Repeated traumatic brain injury and risk of epilepsy: a Danish nationwide cohort study

Incidence and Prevalence of Concussion in Denmark from 1999-2018: A Nationwide Cohort Study

Concussion is a common diagnosis in emergency rooms, yet contemporary incidence and prevalence estimates are sparse and rely on self-reported data. A nationwide cohort study was conducted to provide up-to-date information, covering the entire Danish population from 1999 to 2018. Hospital contacts with a concussion diagnosis, including emergency room visits, hospital admissions, and outpatient contacts, were retrieved from the Danish National Patient Registry (DNPR), and incidence rates were age-standardized and stratified. The 20-year prevalence was defined as the percentage of Danes alive in 2018 who had experienced a concussion since 1999. The diagnostic codes used were the ICD-10 code S06.0 and a local Danish code for 'observation for concussion' (DZ033D). Additional data on activities related to concussion injuries were obtained from the Accident Analysis Group at Odense University Hospital through DNPR. Findings from the study indicated that during the period 1999-2018, the total age-standardized concussion incidence rate increased by 10% to 308 per 100,000 person-years (95% confidence interval (CI): 304-313). Notable time trends included 1) a reduced sex difference from 40% to 6% (95% CI: 3%-9%), 2) a doubled incidence rate in children aged 0-1 and in seniors aged over 80, 3) an increased utilization of head imaging across all age groups, except children, 4) a decline in the proportion of traffic-related concussions, and 5) a prevalence of concussion of 4.9% (95% CI: 4.89% - 4.93%) in 2018. The increasing incidence of concussions among the elderly is concerning in light of an aging population, and warrants further investigation, as evidence-based preventive interventions for falls exist. Additionally, the increased utilization of head imaging across all age groups except children calls for attention toward avoidance of unnecessary radiation exposure. Despite a drop in traffic-related cases, concussions remain highly prevalent. In conclusion, these findings indicate that concussions are an important public health concern, necessitating ongoing surveillance, research, and targeted resource allocation to address concussion management and prevention effectively.

Do high-risk head trauma sports athletes have impaired vestibular function?

PURPOSE

The primary aim of this study was to examine the vestibular function of athletes involved in high-risk head trauma sports by means of complete vHIT testing of all six semicircular canals (SCCs). The secondary objective was to investigate whether the vestibular function is significantly reduced among athletes within certain high-risk sports.

METHODS

A prospective cross-sectional study of 137 adult athletes in football, handball, boxing, horseback riding, and ice hockey with a minimum of one reported sports-related head injury within the past five years. All subjects underwent screening with a complete examination of all six SCCs with vHIT and fulfillment of the dizziness handicap inventory (DHI).

RESULTS

Two subjects (1.5 %) fulfilled the criteria of having a pathological vHIT. Some degree of impairment of the vestibular function was seen when data was divided into individual sports and time since the last head injury. Likewise, no subjective dizziness was seen in the group of athletes when evaluated by total DHI scores. This score did not differ significantly between groups when subgrouped into number of head injuries or time since the last head injury. When divided into type of sport, total DHI scores differed significantly between groups. These total DHI-scores did, however, all fall within the range of the "no dizziness handicap" classification.

CONCLUSION

The results suggest that the vestibular function of athletes in high-risk head trauma sports is unaffected by the practice of a high-risk head trauma sport. Therefore, vHIT has no clinical utility in the assessment of a sports-related concussion (SRC) in athletes with no subjective feeling of dizziness.

Molecular Genetics of Acquired Temporal Lobe Epilepsy

An epilepsy diagnosis reduces a patient's quality of life tremendously, and it is a fate shared by over 50 million people worldwide. Temporal lobe epilepsy (TLE) is largely considered a nongenetic or acquired form of epilepsy that develops in consequence of neuronal trauma by injury, malformations, inflammation, or a prolonged (febrile) seizure. Although extensive research has been conducted to understand the process of epileptogenesis, a therapeutic approach to stop its manifestation or to reliably cure the disease has yet to be developed. In this review, we briefly summarize the current literature predominately based on data from excitotoxic rodent models on the cellular events proposed to drive epileptogenesis and thoroughly discuss the major molecular pathways involved, with a focus on neurogenesis-related processes and transcription factors. Furthermore, recent investigations emphasized the role of the genetic background for the acquisition of epilepsy, including variants of neurodevelopmental genes. Mutations in associated transcription factors may have the potential to innately increase the vulnerability of the hippocampus to develop epilepsy following an injury-an emerging perspective on the epileptogenic process in acquired forms of epilepsy.

