Prognosis
The mortality rate for SIS approaches 50%, and morbidity (disability) is almost 100%. Since the condition is so rare, the connection between SIS and future disability has been difficult to establish and is therefore poorly understood.
When SIS is not fatal, the effects similar to those of severe traumatic brain injury can occur, including persistent muscle spasms and tenseness, emotional instability, hallucinations, post-traumatic epilepsy, mental disability, paralysis, coma, and brain death.
Read more about this topic: Second-impact Syndrome