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Sports Concussions and Second Impact Syndrome

Concussions in sports, which athletes may refer to as dings, knocks, having your bell rung, and seeing stars, have received increasing attention due to concerns about longer-term effects. Media attention has also focussed on athletes who are suffering sequelae of multiple or catastrophic concussions, such as high-school football player Brandon Schultz, University of Oklahoma basketball star Eduardo Najera, SF Forty-Niners quarterback Steve Young, John Mangum of the Chicago Bears, and New York Ranger Pat LaFontaine.

Concussions are the mildest form of brain injury, and the CDC estimates at least 300,000 sports-related concussions occur in the United States each year. Although certain sports such as football, rugby, ice hockey and martial arts are considered to be more prone to incidences of concussion, other forms of recreational sports, such as horseback riding, soccer, bicycling, and skiing also carry a significant risk of concussion. Many concussions cause only temporary disruption of brain function and resulting problems fade within a week or two. However, fully 60% of people who sustain a concussion still encounter neurological problems one-month post- injury(5).

Concussions have multiple definitions which vary widely, but a concussion is typically defined as a patient with a Glasgow Coma Scale of 13-15, loss of consciousness (LOC) of less than 30 minutes, and posttraumatic amnesia (PTA) of less than 12-24 hours(3). However, the minimum criteria needed to establish that a concussion has occurred remains hotly debated, from self-reported alteration of consciousness and mental status changes, to witnessed loss of consciousness for a long period of time. There are several different schemas for grading levels of concussion, and unfortunately, none of the current guidelines meet the standards of evidence-based guidelines(1). (see Table 1 for the American Academy of Neurology Concussion Guidelines).

Second Impact Syndrome

Second-impact syndrome (SIS) refers to the catastrophic events which may occur when a second concussion occurs while the athlete is still symptomatic and healing from a previous concussion(2). The second injury may occur from days to weeks following the first. Loss of consciousness is not required. The second impact is more likely to cause brain swelling and other widespread damage, and can be fatal.

However, the true incidence and impact of SIS remains a thorny issue. A total of 17 cases have been reported in the literature, and only five cases had confirmed diagnoses of SIS(6). Thus, the claim that SIS is a risk factor for diffuse cerebral swelling has not been supported in the literature.

Repeated Concussions

Even if SIS is not an established problem, there is NO debate that repeat concussions significantly worsen long-term outcomes. After athletes sustain one concussion, they are three times more likely to sustain a second concussion compared to other players who have not been concussed. Repeat concussions, even when mild, can increase the risk of post-concussive symptoms (PCS) such as headaches, memory loss, difficulty concentrating, etc. Chances of PCS are even more increased if the second injury occurs too soon, before recovery from the first has taken place. The higher the rate of concussions, the higher the risk of long-term cognitive dysfunction

Risk of Alzheimer's Disease

Although it can be difficult for young athletes to imagine growing old, repeat concussions are also a concern because they are thought to lower the age at which people will show signs of dementia. Several studies have shown that a significant history of brain injury increases one's risk for Alzheimer's disease at a younger age. Patients with a history of traumatic brain injury were found to express Alzheimer's disease a median of eight years younger than patients without a history of brain injury7

Return to Play

Most clinicians understand that following a significant head impact, athletes with any symptoms of concussion should not return to the sports activity until examined by a physician, and until they are symptom-free. However, knowing that an athlete is truly asymptomatic is very difficult to discern. In the absence of a positive finding on head CT, and without baseline neurocognitive data, a truly informed decision is difficult to make(4).

Clinicians are now recommended to perform simple, baseline cognitive testing on any individual athlete or sports team for which they are responsible. Baseline measures are important to collect PRE-season before any mild injuries may occur(8). The American Academy of Neurology has published a brief Sideline Assessment of Concussion which is short, repeatable, and easily administered (see Table 2). This measure, or other simple neuropsychological tests, can be used to assess athletes at baseline, with repeated administration following an injury. Comparison of post-injury data to baseline neurocognitive function can inform physicians as to when patients truly have no remaining neurological impairment.