Risk of epilepsy after traumatic brain injury: a nationwide Norwegian matched cohort study

Background

Post-traumatic epilepsy (PTE) is a well-known complication of traumatic brain injury (TBI). Although several risk factors have been identified, prediction of PTE is difficult. Changing demographics and advances in TBI treatment may affect the risk of PTE. Our aim was to provide an up-to-date estimate of the incidence of PTE by linking multiple nationwide registers.

Methods

Patients with TBI admitted to hospital 2015-2018 were identified in the Norwegian Trauma Registry and matched to trauma-free controls on sex and birth year according to a matched cohort design. They were followed up for epilepsy in nationwide registers 2015-2020. Cumulative incidence of epilepsy in TBI patients and controls was estimated taking competing risks into account. Analyses stratified by the Abbreviated Injury Scale (AIS) severity score, Glasgow Coma Scale score and age were conducted for the TBI group. Occurrence of PTE in different injury types was visualized using UpSet plots.

Results

In total, 8,660 patients and 84,024 controls were included in the study. Of the patients, 3,029 (35%) had moderate to severe TBI. The cumulative incidence of epilepsy in the TBI group was 3.1% (95% Confidence Interval [CI] 2.8-3.5%) after 2 years and 4.0% (3.6-4.5%) after 5 years. Corresponding cumulative incidences in the control group were 0.2% (95% CI 0.2-0.3%) and 0.5% (0.5-0.6%). The highest incidence was observed in patients with severe TBI according to AIS (11.8% [95% CI 9.7-14.4%] after 2 years and 13.2% [10.8-16.0%] after 5 years) and in patients >40 years of age.

Conclusion

Patients with TBI have significantly higher risk of developing epilepsy compared to population controls. However, PTE incidence following moderate-severe TBI was notably lower than what has been reported in several previously published studies.

Insights into epileptogenesis from post-traumatic epilepsy

Post-traumatic epilepsy (PTE) accounts for 5% of all epilepsies. The incidence of PTE after traumatic brain injury (TBI) depends on the severity of injury, approaching one in three in groups with the most severe injuries. The repeated seizures that characterize PTE impair neurological recovery and increase the risk of poor outcomes after TBI. Given this high risk of recurrent seizures and the relatively short latency period for their development after injury, PTE serves as a model disease to understand human epileptogenesis and trial novel anti-epileptogenic therapies. Epileptogenesis is the process whereby previously normal brain tissue becomes prone to recurrent abnormal electrical activity, ultimately resulting in seizures. In this Review, we describe the clinical course of PTE and highlight promising research into epileptogenesis and treatment using animal models of PTE. Clinical, imaging, EEG and fluid biomarkers are being developed to aid the identification of patients at high risk of PTE who might benefit from anti-epileptogenic therapies. Studies in preclinical models of PTE have identified tractable pathways and novel therapeutic strategies that can potentially prevent epilepsy, which remain to be validated in humans. In addition to improving outcomes after TBI, advances in PTE research are likely to provide therapeutic insights that are relevant to all epilepsies.

Posttraumatic Epilepsy and Dementia Risk

Importance

Although both head injury and epilepsy are associated with long-term dementia risk, posttraumatic epilepsy (PTE) has only been evaluated in association with short-term cognitive outcomes.

Objective

To investigate associations of PTE with dementia risk.

Design, Setting, and Participants

The Atherosclerosis Risk in Communities (ARIC) study initially enrolled participants from 1987 to 1989 and this prospective cohort study uses data through December 31, 2019, with a median follow-up of 25 years. Data were analyzed between March 14, 2023, and January 2, 2024. The study took place in 4 US communities in Minnesota, Maryland, North Carolina, and Mississippi. Of 15 792 ARIC study participants initially enrolled, 2061 were ineligible and 1173 were excluded for missing data, resulting in 12 558 included participants.

Exposures

Head injury was defined by self-report and International Classification of Diseases (ICD) diagnostic codes. Seizure/epilepsy was defined using ICD codes. PTE was defined as a diagnosis of seizure/epilepsy occurring more than 7 days after head injury. Head injury, seizure/epilepsy, and PTE were analyzed as time-varying exposures.

Main Outcomes and Measures

Dementia was defined using cognitive assessments, informant interviews, and ICD and death certificate codes. Adjusted Cox and Fine and Gray proportional hazards models were used to estimate dementia risk.

