Millions of people develop epilepsy each year after a head injury. A new study shows that a blood test can indicate who is at risk – and who is not. This could give doctors a clearer basis for assessing patients after head trauma, says a researcher.
Head injuries are extremely common worldwide.
They can range from a mild concussion to open, life-threatening skull fractures. Some people go on to develop epilepsy – but doctors currently have no reliable way of predicting who will. In addition, the risk rises markedly with the severity of the injury.
Of the 60–70 million people worldwide who suffer a head injury each year, about 2–3% of those with mild injuries develop epilepsy within 30 years versus 15–20% for severe injuries.
A new study now suggests that identifying those at highest risk may be possible – even shortly after the injury. The approach uses a simple blood test and an analysis of a protein already used routinely in accident & emergency departments, meaning that it could, in principle, be implemented without new tests or equipment.
“We know that some people develop epilepsy following a head injury, but we cannot yet predict who will. The findings from this study indicate that a blood test can help us in assessing the risk,” says researchers behind the study, Kasper Lolk, postdoctoral fellow from the Department of Public Health at Aarhus University, Denmark.
The research has been published in Epilepsia.
A blood protein reveals hidden brain injury
The study focused on S100B, a protein present primarily in brain tissue that is released when brain cells are damaged.
After a head injury, the protein can leak into the bloodstream and be detected in a blood test. Accident & emergency departments already use it to rule out brain injury in mild cases – precisely because the level reflects how severely the brain is affected.
Further, it is well known that the risk of epilepsy increases with the severity of the injury – and in the study, S100B levels rose in step.
The researchers therefore investigated whether S100B – currently used to rule out acute brain injury – could also serve as a biomarker for long-term risk.
“The potential is to obtain an early measure of the risk of epilepsy following a head injury to supplement the clinical assessment and, in the longer term, to be able to prevent these patients from developing epilepsy,” says Kasper Lolk.
Danish data link blood marker to later epilepsy
In the study, the researchers linked data from Denmark’s health registers.
They identified more than 10,000 accident & emergency patients between 2013 and 2022 and categorised them according to the severity of their head injuries: no signs of brain injury, concussion and mild traumatic brain injury with visible lesions.
People with severe traumatic brain injuries were not included, nor were those diagnosed with epilepsy before the head injury.
The study found an association between S100B levels at the time of injury and the risk of later epilepsy – with higher levels linked to higher risk – although only among individuals with visible brain damage. Patients with the highest levels had a markedly higher risk than those with low levels.
“The S100B level reflects the severity of the traumatic brain injury, and this is closely linked to the risk of epilepsy. On that basis, it is not unexpected that the findings are limited to patients for whom structural brain damage can be identified,” says Kasper Lolk.
Although the results are promising, they are not yet clear enough for clinical use.
“In the long term, this could become an early marker for identifying who should be closely monitored following a head injury. For now, however, further studies are needed to clarify the link,” says Kasper Lolk.
Signal is strongest among patients already at risk
S100B can also be released into the bloodstream after injuries elsewhere in the body – not just in the brain. A broken arm or a burn, for example, can also raise S100B levels.
Kasper Lolk had therefore expected that detecting a clear signal among people with pre-existing conditions would be more difficult.
In fact, the researchers found the opposite. This led them to look more closely at which conditions are linked to a higher risk of epilepsy when S100B levels are elevated.
They found that people with cerebrovascular disease or alcohol abuse in particular had a higher risk of epilepsy if they also had elevated S100B levels – that is, groups in which the risk of brain injury is already higher.
“This is an interesting finding because people with alcohol abuse have an increased risk of cerebral haemorrhage. It may support the idea that if you have an increased risk of cerebral haemorrhage following a head injury, the S100B level will typically be higher – and the risk of epilepsy correspondingly greater, which points in the same direction as the other results,” says Kasper Lolk.
