Second Impact Syndrome: A Rare, Devastating Consequence of Repetitive Head Injuries

Sports-related concussion has been viewed as a developing public health crisis in recent years. Underrecognition of concussions can lead to premature clearance for athletic participation. Second impact syndrome (SIS) represents a rare, yet devastating, potential outcome of premature return to play. SIS is a condition in which rapid brain swelling occurs as a result of a repeat head injury sustained before symptoms of a previous head injury have resolved. Within minutes of the second impact, diffuse cerebral swelling, brain herniation, and death can occur. There are <20 documented cases of SIS in the world literature to date, and the general understanding of the syndrome is based largely on interpretation of anecdotal cases. This article reviews current understanding of the epidemiology and pathology of SIS. Given neurosurgeons' role in management of head trauma, it is essential that neurosurgeons acquire and maintain thorough knowledge of concussion diagnosis, treatment, and management.