Subconcussion, Concussion, and Cognitive Decline: The Impact of Sports Related Collisions (2022)

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10.52916/jmrs224081 Subconcussion, Concussion, and Cognitive Decline: The Impact of Sports Related Collisions (1)Subconcussion, Concussion, and Cognitive Decline: The Impact of Sports Related Collisions (2)

Abstract Introduction Mechanisms Clinical Relevance Assessment Learning Interventions Research ConclusionConflict of InterestFundingReferences

Emma Dioso1, John Cerillo2, Mohammed Azab3, Devon Foster4, Isaac Smith4, Owen Leary5, Michael Goutnik4, Brandon LuckeWold4*Subconcussion, Concussion, and Cognitive Decline: The Impact of Sports Related Collisions (3)
1Department of Neurosurgery, University of Utah, Salt Lake City, UT2Nova Southeastern University, Dr. Kiran C. Patel College of Osteopathic Medicine, Clearwater, FL
3University of Boise State, Biomedical Science Department, Boise, ID
4University of Florida, Department of Neurosurgery, Gainesville, FL
5Brown University, Department of Neurosurgery, Providence, RI

Correspondence to: Brandon Lucke-Wold, University of Florida, Department of Neurosurgery, Gainesville, FL
Received date: June 23, 2022; Accepted date: July 13, 2022; Published date: July 20, 2022
Citation: Dioso E, Cerillo J, Azab M, et al. Subconcussion, Concussion, and Cognitive Decline: The Impact of Sports Related Collisions. J Med Res Surg. 2022; 3(4):54-63. doi: 10.52916/jmrs224081
Copyright: ©2022 Dioso E, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricteduse, distribution and reproduction in any medium, provided the original author and source are credited.


Subconcussion can cause long-term consequences for patients. Increasing understanding of whatcauses the injury and how it can be assessed is important. This paper focuses on the pathophysiology,epidemiology, and assessment tools. Specific emphasis is placed on early diagnosis to implementtreatment. Current research is targeting improved pharmaceutic and biomechanic innovations. Enhancedunderstanding of subconcussion will improve outcomes for patients and allow clinicians to implementtreatments earlier.


Subconcussion, Assessment, Interventions, Future discoveries.

(Video) Sport-Related Concussions and Repetitive Head Impacts

Introduction :

While subconcussive injuries are not novel in anecdotalobservations or practice, as Martland vividly used the term“punch drunk” in 1928, the literature surrounding the definitionof subconcussion in emerging. Subconcussive head injuries aredefined as injuries in which an impact to the head does notresult in clinical symptoms of a concussion. That is, while theinjury is the result of a traumatic impact from a biomechanicalforce to the head and/or upper body, the impact is notenough to reach the threshold needed to produce concussivesymptoms [1]. Contact and noncontact sports give rise to manycommonplace scenarios that could potentially give rise tosubconcussions, taking a charge on a basketball court, hitting the wall backstroking during a swim meet, heading a ball insoccer, and various others. While each impact may not causeenough damage to reach threshold of noticeable symptoms,repetition of these subconcussive injuries may compound overtime [1]. Together, these cumulative injuries do have dramaticimpacts due to the microstructural and functional changes thatresult in the brain [1,2].

Chronic Traumatic Encephalopathy (CTE) is theneurodegenerative syndrome associated with repetitivesubconcussive traumatic injuries [3]. CTE is characterized bythe “accumulation of abnormal tau in neurons and astrogliadistributed around small blood vessels at the depths of thesulci”[4]. Notably, long-term consequences of subconcussive injuries more commonly present as dementia without p-taupathology or Alzheimer’s disease-like-β-amyloid deposits [5,6].

Patients with histories of subconcussive injuries and other braintrauma that develop dementia often characteristically exhibitdeficits in their episodic, working and spatial memory [7-9]. Asa single subconcussive injury by definition causes no apparentclinical symptoms, the mechanism by which cumulativesubconcussive injuries lead to such detrimental outcomesis not well understood, especially as time between events isseemingly not significant. Consequently, the delayed onset ofdebilitating symptoms and memory loss deem the progressionof subconcussive injuries challenging to evaluate in human andmouse models, though new data and possible mechanisms areemerging [10].

Former athletes developing aggressive behaviors, loss ofcontrol, impaired attention, depression, memory loss, andexecutive dysfunction associated with CTE have been describedin the literature on numerous occasions [11]. In 2013, Stern andcolleagues described two clinical presentations of CTE. The firstvariant presents with mood and behavior changes at an averageof 35 and progresses to severe cognitive symptoms. The secondvariant presents with cognitive symptoms at an average of 60and progresses to encompass mood and behavioral changes[12]. As each impact may cause mechanical loading of sensoryand neural components within the head, various structurescontributing to sensorimotor control of balance may also beimpacted [13].


Concussions and subconcussions are a result of rapidacceleration or deceleration in a linear or rotational plane [14-16]. Most commonly these fast-paced injuries occur during falls,Motor Vehicle Accidents (MVAs), or Sports Related Collisions(SRCs) [15,17]. A direct or indirect blow to the head and neckcan cause the brain and skull to “shake together violently” asintended through the latin root concussus. These injuries leadto a disruption in the neuronal membrane causing an effluxof potassium, influx of calcium, and increased glutamateconcentrations [18-20]. A 2015 study on colligate footballplayers using serial fMRI 1 day, 1 week, and 1 month postconcussion showed that return of cerebral blood flow waspositively correlated with player recovery [21]. Furthermore,decreased cerebral blood flow along with increased lactic acidproduction and intracellular Ca2+ leads to a continuation ofcellular damage [18-20]. These neurometabolic changes lead tochronic depolarization, cellular damage and eventually cognitivesuppression [16,18-20]. Literature suggests when these headinjuries occur in children and adolescents, long term cognitiveand behavioral deficits may persist [22,23].

