Editing Concussion (section)

==Prognosis==
The majority of children and adults fully recover from a concussion, however some may experience a prolonged recovery.<ref>{{cite web|date=2019-03-11|title=Symptoms of Traumatic Brain Injury (TBI) {{!}} Concussion {{!}} Traumatic Brain Injury {{!}} CDC Injury Center|url=https://www.cdc.gov/traumaticbraininjury/symptoms.html|access-date=2020-12-07|website=www.cdc.gov|language=en-us|archive-date=2021-07-10|archive-url=https://web.archive.org/web/20210710114225/https://www.cdc.gov/traumaticbraininjury/symptoms.html|url-status=live}}</ref><ref name="pmid28566342">{{cite journal | vauthors = Iverson GL, Gardner AJ, Terry DP, Ponsford JL, Sills AK, Broshek DK, Solomon GS | title = Predictors of clinical recovery from concussion: a systematic review | journal = British Journal of Sports Medicine | volume = 51 | issue = 12 | pages = 941–948 | date = June 2017 | pmid = 28566342 | pmc = 5466929 | doi = 10.1136/bjsports-2017-097729 }}</ref> There is no single physical test, blood test (or fluid biomarkers), or imaging test that can be used to determine when a person has fully recovered from concussion.<ref name="pmid28455363">{{cite journal | vauthors = Kamins J, Bigler E, Covassin T, Henry L, Kemp S, Leddy JJ, Mayer A, McCrea M, Prins M, Schneider KJ, Valovich McLeod TC, Zemek R, Giza CC | display-authors = 6 | title = What is the physiological time to recovery after concussion? A systematic review | journal = British Journal of Sports Medicine | volume = 51 | issue = 12 | pages = 935–940 | date = June 2017 | pmid = 28455363 | doi = 10.1136/bjsports-2016-097464 | s2cid = 206883066 | doi-access = free }}</ref>

A person's recovery may be influenced by a variety of factors that include age at the time of injury, intellectual abilities, family environment, social support system, occupational status, coping strategies, and financial circumstances.<ref>{{cite book|title=Bradley's neurology in clinical practice.|year=2012|publisher=Elsevier/Saunders|location=Philadelphia, PA|isbn=978-1-4377-0434-1|vauthors=Murray ED, Buttner N, Price BH |volume=1|edition=6th|pages=111|veditors=Bradley WG, Daroff RB, Fenichel GM, Jankovic J |chapter=Depression and Psychosis in Neurological Practice}}</ref> Factors such as a previous head injury or a coexisting medical condition have been found to predict longer-lasting persisting concussion symptoms.<ref name="Hall05">{{cite journal | vauthors = Hall RC, Hall RC, Chapman MJ | title = Definition, diagnosis, and forensic implications of postconcussional syndrome | journal = Psychosomatics | volume = 46 | issue = 3 | pages = 195–202 | year = 2005 | pmid = 15883140 | doi = 10.1176/appi.psy.46.3.195 | doi-access = free }}</ref> 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.<ref name="Iverson2005">{{cite journal | vauthors = Iverson GL | title = Outcome from mild traumatic brain injury | journal = Current Opinion in Psychiatry | volume = 18 | issue = 3 | pages = 301–317 | date = May 2005 | pmid = 16639155 | doi = 10.1097/01.yco.0000165601.29047.ae | s2cid = 23068406 }}</ref> Longer periods of amnesia or loss of consciousness immediately after the injury may indicate longer recovery times from residual symptoms.<ref name="Masferrer" /> Other strong factors include participation in a contact sport and body mass size.<ref name="Schulz04">{{cite journal | vauthors = Schulz MR, Marshall SW, Mueller FO, Yang J, Weaver NL, Kalsbeek WD, Bowling JM | title = Incidence and risk factors for concussion in high school athletes, North Carolina, 1996-1999 | journal = American Journal of Epidemiology | volume = 160 | issue = 10 | pages = 937–944 | date = November 2004 | pmid = 15522850 | doi = 10.1093/aje/kwh304 | doi-access = free }}</ref>

