Concussion Signs and Symptoms
According to the most recent (but soon to be updated) international consensus of concussion experts , concussion signs (those noticed by coaches, parents and teammates) and symptoms (feelings or problems experienced by the athlete) fall into five “clusters”:
- somatic (headache, nausea, vomiting, dizziness, visual problems, sensitivity to light/noise, balance problems);
- cognitive (feeling mentally “foggy,” feeling slowed down, difficulty concentrating and remembering);
- emotional (involuntary crying or uncontrollable episodes of crying and/or laughing)
3. Behavioral changes (irritability, sadness, nervousness, more emotional, depression)
4. Cognitive impairments (slowed reaction times etc.)
5. Sleep disturbance (insomnia, drowsiness, sleeping less than usual, sleeping more than usual) .
Despite widespread concerns about, and repeated studies showing chronic under-reporting by athletes of concussion symptoms, in the absence other ways to accurately diagnose concussions, especially in the absence of objective markers of concussion, clinicians have no choice but to rely on subjective self-reported symptoms in concussion assessment.
Potential signs of concussion requiring removal from play
A concussion should be suspected on the sports sideline, and the athlete immediately removed from play and not permitted to return the same day, if any of the following signs are observed after a direct or indirect blow to the head:
- loss of consciousness (LOC)
- player lying motionless on the ground or is slow to get up
- player exhibits balance or motor coordination problems (athlete stumbles, has slow/labored movements or unsteady gait)
- player is disoriented or confused (inability to respond appropriately to questions; not aware of plays or events)
- player exhibits a loss of memory (post-traumatic amnesia [1,2]
- player has dazed, blank or vacant look on face;
- player has visible facial injury in combination with any of the other signs.
Three symptoms scales
While there are a number of symptom scales currently in use, including the Post-Concussion Symptom Inventory (a version of which can be used for children as young as 5 and which includes a parent version the three main symptom scales in most widespread use are
- The Post-Concussion Symptom Scale (PCSS); 
- The Sport Concussion Assessment Tool 3 (SCAT) – Versions 2 and 3;  and
- The Concussion Symptom Inventory (CSI), a 12-item scale derived from the PCSS and SCAT2. All have been found to be sensitive to the acute effects of concussion in high school, college, and professional athletes. 
Post-Concussion Symptom Scale
How do you feel?
|Time of Injury||2-3 hours post-injury||24 hours post-injury||48 hours post-injury||72 hours post-injury|
|1. Headache (reported as symptom by 94.2% of high school athletes |
|2. Nausea (reported by 31.4% of high school athletes)
|4. Balance problems|
|5. Dizziness (reported as a symptom by 75.6% of concussed high school athletes)|
|7. Trouble falling asleep|
|8. Sleeping more than usual|
|9. Sleeping less than usual|
|11. Light sensitivity (reported as a symptom by 36.0% of concussed high school athletes) |
|12. Noise sensitivity|
|16. Feeling more emotional|
|17. Numbness or tingling|
|18. Feeling slowed down (e.g. slower reaction time)|
|19. Feeling mentally “foggy”|
|20. Difficulty concentrating (54.8% of concussed high school athletes report this symptom) 
|21. Difficulty remembering|
|22. Visual problems|
Grading symptom severity
In using the PCSS, the athlete is asked to rate or score the severity of the symptom on a 7-point (Lykert) scale:
0 = not experiencing symptom
1 = very minor
2 = annoyingly present
3 = moderate level
4 = more significant
5 = intense and disruptive, and
6 = worst and unbearable. 
The PCSS has gained widespread recognition in concussion evaluation. A modified PCSS is used for self-assessment by the athlete on the Sport Concussion Assessment Tool 3 (SCAT3)  and in some computerized neurocognitive tests used by health care professionals in managing concussions, and is an important tool used by clinicians in assessing an athlete’s readiness for return-to-play.
Athletes with pre-injury depression, sleep disturbances, and/or attention-deficit/hyperactivity disorder should not be expected to have a total score of 0 on the PCS scale before they are medically cleared for a return to play because of their elevated baselines.