From an SRC standpoint, head impacts potentially leading toconcussion and sub-concussion can occur during practice,gameplay, and celebration [24-26]. A collegiate ice hockey studyfrom 2014 showed that only half of recorded head impactswere caused between players while the other half occurredwith the environment (boards, ice) or equipment; therefore, itis important to consider non player-to-player contact [25]. It isconsistently noted throughout literature, however, that the vastmajority of sports concussions occur due to collision between players [26,27].

A study from the University of Florida collected practice drillimpact numbers during the 2016-2017 & 2017-2018 footballseasons and found that an average lineman experienced a headimpact >10 g once every 8.3 minutes of drill time. Asken et.alfound that limiting time of specific drill types could lead todecreased exposure of repetitive head impacts [24].

Adolescent, colligate, and professional sports have been thefocus of concussion research for the past decade. Studyingthese populations is vital, as contact sports including football,soccer, hockey, wrestling, boxing, lacrosse, and basketball haveshown to consistently serve as the most prevalent producers ofhead injuries and subsequent concussions (Figure 1 and Figure2) [19,26,28-31].

Figure 1: National trends in number of emergency department (ED) visits forconcussion due to various contact and non-contact sports among persons ofall ages, as estimated by the National Electronic Injury Surveillance System(NEISS), United States, 2012-2021. Annual gaps in NEISS estimates are due toestimate of less than 1,200 cases, less than 20 cases available for estimate, orcoefficient of variation exceeding 33%.

(Video) What do we know about subconcussion & repetitive head impacts in athletes?

Figure 2: National trends in number of emergency department (ED) visits forconcussion due to contact sports and non-contact sports among athlete agegroup, as estimated by the NEISS, United States, 2012-2021. Annual gaps inNEISS estimates are due to estimate of less than 1,200 cases, less than 20cases available for estimate, or coefficient of variation exceeding 33%.

Veliz et al., reported that 28% of collegiate athletes between2014-2016 reported at-least one concussion over their lifetime[32]. In an additional study, Veliz et al., showed that thenumber of students (grades 8,10,12) who self-reported at-leastone concussion grew from nearly 20% to 24% between 2016and 2020, however this survey was not focused on studentathletes [33]. Although these number are growing, Lincoln described the increase incidence of concussions in youth sportsbe due to increased reporting rather than actual increasedoccurances [28]. In contrast to the prior studies, the NationalElectronic Injury Surveillance System (NEISS-AIP) found thatconcussion rates among <17-year-old athletes declined 27%between 2001-2018. The NEISS-AIP system recorded data froma representative sample of U.S emergency departments andfound that 45% of head injury visits among adolescents weredue to contact sports [34,35].

As for professional sports, A 2018 study on concussion numbersin National Football League (NFL) reported an average greaterthan one concussion for every two games [36]. While a 2022study reported concussion prevalence in the National HockeyLeague (NHL) to be one concussion for every 17 games [37].

Clinical Relevance

Traumatic brain injuries are associated with significantmorbidities and mortalities [17]. According to CDC surveillancestudy, TBIs related deaths represented about 30% of all injuryrelated deaths [38]. Moreover, the rate of emergency roomvisits due to all TBIs increased by 70% from 2001 to 2010 [39].The increased rate of TBI-related hospitalization may be relatedto the increased awareness among people regarding the hazardsof concussion and related consequences leading to more ERvisits [17]. TBIs related health services are considered highlycostly for the community [40]. The national institute of healthreported that the costs of TBIs exceeds other chronic medicalconditions [41]. The rates of admission are higher among theelderly people (age >75), (2,232.2 per 100,000 population) andthose 15-24 years (1,080.7) according to a CDC report [17]. Inrecent years, studies have reported a marked increase in thenumber of annual pediatric ED visits related to concussion [42].About 5.3 million Americans are suffering from TBI relateddisabilities [43]. The rates of hospitalizations and deaths werealso higher among the elderly group [17].

Studies involving the medical costs of TBIs are deficient [44].The study conducted by Brooks and colleagues involved only asmall sample of population [45]. While McGarry and colleaguesinvestigated a larger population, they excluded the young folks[45,46]. Moreover, the assessment of the costs included onlythose covered by health maintenance organizations and thoseassociated with acute care services [47,48]. The early treatmentof intracranial complications of TBIs and the somatic, affective,and cognitive complications are expensive. The highestindividual costs are caused by the most severe forms of TBI [49].Research is directed towards implementing methods to studythe costs of health care services related to TBIs and to mitigatethe costs.