=== Pediatric concussion ===
Most children recover completely from concussion in less than four weeks, however 15–30% of youth may experience symptoms that last longer than a month.<ref name="Prognosticators of persistent sympt">{{cite journal | vauthors = Zemek RL, Farion KJ, Sampson M, McGahern C | title = Prognosticators of persistent symptoms following pediatric concussion: a systematic review | journal = JAMA Pediatrics | volume = 167 | issue = 3 | pages = 259–265 | date = March 2013 | pmid = 23303474 | doi = 10.1001/2013.jamapediatrics.216 }}</ref><ref name="CDC2018JAMA">{{cite journal | vauthors = Lumba-Brown A, Yeates KO, Sarmiento K, Breiding MJ, Haegerich TM, Gioia GA, Turner M, Benzel EC, Suskauer SJ, Giza CC, Joseph M, Broomand C, Weissman B, Gordon W, Wright DW, Moser RS, McAvoy K, Ewing-Cobbs L, Duhaime AC, Putukian M, Holshouser B, Paulk D, Wade SL, Herring SA, Halstead M, Keenan HT, Choe M, Christian CW, Guskiewicz K, Raksin PB, Gregory A, Mucha A, Taylor HG, Callahan JM, DeWitt J, Collins MW, Kirkwood MW, Ragheb J, Ellenbogen RG, Spinks TJ, Ganiats TG, Sabelhaus LJ, Altenhofen K, Hoffman R, Getchius T, Gronseth G, Donnell Z, O'Connor RE, Timmons SD | display-authors = 6 | title = Centers for Disease Control and Prevention Guideline on the Diagnosis and Management of Mild Traumatic Brain Injury Among Children | journal = JAMA Pediatrics | volume = 172 | issue = 11 | pages = e182853 | date = November 2018 | pmid = 30193284 | pmc = 7006878 | doi = 10.1001/jamapediatrics.2018.2853 }}</ref><ref name="Zimmerman_2021" />

=== People aged 65+ with concussion ===
Mild traumatic brain injury recovery time in people over age 65 may have increased complications due to elevated health concerns, or [[comorbidities]].<ref name="Flanagan_2005">{{cite journal | vauthors = Flanagan SR, Hibbard MR, Gordon WA | title = The impact of age on traumatic brain injury | journal = Physical Medicine and Rehabilitation Clinics of North America | volume = 16 | issue = 1 | pages = 163–177 | date = February 2005 | pmid = 15561549 | doi = 10.1016/j.pmr.2004.06.012 }}</ref> This often results in longer hospitalization duration, poorer cognitive outcomes, and higher mortality rates.<ref name="Flanagan_2005" />

=== Repeat concussion ===
For unknown reasons, having had one concussion significantly increases a person's risk of having another.<ref name="moser" /><ref name="Merck2017" /> Having previously sustained a sports concussion has been found to be a strong factor increasing the likelihood of a concussion in the future. People who have had a concussion seem more susceptible to another one, particularly if the new injury occurs before symptoms from the previous concussion have completely gone away. It is also a negative process if smaller impacts cause the same symptom severity.<ref name="2008 Consensus Statement">{{cite journal | vauthors = McCrory P, Meeuwisse W, Johnston K, Dvorak J, Aubry M, Molloy M, Cantu R | title = Consensus statement on concussion in sport: the 3rd International Conference on Concussion in Sport held in Zurich, November 2008 | journal = Journal of Athletic Training | volume = 44 | issue = 4 | pages = 434–448 | date = Jul–Aug 2009 | pmid = 19593427 | pmc = 2707064 | doi = 10.4085/1062-6050-44.4.434 }}</ref> Repeated concussions may increase a person's risk in later life for dementia, Parkinson's disease, and depression.<ref name="Merck2017" />