Results

Participants had a mean (SD) age of 54.3 (5.8) years at baseline, 57.7% were female, 28.2% were of self-reported Black race, 14.4% were ultimately categorized as having head injury, 5.1% as having seizure/epilepsy, and 1.2% as having PTE. Over a median follow-up of 25 (25th to 75th percentile, 17-30) years, 19.9% developed dementia. In fully adjusted models, compared with no head injury and no seizure/epilepsy, PTE was associated with 4.56 (95% CI, 4.49-5.95) times the risk of dementia, while seizure/epilepsy was associated with 2.61 (95% CI, 2.21-3.07) times the risk and head injury with 1.63 (95% CI, 1.47-1.80) times the risk. The risk of dementia associated with PTE was significantly higher than the risk associated with head injury alone and with nontraumatic seizure/epilepsy alone. Results were slightly attenuated in models accounting for the competing risks of mortality and stroke, but patterns of association remained similar. In secondary analyses, the increased dementia risk associated with PTE occurring after first vs second head injury and after mild vs moderate/severe injury was similar.

Conclusions and Relevance

In this community-based cohort, there was an increased risk of dementia associated with PTE that was significantly higher than the risk associated with head injury or seizure/epilepsy alone. These findings provide evidence that PTE is associated with long-term outcomes and supports both the prevention of head injuries via public health measures and further research into the underlying mechanisms and the risk factors for the development of PTE, so that efforts can also be focused on the prevention of PTE after a head injury.

Hippocampal interneuronal dysfunction and hyperexcitability in a porcine model of concussion

Cognitive impairment is a common symptom following mild traumatic brain injury (mTBI or concussion) and can persist for years in some individuals. Hippocampal slice preparations following closed-head, rotational acceleration injury in swine have previously demonstrated reduced axonal function and hippocampal circuitry disruption. However, electrophysiological changes in hippocampal neurons and their subtypes in a large animal mTBI model have not been examined. Using in vivo electrophysiology techniques, we examined laminar oscillatory field potentials and single unit activity in the hippocampal network 7 days post-injury in anesthetized minipigs. Concussion altered the electrophysiological properties of pyramidal cells and interneurons differently in area CA1. While the firing rate, spike width and amplitude of CA1 interneurons were significantly decreased post-mTBI, these parameters were unchanged in CA1 pyramidal neurons. In addition, CA1 pyramidal neurons in TBI animals were less entrained to hippocampal gamma (40-80 Hz) oscillations. Stimulation of the Schaffer collaterals also revealed hyperexcitability across the CA1 lamina post-mTBI. Computational simulations suggest that reported changes in interneuronal physiology may be due to alterations in voltage-gated sodium channels. These data demonstrate that a single concussion can lead to significant neuronal and circuit level changes in the hippocampus, which may contribute to cognitive dysfunction following mTBI.

Traumatic brain injury, stroke, and epilepsy: A mediation study in a Danish nationwide cohort

OBJECTIVE

Traumatic brain injury (TBI) and stroke are well-known causes of acquired epilepsy. TBI is also a risk factor for stroke, and injury-induced stroke may indirectly convey a proportion of the epilepsy risk following TBI. We studied the extent to which the effect of TBI on epilepsy operated through intermediary stroke.

METHODS

We analyzed a nationwide, matched, register-based cohort of adults ≥ 40 years of age whose first TBI at Danish hospitals was recorded between 2004 and 2016. A matched reference population was sampled for comparison. During follow-up, we recorded all acute strokes. Cox proportional hazard models and the difference method were used to estimate the total and controlled direct effect hazard ratios (HRs) of TBI on epilepsy and the indirect effect HRs of TBI on epilepsy operating through stroke, and to calculate the proportion eliminated. Analyses were stratified by severity of, age at, and time since TBI.

RESULTS

We followed 57 900 persons with TBI (48.6% males) from median age 61 years (interquartile range = 51-75), and 561 977 age- and sex-matched references. The total effect of TBI on epilepsy was higher for persons aged 40-59 years (HR = 5.15, 95% confidence interval [CI] = 4.65-5.72) than for persons aged ≥ 60 years (HR = 4.55, 95% CI = 4.19-4.95). In contrast, the indirect effect of TBI mediated by stroke was lower for persons aged 40-59 years (HR = 1.02, 95% CI = 1.02-1.03) than for persons aged ≥ 60 years (HR = 1.05, 95% CI = 1.04-1.06). We estimated 2.3% and 5.6% of the risk of epilepsy after TBI to operate through stroke for these age groups, respectively.