In addition, because the PCSS contains 22 symptoms that are not specific to concussion and overlap with other disorders (e.g. sleep disturbances, depression, attention deficit disorder), some non-injured athletes may report symptoms.  In fact, between 50 and 84% of high school athletes report similar symptoms of concussion at baseline.  One 2005 study  found, for instance, that the mean symptom score for non-injured high school males was 5.8, despite the fact that such athletes had never suffered a concussion. As a result, the generally accepted threshold for return to play is 7. [6,7]
As a result, some have criticized use of symptom scales as attributing to concussion nonspecific symptoms and diagnosing individuals with whiplash, affective disorders (e.g. depression), or inner ear problems (vertigo, dizziness) as having a brain injury, and have called for concussion management guidelines to consider non-brain based conditions that might better account for the patient’s symptoms.
In patients with pre-existing mental health disorders, concussion may make symptoms such as depression, anxiety or attention-deficit disorder worse and make them more difficult to control.
Whatever the symptom scale, it should be used not only for the initial evaluation but for each subsequent follow-up assessment until all signs and symptoms have cleared both at rest and with physical exertion. Symptom checklist scores and the ability of the scales to detect concussion, however, typically diminish with the passage of time due to the natural course of recovery from mild traumatic brain injury (mTBI). 
Difficult to spot or diagnose
The process of determining whether an athlete has suffered a concussion or mTBI (note that the use of the terms interchangeably with concussion has generated controversy, because while all concussions are mTBIs, not all mTBIs are concussions; concussions are a subset of mTBIs, on th less-severe end of the brain injury spectrum)  is complicated by a number of factors:
- Because athletes who suffer concussions are not functioning at their cognitive baseline, they may not recognize they have suffered injury;
- There may be no specific impact event to alert the athlete or sideline personnel to concussion (a third of diagnosed concussions in a 2012 study of college athletes  were not associated with a specific impact event);
- Many athletes do not experience symptoms right away after an impact event: of 31 diagnosed concussions in a 2012 study associated with an identified specific impact,  19 experienced immediate or near-immediate onset of symptoms, but 3 had delayed onset on the same day, 2 first experienced symptoms the next day, and in 7 the timing of onset of concussion symptoms was unknown. Of the 13 players with diagnosed concussion without a specific identified single impact, 6 had delayed symptom onset after play (after play or in subsequent days), and in 2 the timing of symptom onset was unknown. Commenting on the results of that study, one prominent concussion expert was left to “wonder[ ] how many concussions were missed … given that 23% of the diagnoses reported were delayed (average of 17 hours) and another 27% had unspecified onset.” 
Gender differences in symptomology?
Some studies suggest that symptoms also can vary by gender.
A 2011 study in the Journal of Athletic Training, for instance, found that female high school athletes were more likely than males to report drowsiness and sensitivity to noise which, “[w]ithout adequate symptom assessment … may be more easily missed or attributed to other conditions, such as stress, depression or anxiety.”  As a result, the study says such symptoms reported by females should be considered signs of concussion until they can be more definitively attributed to pre-existing neuropsychological conditions and concussion ruled out.
But a recent position statement  states that “[t]here have been no consistently demonstrated differences in the symptoms reported between male and female athletes.” (citing studies, including n.10 below).
Loss of consciousness
While one recent study found that LOC occurs in fewer than 5% of concussions at the high school level (less than half the 10-11% rate found in earlier studies),  LOC, especially for a minute or more, is still considered an important potential sign of a more serious concussion, [1,16] and a head injury that may require further imaging and intervention. [16,18]
No same day return to play
The most recent international conference of concussion experts  unanimously agreed that no RTP [return to play] on the day of suspected concussive injury should occur for high school and college athletes, especially as studies show that college and high school athletes allowed to return to play on the same day may demonstrate neuropsychological deficits that may not be evident during an initial sideline evaluation and are more likely than adult athletes to have delayed onset of symptoms. (citing studies @ notes 59-65)
As a result, the Zurich Consensus Statement emphasizes the importance of treating athletes under 18-years-old more conservatively(such as by extending the amount of time of asymptomatic rest and/or the length of time for completing the symptom-limited, exercise program it recommends before return to play), even if the resources (e.g. the presence of team physicians or athletic trainers experienced in concussion management, access to neuropsychologists, consultants, neuroimaging etc.) are the same as for an older, professional athlete.
