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Concussions Main

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Other Names

  • Mild TBI
  • Mild Traumatic Brain Injury


  • Concussion is a subset of mild traumatic brain injury (mild TBI) defined as a traumatically induced transient disturbance of brain function that involves a complex pathophysiological process.


  • Characterized by a force delivered to the brain that causing motion of the brain inside the skull and stretches the neuronal cell membranes and axons
  • This force leads to microstructural injury to the neurons that can affect neuronal metabolism, ionic balance, and neurotransmission.
  • The mechanism of injury is typically an impulsive force from a blow to the body that causes motion of the brain inside the skull. This motion stretches the neuronal cell membranes and axons, causing microstructural damage.
  • Causes a complex cascade of ionic, metabolic and pathophysiological events that changes intracellular ion concentrations, release of neurotransmitters, and causes mitochondrial dysfunction [1]
  • Leads to increased reactive oxygen species, increased utilization of glucose and a decrease in resting cerebral blood flow
  • Inflammatory cell activation along with alteration of the blood brain barrier, axonal degeneration and altered neuroplasticity may occur more often in the chronic stages of concussion. [2]

Risk Factors for Sustaining a Concussion

Risk factors for concussions include but are not limited to:[3]

  • Being in a motor vehicle accident
  • Being in the military and engaged in combat
  • Being a victim of physical abuse
  • Having increased fall risk
  • Having a previous concussion
  • Females
  • Engaging in sports
    • Sports with increased contact increase risk e.g.: Football, men’s ice hockey, women’s soccer
    • An athlete’s position may alter concussion risk

Female Collegiate Athletes [4]

  • Ice hockey RR = 7.2
  • Basketball 5.3
  • Soccer 3.3
  • Lacrosse 3.2
  • Volleyball 2.8
  • Softball 2.4

Male Collegiate Athletes

  • Wrestling is #1 with RR of 7.9
  • Ice Hockey 6.9
  • Football 5.3
  • Basketball 3.9
  • Lacrosse 2.5
  • Soccer 1.6
  • Baseball 0.7

Risk Factors for Prolonged Recovery

  • Migraines
  • Depression
  • Anxiety
  • History of multiple concussions/overlapping concussions
  • Attention-deficit/hyperactivity disorder(ADHD)
  • Learning disability
  • Post-traumatic stress shortly after injury (~5 days)
  • Young athletes
  • Females historically are more symptomatic and take longer to recover than males
    • Learning disability and ADHD as risk factors have recently come into question as a risk factor [5]

Differential Diagnosis

  • Intracranial injury
    • Epidural or subdural hematoma
  • Heat illness
  • Hypoglycemia
  • Dehydration
  • Syncope
  • Cranial Nerve Injury
  • Primary headache
    • Migraine, tension, cluster
  • Psychiatric disorder
    • ADHD, Anxiety, Depression, Acute stress disorder, Post-traumatic stress disorder
  • Overtraining syndrome
  • Malingering

Clinical Features

  • Based on clinical experience
    • Complicated by lack of validated objective tests and reliance on self-reported symptoms
    • Symptoms vary between patients and within patients with multiple concussions
  • Common symptoms (may be unrecognized, delayed or unreported) [6]
  • Affective/ emotional function
    • Irritability
    • Changes in mood
  • Cognition
    • Confusion/ disoriented
    • Amnesia (retrograde or anterograde)
    • Mental fogginess
    • Poor concentration
    • Cognitive fatigue
  • Somatic/ Physical
    • Headache (most common)
    • Dizziness
    • Decrease balance, unsteady gait
    • Visual changes
    • Neck pain
    • Fatigue
    • Vomiting
  • Sleep
    • Drowsiness
    • Sleeping more or less than usual
    • Difficulty falling asleep
  • Loss of consciousness (LOC) has been reported in mTBI cases. However, it is very uncommon; as less than 10% of the population experiences LOC
  • If a patient has severe symptoms of one kind e.g. vestibular, it is recommended to refer that patient to a specialist for treatment.