SIGNIFICANCE

Less than 6% of the risk of epilepsy following TBI operated through intermediary stroke. However, this mechanism seems to play an increasing role with age and for late onset epilepsies. This warrants further investigation.

Perinatal adversities and risk of epilepsy after traumatic brain injury: A Danish nationwide cohort study

Objectives

Traumatic brain injury (TBI) and perinatal adversities such as low gestational age at birth, low birth weight, low Apgar, and being born small for gestational age are well‐established risk factors for epilepsy. We examined whether perinatal adversities modified the risk of epilepsy after TBI in a nationwide cohort study of Danish singletons born from 1982 to 2011.

Materials and Methods

We categorized perinatal adversities as a composite measure of preterm delivery, low birth weight, low Apgar score, or being born small for gestational age. Cox regression and competing risk regression were used to estimate the risk of epilepsy after TBI according to such perinatal adversities. The study included 1,715,095 singletons (51.1% males). The mean age at end of follow‐up was 19.3 years (Interquartile range [IQR] = 12.1–26.3). During follow‐up, 85,636 persons (58.2% males) sustained a TBI and 18,064 developed epilepsy (50.7% males), of whom 1329 persons had a preceding TBI.

Results

The hazard ratio (HR) of epilepsy in persons with perinatal adversities was 1.19 (95% confidence interval [CI] 1.15–1.24), compared to persons without. The HR of epilepsy in persons with TBI was 2.31 (95% CI 2.18–2.45) compared to persons without TBI, but this risk was not modified by perinatal adversities (p = 0.2460).

Conclusions

Perinatal adversities and TBI both increased the risk of epilepsy, but the risk of epilepsy after TBI was not modified by these perinatal adversities.

[Features of the patient management with traumatic brain injury]

The aim of our study was to consider features of pathogenesis, diagnosis and therapy of traumatic brain injury (TBI) from the viewpoint of neurologist. The mechanisms of emerging injury of the central nervous system, including neuro-inflammation and oxidative stress in patients with TBI, and correlations between clinical manifestations and severity of TBI are discussed. Special attention is paid to the description of certain TBI consequences, e.g. structural drug-resistant epilepsy and post-traumatic stress disorder. We provide evidence for difficulties and lesser availability of rehabilitation programs to patients with TBI during COVID-19 pandemics. One should mention a need for administration of Mexidol as the antioxidant/antihypoxant drug into complex therapy of TBI in such patients. In the period of COVID-19 pandemics, the role of neurologist in management of TBI patients still increases, especially, at the outpatient treatment stage, and when carrying out therapy and medical rehabilitation programs.

Risky Business: Traumatic Brain Injury and Epilepsy

Repeated Traumatic Brain Injury and Risk of Epilepsy: A Danish Nationwide Cohort Study Lolk K, Dreier JW, Christensen J. Brain . 2021;awaa448. doi:10.1093/brain/awaa448 Traumatic brain injury is associated with increased risk of epilepsy, but the importance of repeated traumatic brain injuries has not yet been established. We performed a nationwide population-based cohort study of 2 476 905 individuals born in Denmark between 1977 and 2016. We estimated hazard ratios (HRs) and the cumulative incidence of epilepsy following traumatic brain injury using Cox and competing risk regression, respectively. To estimate the cumulative incidence of epilepsy in the population without traumatic brain injury, we matched 10 controls for each subject with traumatic brain injury on year of birth, sex, and date of brain insult in the index person. In the cohort, traumatic brain injury was sustained by 167 051 subjects (71 162 females and 95 889 males), and 37 200 individuals developed epilepsy (17 905 females and 19 295 males). Compared with subjects without traumatic brain injury, the relative risk of epilepsy increased after a first traumatic brain injury (HR: 2.04, 95% confidence interval (CI): 1.96-2.13) and even more after a second traumatic brain injury (HR: 4.45, 95% CI: 4.09-4.84). The risk increased with the severity of the first and the second traumatic brain injury, most notably after severe traumatic brain injuries. Females were more likely than males to develop epilepsy after mild traumatic brain injury (HR: 2.13, 95% CI: 2.00-2.28 vs HR: 1.77, 95% CI: 1.66-1.88; P < .0001); in contrast, males were more likely than females to develop epilepsy after severe traumatic brain injury (HR: 5.00, 95% CI: 4.31-5.80 vs HR: 3.21, 95% CI: 2.56-4.03; P = .0012). The risk remained increased for decades after the traumatic brain injury. This knowledge may inform efforts to prevent the development of post-traumatic epilepsy.