The Zurich Consensus Statement recommendations are embodied in the laws of all 50 states, which require immediate removal of an athlete from a game or practice if a concussion is suspected, ban same day return to play, and require written clearance from a concussion specialist before an athlete is allowed to begin practicing or playing again.
For more about the 6-step, exercise-limited, program experts recommend that an athlete complete before a full return to play (and that at least one state (California) now mandates be completed before return to play, click here.
Different symptoms for children aged 5 to 12: Child SCAT3
The use of these symptom scales has yet to be adequately studied in the grade-school athlete. Because athletes below age 13 report symptoms different from adults, and a clinical evaluation by the health care professional should include input not only from the athlete but from parents, and possibly teachers and school personnel,  the Zurich concussion conference resulted in the issuance of a new Child SCAT3  for use in assessing concussion for children aged 5-12 years, which includes symptom scales to be completed by the child and their parent:
Child – SCAT3 Symptom Evaluation
|1. I have trouble paying attention|
|2. I get distracted easily|
|3. I have a hard time concentrating|
|4. I have problems remembering what people tell me|
|5, I have problems following directions|
|6. I daydream too much|
|7. I get confused|
|8. I forget things|
|9. I have problems finishing things|
|10. I have trouble figuring things out|
|11. It’s hard for me to learn new things|
|12. I have headaches|
|13, I feel dizzy|
|14. I feel like the room is spinning|
|15. I feel like I’m going to faint|
|16. Things are blurry when I look at them|
|17. I see double|
|18. I feel sick to my stomach|
|19. I get tired a lot|
|20. I get tired easily|
|21. Difficulty remembering|
|22. Visual problems|
|1. has trouble sustaining attention|
|2. is easily distracted|
|3. has difficulty concentrating|
|4. has problems remembering what he/she is told|
|5. has difficulty following directions|
|6. tends to daydream|
|7. gets confused|
|8. is forgetful|
|9. has difficulty completing tasks|
|10. has poor problem solving skills|
|11. has problems learning|
|12. has headaches|
|13. feels dizzy|
|14. has a feeling the room is spinning|
|15. feels faint|
|16. has blurred vision|
|17. has double vision|
|18. experiences nausea|
|19. gets tired a lot|
|20. gets tired easily|
As with the other symptoms scales, however, the child- and parent-symptom scales have not yet been the subject of large scale, controlled studies to establish their effectiveness in identifying young athletes with concussion.
Critical component of concussion assessment
Symptom scales by themselves do not diagnose whether a concussion has occurred; rather, they provide information that can help a health care professional in making an overal diagnosis, in gauging injury severity, in assessing recovery, and in making the all-important return-to-play determination, although because of the unreliability of athletes’ reports of being symptom-free  and a “good old days bias”  (the normal human tendency to selectively remember being healthier in the past and to fail to remember having health problems, which, in the context of mTBI, could play a role in the perceived persistence of post-concussion symptomatology by minimizing the likelihood that such symptoms existed prior to the injury and attributing the current symptoms directly to the injury) they are only one factor. 
As the authors of a 2013 study  noted, “[a]lthough concerns are routinely expressed about athletes under-reporting concussion or the resulting symptoms,”  their “review suggests that symptom assessment remains a critical component of concussion assessment. … In sum, the literature clearly supports the continued use of symptom scales in the assessment of concussed athletes, ideally in combination with other functional [(e.g. neurocognitive, balance)] tests.”
Another 2013 study  while saying that symptom scales “remain the gold standard for determining outcome” after mild traumatic brain injury, noted that they “remain one of the very few scales without good normative data comparisons,” and called for the development of such data and reliable change indices for symptom scales to overcome the “good old days” bias.
1. McCrory P, et al. Consensus statement on concussion in sport: the 4th International Conference on Concussion in Sport held in Zurich, November 2012. Br J Sports Med 2013;47:250-258.
2. Mcrea M, Iverson G, Echemendia, et al. Day of injury assessment of sport-related concussion. Br J Sports Med 2013;47:272-284.
4. Marar M, McIlvain NM, Fields SK, Comstock RD. Epidemiology of Concussions Among United States High School Athletes in 20 Sports. Am J Sports Med 2012;40(4):747-755.
5. Symptom descriptions courtesy of Robin Karpf,M.D., Medical Director, Al Rashid Health and Wellness Center, The Lawrenceville School, Lawrenceville, New Jersey.
