A concussion is basically a mild traumatic
brain injury. To be considered a concussion, there must be some alteration of
mental status such as confusion, difficulty concentrating, amnesia, or even a
loss of consciousness. Studies on animals suggest that after a head injury,
the brain requires more oxygen, but blood flow to the brain actually
decreases. This mismatch in the supply and demand for oxygen for the brain may
persist for many days. As a result, subsequent injuries during this time may
not be as well tolerated as they otherwise would, resulting in severe,
possibly fatal outcomes.
The most common symptom of a concussion is a
headache. However, a headache after head trauma does not equate to a
concussion if there is no alteration of mental status. Furthermore, it is
important to remember that headaches that do follow concussions may not
manifest for several hours. Sometimes the headaches are so severe, and
accompanied by nausea or hypersensitivity to noise or light, that they have
been described as being post-traumatic migraines.
Those who are not truly confused, but just
feel “foggy”, after concussions process information slower, and therefore have
slower reaction times. Returning to play at that point may not only result in
less effective performance, but also risk further trauma by not being able to
avoid injury as well as otherwise.
Amnesia following concussion can involve loss
of memory for events in a time period after the injury (referred to as
“antegrade” or “post-traumatic”) or for a time period prior to the injury
(referred to as “retrograde”), or both. Although the time period covered by
the amnesia will typically shrink as the individual recovers, there typically
will be some permanent loss of memory. It can be very difficult to evaluate
amnesia in the face of confusion.
Fortunately, loss of consciousness following
concussion is typically brief, and occurs in less than 10% of these injuries.
More subtle sequelae include emotional irritability, anxiety, or
even depression. Prolonged disturbances in sleep have also been reported.
Those with a previous history of concussion are more likely to have subsequent
ones. Furthermore, a recent investigation has shown that following a
concussion, female soccer players have more symptoms and perform less well on
neurocognitive testing than their male counterparts.
The major concern about concussion is that
premature return to play and subsequent re-injury before fully recovering from
the first injury can lead to severe symptoms and even death – even though the
second injury may not be very severe. This “second impact syndrome” occurs
more often in younger (e.g. high school) athletes than in somewhat older
competitive athletes (e.g. college and professional). In fact, all of
approximately 3 dozen reported deaths from second impact syndrome have been in
athletes aged 13 to 18. Furthermore, younger athletes take longer to return to
baseline levels of performance. One study revealed high school athletes
returning to normal verbal memory skills 7 days following concussions compared
to 3 days for college athletes playing similar sports and having similar
severity head injuries.
Classification systems have been developed to
help grade the severity of concussion, and by so doing help determine and
guide time to return to contact sports. There are numerous grading schemes
currently in use, indicating a significant lack of consensus among physicians
evaluating and treating athletes with concussions.
There does seem to be agreement on some
guidelines, however. If there is complete elimination of signs and symptoms of
a first time concussion without loss of consciousness, and the athlete has no
symptoms even upon exertion, returning to play the same day of the injury is
reasonable. Those with persistent symptoms or signs should not return to play.
There is less agreement about other aspects of concussion management,
including the need for imaging studies such as CT scans. Those with multiple
concussions from sports should consider avoiding further participation in
those sports as there can be cumulative damage from successive concussions
leading to the development of long-term and irreversible brain damage and