  • PPE (Pre-participation exam)
    • History of TBI, premorbid/comorbid conditions, risk factors
  • Baseline neuropsychiatric testing done within some health systems and is required by many schools in the U.S.
    • Many availiable (SCAT5, Impact, Cogsport, etc)
      • Should include baseline symptom score, balance assessment
  • Baseline sideline testing before the season and should be geared towards testing that is performed by the provider/health system
    • King-Devick, VOMS (Vestibular/ocular motor screening), etc.

Sideline Assessment

  • It is important to screen any athlete who may have a suspected head injury during a practice or game, as they are at risk for Second Impact Syndrome [7]
    • Loss of consciousness (LOC), impact seizure, tonic posturing, gross motor instability, confusion or amnesia, incoordination or balance problems, having a blank or vacant look, or repeated shaking of the head should always result in immediate removal from play and evaluation
    • Some of the above symptoms may indicate more severe injuries, therefore careful evaluations are important. Concerns for more serious head injury including prolonged LOC, severe or worsening headache, repeated emesis, declining mental status, focal neurological deficit or suspicion of significant cervical spine injury should trigger activation of the emergency action plan (EAP) [8]
  • Brief history needed followed by cervical and neurologic examination
    • Many providers will move athlete to quiet environment and give short rest before neuropsychiatric evaluation (SCAT 5, Child SCAT 5, King-Devick, VOMs, SAC, Balance Error Scoring System (BESS))
  • The goal is to determine probability athlete has sustained a concussion and remove the athlete if the provider feels this probability is high
    • Accurate diagnosis of a concussion is important because the risk of Second Impact Syndrome, a condition in which a patient sustains multiple concussions simultaneously. This condition can result is severe brain damage and death.
    • If an athlete is diagnosed with a concussion, they should be removed from sport until they complete the Return to Play protocol

Office Assessment

  • Comprehensive history and neurological examination
    • Should include mechanism of injury, sleep/wake disturbance, vestibular function (VOMS testing), ocular function (including fundoscopic exam), gait, balance, cervical spine exam
  • Neuropsychiatric testing (Impact, Cogsport, SCAT5) may be performed and symptom checklist should be done
  • Other pathologies such as cervicogenic pain, primary headache disorder, mood disorder should be ruled out if symptoms persist
  • The Buffalo Concussion Physical Exam is a recommended tool for clinicians diagnosing mTBI in an office setting and includes:[9]
    • Vital Signs
    • Neck/ Sub-occipital Region Exam
    • Head and Face exam
    • Cranial Nerve Testing
    • Fundoscopy
    • Pupil Reactivity
    • Visual Tracking
    • Smooth Pursuits
    • Repetitive Saccades
    • Vestibulo-occular Reflex (VOR) or Gaze Stability Test
    • Near Point of Convergence (NPC) and Accommodation
    • Tandem Gait with Eyes Open and Close, and Tandem Stance
  • The Buffalo Concussion Treadmill Test (BCTT) is used to assess exercise intolerance in concussed patients [10]
    • The BCTT is a graded exercise test that allows clinicians to assess the level of exertion a patient can withstand in order to create a sub-threshold exercise program for the patient
    • Aerobic exercise has been shown to improve the prognosis of concussions


  • Grading concussions based on symptoms or loss of consciousness is not recommended


  • Most adults (more than 80%) will recover spontaneously within two weeks of the injury and the majority of children will recover within four weeks [11]
  • Symptom checklist should be implemented at each follow up visit
  • Persistent headache, depression and PTSD symptoms should be noted and have been shown to predict symptoms lasting >1 month [12]
  • After acute onset, rest is generally prescribed for 24-48 hours
  • Rest is followed by gradual increase in physical and cognitive activity over the course of a few days
    • Ensure the patient stays below symptom exacerbation threshold as to not worsen their concussion symptoms
  • Emerging data suggesting that both children and adults recover more quickly when subsymptom threshold exercise is performed and has been shown to be safe [13]
  • Graded return to play protocol started once symptoms have subsided
  • Despite great interest, no proven pharmaceutical agents shown to prevent or decrease symptoms in humans
    • Rodent studies have shown improvement with omega-3 fatty acids, B-vitamins, N-methyl-D-aspartate, vitamin D

