Brain concussion

Template:DiseaseDisorder infobox Concussion, or mild traumatic brain injury (MTBI), is the most common and least serious type of traumatic brain injury. A milder type of diffuse axonal injury, concussion involves a transient loss of mental function. A loss of conciousness is infrequent although some definitions require a loss of conciousness. It can be caused by acceleration or deceleration forces, or by a direct blow. Concussion is generally not associated with penetrating injuries, but instead with blunt trauma.

Classification

Grades

Concussion is classified into five grades

1. The mildest, grade I, involves only confusion .
2. Grade II involves anterograde amnesia that lasts less than five minutes as well as confusion.
3. Grade III involves the symptoms above, as well as retrograde amnesia and unconsciousness for less than five minutes .
4. Grade IV involves all of the above symptoms, as well as unconsciousness that lasts between 5 and 10 minutes .
5. Grade V is the same as grade IV, with unconsciousness lasting longer than ten minutes.

The American Academy of Neurology clinical practice guidelines make it clear that permanent brain injury can occur with either Grade 2 or Grade 3 concussion. Thus, it is clear that subtle brain injury can have permanent consequences if the acute symptoms of the concussion continue for more than 15 minutes.

Pathophysiology

The brain floats within the skull surrounded by cerebrospinal fluid (CSF), one of the functions of which is to protect the brain from normal light "trauma", e.g., being jostled in the skull by walking, jumping, etc., as well as mild head impacts. More severe impacts or the forces associated with rapid acceleration/deceleration may not be absorbed by this cushion.

Concussion is considered a type of diffuse, as opposed to focal, brain injury, meaning that the dysfunction occurs over a more widespread area of the brain.

Excitatory neurotransmitters are released as the result of the traumatic injury and cause the brain to enter a state of hypermetabolism which can last for 7 to 10 days . During this time, the brain needs extra nutrients and is especially sensitive to inadequate blood flow.

Areas of the brain whose function is commonly disturbed in concussion include the reticular formation or the deep structures of the brain, the brainstem or cortices . Damage to cranial nerves and other white matter tracts may be temporary or permanent . Other theories hold that concussion is a diffuse injury affecting all parts of the brain, caused by physical trauma that alters neuronal metabolism and excitability through molecular commotion. Having a concussion does not mean that the patient does not have another brain injury as well; in fact, more serious brain trauma is almost always accompanied by concussion .

Symptoms

The frequency of various symptoms has been studied using collegiate football players: the NCAA Concussion Study.

Symptoms in the NCAA Concussion Study

	Frequency
No loss of consciousness no amnesia	78%
Loss of consciousness	6% (median duration, 30 seconds)
Anterograde amnesia Events after the injury such as exiting the field	19% (median duration, 90 minutes)
Retrograde amnesia Events before the injurty such as inability to recall aspects of the play	7% (median duration, 120 minutes)
Delayed onset of symptoms	12% (mean delay; 14+15 minutes)

Prognosis

A cohort study of NCAA football players found most signs and symptoms after a concussion resolve by one week. In the same cohort, slow recovery from concussion is more likely among players with a history of previous concussions.

Second Impact Syndrome

If a patient receives a second blow days or weeks after a concussion, before concussion symptoms have gone away, they are at risk of developing Second Impact Syndrome (SIS) or recurrent traumatic brain injury. In this rare condition, the brain swells dangerously after a minor blow. No one is certain of the cause of this often fatal complication, but some think the swelling is due to the brain's arterioles' loss of ability to regulate their diameter, and therefore a loss of control over cerebral blood flow .

In this dangerous condition, intracranial pressure rapidly rises, the brain can herniate, and brainstem failure can occur within five minutes . When this condition occurs, surgery does not help and there is little hope for recovery . When it is not fatal, the patient can experience persistent muscle spasms and tenseness, emotional instability, hallucinations, and cognitive problems . The condition is fairly rare, with only 35 recorded cases in a 13 year period from football injuries, not all of which were confirmed to be due to SIS .

