The majority of patients with sport-related concussion recover within a 7-to-10 day period, although children and adolescents require more time to recover than do collegiate or professional athletes. [10,11] But, for reasons that are still unknown,  5-10 percent of those who experience a concussion have symptoms that persist beyond the generally accepted time frame for recovery (one month under one classification,  beyond 3 months in another, at which point they are typically diagnosed as having post-concussion syndrome (PCS).
Whether PCS is experienced following a concussion seems to be dependent on a combination of factors, including premorbid vulnerabilty (eg. pre-existing medical conditions), postinjury psychological adjustment, and post-injury changes in brain function, and physiology (such as disruption of the blood brain barrier). [9,10]
Studies suggest that children who are not given adequate time to rest, sleep and heal after an injury are much more likely to develop PCS, and to suffer from it for longer periods of time.  In fact, studies of high school students have shown that athletes who were allowed to rest after injury recovered twice as quickly as those who were not. 
PCS can result in signficant physical, emotional, and cognitive stress, and be "significantly disabling, often resulting in an inabilty to attend school, complete academic work, participate in sporting and extracurricular activities and interact socially with peers."  After 3 weeks, patients (especially athletes) begin to worry about when they will recover, and by 6 weeks, if symptoms persist, PCS can alter their lives. 
Hard to diagnose/predict
As a recent study notes, "there is considerable controversy regarding PCS because of the nonspecificity of symptoms and the fact that most cognitive deficits resolve within 1 to 3 months after mild TBI in the majority of patients." The challenge for doctors is to determine whether prolonged symptoms are the result of the concussion or from other causes, such as pre-existing clinical depression or migraine headaches. If symptoms that were experienced early after the injury are worse with exertion, but improved with rest, then the original concussion is the likely reason for the persisting symptoms; but if the ongoing symptoms are made worse by even minimal exercise and no longer respond to rest, it may represent psychologic symptoms related to prolonged inactivity and frustration with inability to return to usual activities, including sports. (citing studies)
Predictors of PCS are not known with certainty, but some clinical variables appear to increase the risk, including a history of concussions, female sex, younger age, history of cognitive dysfunction, and affective disorders, such as anxiety and depression. (citing studies).
Children more susceptible to PCS
While children report a PCS that is similar to adults and may suffer from the same behavioral, emotional and somatic difficulties following mTBI such as concussion, youth are more susceptible to PCS. Because the developing brain is more "plastic" than the mature brain, younger age at the time of mTBI was originally thought to have a beneficial effect on recovery and expected outcome, allowing a younger athlete to better compensate and recover after brain injury. Current literature, however, indicates that the developing brain may actually be more susceptible and vulnerable to diffuse brain injury, which leads to more pronounced and prolonged cognitive deficits and hyperactivity. The most methodologically sound studies have found that children report worse cognitive symptoms more than a year after concussions than adults. 
These deficits affect the child's school work and ability to function at home.
- Children aged 6 to 12 years with mTBI have impaired executive functioning and attention 1 year after injury compared with noninjured controls;
- TBI experienced in middle childhood and later appears to be less detrimental than injuries sustained earlier;
- An mTBI may also cause linquistic changes that adversely affect Verbal IQ and expressive language;
- In cases where symptoms persist, PCS may adversely affect a child's conduct and personality, and can lead to extended school absence and limitations on athletic play;
- Children with higher cognitive ability have better outcomes following head injury, because they may be able to recruit alternative and additional brain resources to compensate for tissue damage;
- A concussion may alter a child's long-term developmental trajectory years after the symptoms of PCS subside (although most studies of PCS typically only follow children for up to a year after injury, potentially before the full effects of the injury are seen), although these findings may in part be due to undiagnosed mood or conduct disorders in children, which resulted in an original injury. The long-term effects on cognitive processing, mood, and behavior suggest the need for continued monitoring and intervention in children, even years after initial concussion.
