Brain recovery is defined as resolution of symptoms, return to baseline cognitive performance, and no symptoms on exertion. A common misconception is that almost all patients with mild TBI will make a full recovery.[2]Maas AIR, Menon DK, Manley GT, et al. Traumatic brain injury: progress and challenges in prevention, clinical care, and research. Lancet Neurol. 2022 Nov;21(11):1004-60.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10427240
http://www.ncbi.nlm.nih.gov/pubmed/36183712?tool=bestpractice.com
Although some systematic reviews suggested recovery from symptoms by 3-12 months post-injury, these reviews included studies with small sample sizes and high loss-to-follow-up rates.[78]Cassidy JD, Cancelliere C, Carroll LJ, et al. Systematic review of self-reported prognosis in adults after mild traumatic brain injury: results of the International Collaboration on Mild Traumatic Brain Injury Prognosis. Arch Phys Med Rehabil. 2014 Mar;95(3 Suppl):S132-51.
http://www.ncbi.nlm.nih.gov/pubmed/24581902?tool=bestpractice.com
[79]Carroll LJ, Cassidy JD, Peloso PM, et al. Prognosis for mild traumatic brain injury: results of the WHO Collaborating Centre Task Force on Mild Traumatic Brain Injury. J Rehabil Med. 2004 Feb;(43 suppl):84-105.
http://www.ncbi.nlm.nih.gov/pubmed/15083873?tool=bestpractice.com
[80]Machamer J, Temkin N, Dikmen S, et al. Symptom frequency and persistence in the first year after traumatic brain injury: a TRACK-TBI study. J Neurotrauma. 2022 Mar;39(5-6):358-70.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8892966
http://www.ncbi.nlm.nih.gov/pubmed/35078327?tool=bestpractice.com
Subsequent longitudinal research suggests that more than half of patients with mild TBI have functional impairments (e.g., reduced work capacity, problems with social function, family disruption) at 12 months after injury and 42% to 49% of those with mild TBI experience at least four symptoms at 12 months.[80]Machamer J, Temkin N, Dikmen S, et al. Symptom frequency and persistence in the first year after traumatic brain injury: a TRACK-TBI study. J Neurotrauma. 2022 Mar;39(5-6):358-70.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8892966
http://www.ncbi.nlm.nih.gov/pubmed/35078327?tool=bestpractice.com
[81]Theadom A, Parag V, Dowell T, et al. Persistent problems 1 year after mild traumatic brain injury: a longitudinal population study in New Zealand. Br J Gen Pract. 2016 Jan;66(642):e16-23.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4684031
http://www.ncbi.nlm.nih.gov/pubmed/26719482?tool=bestpractice.com
The most prevalent chronic symptoms are headaches, difficulty concentrating, fatigue, and dizziness.[82]Hiploylee C, Dufort PA, Davis HS, et al. Longitudinal study of postconcussion syndrome: not everyone recovers. J Neurotrauma. 2017 Apr 15;34(8):1511-23.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5397249
http://www.ncbi.nlm.nih.gov/pubmed/27784191?tool=bestpractice.com
Physical symptoms decline more markedly over time, whereas cognitive symptoms are more constant over time and become the most prevalent of the two by 3-6 months post-injury.[80]Machamer J, Temkin N, Dikmen S, et al. Symptom frequency and persistence in the first year after traumatic brain injury: a TRACK-TBI study. J Neurotrauma. 2022 Mar;39(5-6):358-70.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8892966
http://www.ncbi.nlm.nih.gov/pubmed/35078327?tool=bestpractice.com
One observational prospective cohort study showed accuracy of clinical gestalt for predicting mild TBI outcomes is poor. Of 217 mild TBI cases, whilst clinicians predicted that 90% of patients would fully recover by 6 months, only 50% achieved full functional and symptomatic recovery.[83]Korley FK, Peacock WF, Eckner JT, et al. Clinical gestalt for early prediction of delayed functional and symptomatic recovery from mild traumatic brain injury is inadequate. Acad Emerg Med. 2019 Dec;26(12):1384-7.
https://onlinelibrary.wiley.com/doi/10.1111/acem.13844
http://www.ncbi.nlm.nih.gov/pubmed/31397520?tool=bestpractice.com
In one study of concussed athletes (n=1751, 19.2 years, 63.2% male) participants in 22 different sports began the return to participation (RTP) protocol in a median of 6.4 days and the median total RTP duration was 12.8 days.[84]Broglio SP, McAllister T, Katz BP, et al. The natural history of sport-related concussion in collegiate athletes: findings from the NCAA-DoD CARE Consortium. Sports Med. 2022 Feb;52(2):403-15.
http://www.ncbi.nlm.nih.gov/pubmed/34427877?tool=bestpractice.com
Clinical symptoms of sports-related mild TBI typically resolve spontaneously, with 80% to 90% of concussed older adolescents and adults returning to preinjury levels of clinical function within 2 weeks.[3]Harmon KG, Clugston JR, Dec K, et al. American Medical Society for Sports Medicine position statement on concussion in sport. Clin J Sport Med. 2019 Mar;29(2):87-100.
https://journals.lww.com/cjsportsmed/fulltext/2019/03000/american_medical_society_for_sports_medicine.1.aspx
http://www.ncbi.nlm.nih.gov/pubmed/30730386?tool=bestpractice.com
[85]McCrea M, Guskiewicz K, Randolph C, et al. Incidence, clinical course, and predictors of prolonged recovery time following sport-related concussion in high school and college athletes. J Int Neuropsychol Soc. 2013 Jan;19(1):22-33.