===Post-concussion syndrome===
{{Main|Post-concussion syndrome}}
In post-concussion syndrome, symptoms do not resolve for weeks, months, or years after a concussion, and may occasionally be permanent.<ref name="Ryan03">{{cite journal | vauthors = Ryan LM, Warden DL | title = Post concussion syndrome | journal = International Review of Psychiatry | volume = 15 | issue = 4 | pages = 310–316 | date = November 2003 | pmid = 15276952 | doi = 10.1080/09540260310001606692 | url = https://zenodo.org/record/1234457 | access-date = 2019-07-13 | url-status = live | s2cid = 32790756 | archive-url = https://web.archive.org/web/20191210010140/https://zenodo.org/record/1234457 | archive-date = 2019-12-10 }}</ref> About 10% to 20% of people have persisting concussion symptoms for more than a month.<ref name="Prognosticators of persistent sympt"/> Symptoms may include headaches, dizziness, fatigue, [[anxiety]], memory and attention problems, sleep problems, and irritability.<ref name="Boake">{{cite journal | vauthors = Boake C, McCauley SR, Levin HS, Pedroza C, Contant CF, Song JX, Brown SA, Goodman H, Brundage SI, Diaz-Marchan PJ | display-authors = 6 | title = Diagnostic criteria for postconcussional syndrome after mild to moderate traumatic brain injury | journal = The Journal of Neuropsychiatry and Clinical Neurosciences | volume = 17 | issue = 3 | pages = 350–356 | year = 2005 | pmid = 16179657 | doi = 10.1176/appi.neuropsych.17.3.350 | url = http://neuro.psychiatryonline.org/cgi/content/full/17/3/350 | url-status = dead | archive-url = https://archive.today/20061006012312/http://neuro.psychiatryonline.org/cgi/content/full/17/3/350 | archive-date = 2006-10-06 | url-access = subscription }}</ref> Rest, a previously recommended recovery technique, has limited effectiveness.<ref name="Willer06">
{{cite journal | vauthors = Willer B, Leddy JJ | title = Management of concussion and post-concussion syndrome | journal = Current Treatment Options in Neurology | volume = 8 | issue = 5 | pages = 415–426 | date = September 2006 | pmid = 16901381 | doi = 10.1007/s11940-006-0031-9 | s2cid = 15289680 }}
</ref> A recommended treatment in both children and adults with symptoms beyond 4 weeks involves an active rehabilitation program with reintroduction of non-contact aerobic activity.<ref name="CDC2018JAMA"/> Progressive physical exercise has been shown to reduce long-term post-concussive symptoms.<ref name="CDC2018JAMA" /> Symptoms usually go away on their own within months<ref name=ParikhKoch/> but may last for years.<ref>{{cite journal|vauthors=Klein A|title=Pure oxygen can help concussion|journal=New Scientist|volume=236|issue=3151|pages=10|date=Nov 11, 2017|url=https://www.newscientist.com/article/mg23631514-600|bibcode=2017NewSc.236...10K|doi=10.1016/S0262-4079(17)32192-9|access-date=November 11, 2017|archive-date=March 8, 2021|archive-url=https://web.archive.org/web/20210308215748/https://www.newscientist.com/article/2152247-breathing-pure-oxygen-could-heal-footballers-with-concussion/|url-status=live|url-access=subscription}}</ref><ref name="pmid29376093">{{cite journal | vauthors = Mouzon BC, Bachmeier C, Ojo JO, Acker CM, Ferguson S, Paris D, Ait-Ghezala G, Crynen G, Davies P, Mullan M, Stewart W, Crawford F | display-authors = 6 | title = Lifelong behavioral and neuropathological consequences of repetitive mild traumatic brain injury | journal = Annals of Clinical and Translational Neurology | volume = 5 | issue = 1 | pages = 64–80 | date = January 2018 | pmid = 29376093 | pmc = 5771321 | doi = 10.1002/acn3.510 }} *{{lay source |template = cite web|url = https://www.sciencedaily.com/releases/2017/12/171214100835.htm|title = Mild traumatic brain injury causes long-term damage in mice|date = December 14, 2017 |website = Science Daily  }}</ref> The question of whether the syndrome is due to structural damage or other factors such as psychological ones, or a combination of these, has long been the subject of debate.<ref name="Bryant08">{{cite journal | vauthors = Bryant RA | title = Disentangling mild traumatic brain injury and stress reactions | journal = The New England Journal of Medicine | volume = 358 | issue = 5 | pages = 525–527 | date = January 2008 | pmid = 18234757 | doi = 10.1056/NEJMe078235 }}</ref>

===Cumulative effects===
As of 1999, cumulative effects of concussions were poorly understood, especially the effects on children. 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.<ref name="harmon">{{cite journal | vauthors = Harmon KG | title = Assessment and management of concussion in sports | journal = American Family Physician | volume = 60 | issue = 3 | pages = 887–92, 894 | date = September 1999 | pmid = 10498114 | url = http://www.aafp.org/afp/990901ap/887.html | access-date = 2008-01-09 | url-status = dead | archive-url = https://web.archive.org/web/20210304133621/https://www.aafp.org/afp/1999/0901/p887.html | archive-date = 2021-03-04 }}</ref> Symptoms may be more severe and changes in [[neurophysiology]] can occur with the third and subsequent concussions.<ref name=moser/> As of 2006, studies 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.<ref name="Pellman">{{cite journal | vauthors = Pellman EJ, Viano DC | title = Concussion in professional football: summary of the research conducted by the National Football League's Committee on Mild Traumatic Brain Injury | journal = Neurosurgical Focus | volume = 21 | issue = 4 | pages = E12 | date = October 2006 | pmid = 17112190 | doi = 10.3171/foc.2006.21.4.13 | doi-access = free }}</ref>

