Parkinson's Disease: Another Result of Brain Injury?

I’m willing to bet that you have heard of the boxing legend Muhammad Ali. If you haven’t, I would definitely recommend watching some of the highlights of his illustrious career in the boxing ring. The guy was amazing. However, the guy also took some very heavy blows to the head throughout his time in the ring. That’s not surprising, though – boxing is an extremely brutal sport that comes with high risk of    injury. But research into the neurological effects of traumatic brain injury suggest that this “injury” may be more than just a temporary painful experience. The unfortunate reality of Muhammad Ali’s life today is that he suffers from Parkinson’s Disease, or PD, and the connection between his diagnosis and history of boxing raises many questions.
 
What exactly is PD? It is widely known that PD is a progressive disorder of the nervous system that affects movement – a symptom that stems from the loss of dopaminergic neurons in the substantia nigra, a region in the midbrain. The role of abnormal protein kinase function, which leads to the elevated phosphorylation of the PD-defining pathological protein alpha-synuclein, has been implicated in having an effect on the loss of neurons. This depletion of neurons, shown in the picture below, leads to a decreased supply of dopamine in the brain, which is responsible for many functions such as movement control. Typically, PD patients exhibit this loss of control through slowed and jerky movements. This video shows the effects of PD on Muhammad Ali himself, in comparison to before he developed the disease.
 
But why did he develop PD? Could there be a connection to the years and years of taking punches to the head? Researchers at UCLA have done extensive work on traumatic brain injury (TBI) and its connection with the development of Parkinson’s Disease (PD). They have found that having experienced a TBI doesn’t necessarily cause PD, but dramatically increases    the risk of developing the disease. One of the researchers leading the study explained that, “With a moderate traumatic brain injury, the loss of neurons was too small in number to cause Parkinson’s disease, but it is enough to increase the risk of PD. By decreasing the number of dopaminergic neurons, any further insult to the brain will be attacking a smaller number of neurons; as a result, the threshold for symptoms would be reached faster.”
 
In the long-term study, found here, the rats’ brains showed a 30 percent loss of dopaminergic neurons 26 weeks after the injury. This finding suggests that traumatic brain injury alone is sufficient to induce a progressive degeneration of dopaminergic neurons in the long term. Additionally, this research supports the finding that with a first moderate brain injury, the susceptibility to another increases drastically.
 
Isn’t this a scary thought? Not only does an injury to the brain lead to immediate effects such as concussion development, but it can also lead to the loss of neurons responsible for coordinating muscle movement in the body. And with the buzz surrounding the concussion policy of the National Football League as well as the seemingly endless cases of chronic traumatic encephalopathy (CTE) former NFL players have developed, it seems that the impacts of brain injury are even more severe than previously imagined.