Second impact syndrome, or SIS, happens when the brain swells rapidly shortly after a person suffers a second concussion before symptoms from an earlier concussion have subsided. This event is rare, but when it does happen, it is most often fatal. The few who do not die from such an event are usually left severely disabled for life.
It is a devastating event because young, otherwise healthy patients can die within a few minutes of suffering the second concussion. Death or lifelong disability occurs because the brain suddenly loses its ability to regulate cerebral spinal fluid pressure, leading to severe swelling of the brain and possible herniation of the brain.
The impact of the second event does not have to be strong to trigger second impact syndrome. A minor blow to the head, chest or back that snaps the head enough to cause the brain to move inside the skull can trigger the usually lethal damage.
Signs and symptoms
When a concussion patient whose symptoms have not yet resolved sustains a second impact, they may not even lose consciousness at the moment of the impact, but they may look stunned. They may even complete a play in a game and make it to the sideline themselves, but then collapse within a minute or two. The patient’s condition then worsens rapidly with loss of consciousness, loss of eye movement, dilated pupils, then respiratory failure. This can all take place within a few minutes.
Diagnosis and treatment
Whenever there is suspicion of a serious brain injury, or second impact syndrome, the patient must immediately go to the nearest emergency center, not urgent care, to have a CT scan of the head that will evaluate for swelling and/or bleeding in the brain. A thorough medical history of the patient’s head injury and the mechanism of injury is needed from an eyewitness of the event.
Preventing second impact syndrome
Obviously the most sensible approach to prevention of SIS is to prevent the first concussion from happening by following rules for safety and using well maintained appropriate sports equipment
consistently and correctly.
Any concussed patient who still shows signs of concussion should not be allowed to return to play or engage in any activities where impact is possible. Such signs include fatigue, headache, disorientation, nausea, vomiting, feeling “in a fog” or “slowed down,” as well as other difference from the patient’s baseline function.
When in doubt, sit it out!
A patient should be seen in an emergency department right away if symptoms worsen and/or if the patient has: one pupil larger than the other, worsening headaches, seizures, neck pain, unusual behavior change, increased drowsiness, repeated vomiting, slurred speech, problems recognizing people or places, increased confusion, weakness or numbness in arms or legs, or if the patient can’t be awakened or is less responsive than usual.