Concussion
| Concussion | |
|---|---|
| Specialty | Emergency medicine, neurology  |
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.
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 brain injury, 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.[1] During this time, the brain needs extra nutrients and is especially sensitive to inadequate blood flow.
Areas of the brain whose functions are commonly disturbed in concussion include the reticular formation or the deep structures of the brain, the brainstem or cerebral cortex.[2] Damage to cranial nerves and other white matter tracts may be temporary or permanent.[3] 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.[4]
Symptoms
Symptoms of concussion can include a period of unconsciousness for less than 30 minutes,[5] 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).[1] In concussion, amnesia is much more likely to be anterograde (also called Post Traumatic Amnesia or PTA). This type of amnesia is the inability to create and save new memories, much like the process of saving something from the RAM on a computer to its hard drive. Amnesia may not become apparent until the next day or the next week. A common example in sports concussion is the quarterback who was able to conduct all the complicated mental tasks of leading a football team after a concussion, but has no recollection the next day of the part of the game that took place after the concussion.
Patients with concussion may act confused, for example repeatedly asking the same questions, or forgetting where they are. Patients may have focal neurological deficits, signs that a specific part of the brain is not working correctly.[6]
Since concussions may not include damage to the brain's structure, the condition of patients with uncomplicated concussions often either improves or stays the same. But brain damage is a process, and not an event, that may set into motion many different pathological processes. The concussions that result in permanent long term deficits, often do get worse over the first few days. A deteriorating level of consciousness may mean that the patient has another problem such as a worse type of head injury. Similarly, persistent vomiting, worsening headache, ringing in the ears (tinnitus), drowsiness, unequal pupil size, and increasing disorientation are all indicative of a rise in intracranial pressure (ICP).[7] More likely in the typical concussion, the process of axonal injury and damage is progressing. Over the first 72 hours, a stretched or damaged axon, may be further damaged or killed by ionic fluctuations. [8]
The most critical mistake for those suffering from concussion, is not returning for further medical care and evaluation in the time period of 24 to 72 hours after the concussive event, if the symptoms are getting worse. Athletes, especially intercollegiate or professional athletes would typically be followed closely by team trainers during such period. But those injured in accidents may be sent home with no medical person monitoring them unless the situation gets worse. If the person had a concussion yesterday, and they don't have a clear recollection of the time period between the concussion and today, then they are likely suffering from Post Traumatic Amnesia, and are more likely to have a long term or permanent problems.
Grades
Concussion is classified into five grades
- The mildest, grade I, involves only confusion.[9]
- Grade II involves anterograde amnesia that lasts less than five minutes as well as confusion.
- Grade III involves the symptoms above, as well as retrograde amnesia and unconsciousness for less than five minutes.[9]
- Grade IV involves all of the above symptoms, as well as unconsciousness that lasts between 5 and 10 minutes.[9]
- Grade V is the same as grade IV, with unconsciousness lasting longer than ten minutes.
The American Academy of Neurology (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.
Each grade comes with different recommendations for patients who play sports:[10]
- In grade I, the patient may return to contact sports in 1 week.
- A patient with a second time grade I concussion may return to play contact sports in 2 weeks after being asymptomatic for a week.
- In grade II, the patient may return to contact sports in 1 week of being asymptomatic.[10]
- A second time grade II may return to play contact sports 1 month after being asymptomatic for a week.
- In grade III, the patient may return to contact sports in 1 month.
- For a patient with a second time grade III concussion, the season is over.
However, if the patient has repeated concussions after contact sports, grade I x 3, grade II x 2, and especially grade III x 2, then it should be recommended that the season is over and a thorough medical evaluation should be considered mandatory.
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.[9][11]
Post-concussion syndrome
In post-concussion 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.[9] Children commonly experience more severe symptoms of postconcussion syndrome than adults do.[9] Physical therapy plus rest is the best recovery technique, and symptoms usually go away on their own.
Dementia pugilistica
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.[12]
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.[11]
In this dangerous condition, intracranial pressure rapidly rises, the brain can herniate, and brainstem failure can occur within five minutes.[12] When this condition occurs, surgery does not help and there is little hope for recovery.[11] When it is not fatal, the patient can experience persistent muscle spasms and tenseness, emotional instability, hallucinations, and cognitive problems.[3] 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.[12]
See also
References
- ^ a b Orlando Regional Healthcare, Education and Development (2004). "Overview of Adult Traumatic Brain Injuries" (PDF). Retrieved 2006-10-20.
- ^ Dawodu S (July 15, 2005). "Traumatic Brain Injury: Definition, Epidemiology, Pathophysiology". eMedicine.com. Retrieved 2006-10-20.
- ^ a b Brain Injury Association of America. "Types of Brain Injury". Retrieved 2006-10-20. Cite error: The named reference "baiusa" was defined multiple times with different content (see the help page).
- ^ University of Vermont College of Medicine. "Neuropathology: Trauma to the CNS." Accessed through web archive. Retrieved on February 6, 2007.
- ^ Smith D and Greenwald B (December 19, 2003). "Management and Staging of Traumatic Brain Injury". eMedicine.com. Retrieved 2006-10-20.
- ^ Boon R and de Montfor GJ (2002). "Brain Injury". Learning Discoveries Psychological Services. Retrieved 2006-10-20.
- ^ Bernhardt D (July 5, 2006). "Concussion". eMedicine.com. Retrieved 2006-10-20.
- ^ Johnson, G. "Subtle Brain Injury".
- ^ a b c d e f Shepherd S (August 20, 2004). "Head Trauma". eMedicine.com. Retrieved 2006-10-20.
- ^ a b "Heads Up: Concussion in High School Sports: Management of Concussion in Sports". Centers for Disease Control and Prevention. Retrieved 2006-02-06.
- ^ a b c Tolias C and Sgouros S (February 4, 2005). "Initial Evaluation and Management of CNS Injury". eMedicine.com. Retrieved 2006-10-20.
- ^ a b c Drake D and Cifu D (August 17, 2006). "Repetitive Head Injury Syndrome". eMedicine.com. Retrieved 2006-10-20. Cite error: The named reference "drake" was defined multiple times with different content (see the help page).