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. 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.

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

Symptoms of concussion can include a period of unconsciousness for less than 30 minutes , vomiting, confusion, and visual disturbances. Amnesia, the hallmark sign of concussion, can be retrograde amnesia (loss of memories that were formed before the injury) or anterograde amnesia (loss of memories formed post-injury) . Patients with concussion may act confused, for example repeating the same sentences or forgetting where they are. Patients with concussion may have focal neurological deficits, signs that a specific part of the brain is not working correctly .

Since concussions do not include damage to the brain's structure, the condition of patients with uncomplicated concussions always either improves or stays the same. Thus, a deteriorating level of consciousness means that the patient has another problem such as a worse type of head injury. Similarly, persistent vomiting, worsening headache, and increasing disorientation are all indicative of a rise in intracranial pressure (ICP) .

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 AAN 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.

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 .

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 .

See also

• Head injury