Health care utilization and the possible related aspects arepoorly characterized especially in persons living with TBIsequelae [50]. The systems of care for TBIs vary between andwithin countries [51]. The clinical care setting is variable andranges from immediate on-site management to long term care.This variation in care is due to the heterogeneity in resourcesand financial settings [52]. The emergency room is the initialmeeting zone with the concussion patient. Transfer of thepatients from non-specialist hospitals to highly specializedtrauma centers have a positive impact on outcome and costs [53,54]. Several studies categorized TBI patients regardingthe utilization of health services into superutilizers andunderutilizers [55,56]. Salisbury and colleagues consideredsuperutilizers as those patients who have more than 3 hospitalencounters per year one year after trauma which was the samefor the study conducted by Eliacin and colleagues [56]. Between2001 and 2009, the number of children seeking treatment formild TBI increased by 62%. [57]. A large proportion of pediatricpopulation presenting with concussion undergo CT scan fordiagnosis [58,59]. A variety of studies have been designed tocategorize the patients with TBIs according to the need for CTscan in the ED [60-62]. In the United States, about one-thirdof the 80 million CTs requested each year are ordered fromthe ED, nearly half of them involve the brain [63]. There isnot much evidence on the methods of pain management andtheir related costs for patients presenting with concussion [64].Meticulous research should be designed to develop ways toreduce the unnecessary admissions and resource utilizationfor superutilizers. Among TBI survivors, there is not muchdata regarding the aspects of health care utilization long-term(Figure 3) [56].

Figure 3: Utilization pathway of health care and resources by TBI patients.


Signs and symptoms of concussion may potentially be delayed,subtle, or variable in nature. Reliance on athlete-reportedsymptoms make diagnosing concussions on the spot a challengewhen determining if it is safe for an athlete to resume activity[65]. Current assessment strategies for assessing concussionsstart at recognition of injury. After identifying an injury with thepotential of causing a concussion, an assessment of symptomsis performed where cognitive function, cranial nerve function,balance, and potential intercranial bleeding are assessed [66-68].

While concussions exhibit symptoms that can be observed,subconcussions do not, making them more difficult to diagnose.This makes it difficult to determine if it is appropriate for anathlete to return to activity. Acute repetitive trauma to the head has been linked to long-term risk for cognitive decline,neurobehavioral changes, and neurodegenerative disease. Dueto the difficulty in diagnosing subconcussions due to their lackof symptoms, removing athletes from a sporting event afterexperiencing a potentially traumatic head impact is used as apreventative measure [69-71].

The Immediate Postconcussion Assessment and CognitiveTesting 2.0 program (ImPACT) is a computerized test used tomanage sports related concussions by testing cognitive functionof athletes before and after a concussion [72]. Measurementscollected by head-impact monitoring systems provided realtime data, but lacked clinical utility due to error rates andlow specificity in predictive concussion [73] However, thesemonitoring systems did indicate that sustaining an impact of 90 gdoes not result in acute observable balance and neurocognitiveimpairments [74]. This monitoring system is unique in that itoffers to provide objective data, not of the results of an impactof a head injury, but the impact itself -something that theImPACT assessment is incapable of. An Electroencephalographic(EEG) index has been used to track quantitative brain activity ina group of athletes recovering from concussion. An algorithmwas developed for normal brain electrical activity and comparedto the abnormal features of brain electrical activity that wasdetected in athletes recovering from concussion [75]. Whilesimilar to that of the ImPACT assessment in that measurementscan be compared from before and after a concussion occurred,quantitative EEG does not appear useful as a routine screeningmeasure of traumatic brain injury or postconcussive symptoms(Figure 4) [76].

(Video) Studying the Nuances of Sports-Related Subconcussive Hits

Figure 4: Should an Athlete Return to Play?


Concussive effects on learning are well reported: increasedirritability and frustration, decreased attention, difficultywith memory [77,78]. Subconcussive pathology, despite thedisease being poorly understood overall, is also well reported,with CTE being perhaps the most notable long-term sequala [79-81]. A positive correlation exists between the frequencyand magnitude of subconcussive head injury and levels ofTBI biomarkers in the blood [82]. Variability in default modenetwork signaling has also been found in brains of high schoolfootball players in a manner consistent with the effects ofconcussive blows [83].

Subconcussive injury’s relationship to learning, however, is notwell understood. While sharing similar pathophysiology withits more severe counterpart, the absence of clinical signs is ahallmark of subconcussive TBI. This makes recognizing patternsin the classroom elusive as no valid academic metrics identifyingsubconcussive TBI exist.

Talavage et al. [84], found that significantly lower ImPACTneurocognitive test scores corresponded with dorsolateralprefrontal cortex injury in football players during the season.Another study compared ImPACT scores between nonconcussedathletes of high-and low-contact sports and found significantdifferences in Processing Speed and Reaction Time scores, butnot in Verbal Memory, Visual Memory, or Total Symptoms [85].Several studies have examined the effects of headers in socceron school-age children and failed to establish a correlationbetween repeated exposure to the subconcussive hits anddiminished neuropsychological performance [86]. It is importantto note, therefore, that across these studies and in the literaturemore broadly, subconcussed patients are asymptomatic. In theliterature, the deficits are identified only because the studentsare enrolled in TBI studies. Of the subconcussion group, Talavageet al. [84], writes that the “players failed to accrue sufficientshort-term damage to integrative neural systems that theyexhibited externally observable symptoms”. This is emblematicof how the disease manifests in the classroom.

