It is a very common complaint of victims of traumatic brain injury that since the injury they experience extreme bouts of fatigue. Symptoms of “fatigue” are often ignored or downplayed by doctors because it is considered a “vague” symptom. It is also a symptom that has not been specifically linked to any known mechanism or area of damage in of the brain.
Like many other aspects of brain injury, this symptom of fatigue is now being studied and explained in much greater detail than done before. This is once again thanks to the sacrifice our soldiers have made in Iraq and Afghanistan and the Army researchers trying to help them.
The first thing we know about the creation of fatigue is that in functional MRI testing, TBI victims with frontal lobe injury, when asked to perform spelling or math problems, have a much higher rate of “brain recruitment”. Brain recruitment means what part of the brain and how much of the brain is activated by doing a given task. By these recent studies we know that the person with the injured brain is forced to recruit a larger percentage of their brain to complete a certain task, whereas an uninjured person would be activating a much lower percentage of their brain. The brain burns up about 30% of the bodies energy on a given day. Thus, over-recruitment of the brain because of injury is literally fatiguing, since it is costing a much higher rate of energy to do things that previously cost the body much less energy. It would be the same as putting 5 lb weights on each hand throughout the day. It explains nicely why there is such widespread and debilitating fatigue with TBI survivors.
In another recent study (Vanzuiden M et al., 2012) soldiers were tested before and after deployment regarding reports of severe fatigue. It was found that severe fatigue was associated with higher reactivity to IL-1 beta and it was found in higher levels in those with severe fatigue. TBI also plays a part in increasing what is known as pro-inflammatory cytokines in the blood for many months or years after injury. This can explain the very high level of severe fatigue found in TBI survivors. If a way can be found to decrease the reactivity to the immune system of the IL-1 beta, treatment could be found.