Chronic Traumatic Encephalopathy in the Brains of Military Personnel
Priemer DS, Iacono D, Rhodes CH, Olsen CH, Perl DP. N Engl J Med. 2022 Jun 9;386(23):2169-2177. doi: 10.1056/NEJMoa2203199.
Chronic traumatic encephalopathy (CTE) pathology was detected in 4% (10 cases) of 225 military members in a brain bank.
Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease, which can only be diagnosed after death. Many investigators have suggested that a history of previous brain injuries or participating in contact sports relates to developing CTE. Military service members could be at risk of developing CTE due to the repeated head impacts sustained during combat. However, this population remains understudied.
The authors evaluated brain tissue from the Department of Defense Uniformed Services University Brain Tissue Repository to assess the incidence of brain injury, psychiatric disease, substance abuse, and suicidality in service members with or without CTE.
The investigators assessed 225 consecutively donated brains (96% male; ~48 years of age) for signs of CTE. For example, they examined the extent of tau pathology by immunohistochemistry (a method that allows proteins to glow when bonded to an antibody). The authors also retrospectively evaluated clinical and demographic characteristics regarding their history of 1) brain injury, 2) blast exposure, 3) contact sport participation, and 4) neuropsychiatric disorders.
The authors found lesions of CTE in 10 of the 225 cases (4%). Half of the cases had only 1 lesion, 2 had four lesions, and 1 had five lesions. Two of the brains with CTE were 72 and 87 years of age, with pathological changes consistent with Alzheimer’s disease. All 10 CTE cases were among the 60 people (~27%) with a history of participating in a contact sport (5 in football, 5 in combat sport). Additionally, 7 CTE cases occurred among the 44 people with at least one civilian non-sports-related brain injury (e.g., fall, motor vehicle accident, assault). The authors also noted that 3 CTE cases occurred among the 45 people with a history of blast injury.
Overall, 88 (39%) people had reported at least 1 psychiatric disorder. Among these 88 people, 59% had a history of post-traumatic stress disorder, 50% had a history of depression, and 28% suffered from anxiety. Regarding CTE cases, 6 people (60%) had a history of psychiatric disorder: 5 had a history of post-traumatic stress disorder, and 7 had a history of substance abuse. Overall, 49 (22%) people died by suicide, but among those with CTE, 4 had suicidality.
Overall, the authors found CTE in 4% of the brains, with 5 brains having minimal pathology, making it unclear whether these findings were clinically significant. Two of the CTE cases involved brains of elderly individuals with neuropathological changes consistent with Alzheimer’s, making interpretation of these findings challenging. Furthermore, the 4% prevalence of CTE may be higher in this sample than among other military service members because families may have been more likely to donate a brain to the brain bank if they suspected CTE might be prevalent. The small number of CTE cases in the blast injury group also makes it hard to discern whether that type of brain injury could be associated with CTE. Meanwhile, all the CTE cases had a history of contact sports participation, which is consistent with previous reports. However, CTE has been found in non-contact sports populations. Also, psychiatric conditions were frequent among those with evidence of CTE. However, we cannot confirm whether the psychiatric disease developed before or after CTE.
Clinicians can reassure military service members that the authors infrequently detected CTE in this study, which may overestimate how common CTE is in this population. Clinicians should also encourage positive brain health by limiting repetitive head impacts by improving rules and regulations in contact sports and limiting contact during practices.
Questions for Discussion
Do you believe there would be an increased risk of CTE pathology in military members? How do you educate your patients regarding CTE?
- Treatable Conditions Should be Explored in Former Athletes with CTE-Like Symptoms
- CTE Found In People with No History of Contact Sports
- When it Comes to Chronic Traumatic Encephalopathy (CTE): Perhaps Mother Doesn’t Know Best
- Could Playing Contact Sports in High School and College Increase Risk of CTE?
- Disconnect Between Concussion Education and CTE
Written by: Jane McDevitt
Reviewed by: Jeffrey Driban