single pulses of electrical stimulation (SPES), via implanted electrodes beneath the scalp. These techniques usually only require a few hours of recording time (far less than the traditional EEG), but it remains to be seen whether they can help to improve the accuracy with which seizure origins are identified.
Professor Matthew Walker and colleagues from the Institute of Neurology, University, College, London, in collaboration with Kings College Hospital, London, have been awarded £90,923 over 36 months for a project entitled Novel methods for presurgical assessment of epilepsy. In this study, the team will recruit people with different kinds of epilepsy and use first the HFO then the SPES method to locate the seizure origin of each. They will take recordings both before a seizure and at the very beginning of a seizure, to try to work out where it starts. The researchers will be looking to see firstly, if it is possible to record HFOs in this way and secondly, if the results of both techniques identify the same seizure origin.
Magnetoencephalography (MEG) is an entirely different method that can detect HFOs by measuring changes in magnetic field at the scalp surface, due to underlying neuronal activity. A major advantage of MEG is that it is not invasive, and so is a more appealing technique from a patient perspective than invasive EEG. However its accuracy in terms of finding the seizure location is not known. Professor Walker and his group will therefore use MEG to locate the seizure origin of all study participants and compare the results to those found with the other two methods. If they are found to correlate, MEG could potentially be an accurate and non-invasive method for pre-surgery assessment in the future, removing the need for invasive EEGs.
This project will possibly lead to further studies, in which the seizure freedom rate of epilepsy surgery after MEG assessment is assessed. These will hopefully show an improvement on current rates.