Concussion natural history, complications and prognosis

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MTBI has a mortality rate of almost zero. The symptoms of most concussions resolve within weeks, but problems may persist. It is not common for problems to be permanent, and outcome is usually excellent.[1] People over age 55 may take longer to heal from MTBI or may heal incompletely.[2] Similarly, factors such as a previous head injury or a coexisting medical condition have been found to predict longer-lasting post-concussion symptoms. Other factors that may lengthen recovery time after MTBI include psychological problems such as substance abuse or clinical depression, poor health before the injury or additional injuries sustained during it, and life stress.[1] Longer periods of amnesia or loss of consciousness immediately after the injury may indicate longer recovery times from residual symptoms. For unknown reasons, having had one concussion significantly increases a person's risk of having another. The prognosis may differ between concussed adults and children. Little research has been done on concussion in the pediatric population, but concern exists that severe concussions could interfere with brain development in children.


Post-concussion Syndrome

In post-concussion syndrome, symptoms do not resolve for weeks, months, or years after a concussion, and may occasionally be permanent.[3] Symptoms may include headaches, dizziness, fatigue, anxiety, memory and attention problems, sleep problems, and irritability.[4] There is no scientifically established treatment and rest, a recommended recovery technique, has limited effectiveness. Symptoms usually go away on their own within months. The question of whether the syndrome is the result of structural damage or other factors such as psychological ones, or a combination of these, has long been the subject of debate.[5]

Cumulative Effects

Cumulative effects of concussions are poorly understood. The severity of concussions and their symptoms may worsen with successive injuries, even if a subsequent injury occurs months or years after an initial one.[6] Symptoms may be more severe and changes in neurophysiology can occur with the third and subsequent concussions. Studies have had conflicting findings on whether athletes have longer recovery times after repeat concussions and whether cumulative effects such as impairment in cognition and memory occur.[7]

Cumulative effects may include psychiatric disorders and loss of long-term memory. For example, the risk of developing clinical depression has been found to be significantly greater for retired football players with a history of three or more concussions than for those with no concussion history.[8] Three or more concussions is also associated with a five-fold greater chance of developing Alzheimer's disease earlier and a three-fold greater chance of developing memory deficits.[8]

Second-impact Syndrome

Second-impact syndrome, in which the brain swells dangerously after a minor blow, may occur in very rare cases. The condition may develop in people who receive a second blow days or weeks after an initial concussion, before its symptoms have gone away. No one is certain of the cause of this often fatal complication, but it is commonly thought that the swelling occurs because the brain's arterioles lose the ability to regulate their diameter, causing a loss of control over cerebral blood flow. As the brain swells, intracranial pressure rapidly rises. The brain can herniate, and the brain stem can fail within five minutes. Except in boxing, all cases have occurred in athletes under age 20. Due to the very small number of documented cases, the diagnosis is controversial, and doubt exists about its validity.[9]

Dementia Pugilistica

Chronic encephalopathy is an example of the cumulative damage that can occur as the result of multiple concussions or less severe blows to the head. The condition called dementia pugilistica, or "punch drunk" syndrome, which is associated with boxers, can result in cognitive and physical deficits such as parkinsonism, speech and memory problems, slowed mental processing, tremor, and inappropriate behavior.[10] It shares features with Alzheimer's disease.[11]


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  3. Ryan LM, Warden DL (2003). "Post concussion syndrome". International Review of Psychiatry. 15 (4): 310–316. doi:10.1080/09540260310001606692. PMID 15276952.
  4. Boake C, McCauley SR, Levin HS, Pedroza C, Contant CF, Song JX; et al. (2005). "Diagnostic criteria for postconcussional syndrome after mild to moderate traumatic brain injury". Journal of Neuropsychiatry and Clinical Neurosciences. 17 (3): 350–356. doi:doi: 10.1176/appi.neuropsych.17.3.350 Check |doi= value (help). PMID 16179657.
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  8. 8.0 8.1 Cantu RC (2007). "Chronic traumatic encephalopathy in the National Football League". Neurosurgery. 61 (2): 223–225. doi:10.1227/01.NEU.0000255514.73967.90. PMID 17762733.
  9. McCrory P (2001). "Does second impact syndrome exist?". Clinical Journal of Sport Medicine. 11 (3): 144–149. PMID 11495318.
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