On Sunday, the largest-ever neuroimaging study of epilepsy patients showed that the disorder involves more widespread corporal differences than researchers previously assumed. Types of epilepsy, which are usually considered to be more benign if seizures are under control, were also included in the study. The abnormalities discovered in the brain were subtle and have not yet been linked to any loss of function.
The study’s lead author, Professor Sanjay Sisodiya of the UCL Institute of Neurology & Epilepsy Society, said “We found differences in brain matter even in common epilepsies that are often considered to be comparatively benign. While we haven’t yet assessed the impact of these differences, our findings suggest there’s more to epilepsy than we realize, and now we need to do more research to understand the causes of these differences.”
Reduced grey matter thickness found in patients
The neurological disorder affects 0.6–1.5 percent of the global population. It is comprised of many different syndromes and health conditions and is primarily defined by the tendency for seizures. The study, conducted by the global ENIGMA-Epilepsy consortium, pooled data from 24 research centers across Europe, America, Asia, and Australia. Structural brain measurements were taken from MRI scans of 2,149 people with the disorder and compared with 1,727 healthy controls. The study group of epilepsy patients was analyzed together to observe common patterns and then divided into four subgroups to identify differences.
The main difference found was reduced grey matter thickness in the brain’s cortex, or outer layer, and reduced volume in subcortical regions in all groups when compared to the control group. The longer a patient had the disorder, the more volume reduction and thickness was present.
According to study author Dr. Christopher Whelan, “Some of the differences we found were so subtle they could only be detected due to the large sample size that provided us with very robust, detailed data.”
They also found differences between the subgroups, which may suggest underlying biological differences as suggested by recent genetic studies.
“We have identified a common neuroanatomical signature of epilepsy, across multiple epilepsy types. We found that structural changes are present in multiple brain regions, which informs our understanding of epilepsy as a network disorder,” Dr. Whelan added.
According to the authors, longitudinal and genetic study follow-ups need to be conducted to clarify the cause of these structural differences.
“From our study, we cannot tell whether the structural brain differences are caused by seizures, or perhaps an initial insult to the brain, or other consequences of seizures—nor do we know how this might progress over time,” said Professor Sisodiya. “But by identifying these patterns, we are developing a neuroanatomical map showing which brain measures are key for further studies that could improve our understanding and treatment of the epilepsies.”
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