Concussion Fatigue – Overview
Our understanding about concussion fatigue is still developing. This is because our knowledge of what causes Concussion and Post-concussion Syndrome (PCS) and how it should be best treated continues to evolve. Many things may be causing a concussed person’s fatigue including: increased mental effort, sleep disturbances, anxiety/depression, hypothyroidism, etc. Proposed treatments include: cardiorespiratory exercise, mindfulness-based stress reduction, bright light therapy, and medication. While these treatments will likely help, the bottom line is that Concussion and PCS fatigue is still relatively poorly understood, and there are no gold standard treatments for it yet.
Concussion Fatigue – More in-depth
Concussion Fatigue – Causes
Concussion fatigue is arguably one of the most debilitating & resistant to treatment symptom. It has been defined by one group as: “the awareness of a decreased capacity for physical and/or mental activity due to the imbalance in the availability, utilization, and/or restoration of resources needed to perform activity.”1
Van Zomeren & Broumer have a hypothesis for the origins of mental fatigue called the “Coping Hypothesis.”2 It proposes that fatigue arises in various brain conditions because their associated cognitive deficits make activities more mentally taxing. In other words, for a patient with a Traumatic brain Injury (TBI) to do a given task, they will need to expend more mental effort to accomplish the same amount activity than they did before the TBI. One study looking at this compared the association between vigilance and subjective/objective levels of fatigue. Vigilance was measured with a standardized 45 minute task; subjective fatigue by the Visual Analogue Scale for Fatigue (VAS-F); objective fatigue was measured by increases in blood pressure.3 The results of the study supported the Coping Hypothesis: compared to controls, TBI patients expended more effort to maintain their performance & reported a higher subjective sense of fatigue. In addition, the authors propose that this increased effort may stress the individual, leading in turn to the greater depression and anxiety observed in TBI.
However, increased effort is not the only potential source of fatigue. Other studies have noted greater incidence of sleep disturbances (e.g. decreased onset of sleep, decreased sleep efficiency, increased time spent awake after initially falling asleep and more slow-wave sleep).4 These results were true even after controlling for depression and fatigue. This means that, while depression and anxiety can worsen the fatigue issue, they cannot fully explain it in concussions (mTBI) and TBI patients. With varying degrees of evidence, other fatigue mechanisms have been proposed including: hypothyroidism, injuries to the reticular activating system, limbic system and the basal ganglia. In reality, fatigue in concussions is likely caused by many factors that at times overlap and compound one another.
Categorization of Fatigue
It can be categorized in a number of ways:2
- Physiologic Fatigue = “functional organ failure, generally caused by excessive energy consumption; depletion of essential substrate functioning…” For example muscle fatigue.
- Central Fatigue = arises from an impairment in the CNS (e.g. hypothalamus), or impaired transmission between the CNS and the PNS.
- Peripheral Fatigue = arises as a result of a malfunction in the PNS (e.g. the motor end points).
- Psychologic Fatigue = “a state of weariness related to reduced motivation, prolonged mental activity or boredom that occurs in situations of chronic stress, anxiety or depression.”
Fatigue can also be categorized as
- Primary Fatigue = Fatigue caused by a disorder (e.g. M.S.)
- Secondary Fatigue = Fatigue worsened by such things as physiological distress, sleep disturbance, and pain.
So using this framework, fatigue in a TBI could be conceived as part primary fatigue, arising from “diffuse axonal injury, impaired excitability…and hypothyroidism,” and part secondary fatigue, arising from “sleep disorders, pain, & depression.”2
Outcome Measures for Fatigue
There are a number of outcomes measures for fatigue. Each seems to measure different aspects of the issue and therefore have different uses and limitations. These include:
- Fatigue Severity Scale (FSS). Measures the behavioural consequences of fatigue and its impact on ADLs for M.S. patients. However able to distinguish brain injured patients from healthy controls.5
- Visual Analogue Scale for Fatigue (VAS-F). Measures the individual’s subjective fatigue levels.6
- Ziino and Ponsford proposed an outcome measure for the causes of Fatigue Questionnaire (COF). It has two parts: one that captures physical activity that causes fatigue (COF-PE) and another the mental effort that causes fatigue (COF-ME)2
- Mental Fatigue Scale (MSF). Incorporates affective, cognitive and sensory symptoms, duration of sleep and daytime variation in symptom severity.7
Treatments for Fatigue
There are some non-pharmacological treatments that have a role to play including:
- Cardiorespiratory exercise. According to Sullivan et al. cardio programs have been found to be helpful in reducing physical fatigue more so than mental fatigue.2 However cardio programs tailored to mTBI have other effects that can relieve the secondary effects sources of fatigue (i.e. sleep disturbance, depression and anxiety).
- Mindful-based Stress Reduction (MBSR). MSBR programs have been found to be effective, but are time consuming and require very good compliance.7
- Bright Light Therapy. One study using a month-long program of short wavelength (blue) light therapy found a reduction in subjective fatigue and sleepiness in TBI patients.8 However, this study used only a small sample size and reports some conflicts of interests.
There are a number of medications showing promise as fatigue relievers including: Methylphenidate and OSU6162.7 Other medications target improving sleep quality, for example prolonged-release melatonin (Circadin).2 The patient needs to consult their GP, who may in turn want to refer them on to an appropriate specialist like a psychiatrist or an MD specializing in sleep assessment and treatment.
One caution is that many of the studies cited were investigating TBI, rather than specifically concussions (mTBI). However one group found no significant association with severity of TBI injury and the levels of fatigue reported.2
References
1. Aaronson L. et al. Defining and measuring fatigue. Image J Nurs Sch. 1999; 31: 45-50.
2. Ponsford J. et al. Fatigue and Sleep Disturbance following Traumatic Brain Injury – Their Nature, Causes, and Potential Treatments. J Head Trauma Rehab. 2012; 27, 3: 224-233.
3. Ziino C., Ponsford J. Vigilance and fatigue following traumatic brain injury. J Int Neuropsychol Soc. 2006; 12: 100-110.
4. Shekleton J., et al. Sleep disturbance and melatonin levels following traumatic brain injury. Neurology 2010; 74 (21): 1732-1738.
5. Krupp L., et al. The fatigue severity scale: application to patients with multiple sclerosis and systemic lupus erythematosus. Arch Neurol. 1989; 46: 1121-1123.
6. Lee K. et al. Validity and reliability of a scale to measure fatigue. Psychiatry Res. 1991; 36: 291-298.
7. Johansson B., Ronnback L. Assessment and treatment of mental fatigue after a traumatic brain injury. Neuropsychological Rehabilitation, 27:7, 1047-1055.
8. Sinclair K., et al. Randomized controlled trial of light therapy for fatigue following traumatic brain injury. Neurorehabilitation and Neural Repair. 28(4), 3013-313.
