Yesterday, we talked about the practicalities of TBI and combat. Perhaps the best way to visualize those practical problems is to watch the opening scenes of the movie, Saving Private Ryan. A clip of the first 10 minutes can be found at YouTube here: http://www.youtube.com/watch?v=kx7dFp0WhN4&feature=related At eight minutes into this clip, the lead character, Captain John Miller, played by Tom Hanks, is near a mortar or artillery shell which explodes upon the Allied troops as they land at Omaha Beach. Captain Miller clearly suffers a concussion in this blast without any apparent loss of consciousness.
The next minute of this clip is the most honest treatment of concussion I have seen from Hollywood. Captain Miller struggles to his knees, helmet in hand. For the next minute he does nothing, seemingly unable to comprehend that he has been hurt, that he is in combat, that he should put his helmet back on. In almost a childlike gaze, he takes in the horror that surrounds him. His hearing, his balance are impaired. The viewer gets the sense of this because Director Steven Spielberg cuts all sound, the viewer, like the concussed soldier becomes deaf. Captain Miller, as we watch in horror, does virtually nothing to defend himself, despite the cataclysm which surrounds him. After 90 seconds, his thinking clears and he regains his ability to command. He is able to save his life, those of most of his troop and Private Ryan.
This portrayal of concussion by Hanks may be fictional, but it is a classic example of art showing us what is real. Hanks and director Spielberg have gotten this just right, at least in the acute stage of the concussion. What I believe is most important about this portrayal of concussion is that it demonstrates the combat challenges in avoiding second impact syndrome and simultaneous PCS and PTSD.
Second Impact Syndrome. The big impetus for the sport and concussion movement that has so changed how the world views concussion, was a 1991 description of the “second impact syndrome. See Kelly, JP, JAMA. 1991 Nov 27;266(20):2867-9. “Concussion in sports. Guidelines for the prevention of catastrophic outcome.” http://www.ncbi.nlm.nih.gov/pubmed/1942455 The concern in second impact syndrome is that a concussed brain is no better at defending against a catastrophic increase in brain blood pressure, than the Captain is in avoiding bullets. For the sake of illustration, the brain becomes confused as to how to regulate its blood pressure by the first concussion. When the second impact puts an added strain on such regulatory apparatus, the brain has no remaining defenses. Death or severe injury results.
What makes second impact such a practical problem in combat is the increased risk of second concussion because of the disorientation and confusion from the first concussion. While such is also true in sports, the risk factors of the second injury are so much greater in combat. No injury timeouts in combat. As you watch Saving Private Ryan, you realize how vulnerable a soldier with a 90 second disorientation is. He is in the line of fire, without his helmet, completely confused as to what to do, what has happened. There is probably nothing we can practically do to reduce the risk of the contemporaneous second concussion in combat. But what me must do is make sure we don’t send the soldier back into a combat zone in the days and weeks afterwards. That is where battlefield screening would be so important.p>
Interplay Between Concussion and PTSD. While the science in this area is still evolving, I am completely convinced that Post Concussion Syndrome (PCS) has as its core problem, a compromised attentional capacity. When compromised attentional resources are combined with emotional stressors (of which combat based PTSD would be among the worst) the likelihood of a disability multiplies.
The least understood but potentially most serious pathology after a mild traumatic brain injury (MTBI) is compromised brain signaling between limbic structures like the amygdala and hippocampus and the frontal lobes. Communication in the brain is electrical, with the electrical impulse being carried from one neuron to another down axons. Fiber tracts are the bundles of axonal fibers that connect one part of the brain to other part of the brain or to the nervous system. See http://www.subtlebraininjury.com/neuron.php One of the most exciting new developments in the last decade is the capacity to see damage axonal tracts on MRI through the use of Diffusion Tensor Imaging (DTI). Even though axons are far too small to be seen on MRI, DTI can see the cumulative effect of axonal injury because of its ability to see an interruption in the fiber tracts. See http://www.tbilaw.com/blog/tag/dti
Unfortunately, not enough DTI research is being done on what I believe to be the biggest culprit in PCS, the uncinate fasciculus. The uncinate fasciculus is a fiber tract that connects the limbic system to the frontal lobes. http://www.ajnr.org/cgi/content-nw/full/25/5/677/F11 Add structural injury to either the limbic or frontal lobes to damage to this fiber tract and the brain dysfunction can hit critical mass.
One issue this week has been what the Pentagon has done with the $1.5 billion that has been spent on TBI. I can categorically say that if war is anything like Saving Private Ryan, the U.S. military owes it to its soldiers and Veterans to prioritize research into the limbic system, uncinate fasciculus and frontal lobe injury. Lt. Col. Michael Russell, head of the Army’s ANAM program says there are too many “false positives” for TBI when administering the test mandated by Congress. One of the reasons there are so many is that the emotional stress of combat alone could impact the brain’s panic and emotional centers. Add diminished attentional capacity and compromised axonal tracts which arise from MTBI and the risk of a catastrophic result will still be there when the bullets stop flying.