http://www.ncbi.nlm.nih.gov/pubmed/23058235?tool=bestpractice.com
In younger athletes, clinical recovery may take longer, with return to preinjury levels of function within 4 weeks.[3]Harmon KG, Clugston JR, Dec K, et al. American Medical Society for Sports Medicine position statement on concussion in sport. Clin J Sport Med. 2019 Mar;29(2):87-100.
https://journals.lww.com/cjsportsmed/fulltext/2019/03000/american_medical_society_for_sports_medicine.1.aspx
http://www.ncbi.nlm.nih.gov/pubmed/30730386?tool=bestpractice.com
[86]Zemek R, Barrowman N, Freedman SB, et al. Clinical risk score for persistent postconcussion symptoms among children with acute concussion in the ED. JAMA. 2016 Mar 8;315(10):1014-25.
https://jamanetwork.com/journals/jama/fullarticle/2499274
http://www.ncbi.nlm.nih.gov/pubmed/26954410?tool=bestpractice.com
One systematic review revealed that 93% of athletes of all ages have a full return to learning with no additional academic support by 10 days.[87]Putukian M, Purcell L, Schneider KJ, et al. Clinical recovery from concussion-return to school and sport: a systematic review and meta-analysis. Br J Sports Med. 2023 Jun;57(12):798-809.
http://www.ncbi.nlm.nih.gov/pubmed/37316183?tool=bestpractice.com
While many students can quickly return to learning with no or minimal difficulty, the process can be more challenging for those who have specific considerations (eg, high acute symptom severity, a prior learning disability) that may affect recovery.[7]Patricios JS, Schneider KJ, Dvorak J, et al. Consensus statement on concussion in sport: the 6th International Conference on Concussion in Sport-Amsterdam, October 2022. Br J Sports Med. 2023 Jun;57(11):695-711.
https://publications.aap.org/pediatrics/article/142/6/e20183074/37534/Sport-Related-Concussion-in-Children-and
http://www.ncbi.nlm.nih.gov/pubmed/37316210?tool=bestpractice.com
Other prognostic factors include:
Psychiatric comorbidity: In adults, pre-injury mental health problems and post-injury psychological distress (symptoms of depression and anxiety) are robust predictors of prolonged recovery.[88]Silverberg ND, Gardner AJ, Brubacher JR, et al. Systematic review of multivariable prognostic models for mild traumatic brain injury. J Neurotrauma. 2015 Apr 15;32(8):517-26.
http://www.ncbi.nlm.nih.gov/pubmed/25222514?tool=bestpractice.com
[89]Iverson GL, Gardner AJ, Terry DP, et al. Predictors of clinical recovery from concussion: a systematic review. Br J Sports Med. 2017 Jun;51(12):941-8.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5466929
http://www.ncbi.nlm.nih.gov/pubmed/28566342?tool=bestpractice.com
[90]Silverberg ND, Iaccarino MA, Panenka WJ, et al. Management of concussion and mild traumatic brain injury: a synthesis of practice guidelines. Arch Phys Med Rehabil. 2020 Feb;101(2):382-93.
https://www.archives-pmr.org/article/S0003-9993(19)31305-X/fulltext
http://www.ncbi.nlm.nih.gov/pubmed/31654620?tool=bestpractice.com
Depression and/or PTSD are associated with a considerable decrease in functional outcome and health-related quality of life.[91]Haagsma JA, Scholten AC, Andriessen TM, et al. Impact of depression and post-traumatic stress disorder on functional outcome and health-related quality of life of patients with mild traumatic brain injury. J Neurotrauma. 2015 Jun 1;32(11):853-62.
http://www.ncbi.nlm.nih.gov/pubmed/25320845?tool=bestpractice.com
Previous injuries: prior injuries increase the likelihood for future injury and complicate symptom resolution.[4]Mayer AR, Quinn DK, Master CL. The spectrum of mild traumatic brain injury: A review. Neurology. 2017 Aug 8;89(6):623-32.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5562956
http://www.ncbi.nlm.nih.gov/pubmed/28701496?tool=bestpractice.com
[81]Theadom A, Parag V, Dowell T, et al. Persistent problems 1 year after mild traumatic brain injury: a longitudinal population study in New Zealand. Br J Gen Pract. 2016 Jan;66(642):e16-23.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4684031
http://www.ncbi.nlm.nih.gov/pubmed/26719482?tool=bestpractice.com
[92]van Ierssel J, Osmond M, Hamid J, et al. What is the risk of recurrent concussion in children and adolescents aged 5-18 years? A systematic review and meta-analysis. Br J Sports Med. 2021 Jun;55(12):663-9.
http://www.ncbi.nlm.nih.gov/pubmed/33077482?tool=bestpractice.com
Female sex: retrospective analysis of young athletes (aged 11-18 years) with a first-time mild TBI sustained while playing organised sport found that female athletes remained symptomatic for a median 28 days, compared with 11 days for male athletes of similar age, irrespective of the sport played.[93]Neidecker JM, Gealt DB, Luksch JR, et al. First-time sports-related concussion recovery: the role of sex, age, and sport. J Am Osteopath Assoc. 2017 Oct 1;117(10):635-42.
http://jaoa.org/article.aspx?articleid=2656577
http://www.ncbi.nlm.nih.gov/pubmed/28973180?tool=bestpractice.com