Second Impact Syndrome

What is Second
Impact Syndrome?

This occurs when an athlete, who has already sustained a head injury, sustains a second head injury before symptoms have cleared from the first injury. Many times this occurs because the athlete has returned to competition and play before his or her first injury symptoms resolve. Coaches and athletes do not realize that days or weeks may be needed before concussion symptoms resolve.

Pathophysiology

A second blow to the head, even if it is a minor one, can result in a loss of auto regulation of the brain's blood supply. Loss of autoregulation leads to brain swelling. This results in increased intracranial pressure and leads to herniation of the brain. The average time from second impact to brainstem failure is quite rapid, taking two to five minutes. Once herniation and brainstem compromise occur, ocular movement and respiratory failure are likely to result.

How can Second
Impact Syndrome
be detected?

Even though fatal effects of Second Impact Syndrome can occur rapidly, some measures can be taken to investigate the damage or catastrophic effects. Magnetic Resonance Imaging (MRI) is more sensitive to traumatic brain injuries (e.g., oedema) compared to Computed Tomography (CT Scan) which is used for showing bleeding or midline shifts in the brain requiring neurosurgery.
The most obvious prevention of second impact syndrome is to recognize symptoms of concussion and do not return athletes to competition prematurely or before symptoms have resolved.

Athlete Reaction to
Second Impact Syndrome

Within seconds or minutes of the second impact, the athlete who is conscious, yet stunned may:
         -collapse to the ground
         -semicomatose with rapidly dilating pupils
         -loss of eye movement
         -evidence of respiratory failure

Incidence

Second impact syndrome most likely affects young athletes (junior and senior high school), however, any athlete who returns to play too soon is a possible candidate. Incidence of second impact syndrome is hard to calculate because the population at risk is unknown. However, between 1992-1997, 17 cases of second impact syndrome were reported due to football injuries alone. Football, as well as many other sports (e.g., hockey, boxing, skiing, etc.) can cause successive injuries leading to this syndrome. Following are examples of when an injury can be proven to be fatal.

This information was compiled from:

Cantu, R. C. (1996). Head injuries in sport. British Journal of Sports Medicine, 30, 289-296.

Case Studies....
examples of how fatal Second Impact Syndromes can be

Ice Hockey Player, age 16	First Injury: struck back of head on the ice; brief loss of consciousness Postconcussion symptoms: headache, unsteadiness Second Impact: 4 days later, athlete struck left temple on ice causing a loss of consciousness (duration unknown). Outcome: Cerebral swelling, hematoma, hemorrhaging caused this athlete to die 2 hours following the second impact.
Football Player, age 17	First injury: Grade 1 concussion during football game; brief loss of consciousness Postconcussion symptoms: headache Second Impact: 1 week later, athlete suffered successive strikes to the head play after play finally causing athlete to collapse. Outcome: Cerebral swelling, hydrocephalus, hematoma, and hemorrhaging caused athlete to die 15 hours following second impact.
Amateur Boxer, age 17	First injury: Motor vehicle accident causing head impact morning before competition Postconcussion symptoms: headache Second Impact: 2 days later, athlete collapsed during round 2 following few "minor" blows to the head. Outcome: Seizure, hematoma, cerebral edema caused athlete to die 1 week after second impact.
Amateur Boxer, age 19	First injury: Knocked out during fight Postconcussion symptoms: headache Second Impact: 1 day later, athlete collapsed during round 2 following "minor" blows to the head. Outcome: Seizure, cerebral edema, and hematoma caused athlete to die 6 days after second impact.
Amateur Boxer, age 17	First injury: Repeated blows to the head during fight Postconcussion symptoms: psychiatric disturbance Second Impact: 6 hours later, athlete collapsed in round 2 Outcome: Cerebral edema and brainstem herniation caused athlete to die 2 days after second impact.

This information was compiled from:

McCrory, R., & Berkovic, S. F. (1998). Second impact syndrome. Neurology, 50, 677-683.


UNL	Sport	TBI