Bearing in mind that repeated subconcussive injury predisposesto concussion and has significant, symptomatic long-termeffects, the absence of cardinal academic signs should not leadone to conclude the relationship is benign [80,87]. It may bethat the brain is too resilient for subconcussive injury to effectlearning in the timeframes studied, or that the severity andrate of manifestation depends on duration and magnitudeof subconcussive exposure. As Ntikas et al. [88], suggested,knowing more about the disease does not ensure that areliable gold-standard assessment, relying on gross cognitivedeficits, would pick up on the effects of subconcussive trauma.Ultimately, the effects on learning will be greatly aided by amore precise definition of what constitutes subconcussive TBIand by enhanced understanding of the mechanism of disease(Table 1) [81,88].





Functionally-Detected Cognitive Impairment in High School Football Players without ClinicallyDiagnosed Concussion [84] 23 males, ages 15-19 years. High school football. Head collisions during season measured with HIT, ImPACT neurocognitive testing before, during, and after season. fMRI imaging. 4 participants exhibited reduced ImPACT scores, reduced fMRI activity in DLPFC despite no clinical signs of TBI.
Are There Subconcussive Neuropsychological Effects in Youth Sports? An Exploratory Study of High- and Low-Contact Sports [85] 282 nonconcussed male high school athletes. High- and low-contact sports. ImPACT scores Significantly faster ImPACT Processing Speed and Reaction Time in low-contact group.
Effects of sub-concussion on neuropsychological performance and its potential mechanisms: A narrative review [86] 18 studies relevant to learning reviewed. Neuropsych. impairment, neuromotor deficit, memory, attention. Evidence in the literature conflicts on neuropsych, impairment, neuromotor deficits, and memory impairment. Subconcussion does impair attention.


Concussive and subconcussive brain injuries can lead tooccupational challenges for affected individuals across theage spectrum, as well as problems with educational activities,sleep, social participation, and activities of daily living [89-91].Such challenges following mild TBI are common and imposea significant economic burden on the healthcare system[92]. Among secondary school- and college-aged studentsexperiencing concussive injuries, a population in which mildTBI is particularly prevalent, ongoing occupational performancelimitations have been reported in as many as 89% of affectedpatients [91]. Further, it has been observed that children with mild TBI may be even more likely to have unmet functional needsrelated to education and occupational limitations compared topatients with moderate and severe injuries, in whom limitationsmay be more readily apparent [93]. Accordingly, proactiveimplementation of occupational therapy interventions mayimprove time to neurologic recovery and promote rapid returnto function [89,94].

Several observational and pilot studies have been conductedto investigate the impact of occupational therapy and variousrelated interventions on functional improvement following TBI,though there remains significant opportunity for further studyof such interventions in mild TBI specifically. First of all, includingoccupational therapists in the initial evaluation of patients withmild TBI has been shown to improve identification of functionalimpairments that may otherwise have been missed [95]. Earlyfocus on improving executive function during acute inpatientrehabilitation following TBI has been shown to modestlyimprove community participation and functional independence1 year after discharge in a heterogenous cohort of patients withcomplicated mild, moderate, and severe TBI [96]. Similarly,increasing the proportion of contextualized functional therapies(versus decontextualized, clinic-based therapies) as part of theOT regimen following TBI has been found to increase treatmentefficacy in a similarly heterogeneous cohort [97]. Oculomotorimpairment has been implicated as a contributor to long-termfunctional impairment following mild TBI, and pilot study datahas suggested that closer collaboration between occupationaltherapy and optometry may be indicated for patients with thesesymptoms [98]. Occupational therapy targeting impairments inability to drive a vehicle have also been shown to be effective ina cohort of returning combat veterans who suffered mild TBI aswell as other injuries [99]. Finally, there is some early evidencethat better patient engagement with occupational therapy aftersustaining combat-related mild TBI may somewhat mitigate riskof suicidal ideation [100].

(Video) Are Concussions Deadly?

Challenges persist in the identification of effective occupationaltherapies for patients with mild TBI, as well as in maximizing theutilization of available resources. The intrinsic heterogeneity of TBI makes it difficult to study, an issue further exacerbated by thelimited availability of high-quality evaluation tools particularlyfor those with mild injuries [96,101]. Furthermore, there are alack of evidence-based guidelines related to when occupationaltherapy should be employed in the post-TBI recovery process,leading to inconsistent referral patterns, and which techniquesshould be utilized, though practice recommendations have beenpreviously published amidst these limitations (Clinical PracticeGuidance: Occupational Therapy and Physical Therapy for MildTraumatic Brain Injury, 2009) [95,102-105]. Recent studies,including a survey of clinicians caring for pediatric mild TBIpatients, have identified that occupational therapy is routinelyutilized for only a minority of patients who may benefit fromit following mild TBI [103,105]. Another study contextualizedthis trend by identifying that utilization may be disparatewith respect to geographic and/or socioeconomic factors[106]. Another study which surveyed practicing occupationaltherapists regarding their confidence in managing concussionand mild TBI found clinician comfort to be highly variable, withclinicians who proactively engaged in continuing educationrelated to concussion being more confident in managingpatients with these injuries [107].


There is a great need for research into imaging, molecular,and clinical correlates of subconcussive and concussive events.Using advanced neuroimaging, including modalities likeTranscranial Magnetic Stimulation (TMS) and Diffusion TensorImaging (DTI), to identify those at risk of long-term sequelae ofrepetitive subconcussive hits is an area to explore [70,108-110].For example, using temporal and spatial data from helmetsduring a football season, combined with fractional anisotropy(measured via DTI), may help inform return to play decisions[108]. Similarly, TMS may help confirm corticomotor inhibitionand GABAergic dysfunction after repetitive subconcussive injury[109,110]. Future work should apply TMS on a larger scale andperhaps incorporate dose-response.

