It is estimated that around 69 million people worldwide suffer a traumatic brain injury each year. Many of these heal without any reliquary, even in the long term, but a considerable percentage of them can face significant sequelae.
Epidemiological studies estimated that over three million individuals are living with sequelae due to brain trauma in the United States.
Furthermore, it is important to consider that also mild brain injuries can cause significant long-term health effects. Particularly, brain trauma can be associated with persistent functional and neurological deficits, with an increased risk of developing epilepsy.
A new research, published in Occupational & Environmental Medicine, a journal of the British Medical Journal group, evaluated the risk of epilepsy following a first and a second traumatic brain injury.
In this study, a group of researchers from the National Center for Register-Based Research, of the University of Aarhus, in Denmark, analyzed data from more than two million individuals, born between 1977 and 2016, collected in the Danish National Patient Registry.
Patients were classified into three groups based on the diagnosis of head injury: mild traumatic brain injury, severe traumatic brain injury, or skull fracture. The median age of the subjects at the end of the follow-up was 18.8 years.
To estimate the cumulative incidence of epilepsy in the population without traumatic brain injury, ten control subjects were compared for each subject with traumatic brain injury, matched by year of birth, sex, and date of brain trauma.
During the observation period, more than 160.000 subjects suffered brain trauma. 12.7% of them suffered a second brain injury in a median of 2.5 years.
During the follow-up, 37,200 individuals developed episodes of epilepsy. Compared to control subjects, without traumatic brain injury, the relative risk of developing epilepsy increased by approximately double after the first traumatic injury and more than fourfold after a second traumatic brain injury.
The risk was found to increase with the severity of the first and second traumatic injuries, particularly after severe traumatic brain injury. Females were more likely than males to develop epilepsy after a mild traumatic brain injury, while males were more likely than females to develop epilepsy after a severe traumatic brain injury.
The greatest risk was found after two severe traumas, with an increase of more than 16 times compared to the control group (HR 16,24).
Of particular interest is the fact that the increased risk of epilepsy remained substantial for decades after traumatic brain injury. In particular, the 20-year cumulative risk of developing epilepsy was 2.22% after a mild traumatic brain injury, 2.32% after a skull fracture and 5.63% after a severe traumatic brain injury, compared to 1.27% recorded in the control subjects.
This study has the advantage of providing precise information on the risk of developing epilepsy in subjects after brain trauma. The findings suggest that repeated, mild or severe, trauma increases the risk of developing epilepsy. With some gender peculiarities, this risk appears to remain high for decades.
The results obtained in this research may have been partially undermined by the fact that some subjects with mild brain trauma may escape observation by the doctor, and by a possible delay in diagnosis, from the occurrence of the first attack to the diagnosis of epilepsy. However, the large cohort studied, and the long follow-up, make it a solid study.
The authors conclude that further research will be needed, to elucidate the underlying mechanisms and identify potential interventions that can prevent the development of post-traumatic epilepsy.
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