Even Mild TBI Significantly Increases Epilepsy Risk in Children and Young Adults

Caroline Cassels

December 05, 2007

December 5, 2007 (Philadelphia) -- A large population-based study shows even mild head injury in children and young adults significantly increases epilepsy risk up to 10 years following the initial accident and possibly beyond.

Presented here at the American Epilepsy Society 61st Annual Meeting, the study showed a 2-fold increased epilepsy risk 10 years after sustaining a mild brain injury.

"Although the risk gradually levels off over time, we see from this study there is still a 5-fold increased epilepsy risk associated with severe injury and a doubling of the risk with mild injury and skull fracture as late as 10 years out," study investigator Jakob Christensen, MD, PhD, from Aarhus University Hospital, in Denmark, told Medscape Neurology & Neurosurgery.

With more than 82,000 subjects, the study is the largest to date to examine the link between traumatic brain injury (TBI) and subsequent epilepsy risk and confirms findings of earlier research published in 1998 by Annegers and colleagues looking at this risk in 4541 children and adults (Annegers JF et al. N Engl J Med 1998;338:20-24).

"This earlier study showed there was a very high increased incidence of epilepsy in the immediate period, shortly after traumatic brain injury, but that it was still increased more than 10 years later. We wanted to replicate these findings in a much larger and somewhat different population," said Dr. Christensen.

Six-Month Postinjury Peak

Using data from used the Danish Civil Registration System, the investigators identified all persons born in Denmark between 1977 and 2002. In addition, they used data from the Danish National Hospital Register to identify patients registered with TBI and epilepsy.

TBI was categorized according to clinical severity as mild (brain concussion), cranial fractures, or severe (structural brain injury). Of 1,605,216 persons born in Denmark between 1977 and 2002, 73,326 individuals sustained mild brain injury, 5099 had skull fracture, and 3850 had severe TBI.

A total of 1031 individuals developed epilepsy following brain injury. Of these, 837 had mild brain injury, 116 had structural brain injury, and 78 had skull fractures.

"There are a much larger number of cases of epilepsy following mild brain injury, but this is simply due to the fact that there are so many more cases of mild injury than severe TBI," said Dr. Christensen.

Overall, individuals who sustained severe brain injury had almost a 7.5-fold increased relative risk of developing subsequent epilepsy. However, this risk was increased more than 20-fold in the first 6 months following severe TBI, with a 5- and 2-fold increased relative risk at 6 months for mild brain injury and skull fracture, respectively.

Need for Careful Screening

Additional study findings demonstrated a correlation between age and brain injury, so that the older an individual is, the more likely he or she is to develop epilepsy.

The study also found epilepsy risk correlated with the duration of hospitalization, so that the longer TBI patients were hospitalized for their injury, the more likely it was that they would develop the condition.

Furthermore, because of the large data set, investigators were also able to look at the impact of repeated head injury. Patients with mild TBI who injured their head more than once had a doubling of epilepsy risk.

In addition, individuals who had a family history of epilepsy were at greater risk for epilepsy following TBI compared with their counterparts without a family history of epilepsy.

The study's results, he added, indicate a need for clinicians to carefully screen patients for a history of TBI. This is particularly important in individuals who may not present with generalized seizures but who display some of the more "subtle" signs of epilepsy that may include symptoms such as brief moments of unresponsiveness, jerking of the extremities, and/or cognitive impairment.

Patients with a positive history need to be appropriately followed up with imaging and other tests to rule out epilepsy.

"There is a significant increase in epilepsy risk in the immediate period following any type of brain injury, but it is important to understand that the risk can continue up to 10 years later and maybe even beyond this time period," he said.

The study was funded by the Research Initiative of Aarhus University Hospital, the Stanley Research Institute, and the Danish Medical Research Council.

American Epilepsy Society 61st Annual Meeting: Abstract 1.210 Presented December 1, 2007.


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