Return to Sport

  • Also known as Return to Play (RTP)
  • Return to Play (RTP) is the protocol clinicians use to slowly acclimate athletes back to sport after being removed due to concussion
  • RTP can be started once symptoms have resolved at rest (usually 24-48 hours)
    • Symptoms may be exacerbated during exercise
  • Graded return to sport involves a gradual, stepwise progression into physical activity and sport-specific activities without a return of symptoms
    • Typically, this is a 5-day progression but can be modified based on an individual’s needs [14]
    • Each stage of the progression should be at least 24 hours without return of symptoms before progressing to the next stage
  • Program should be supervised by provider that is familiar with the athlete if possible
    • Individualized depending on prior injury, age, level of play

Return to Learn

  • Process of transitioning students back to the classroom following concussion
  • School personnel (teachers, guidance counselors, etc.) should be informed of a concussive injury and support plan should be shared
    • Most will return to school within timeframe of return to sport
  • Can progress back into school with modifications such as half days, ability to wear sunglasses, extra time for tests and assignments, ability to take tests in a separate environment, ability to take cognitive rest breaks, take home assignments, etc.
  • Persistent symptoms should be provided an individualized program depending on classes that make symptoms worse and may need to do schoolwork from home in a less stimulating environment
  • Return to learn should be implemented in tandem with return to sport


  • Complications of concussion include but are not limited to:
    • Prolonged Recovery
    • Overlapping concussion Syndrome
    • Secondary Impact Syndrome
  • Potential complications that have less evidence in literature include:
  • Mental Illness: e.g. Depression, Generalized Anxiety Disorder, etc.
  • Cognitive Deficits
  • Neurodegenerative disease
  • Chronic Traumatic Encephalopathy (CTE)

See Also


  1. Giza CC, Hovda DA. The new neurometabolic cascade of concussion. Neurosurgery. 2014;75 Suppl 4:S24-33.
  2. Kumar A., Loane D. J. (2012). Neuroinflammation after traumatic brain injury: opportunities for therapeutic intervention. Brain Behav. Immun. 26, 1191–1201 10.1016/j.bbi.2012.06.008
  3. Scopaz KA, Hatzenbuehler JR. Risk modifiers for concussion and prolonged recovery. Sports Health. 2013;5(6):537-541.
  4. Kerr ZY, Roos KG, Djoko A, et al. Epidemiologic Measures for Quantifying the Incidence of Concussion in National Collegiate Athletic Association Sports. Journal of Athletic Training. 2017;52(3):167-174. doi:10.4085/1062-6050-51.6.05.
  5. Iverson GL , Gardner AJ , Terry DP , et al . Predictors of clinical recovery from concussion: a systematic review. Br J Sports Med 2017;51:941–8.
  6. Ferry B, DeCastro A. Concussion. In: StatPearls. Treasure Island (FL)2020
  7. May T, Foris LA, Donnally IC. Second Impact Syndrome. In: StatPearls. Treasure Island (FL)2020.
  8. Harmon KG, Clugston JR, Dec K, et al. American Medical Society for Sports Medicine position statement on concussion in sport Br J Sports Med 2019;53:213-225.
  9. Leddy, J., et al. (2017). "A Physiological Approach to Prolonged Recovery From Sport-Related Concussion." J Athl Train 52(3): 299-308.
  10. Haider MN, Leddy JJ, Wilber CG, et al. The Predictive Capacity of the Buffalo Concussion Treadmill Test After Sport-Related Concussion in Adolescents. Front Neurol. 2019;10:395.
  11. 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;19:22–33
  12. Iverson GL , Gardner AJ , Terry DP , et al . Predictors of clinical recovery from concussion: a systematic review. Br J Sports Med 2017;51:941–8.
  13. Leddy JJ , Haider MN , Hinds AL , et al . A Preliminary Study of the Effect of Early Aerobic Exercise Treatment for Sport-Related Concussion in Males. Clin J Sport Med. In Press. 2018:1.
  14. Davis GA, Ellenbogen RG, Bailes J, et al. The Berlin International Consensus Meeting on Concussion in Sport. Neurosurgery. 2018;82(2):232-236
Created by:
John Kiel on 8 June 2019 18:56:35
Last edited:
27 April 2023 03:52:28