By NCAA Sport Science Institute
There are more than 40 definitions of concussion, with a common thread that concussion is a brain injury that is defined as a complex pathophysiological process affecting the brain, induced by biomechanical forces. There are numerous clinical presentations of concussion, which are influenced by a combination of the person’s pre-morbid state, genetics, biomechanical forces, location of injury, and management. To date, there are no objective biomarkers that are accepted as standard tools in either the diagnosis or management of concussion. Thus, concussion is a clinical diagnosis without objective markers to stage this condition. This makes the diagnosis and management of concussion difficult enough, and the difficulty is compounded when symptoms of concussion linger for weeks, months or even longer.
Three conditions have been described following concussion, all without a clear cause-and-effect relationship:
Post-concussion syndrome must be differentiated from concussion, CNI and CTE.
Concussion leads to a change in the brain’s physiology, with a resultant mismatch in blood flow and available energy substrate. This mismatch corrects over a period of seven to 10 days, which is the duration of time in which the majority of athletes recover completely from concussion. When symptoms persist beyond this time frame, the athlete should be reevaluated by a physician with expertise in concussion and brain injury to rule out a condition that might mimic concussion.
CNI is a condition in which individuals who have suffered prior concussion develop a reduction in cognitive function relative to pre-morbid function. CNI is generally considered a non-progressive condition, and it has been more consistently reported in former professional athletes – in a dose response manner – who have suffered with numerous concussions. Reports of CNI are variable in amateur athletes, with some studies suggesting a relationship to prior concussion, and other studies showing no evidence of CNI in amateur athletes.
CTE is a neurodegenerative disease that has been described in case reports/case series, but has never been described as part of a prospective, longitudinal study. In the case reports to date, CTE manifests as a progressive decline in intellect and neuropsychiatric function. Brain pathology demonstrates a striking abnormal deposition of tau proteins, which normally serve to stabilize brain microtubules. Although CTE has been described primarily in former football players, the case reports result from a selection bias. Most scientists agree that there is no clear causal relationship between concussion or subconcussive impact and CTE. There may well be a correlation, but it is also likely that there is a genetic or biomarker predisposition that is a necessary component of this condition.
Post-concussion syndrome is not truly a “syndrome” because there is no core of consistent symptoms. Post-concussion syndrome refers to a constellation of symptoms that develop or persist following concussion, but the cause is not clear. There is no direct relationship between the development of post-concussion syndrome and the type or severity of concussion. There is also no relationship between post-concussion syndrome and CNI or CTE. Post-concussion syndrome is best considered a neuro-psychiatric condition that results from a combination of factors including concussion, pre-morbid state, co-morbid psychiatric history and post-concussion perceptions from both the athlete and the treating medical team. Symptoms include neurologic (dizziness, sensitivity to light/sound), cognitive (memory, attention deficits) and psychological/emotional (anxiety, depression, insomnia).
Post-concussion syndrome is often mismanaged as prolonged concussion in that athletes are advised to continue both physical and cognitive rest. Whereas physical and cognitive rest are part of the mainstay of initial concussion management, they can help to perpetuate post-concussion syndrome manifestations because the athlete can become increasingly isolated or despondent with ongoing symptoms and no clear management plan. Post-concussion syndrome is best managed in a multi-disciplinary manner, with clinicians who have expertise in neurology, psychology, psychiatry, physiatry and vestibular disorders. Athletes with post-concussion syndrome are reassured that they are not suffering with ongoing concussion or with another neurological process. This reassurance is therapeutic in and of itself. The underlying symptoms are then addressed both piecemeal and as part of a team approach.
It is noteworthy that many symptoms of post-concussion syndrome and post-traumatic stress disorder are similar; thus, the discerning clinician should assess for the possibility that the concussion injury became an inciting event for a more severe psychiatric disturbance.
Last Updated: Aug 8, 2013