A concussion is the most common and least serious type of traumatic brain injury. Spinal fluid surrounds and cushions the brain encased in the skull. A hard enough blow to the head will cause the brain to move around in the skull and causes bruising, blood vessel damage, and nerve injury.
Signs of a concussion include:
• Blurry vision
• Light sensitivity
• Sleep problems
• Mood changes
Second Impact Syndrome
Second Impact Syndrome (SIS) refers to sustaining a second concussion or severe head injury before the post-concussive symptoms of a previous concussion have fully healed. Although SIS is a rare occurrence, its consequences are severe and often result in death within minutes. A concussion is defined as a loss of consciousness followed by a short duration of amnesia after a head injury.
Post-concussive symptoms consist of:
• Alcohol intolerance
• Trouble with concentration and memory
• Intellectual difficulties
• Confusion or feeling as if in a fog
• Ringing in the ears
• Slurred speech
• Sleep disturbances
• Personality changes
Why the Second Impact is More Damaging
The initial concussion can cause cerebral edema, an excessive build-up of fluid in the brain. This is the cause of loss of consciousness, memory problems and disorientation. After an initial concussion, the brain has mechanisms to compensate for the stress put on the brain by fluid build-up and protect against a massive swelling. It is believed this happens by limiting blood flow in the brain. Altered brain metabolism lasts up to ten days, during which there is a decrease in protein synthesis and a reduction in oxidative capacity. Experiments have been done that suggest the brain is more vulnerable to the initial trauma. The changes in metabolism make the brain much more susceptible to death because it cannot use the autoregulatory mechanisms to control cerebral blood flow pressure after a second blow even if less intense than the first.
Second Impact Syndrome Symptoms
The symptoms of SIS occur immediately and progress quickly. The symptoms include:
• Dilated pupils
• Respiratory failure
• No eye movement
Most at Risk for Second Impact Syndrome
Young children are at the highest risk for concussion. Concussions in children between the ages of 5-14 are most often caused by bicycle accidents and sporting activities. Concussions in adults are often caused by falls and car accidents. Young athletes are the highest risk of SIS especially in sports such as skiing, boxing, hockey, and football. A study was done that classified 35 cases as SIS in American football players. This number is not supported by similar Australian football reports, though. Australian football causes eight times more concussions than American football. Despite this, an article in the American Journal of Sports Medicine mentioned that American high school and college football players suffered 94 catastrophic head traumas over a duration of 13 years.
Prognosis of Second Impact Syndrome
SIS can lead to brain herniation and death with 2-5 minutes. Although rare, it is terrible when this happens to a young and healthy person. Children have more significant brain swelling from a minor head trauma than adults. It is most important to focus immediately on airways, breathing, and circulation. Although unproven as yet, some doctors have found that rapid intubation and mannitol lessen morbidity. A CT scan should be done to check for any bleeding problems and a neurosurgeon consulted if necessary.