Because the accepted time frame for recovery from concussion is not scientifically established and, in part, because PCS is diagnosed according to clinical criteria, there is some uncertainty about its definition. Here are the two most commonly used definitions:
- Headache, dizziness, malaise, fatigue, noise intolerance
- Irritability, depression, anxiety, emotional lability
- Subjective concentration, memory, or intellectual difficulties without neuropsychological evidence of marked impairment
- Reduced alcohol intolerance
- Disordered sleep
- Irritability or agression with little or no provocation
- Anxiety, depression, or affect lability
- Changes in personality
- Apathy or lack of spontaneity
| Characteristics of Post-Concussion Syndrome according to
The International Classification of Diseases, 10th Revision (ICD-10)2
History of head trauma with loss of consciousness precedes symptom onset by a maximum of 4 weeks
Three or more symptom categories:
Note: A recent study (10) says that use of these criteria is 6 times more sensitive in identifying patients with PCS.
Characteristics of Post-Concussion Syndrome according to the American Psychiatric Association
Diagnostic and statistical manual of mental disorders. 4th edition. Washington, DC. American Psychiatric Association; 1994 (DSM-IV-R)3
A history of head trauma that has caused significant cerebral concussion (eg, with a loss of consciousness, posttraumatic amnesia, or seizures)
Neuropsychological evidence of difficulty in attention or memory
Three or more symptoms that last at least 3 months and have an onset shortly after head trauma or represent substantial worsening of previous symptoms:
The symptoms result in significant impairment in daily functioning that reflects a decline from previous level.
Note: A recent study viewed these criteria as too conservative. (10)
1. Barlow K, et. al. Epidemiology of Postconcussion Syndrome in Pediatric Mild Traumatic Brain Injury. Pediatrics 2010;126(2):e374-381.
2 World Health Organization. The ICD-10 classification of mental and behavioural disorders: diagnostic criteria for research. Geneva (Switzerland): World Health Organization;1993.
3. APA. Diagnostic and statistical manual of mental disorders. 4th edition. Washington, DC: APA; 1994.
4. Moser RS. Ahead of the Game: The Parents' Guide to Youth Sport Concussion (University Press of New England 2012) at 41.
5. Lovell M, Pardini J, Welling J, Collins M, et al. Functional brain abnormalities are related to clinical recovery and time to return-to-play in athletes. Neurosurgery 2007;61(2):352-360.
6. Reddy CC, Collins M, Lovell M, Kontos A. Efficacy of AmantadineTreatment on Symptoms and Neurocognitive Performance Among Adolescents Following Sport-Related Concussion. J Head Trauma Rehab 2012: DOI: 10.1097/HTR.0b013e318257fbc6 (published online ahead of print)(accessed December 13, 2012).
7. Field M, Collins MW, Lovell MR, Maroon J. Does age play a role in recovery from sports related concussion? A comparison of high school and collegiate athletes. J Pediatr. 2003;414:546-553.
8. Daneshvar D, Riley D, Nowinski C, McKee A, Stern R, Cantu R. Long-Term Consequences: Effects on Normal Development Profile After Concussion. Phys Med Rehabil Clin N Am 22 (2011) 683-700.
9. Korn A, Golan H. Melamed I, Pasqual-Marqui R, Friedman A. Focal cortical dysfunction and blood-brain barrier disruption in patients with postconcussion syndrome. J Clin Neurosurg 2005;22:1-9.
10. Leddy J, Sandhu H, Sodi V, Baker J, Willer B. Rehabilitation of Concussion and Post-concussion syndrome. Sports Health: A Multidisciplinary Approach. 2013;4(2):147-154,
11. Belanger H, Vandeerploeg R. The neuropsychological impact of sport-related concussion: a meta-analysis. J Int Neuropsychol Soc. 2005;11(4):345-357.
12. McCrea M, Guskiewicz K, Marshall S, et al. Acute effects and recovery time following concussion in collegiate football players: the