Some biomarkers like Neurofilament Light (NfL), a biomarkerof axonal injury, may potentially be tracked over a full season with thresholds set for predicting those with potential for longterm consequences [70]. Furthermore, as demonstrated in a ratmodel, repetitive subconcussive injury may lead to neuromotordecline as a result of ventriculomegaly, which itself results froma perturbation of the blood-brain barrier [111]. Hiles-Murisonet al., hypothesized the increased permeability of the bloodbrain barrier may result from increased systemic inflammation[111], but did not find any signs of neuroinflammation, whichmay be the result of only two weeks of subconcussive injuryexposure. The authors did find non-significant lipid olefinicreductions in the corpus callosum and cortex of rats exposed torepetitive subconcussive impacts [111]. Thus, more work needsto be done to assess the potential role of inflammation and lipidhomeostasis in the pathogenesis of repetitive subconcussiveinjury, as inflammatory and lipid biomarkers may perhaps beable to assess the “dose” of injury and predict long-term effects.Other work has highlighted the potential role of salivary IgAautoantibodies to the brain-enriched and apoptosis-regulatingproteins HTR1A, SRRM4, and FAS [112]. This is promising inthat obtaining saliva is non-invasive and may provide rapidevaluation.

Clinical measures and cognitive assessments may also helpquickly assess the effects of cumulative impacts. For example,ocular motor examination may serve useful in diagnosingpatients and predicting effects of subconcussive and concussiveimpacts [113]. Furthermore, Electroencephalography (EEG)has been successfully employed to assess the dose responseof repetitive subconcussive injury on brain vital signs [114].Thus, with enough easily obtained data, more specific cognitiveassessments may be developed in routine practice.


Understanding the mechanism of injury and the tolerancewithin humans in regard to repetitive subconcussive injuriesis vital in developing diagnosis and treatment models. Arelationship between repetitive subconcussive injuries andthe resulting insidious behavioral and pathological outcomeshas yet to be defined in a study that translates to humanphysiology and subconcussive biomechanical characteristics[115-118]. Much of the human studies literature is subject tosignificant variability, particularly in frequency and magnitudeof subconcussive impacts. Preclinical models to define acausative relationship of impact to outcome are promising, asthey provide the most control of variables. In 2022, Stemperand colleagues developed a preliminary preclinical modelincorporating head rotational acceleration. Their data suggeststhe ability to scale human subconcussive injury characteristicsdown to a rodent model with greater accuracy in order toassess the behavioral and physical consequences [119]. Furtherresearch in understanding the mechanism and thresholdsof subconcussive injury specific to humans is necessary andongoing, particularly in regard to frequency of injury exposuresand resulting long-term symptoms.

Acute sensorimotor changes (i.e., standing balance) have alsobeen detected in athletes that experienced a head impact thatdid not result clinical concussions, suggesting subconcussiveinjuries [13,120,121]. Balance assessments are commonplacewithin clinical concussion evaluations, as 30% of patients withconcussions from sports related injuries exhibit acute balance problems [122]. 67-77% of patients report dizziness [26] and69% exhibit visual deficits [123], likely also contributing tobalance problems. While direct head impacts are believedto acutely affect sensorimotor function via mechanicaldeformations of brain tissue [124], much of literature focuseson the biomechanical parameters regarding concussions. Aconsiderable gap exists in understanding the biomechanicalfactors within subconcussive injuries and the resulting acutesensorimotor outcomes. In 2021, Qiao and colleagues soughtto evaluate a link between head impact biomechanics andresulting balance deficits. They found substantial variabilityand inconsistencies among balance testing studies followingsubconcussive injuries [13]. Further research with considerationfor the subtly and variety of these sensorimotor deficits insubconcussive injuries, compared to the grandiosity of thedeficits in concussive injuries, is necessary.

At a cellular level, the relationship between multiple serumbiomarkers and repeated subconcussive injuries has becomean area of study. Multiple groups have studied increasedserum NfL as a measure of repeated subconcussive injuriesin soccer and American football athletes [125-129]. Otherstudies have evaluated S100B levels before and after footballpractice, suggesting increased S100B with increased frequencyof subconcussive impacts acutely, but not over the entireseason [130]. Other studies found GFAP, ubiquitin C-terminalhydrolase-L1 (UCH-L1), and S100B biomarkers to all showan increase in patients with subconcussive injuries versuscontrols [131]. In a 2021 review of the literature, Hier andcolleagues found GFAP, S100B and Glial Fibrillary Acidic Protein(GFAP) exhibited a modest ability to discriminate between CTpositive and CT-negative subconcussive patients, though moreaccurately than tau and NfL. Literature regarding the use ofthese biomarkers to predict severity of injury and outcomesis variable and inconclusive [132]. Additionally, literatureregarding alternate routes of biomarker entry to blood ingrowing, suggesting a disruption of the blood brain barrier isnot necessary for entry (i.e., through intramural periarterialdrainage system and glymphatic system) [133]. Preliminaryresearch regarding the use of serum biomarkers in the diagnosisand treatment of subconcussive injuries is a promising concept,but requires much further evaluation into the nuances andconfounding factors.

Conflict of Interest

The authors have no known conflict of interest to disclose.