Cumulative effects may include [[chronic traumatic encephalopathy]], [[mental disorder|psychiatric disorder]]s and loss of [[long-term memory]]. For example, the risk of developing clinical depression has been found to be significantly greater for retired [[American football]] players with a history of three or more concussions than for those with no concussion history.<ref name="cantuCTE">{{cite journal | vauthors = Cantu RC | title = Chronic traumatic encephalopathy in the National Football League | journal = Neurosurgery | volume = 61 | issue = 2 | pages = 223–225 | date = August 2007 | pmid = 17762733 | doi = 10.1227/01.NEU.0000255514.73967.90 | title-link = Chronic traumatic encephalopathy }}</ref> An experience of three or more concussions is associated with a fivefold greater chance of developing [[Alzheimer's disease]] earlier and a threefold greater chance of developing [[memory]] deficits.<ref name=cantuCTE/>

Chronic traumatic encephalopathy, or "CTE", 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 was previously referred to as "dementia pugilistica", or "punch drunk" syndrome, as it was first noted in boxers. The disease can lead to cognitive and physical disabilities such as [[parkinsonism]], speech and memory problems, slowed mental processing, tremor, depression, and inappropriate behavior.<ref name="Mendez">{{cite journal | vauthors = Mendez MF | title = The neuropsychiatric aspects of boxing | journal = International Journal of Psychiatry in Medicine | volume = 25 | issue = 3 | pages = 249–262 | year = 1995 | pmid = 8567192 | doi = 10.2190/CUMK-THT1-X98M-WB4C | s2cid = 20238578 }}</ref> It shares features with Alzheimer's disease.<ref name="Jordan00">{{cite journal | vauthors = Jordan BD | title = Chronic traumatic brain injury associated with boxing | journal = Seminars in Neurology | volume = 20 | issue = 2 | pages = 179–185 | year = 2000 | pmid = 10946737 | doi = 10.1055/s-2000-9826 | s2cid = 41087553 }}</ref>

===Second-impact syndrome===
{{Main|Second-impact syndrome}}
Second-impact syndrome, in which the brain swells dangerously after a minor blow, may occur in very rare cases.<ref>{{cite web |title=Second Impact Syndrome: the Dangerous Effect of Multiple Concussions |url=https://reverehealth.com/live-better/second-impact-syndrome-dangerous-effect-multiple-concussions/#:~:text=Second%20impact%20syndrome%20(SIS)%20occurs,rapid%20and%20severe%20brain%20swelling. |website=Revere Health |access-date=10 November 2022}}</ref> The condition may develop in people who receive a second blow days or weeks after an initial concussion before its symptoms have gone away.<ref name=Bowen03/> 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 [[arteriole]]s lose the ability to regulate their diameter, causing a loss of control over cerebral blood flow.<ref name=moser/> As the brain [[Swelling (medical)|swells]], intracranial pressure rapidly rises.<ref name=CookSchweer/> The brain can [[brain herniation|herniate]], and the brain stem can fail within five minutes.<ref name=Bowen03/> Except in boxing, all cases have occurred in athletes under age&nbsp;20.<ref name=Team/> Due to the very small number of documented cases, the diagnosis is controversial, and doubt exists about its validity.<ref name="McCroryP01">{{cite journal | vauthors = McCrory P | title = Does second impact syndrome exist? | journal = Clinical Journal of Sport Medicine | volume = 11 | issue = 3 | pages = 144–149 | date = July 2001 | pmid = 11495318 | doi = 10.1097/00042752-200107000-00004 }}</ref> A 2010 ''Pediatrics'' review article stated that there is debate whether the brain swelling is due to two separate hits or to just one hit, but in either case, catastrophic football head injuries are three times more likely in high school athletes than in college athletes.<ref name=Peds2010/>