A concussion usually occurs from a blow to the head resulting in symptoms including a possible temporary loss of consciousness, headache, confusion, nausea, and/or fatigue. At the cellular level, a concussion is causing microstructural injury to neural tissue in the brain. Axonal injuries caused by concussions can impair cognitive function, reaction time, spatial learning, and memory. Furthermore, concussions can impair brain function through energy malfunction, inflammation, and altered protein degradation.
After sustaining a concussion, cellular changes such as increases in ionic fluxes, indiscriminant glutamate release, and metabolic changes are thought to last up to 10 days. While the brain is still recovering from the injury, it is vitally important to protect the head and refrain from participating in a situation that could result in another blow to the head. Unfortunately, getting hit a second time during cellular unrest could result in injuries far worse than concussion symptoms.
Second impact syndrome (SIS) occurs when someone has recently sustained a head injury and another impact is taken to the head before the symptoms of an initial concussion have subsided. SIS is particularly devastating because it can result in death or severe disability. SIS is rare and there is little epidemiological data for the disease, likely because there is controversy over the definition of SIS.
When the patient sustains a “second impact,” the brain loses its ability to auto regulate intracranial and cerebral perfusion pressures due to the cellular changes in ion fluxes, glutamate release, and metabolic changes from the initial concussion. In severe cases of SIS, this may lead to cerebral edema followed by brain herniation. Death has been reported to occur in a matter of two to five minutes, usually without time to stabilize or transport an athlete from the playing field to the emergency department. Prevention of SIS occurs when a player is not allowed to return to a contact sport while still showing signs of concussion.
Resulting in the phrase: “When in doubt, sit them out”
This seems like a reasonable way to think about prevention after sustaining a concussion. Unfortunately, however, a concussion diagnosis isn’t always straightforward and clear. For example migraines have several symptoms in common with those of a typical post concussion. So how do you definitively know if someone has a headache/migraine or if they have symptoms of a concussion when they are consistently participating in situations of high probability contact?
Concussions also don’t have a testable biomarker and imaging of the brain is expensive and not always conclusive. Instead, in most cases, a health professional will diagnose a concussion based on the patient’s emotions and their outward expressions of symptoms. This isn’t fool proof, however, since symptoms of concussions can vary from person to person. In addition, patients might not always be truthful of their symptoms. For example, an athlete may hide their symptoms of concussion in order to continue to get playing time.
With so much on the line, a concussion should not be taken lightly. It is important for athletes, coaches, and parents to know the signs, symptoms, and life changing injuries that can be caused by concussions. Education of concussions might be the best way to make sure that everyone is on the same page of what kind of action to take in the event of a concussion. In this case, the most important action taken in the event of a head injury should be: “when in doubt, sit them out.”
Concussions and the Devastation of Second Impact Syndrome