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(Video) How CTE changes everything about football


Can three concussions cause CTE? ›

If you're a serious athlete who has sustained multiple concussions, you may have been told you have an increased risk of developing a neurodegenerative disease later in life. Studies have shown a link between multiple sports concussions and chronic traumatic encephalopathy (CTE), a kind of dementia.

What happens to your brain after 3 concussions? ›

Sixty athletes with no concussion history were compared with 28 athletes who had had three or more concussions. Those with a history of three or more concussions were significantly more likely to suffer loss of consciousness, anterograde amnesia, and mental status changes lasting longer than 5 minutes.

How can brain trauma in sporting injuries affect cognitive function? ›

While relatively few studies have examined the long-term effects of recurrent, sport-related concussion, several concerning trends have emerged, including increased risk of depression,93 cognitive impairment,131,132 earlier onset Alzheimer's disease,42 dementia,133 and neurodegenerative cause of death.

What are the long-term effects of repeated concussions to athletes in sport? ›

Concussion or mild traumatic brain injury (mTBI) in athletes can cause persistent symptoms, known as post-concussion syndrome (PCS), and repeated injuries may increase the long-term risk for an athlete to develop neurodegenerative diseases such as chronic traumatic encephalopathy (CTE), and Alzheimer's disease (AD).

Does CTE show up on MRI? ›

While chronic traumatic encephalopathy (CTE) cannot yet be diagnosed during life, a new study provides the best evidence to date that a commonly used brain imaging technique, magnetic resonance imaging (MRI), may expedite the ability to diagnose CTE with confidence in the living.

Can MRI show old brain injury? ›

So, what can an MRI see? An MRI can see subarachnoids hemorrhages, bleeding in the brain, old parts of brain damage that where parts of the brain have basically form scarring. That will show up on an MRI often.

What permanent damage can a concussion cause? ›

However, severe or repetitive concussions are likely to result in long-term consequences. Can a concussion cause permanent memory damage? Yes, permanent memory damage and dementia are symptoms of CTE, which is triggered by multiple concussions.

Can a concussion change your personality? ›

FEELING OVERWHELMED, ANXIOUS, SAD OR DEPRESSED? A mild traumatic brain injury (also known as a concussion) may result in changes to your behavior, mood or personality. Other symptoms you may be experiencing—including pain, poor sleep quality and fatigue—could be aggravating these changes.

How Long Can memory loss last after a concussion? ›

People may remain confused and unable to store memories for some time after the injury. The loss of memory from the moment of TBI onward is called post-traumatic amnesia. It can last from a few minutes to several weeks or months, depending on the severity of brain injury.

What are 5 cognitive symptoms of a concussion? ›

You may experience cognitive symptoms, such as: Acting dazed or sluggish. Blurred or double vision. Difficulty maintaining balance.
Such emotional symptoms may include:
  • Anxiety.
  • Irritability.
  • Mood changes.
  • Sadness.

How do you improve cognitive function after a concussion? ›

Cognitive Tricks to Improve Short-Term Memory After Brain Injury
  1. Use Association. One of the best ways to improve your short-term memory after brain injury is to use association. ...
  2. Use Vivid Images. Not all association has to be mnemonic. ...
  3. Space Your Repetition. ...
  4. Listen to Music. ...
  5. Write it Down.
29 Sept 2020

How do you improve cognitive function after brain injury? ›

What can be done to improve attention?
  1. Decrease distractions. ...
  2. Focus on one task at a time.
  3. Break large or complex tasks into smaller tasks.
  4. Practice attention skills on simple but practical activities (such as reading a paragraph or adding numbers) in a quiet room.

What are the long-term effects of concussions and what is post-concussion syndrome? ›

Persistent post-concussive symptoms, also called post-concussion syndrome, occurs when concussion symptoms last beyond the expected recovery period after the initial injury. The usual recovery period is weeks to months. These symptoms may include headaches, dizziness, and problems with concentration and memory.

What happens to the brain after multiple concussions? ›

A person with a history of repeated mild TBIs or concussions may: Experience a longer recovery or more severe symptoms. Have long-term problems, including ongoing problems with concentration, memory, headache, and occasionally, physical skills, such as keeping one's balance.

How long will it take most patients to recover from sports concussion? ›

Concussion recovery and treatment. Approximately 80 percent of concussions resolve over seven to 14 days, with an average of 10 days. People with concussions should never return to sports or other physical activity sooner than one week from sustaining the injury.

Can you check a living person for CTE? ›

There is currently no way to diagnose CTE . It can only be suspected in people who are at high risk due to repeated head trauma over the course of years during their sports or military experiences.

Does CTE affect eyesight? ›

Patients who have suffered an acute concussion commonly report symptoms of visual blur, field loss, diplopia and photosensitivity. Ophthalmic sequelae associated with concussion, TBI and CTE can be visually debilitating and may be sight threatening.

Can you tell if someone has CTE? ›

There's currently no test to diagnose CTE. A diagnosis is based on a history of participating in contact sports, plus the symptoms and clinical features. Your GP will talk to you about the problems you're experiencing and may ask you to carry out some simple mental or physical tasks, such as moving or walking around.

How do you prove brain damage? ›

Imaging tests
  1. Computerized tomography (CT) scan. This test is usually the first performed in an emergency room for a suspected traumatic brain injury. ...
  2. Magnetic resonance imaging (MRI). An MRI uses powerful radio waves and magnets to create a detailed view of the brain.
4 Feb 2021

Can a brain scan show an old concussion? ›

Brain scans are usually not helpful for a concussion.