6. Iverson GL, Lovell MR, Collins MW. Validity of ImPACT for measuring processing speed following sports-related concussion. J Clin Exp Neuropsychol. 2005; 27(6):683-689.
7. Lau BC, Kontos AP, Collisn MW, Mucha A, Lovell MR. Which On-Field Signs/Symptoms Predict Protracted Recovery From Sport-Related Concussion Among High School Football Players? Am J. Sports Med 2011;20(10) DOI:10.1177/0363546511410655 (published June 28, 2011 online ahead of print)(accessed November 5, 2011).
8. Duhaime A, Beckwith J, Maerlender A, McAllister T, Crisco J, Duma S, et. al. Spectrum of acute clinical characteristics of diagnosed concussions in college athletes wearing instrumented helmets. J Neurosurg 2012;117:1092-1099.
9. Ellenbogen R. Sports and concussion. J Neurosurg 2012;117:1089-1091.
10. Frommer L, Gurka K, Cross K, Ingersoll C, Comstock R.D., Saliba S. Sex Differences in Concussion Symptoms of High School Athletes. J Ath. Train. 2011;46(1):000-000.
11. Meehan W, d’Hemecourt P, Comstock D, High School Concussions in the 2008-2009 Academic Year: Mechanism, Symptoms, and Management. Am J Sports. Med. 2010; 38(12): 2405-2409 (accessed December 2, 2010 at http://ajs.sagepub.com/content/38/12/2405.abstract?etoc).
12. Child SCAT3. Br J Sports Med 2013;47:263.
13. Pardini D, Stump JE, Lovell MR, Collins MW, Moritz K, Fu FH. The post-concussion symptom scale (PCSS): a factor analysis. Br. J Sports Med. 2004;38:661-662.
14. Sandel N, Lovell M, Kegel N, Collins M, Kontos A. The Relationship Of Symptoms and Neurocognitive Performance to Perceived Recovery From Sports-Related Concussion Among Adolescent Athletes. Applied Neuropsychology: Child. 2012; DOI:10.1080/21622965.201 2.670680 (published online ahead of print 22 May 2012)(accessed June 5, 2012)
15. McCrea M, Hammeke T, Olsen G, Leo P, Guskiewicz K. Unreported concussion in high school football players – Implications for prevention. Clin J Sport Med 2004;14:13-17.
16. Harmon K, Drezner J, Gammons M, et al. American Medical Society for Sports Medicine position statement: concussion in sport. Br J Sports Med 2013;47:15-26.
17. Giza C, Kutcher J, Ashwal S, et al. Summary of evidence-based guideline update: Evaluation and management of concussion in sports: Report of the Guideline Development Subcommittee of the American Academy of Neurology. (published online ahead of print, March 18, 2013); DOI: 10.1212/WNL.ob013e31828d57dd (accessed March 25, 2013)
18. Halstead, M, Walter, K. Clinical Report – Sport-Related Concussion in Children and Adolescents. Pediatrics 2010;126(3): 597-615 at n.60.
19. Brooks BL, Kadoura B, Turley B, Crawford S, Mikrogianakis A, Barlow KM. Perception of Recovery After Pediatric Mild Traumatic Brain Injury Is Influenced by the “Good Old Days” Bias: Tangible Implications for Clinical Practice and Outcomes Research. Arch Clin Neurospych. 2013;doi:10.1093/arcclin/act083 (epub November 5, 2013)
20. Reneker JC, Cook CE. Dizziness after sports-related concussion: Can physiotherapists offer better treatment than just ‘physical and cognitive rest’? Br J Sports Med 2015;49:491-492. originally published online July 17, 2014.
Blinman TA, Houseknecht E, Snyder C, Wiebe DJ, Nance ML. Postconcussive symptoms in hospitalized pediatric patients after
mild traumatic brain injury. J Pediatr Surg. 2009;44(6):1223-1228.
Gioia, GA. Schneider JC. Vaughan CG. Isquith PK. Which symptom assessments and approaches are uniquely appropriate for pediatric concussion? Br. J. Sports Med. 2009; 43 (suppl1): i13-i22..
Pocket Concussion Recognition Tool. Br J Sports Med 2013;47:267.
Most recently updated April 30, 2016