In a study published in April 2015 in the medical journal Brain Behavior and Immunity, a team of Canadian researchers at McMaster University presents a new understanding of the cause of the wide-array of symptoms experienced by some patients following concussion, such as headaches, dizziness, sleep disturbance, fatigue, cognitive impairment and neuropsychiatric symptoms.

This new paradigm helps to explain why the same pattern of symptoms can be found in some non-head injury patients, such a patient who has experienced infections or a patient diagnosed with post-traumatic stress disorder. It also helps to explain why some patients recover and others do not and why pre-accident experience can influence the course of post-accident recovery.

A pattern of symptoms producing neuroinflammation is described as  Post-Inflammatory Brain Syndrome  (PIBS)

The authors’ analysis of the peer-reviewed literature revealed strong evidence that one of the underlying mechanisms for post-concussion symptoms, as well as similar symptoms found in patients without a history of head injury – such as patients with infections or PTSD -  is a systemic inflammatory and immune response producing neuroinflammation.  The authors suggest that a better term to describe this pattern of symptoms is “post-inflammatory brain syndrome”  or PIBS.

Neuroinflammation is inflammation within the nervous system and includes activation of immune cells (particularly microglia) and non-immune cells, as well as increases in inflammatory mediators (including cytokines.) It has long been known that production of cytokines is increased in the brain following concussions. The authors review evidence supporting the conclusion that inflammation plays a role in producing symptoms such as headache, irritability, depression, sleep disturbance, fatigue, dizziness and memory impairment. The authors conclude that “there are many significant reasons to suspect that the generation of cytokines is involved in the etiology of post-concussion syndrome.” Patients with polytrauma not including TBI may also experience a systemic inflammatory reaction, explaining why they may have similar symptoms. Increased sensitivity to stress, found in patients with a history of depression, can result in an increased inflammatory response, explaining why a history of depression may increase the likelihood of persistent post-concussion symptoms. The authors also point to evidence that subtle genetic differences may influence the extent and persistence of the inflammatory response.

This new paradigm may impact future treatment.  The authors suggest that anti-inflammatory medications being explored for treatment of depression may be a potential avenue for treatment of post-concussion syndrome. The authors also endorse the potential benefits of exercise, which is known to reduce the levels of pro-inflammatory cytokines. Earlier posts in this blog have reviewed evidence on the benefits of controlled exercise as a treatment for persistent post-concussion syndrome. This new paradigm offers an explanation for why these benefits may occur.