Other than cognitive changes, which may be subtle and which may only be able to be evoked with standardized testing, additional warning signs of concussion include:

  • Vacant stare (befuddled facial expression)
  • Delayed verbal and motor responses (slow to answer questions and follow instructions)
  • Inability to focus attention (easily distracted and unable to follow through with normal activities)
  • Disorientation (walking in the wrong direction; unaware of time, date and place)
  • Slurred or incoherent speech (making disjointed or incomprehensible sentences)
  • Gross observable incoordination (stumbling, inability to walk tandem/straight line)
  • Emotionality out of proportion to circumstances (distraught, crying for no apparent reason)
  • Memory deficits (exhibited by the athlete repeatedly asking the same question that has already been answered, or inability to memorize and recall three of three words or three of three objects in five minutes)
  • Any period of loss of consciousness (paralytic coma, unresponsiveness to arousal)
Table 1
There are three grades of concussion, based on the symptoms an individual displays after a suspected concussion

Grade 1 concussions are defined by symptoms of transient confusion without amnesia, no loss of consciousness and concussion symptoms and/or mental status abnormalities that resolve in less than 15 minutes. This is both the most common and the most difficult form of concussion to recognize, as the individual is not rendered unconscious and experiences only momentary confusion. The majority of concussions sustained in sports and recreational activities are this type. Although this type of concussion is often downplayed and referred to in terms of being dinged or having their bell rung, athletes who sustain a Grade 1 concussion should be removed from the game and reevaluated before reentering the playing area

Grade 2 concussion is defined by having transient confusion with amnesia and concussion symptoms and/or mental status abnormalities lasting more than 15 minutes, although there is still no loss of consciousness. With this type of concussion, the individual is not rendered unconscious but does exhibit confusion and post-traumatic amnesia of the events following the impact. In more severe cases, the individual may experience retrograde amnesia of events preceding the injury. After an individual has sustained a Grade 2 concussion, he/she should be removed from play and not allowed to return to the playing area.

Grade 3 concussions are usually quite easy to recognize, and this level of concussion is applied to anyone who experiences loss of consciousness regardless of the length of time and/or the appearance of the player. Initial treatment for Grade 3 concussion - the most severe and serious of the Grades - calls for the individual to be transported to the nearest hospital.

Table 2
Mental Status Testing
Orientation:
The individual is questioned about the time, place, people involved and the situation (circumstances of the injury).
Concentration:
The individual can recite digits backward (i.e., 3-1-7, 4-6-8-2, 5-3-0-7-4).
The individual can recite the months of the year in reverse order.
Memory:
Individual can recite such things as the names of teams from prior contests, the President or other public figures and recent newsworthy events.
Individual can remember and recite three words and three objects at zero and five minutes.
Individual can remember details of the contest (i.e., plays, moves, strategies), if applicable.
Exertional Provocative Tests
Individual can perform a 40-yard sprint.
Individual can perform five push-ups.
Individual can perform five sit-ups.
Individual can perform five knee bends.
(Any appearance of associated symptoms is abnormal, e.g., headache, dizziness, nausea, photophobia, blurred or double vision, emotionality and/or mental status change.)
Neurological Coordination Tests:
Individual can perform finger-nose-finger exercise
Individual can perform tandem walking
Sensation:
Individual performs finger-nose-finger exercise with eyes closed and Romberg
Strength:
Individual is fully strong in all muscle groups.

Mark Shaffrey, M.D., mes8c@virginia.edu

Elana Farace, Ph.D., ef6p@virginia.edu

 

 References

1. Cantu RC: Return to play guidelines after a head injury. Clinics in Sports Medicine 17:45-60, 1998

2. Cantu RC: Second-impact syndrome. Clinics in Sports Medicine 17:37-44, 1998

3. Kay T, Harrington DE, Adams R, et al: Definition of Mild Traumatic Brain Injury. Journal of Head Trauma Rehabilitation 8:86-87, 1993

4. Maroon J, Lovell M, Norwig J, et al: Cerebral concussion in athletes: Evaluationa nd neuropsychological testing. Neurosurgery 47:659-669, 2000

5. McAllister TW: Mild Traumatic Brain Injury and Postconcussive Syndrome, in Silver JM, Yudofsky SC, Hales RE (eds): Neuropsychiatry of Traumatic Brain Injury. Washington: American Psychiatric Press, 1994, pp 357-392

6. McCrory PR, Berkovic SF: Second impact syndrome. Neurology 50:677-83, 1998

7. Nemetz PN, Leibson C, Naessens JM, et al: Traumatic brain injury and time to onset of Alzheimer's disease: a population-based study. American Journal of Epidemiology 149:32-40, 1999

8. Sturmi JE, Smith C, Lombardo JA: Mild brain trauma in sports. Diagnosis and treatment guidelines. Sports Medicine 25:351-8, 1998