Thanks to a friend and follower of the blog I have been looking at some traumatic brain injury (TBI) research. Often you see TBI and concussion near each other; you can think of them as brother and sister. They are cut from the same cloth, meaning it is the same mechanisms that cause both. Concussions are referred to as minor traumatic brain injuries (mTBI) due to the lack of diagnostic (see imaging) findings with altered mental status or signs/symptoms. Regardless traumatizing the brain is not something that is good for you on a consistent basis.
The first article is about the link between TBI and stroke;
If you suffer traumatic brain injury, your risk of having a stroke within three months may increase tenfold, according to a new study reported in Stroke: Journal of the American Heart Association.
“It’s reasonable to assume that cerebrovascular damage in the head caused by a traumatic brain injury can trigger either a hemorrhagic stroke [when a blood vessel bursts inside the brain] or an ischemic stroke [when an artery in the brain is blocked],” said Herng-Ching Lin, Ph.D., senior study author and professor at the School of Health Care Administration, College of Medicine, Taipei Medical University in Taiwan. “However, until now, no research had been done showing a correlation between traumatic brain injury and stroke.”
It is the first study that pinpoints traumatic brain injury as a potential risk factor for subsequent stroke.
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The next article is about the link between TBI and Parkinson’s;
Traumatic brain injury has entered the public’s consciousness as the silent, signature wound brought back by many of our military warriors from Iraq and Afghanistan. But such injuries don’t only happen in warfare, they happen to civilians too. Think car crashes, a slip and fall, two football players colliding helmet to helmet.[…]
Now scientists at UCLA have found the mechanism for this elevated, long-term risk of Parkinson’s: the loss of a specific type of neuron.
In a pre-clinical study, the researchers found that a moderate traumatic brain injury in rats caused a 15 percent loss in the brain cells known as nigrostriatal dopaminergic neurons shortly after the trauma, and that this loss continued to progress to a 30 percent loss 26 weeks after the initial injury.
The loss of these particular neurons can result in the cardinal motor symptoms observed in Parkinson’s patients, including akinesia (problems with movement), postural tremor and rigidity. Further, when combined with a second known risk factor for Parkinson’s, the pesticide paraquat, the loss of dopaminergic neurons doubled to 30 percent much faster.
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Finally the last article linked is about the link between TBI and PTSD;
UCLA life scientists and their colleagues have provided the first evidence of a causal link between traumatic brain injury and an increased susceptibility to post-traumatic stress disorder.
Their new study, published Feb. 15 in the in the journal Biological Psychiatry, also suggests that people who suffer even a mild traumatic brain injury are more likely to develop an anxiety disorder and should take precautions to avoid stressful situations for at least some period of time.
The Concussion Blog 
…and there is research literature correlating concussions / ‘mild’ brain injury and strokes in young children. See the below citation.
Kieslich, M., Fiedler, A., Heller, C., Kreuz, W., & Jacobi, G. (2002). Minor head injury as cause and co-factor in the aetiology of stroke in childhood: A report of eight cases. Journal of Neurology and Neurosurgery Psychiatry, 73(1), 13–16.
We need to stop talking about this like they are separate entities. If you have blood on a CT scan, yes, that is a different injury. mTBI (read concussion) and DAI (diffuse axonal injury, read severe injury) are all the same mechanism, just different severity. Its all on a spectrum. This is why we consider mTBI mild, even though the long term effects may be significant, when you hold it up against DAI (coma, unresponsive, usually leading to death), it is mild.
With all of these injuries you have cellular damage and it triggers the inflamitory cascade. The amount is dictated by the severity of injury. While the inflamitory cascade can and does a lot of good things, it can also have unintended consequenses. It makes sense that with enough inflamitory changes you could have dammage to the blood vessles, leading to stroke, and all of the other long term consequenses we are seeing in these studies.
Great post Doc