The scan can show if there's a fracture or bleeding. An MRI creates clear images of brain tissue. But these scans cannot show if you have a concussion. A concussion is different from a fracture or bleeding.

Can a head injury affect you 10 years later? ›

What's more, it has become increasingly recognized that the effects from head injuries are long-lasting. New research led by the Perelman School of Medicine at the University of Pennsylvania shows that a single head injury could lead to dementia later in life.

Does a concussion count as brain damage? ›

A concussion is a traumatic brain injury that affects your brain function. Effects are usually temporary but can include headaches and problems with concentration, memory, balance and coordination. Concussions are usually caused by a blow to the head.

What is the 3 concussion rule? ›

Part of the neuromythology surrounding concussion is the concept of the “three strike rule”: if an athlete has three concussions then, he or she is ruled out of competition for a period of time. On occasions, this can result in permanent curtailment of sporting participation.

Can a concussion affect your memory? ›

2. Can a Concussion Cause Memory Loss Years Later? Yes, a concussion can cause long-term memory loss and recurring short-term memory loss, even weeks, months, or years after the head trauma. Usually, this is known as a symptom of post-concussion syndrome.

What are two emotional symptoms of a concussion? ›

Emotional/behavioral symptoms:
  • Easily irritable and sometimes aggressive.
  • Depression.
  • Having disturbed sleep and feeling constantly tired.
  • Reduced sex drive.
  • Changes in appetite.
  • Lack of energy and motivation.
  • Sudden outbursts of emotion or mood swings.
9 Mar 2016

What are the mental symptoms of a concussion? ›

Mental health disorders can be new conditions that develop after the concussion/mTBI, or the worsening of a condition that existed before the injury. Symptoms can include irritability, anxiety, mood swings, depressed mood, and apathy (lack of interest).

How does someone act after a concussion? ›

Balance problems or dizziness, or double or blurry vision. Bothered by light or noise. Feeling sluggish, hazy, foggy, or groggy. Confusion, or concentration or memory problems.

What is the best treatment for post-concussion syndrome? ›

There is no specific treatment for persistent post-concussive symptoms. Your doctor will treat the individual symptoms you're experiencing. The types of symptoms and their frequency are different for everyone.

What is the concussion test? ›

Concussion tests assess your brain function after a head injury. Most concussion tests consist of questionnaires or symptom checklists. Concussion tests check for things like alertness, memory, focus, how fast you think and your ability to solve problems. They also check your balance and coordination.

Do neurologists treat concussions? ›

Unfortunately, most neurologists have very little training in treating acute concussions beyond the initial injury assessment. However, there are some neurology specialists who are more familiar with concussions, including sports neurologists. The field of sports neurology is a relatively new and growing specialty.

How do you test for a concussion in the brain? ›

A cranial computerized tomography (CT) scan is the standard test in adults to assess the brain right after injury. A CT scan uses a series of X-rays to obtain cross-sectional images of your skull and brain.

What are 3 tests tools that can be used to help diagnose a concussion? ›

The most commonly used assessments for evaluating individuals with concussions are the Post-Concussion Symptom Scale (PCSS), Standard Assessment of Concussion (SAC), Standard Concussion Assessment Tool (SCAT3), and the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) [6].

How do you test for concussion brain damage? ›

The FDA recently approved a test, called the Brain Trauma Indicator, for adults with concussions. The test measures certain proteins that are released into the bloodstream within 12 hours of a head injury. The test may be able to show how serious the injury is.

What is cognitive rest after concussion? ›

The best way to heal from a concussion is to let your brain rest (known as “cognitive rest”). Cognitive Rest. Just as you rest your body to heal after a physical injury, you need to rest your brain to heal after a concussion. Cognitive rest prevents your brain from working too hard to allow it to heal.

What activities can you do while recovering from a concussion? ›

  • Step 1 - Rest. • Crafts: colouring, drawing. ...
  • Step 2 - Light Activity. • Bird watching. ...
  • Step 3 – Sport-specific Activity. • Crawling. ...
  • Step 4- Non-Contact Practice. • Dance lessons. ...
  • Step 1 - Rest. • Basic board games (i.e. not. ...
  • Step 2- Light Activity. ...
  • Step 3 – Sport-Specific Activity. ...
  • Step 4 – Non-contact Practice.

What is the best therapy for brain injury? ›

Cognitive-behavioral therapy (CBT) is the most scientifically verified psychotherapy treatment. In fact, there are over 1,000 studies on 10,000 patients, all demonstrating its effectiveness. It has successfully treated a variety of disorders, including some of the emotional/behavioral problems from brain injury.

Does memory come back after brain injury? ›

Will I ever get my memories back after brain injury? Personal memories, known as anecdotal memories, can and do often return after brain injury. Sometimes this can take place over the course of the initial recovery period, while other memories may take weeks, months or even years to gradually return.

Is post-concussion syndrome a permanent disability? ›

Approximately 30% of people with concussions develop post-concussion syndrome (PCS), which can last a lifetime. If you live with PCS and can no longer work, you may be eligible for short-term or long-term disability benefits.

What is the difference between a concussion and post-concussion syndrome? ›

Approximately 90 percent of concussion symptoms are transient, and symptoms typically resolve within 10 to 14 days. However, symptoms may linger for weeks. Persistent postconcussive syndrome occurs when symptoms persist beyond 3 months.

