A recent research article by Dr. Bennet Omalu in the journal Neurosurgical Focus highlights a probable connection between blast-related brain injuries common in Iraq and Afghanistan deployments, and a brain disease usually associated with certain sports like boxing, American football, and hockey. This connection was first reported in the New York Times by Nicholas Kristof.
The brain disease in question is chronic traumatic encephalopathy, or CTE, a degenerative brain condition that can result in memory loss, confusion, impulse & anger control problems, and other progressive dementia symptoms. One of the main causes of CTE in professional athletes is a history multiple concussions over a playing career. Chicago Bears safety Dave Duerson showed many signs of CTE in the months leading up to his death in 2011 – CTE typically strikes years after players have received multiple concussions.
Why CTE in Soldiers and Veterans?
The Neurosurgical Focus article brings up an interesting question as to why CTE symptoms and signs are also showing up in US military service members who were exposed to (non-impact) blast-related injuries, rather than multiple (direct impact) concussions spread over several years. I believe part of the answer lies in the high intensity nature of the shock wave generated by IEDs:
Explosive T.N.T. generates shock waves that travel at around Mach 2, or twice the speed of sound.
This energy wave is intense enough to literally shred neurons, snapping axonal connections like twigs. Since this damage is happening at a microscopic level with no obvious external signs, it goes unnoticed and untreated until cognitive and PTSD problems appear later.
The inflammatory response to this type of brain injury can cause a cascade of tau protein neurofibrillary tangles in the brain – a hallmark of both CTE and Alzheimer’s.
Personal Brain Genetics Also Play a Role
I also believe we will find out in the coming years that some people are genetically more prone to long term cognitive trauma caused by concussions and brain injuries. The most likely cause for this is an overactive inflammatory response to brain injury, which can create misfolded tau proteins and amyloid plaques in the brain. Some tantalizing research findings on CNS genes already point in this direction.
This also leads to the future possibility of screening for “concussion resistant” brain genome profiles in applicants and recruits. In addition to the military, I can see how school and professional sports teams would find this capability useful. However, we’re still probably many years away from having a practical screening application on this.