BrainLine sat down with Dr. Nathan Zasler to talk about the issues of fatigue after a traumatic brain injury. Dr. Zasler is an internationally respected neurorehabilitation physician who specializes in brain injury.
BrainLine: Describe fatigue. What exactly is traumatic brain injury-related fatigue?
Dr. Zasler: Think about a car. It needs gas to run. If your tank is low, your car will start sputtering and then stop once you have reached the end of your reserve. It’s the same way with fatigue after TBI. Fatigue is caused by a decrease in physiological reserve, which includes a person’s physical and mental reserves. When your brain is “tapped out,” you feel tired. Basically, when a person’s brain is overtaxed, fatigue will set in.
Although one formal definition of fatigue that has been proposed states that it is the failure to initiate or sustain attention or physical activity that requires self-motivation, there continues to be debate about how best to define "fatigue." In part, it’s difficult to define the term because fatigue is subjective — that is, it is solely based on patient report — and it is really more a symptom than a diagnosis. Just like it is difficult to tell if someone is in pain, it is also challenging to know if someone suffers from fatigue unless they tell you so. But generally, people with TBI have described fatigue as a sense of mental or physical tiredness, exhaustion, lack of energy, and/or low vitality. Unfortunately, we don’t have any definitive screening tools for fatigue, so there is no universal way to measure it.
Cognitive and physical fatigue can occur separately or together, but most people seem to have more problems with the mental side of fatigue after a brain injury. They say they are not as quick as they used to be, mental tasks that were once easy are much more difficult, and they tire far more easily even doing something that used to be simple like reading, studying, or working.
Although there are limited long-term studies, some research indicates that fatigue is usually short-lived after most mild TBIs. And in my experience as a physiatrist, fatigue in patients with mild TBI usually lasts no longer than three to six months. However, for some people with mild TBI, their fatigue is more persistent.
BrainLine: How common is fatigue after a brain injury?
Dr. Zasler: In the general population, fatigue is a common complaint with some studies citing an incidence of 10 percent. But for people with traumatic brain injury, it is one of the most common problems post-injury. Fatigue affects not only people with moderate to severe TBI, but also those with mild TBI. And we still need more research to better understand this issue.
BrainLine: What does fatigue look like after TBI?
Dr. Zasler: The spectrum of fatigue is as broad as the spectrum of traumatic brain injury, itself. Everyone’s brain injury is different and everyone’s symptoms will be different. There are also many variables when it comes to post-TBI fatigue — from levels of severity to pervasiveness. Some people may be very fatigued all the time and others may only be fatigued after mental or physical exertion.
Most people who have fatigue resulting from brain injury only experience the problem at certain times and not all the time. They have more energy in the morning and tend to be more tired later in the day. People’s levels of fatigue also depend on how much they are pushing themselves physically or cognitively, and whether they are making time to rest periodically during the day and pace themselves.
Depression, anxiety, or stress can also contribute to the degree of a person’s fatigue or, alternatively, may even be the cause of the fatigue. Not everyone with a TBI will experience fatigue due to their brain injury. So, each person’s levels of fatigue, if present, may change over time during their recovery, in terms of both cause and level of severity.
BrainLine: Why do these problems occur?
Dr. Zasler: Unfortunately, we don’t really know. There have not been a lot of conclusive studies conducted on fatigue after brain injury. Much of what we are discussing is experiential. Some have theorized that damage to the basal ganglia — which are structures deep in the brain — are the critical areas involved in the generation of fatigue. Others have noted that other areas of the brain may be involved as well.
BrainLine: What kind of information should people with brain injury give their doctor to help the doctor better understand their issues with fatigue?
Dr. Zasler: This is a two-way street, of course. People should give their doctor as much information as they can and, in turn, the doctor needs to ask the right questions and get as full a picture of the symptoms and situation as possible.
First of all, it’s important to establish the cause of fatigue; it may not be a result of the traumatic brain injury. It could be something else, and those other potential causes should first be ruled out. Other common contributing factors for fatigue can include:
- lack of regular and restorative sleep
- psychiatric issues like depression or anxiety
- chronic pain
- chronic stress
There are also less common causes for fatigue that should also be ruled out. They can include:
- seizure-related fatigue
- hormonal abnormalities, like hypothyroidism
- nutritional deficiencies such as low B12, anemia, or blood cancers (i.e., leukemia)
- renal failure
All of these causes, common and less common, should be considered and then ruled out as the sole or contributing cause of a person’s fatigue before considering TBI as the cause.
Once other causes of fatigue are ruled out and the fatigue is found to be neurogenic —related to the damage to the brain’s nerve cells — some of the topics and questions that need to be covered in the doctor’s evaluation include:
- When did the symptoms of post-TBI fatigue start?
- Did the onset of fatigue symptoms correlate with any other event such as starting a new medicine or getting depressed?
- What helps make the fatigue go away, or decrease?
- What aggravates it?
- What triggers it?
- In what ways are you fatigued physically, and when?
- In what ways are you fatigued mentally, and when?
- How is your sleep?
- How is your mood?
Nathan D. Zasler, MD, Nathan Zasler, MD is CEO and medical director for Concussion Care Centre of Virginia, Ltd. as well as CEO and medical director for Tree of Life Services, Inc. He is board certified in physical medicine and rehabilitation and fellowship trained in brain injury.
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