The appearance of a certain set of molecules in the blood can predict an epileptic seizure, according to new research by scientists based at the Royal College of Surgeons in Ireland (RCSI).
There are about 40,000 people with epilepsy in Ireland, and one third of those do not respond to current treatments which means they must live in the knowledge that a seizure could strike at any time.
The scientists are hopeful that their research will lead to the development of a simple, easy-to-use, affordable test, similar to the blood glucose test for diabetics, that people with epilepsy could use themselves.
“This could be something that could give people an understanding of whether they were likely to have a seizure, or whether it was completely unlikely,” said Prof David Henhsall, director of the FutureNeuro research centre at the RCSI.
The current methods used to diagnose and try to predict seizures include EEG and MRI scanning. However, Prof Henshall said these are cumbersome and expensive, often do not provide a result, and in the case of EEG scans, require an implant to be inserted into the brain.
He said these issues led the RCSI researchers to see if a simpler, more effective test for epilepsy and seizures could be found by measuring molecules in the blood.
“We found this new type of molecule, this RNA, which has never been linked to epilepsy before.”
The blood samples for the RCSI study were taken from 32 people with drug-resistant epilepsy, a group that experiences unpredictable seizures, with some people listed as candidates for brain surgery.
It is known that seizures are more likely to occur when a person with epilepsy is under stress
The patients in the study were attending specialist epilepsy monitoring centres at Beaumont Hospital in Dublin and a similar facility in Marburg, Germany. They had blood samples taken at regular intervals during their stay.
The scientists found that a particular type of RNA – which is a chemical cousin of DNA – was “spiking” in the blood samples just before a seizure.
“The levels of these molecules were highest in the samples we took just before the patients took a seizure,” said Prof Henshall.
It is known that seizures are more likely to occur when a person with epilepsy is under stress. The researchers believe that when a brain cell is under stress it begins to cut RNA into small fragments, called tRNA.
In the run up to a seizure, the increasing presence of the tRNA fragments indicates that brain cells are under increasing stress, and a seizure is imminent, Prof Henshall said.
Dr Marion Hogg, honorary lecturer in the department of physiology and medical physics at RCSI, was the lead investigator in the study now published in the Journal of Clinical Investigation. She had been investigating the role of tRNA fragments in motor neurone disease before turning her attention to study epilepsy.
“We have been investigating these fragments in ALS, or motor neurone disease, but these are different from the ones you find in epilepsy so we are not suggesting there is a link,” said Dr Hogg.
The scientific goal now is to develop a device that can measure the RNA molecules present in even a tiny drop of blood, and accurately predict the likelihood of a seizure over a given timeframe, explained Prof Henshall. He said the test they hope to develop would provide people with some certainty about when they were likely to have a seizure and allow them to plan their lives accordingly.