What are 3 complications of a concussion? ›

Concussion may cause a wide range of short- or long-term complications, affecting thinking, sensation, language or emotions. These changes may lead to problems with memory, communication, personality changes, as well as depression and the early onset of dementia.

Can a concussion affect you years later? ›

Concussions are the most common form of mild brain injury, affecting over 42 million people worldwide annually.

Can you recover 100% from a concussion? ›

Concussions are not rare and have several risk factors, including among people who play sports. While symptoms may linger for a few weeks, most people usually make a full or almost full recovery.

Who takes longer to recover from a concussion? ›

The specific timing of concussion resolution varies between individuals. However, despite a lack of research in concussion recovery, it is widely accepted that the majority of young adults will recover in 7–10 days, with youth athletes taking longer.

Do most people recover quickly from concussions? ›

Most children with a concussion feel better within a couple of weeks. However for some, symptoms will last for a month or longer. Concussion symptoms may appear during the normal healing process or as your child gets back to their regular activities.

How many concussions does it take to get CTE? ›

How many concussions cause permanent damage? According to published research, 17 is the average number of concussions that leads to CTE, which is the progressive brain disease that results in these long-term effects of concussions.

Can multiple concussions cause CTE? ›

Causes of CTE

But CTE and concussion are separate conditions. Many people who are concussed do not go on to develop CTE, but evidence suggests a pattern of repeated minor head injuries increases the risk.

Is 3 concussions too many? ›

Is There a Set Number of Concussions That's Too Much. There is no set number as to how many concussions humans can have before they suffer permanent damage. After all, some athletes experience symptoms for years after just one concussion, while others are seemingly okay after having more than one.

How many blows to the head does it take to get CTE? ›

One concussion in the absence of other brain trauma has never been seen to cause CTE. The best evidence available today suggests that while in theory CTE could begin after one brain injury, if it does, it is rare.

Is post-concussion syndrome a permanent disability? ›

Approximately 30% of people with concussions develop post-concussion syndrome (PCS), which can last a lifetime. If you live with PCS and can no longer work, you may be eligible for short-term or long-term disability benefits.

What is the 3 concussion rule? ›

Part of the neuromythology surrounding concussion is the concept of the “three strike rule”: if an athlete has three concussions then, he or she is ruled out of competition for a period of time. On occasions, this can result in permanent curtailment of sporting participation.

How Long Can memory loss last after a concussion? ›

People may remain confused and unable to store memories for some time after the injury. The loss of memory from the moment of TBI onward is called post-traumatic amnesia. It can last from a few minutes to several weeks or months, depending on the severity of brain injury.

What is the life expectancy of someone with CTE? ›

Some researchers believe the severity of the disease might correlate with the length of time a person spend participating in the sport. Unfortunately, a 2009 analysis of 51 people who experience CTE found the average lifespan of those with the disease is just 51 years.

Can a brain injury change your personality? ›

Any type of brain injury, regardless of severity, can cause personality changes — and some patients may not experience any personality changes at all,” said Dr. Thomas. For patients who do experience personality changes, common symptoms include: Becoming quick to anger or frustration.

Can a concussion cause memory loss? ›

Common symptoms after a concussive traumatic brain injury are headache, loss of memory (amnesia) and confusion. The amnesia usually involves forgetting the event that caused the concussion. Physical signs and symptoms of a concussion may include: Headache.

What is the concussion test? ›

Concussion tests assess your brain function after a head injury. Most concussion tests consist of questionnaires or symptom checklists. Concussion tests check for things like alertness, memory, focus, how fast you think and your ability to solve problems. They also check your balance and coordination.

Can concussion cause long-term problems? ›

Persistent post-concussive symptoms, also called post-concussion syndrome, occurs when concussion symptoms last beyond the expected recovery period after the initial injury. The usual recovery period is weeks to months. These symptoms may include headaches, dizziness, and problems with concentration and memory.

What happens to the brain after multiple concussions? ›

A person with a history of repeated mild TBIs or concussions may: Experience a longer recovery or more severe symptoms. Have long-term problems, including ongoing problems with concentration, memory, headache, and occasionally, physical skills, such as keeping one's balance.

Can you live with CTE? ›

Many symptoms of CTE are treatable, and resources are available to help you find support and live a full life. It is also important to know that people who appeared to have CTE while alive have been found not to have CTE upon post-mortem examination of their brain.

Can a concussion affect you years later? ›

Concussions are the most common form of mild brain injury, affecting over 42 million people worldwide annually.

Can a head injury affect you years later? ›

What's more, it has become increasingly recognized that the effects from head injuries are long-lasting. New research led by the Perelman School of Medicine at the University of Pennsylvania shows that a single head injury could lead to dementia later in life.


1. Understanding Concussion
(Neurological Foundation of New Zealand)
2. The Impact of Concussions in Youth and College Sports: Dr. Robert Cantu
3. Long-term Effects of Repetitive Head Trauma in Rugby/Collision Sports | 2020 SUMMER LECTURE SERIES
(Rugby Research & Injury Prevention Group, Inc.)
4. The Origins of the Concussion Crisis | Patrick Kelly
(Patrick Kelly)
5. Concussion Dangers & Long-Term Cognitive Problems
6. C3: Understanding the Lasting Impact of Veteran Brain Injuries
(Elizabeth Dole Foundation)

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