Acute cerebral oedema or ‘second impact syndrome’ has received media attention due to its catastrophic outcomes. Acute cerebral oedema refers to rapid cerebral swelling that can occur when a second concussive injury is sustained during a ‘vulnerable’ period when the brain has not recovered from an initial insult. Animal models have demonstrated that there is a period of vulnerability during which further injury can result in significant axonal injury with associated ion channel damage. It is thought that a second impact may not be needed for the swelling to develop.

The condition is rare and the only available literature consists of case studies which are inadequate to provide a good understanding of the mechanisms and risk factors. Further research is needed to better understand the pathophysiology and risk factors for ‘second impact syndrome’.