Lasting effects

Some concussions can have serious, lasting effects. The symptoms of most concussions are resolved in 48 to 72 hours, but in many patients, problems persist . In postconcussive syndrome (PCS), concussion symptoms do not resolve for weeks, months, or even years, and the patient may have headaches, light and sound sensitivity, memory and attention problems, dizziness, difficulty with directed movements, depression, and anxiety. Symptoms usually peak 4 to 6 weeks after the concussion, but may go on longer, some even lasting a year or more . Children commonly experience more severe symptoms of postconcussion syndrome than adults do . Physical therapy plus rest is the best recovery technique, and symptoms usually go away on their own.

Multiple small head injuries that daze the patient can also result in cognitive and physical deficits that occur in what is commonly known as dementia pugilistica, or "punch drunk" syndrome, which is associated with boxers .

Treatment

Concussion in sports

Clinical practice guidelines from the American Academy of Neurology although not revised since 1996, provide current advice on managing concussion in sports:

Grade 1. If the injured athlete's condition fits the description of a Grade 1 injury as described previously:

1. "Remove from contest"
2. "Examine immediately and at 5 minute intervals for the development of mental status abnormalities or post-concussive symptoms at rest and with exertion."
3. "May return to contest if mental status abnormalities or post-concussive symptoms clear within 15 minutes.
4. "A second Grade 1 concussion in the same contest eliminates the player from competition that day, with the player returning only if asymptomatic for one week at rest and with exercise."

Grade 2. If the injured athlete's condition fits the description of a Grade 2 injury as described previously:

1. "Remove from contest and disallow return that day."
2. "Examine on-site frequently for signs of evolving intracranial pathology."
3. "A trained person should reexamine the athlete the following day."
4. "A physician should perform a neurologic examination to clear the athlete for return to play after 1 full asymptomatic week at rest and with exertion."
5. CT or MRI scanning is recommended in all instances where headache or other associated symptoms worsen or persist longer than one week."
6. Following a second Grade 2 concussion, return to play should be deferred until the athlete has had at least two weeks symptom-free at rest and with exertion."
7. Terminating the season for that player is mandated by any abnormality on CT or MRI scan consistent with brain swelling, contusion, or other intracranial pathology."

Grade 3. If the injured athlete's condition fits the description of a Grade 3 injury as described previously:

1. "Transport the athlete from the field to the nearest emergency department by ambulance if still unconscious or if worrisome signs are detected (with cervical spine immobilization, if indicated)."
2. "A thorough neurologic evaluation should be performed emergently, including appropriate neuroimaging procedures when indicated."
3. "Hospital admission is indicated if any signs of pathology are detected, or if the mental status of the athlete remains abnormal."
4. "If findings are normal at the time of the initial medical evaluation, the athlete may be sent home. Explicit written instructions will help the family or responsible party observe the athlete over a period of time."
5. "Neurologic status should be assessed daily thereafter until all symptoms have stabilized or resolved."
6. "Prolonged unconsciousness, persistent mental status alterations, worsening postconcussion symptoms, or abnormalities on neurologic examination require urgent neurosurgical evaluation or transfer to a trauma center."
7. "After a brief (seconds) Grade 3 concussion, the athlete should be withheld from play until asymptomatic for 1 week at rest and with exertion."
8. "After a prolonged (minutes) Grade 3 concussion, the athlete should be withheld from play for 2 weeks at rest and with exertion."
9. "Following a second Grade 3 concussion, the athlete should be withheld from play for a minimum of 1 asymptomatic month. The evaluating physician may elect to extend that period beyond 1 month, depending on clinical evaluation and other circumstances."
10. "CT or MRI scanning is recommended for athletes whose headache or other associated symptoms worsen or persist longer than 1 week."
11. "Any abnormality on CT or MRI consistent with brain swelling, contusion, or other intracranial pathology should result in termination of the season for that athlete and return to play in the future should be seriously discouraged in discussions with the athlete."

See also

• Head injury