20 “if in doubt, sit them out” how much force and what frequency are required for the pathological changes of CTE to develop. It is also not clear why only some athletes are affected with these symptoms. Properly designed prospective studies, which control for potential confounding variables, are required to improve our understanding of CTE and confirm if there are any links to prior concussion53-55 . Acute cerebral oedema, or ‘second impact syndrome’ is another condition that has received a lot of media attention due to its catastrophic outcomes. This condition, along with CTE, appears to have driven much of the public awareness around concussion. 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 insult56 . 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 damage57 . 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’. Education and prevention Improved education and awareness is critical to improving diagnosis and management of concussion. Such education must include all stakeholders – athletes, parents, coaches, teachers and healthcare professionals. A number of studies have demonstrated that general knowledge about concussion is inadequate. A large survey of community-based Australian coaches and trainers in Australian football and rugby league conducted in 2012 found concussion knowledge to be poor. This indicated that key messages were not reaching community level sport58 . In 2017, a similar study qualified the public level of knowledge as moderate26 . Education programs must target the various groups involved in sport-related concussion in order to effectively improve awareness and understanding in the community31 . To be effective, materials used in concussion education programs should be able to provide clear guidance59 . Athletes need to have a good understanding of concussion in order to appreciate the importance of reporting symptoms and complying with rest and return to sport advice32 . Under-reporting of concussion by athletes still appears to be a problem and legislation alone, without education of the athletes, has proved ineffective in addressing this problem60 . Accordingly, a recent systematic review showed that players who had undergone concussion education were more likely to report a suspected concussion30 . Another study revealed that a sample of young adults, while showing awareness of the risks of playing sport with a concussion, expressed a willingness to risk playing with a concussion themselves27 . Parents and coaches must be able to recognise the symptoms and signs of concussion in order to detect concussions at the community sport level where there is no medical supervision present. Athletes’ parents welcome training in best practice guidelines and support their use28 . Concussion knowledge among healthcare workers should be improved with provision of readily accessible information and resources to those managing concussion. Athletes’ parents have expressed concern about medical doctors’ knowledge of concussion management28 , and recently it has been shown that only 18% of medical aides involved in community rugby union acknowledged the need to use field-side assessment tools31 . Measures which may assist in preventing concussion include the use of protective equipment and rule changes in high-risk sporting codes29 . While use of protective equipment would seem to provide a simple and accessible means of preventing concussion, evidence suggests that the use of helmets, mouth guards or other protective devices to prevent concussion offers little if any benefit29 . It is important to note that these devices are valuable for the prevention of other types of traumatic head injuries such as skull fracture and subdural hematoma. Sporting organisations in Australia have responded to the increased concern regarding concussion. The four major football codes (Australian football, rugby league, rugby union and soccer) have introduced rule changes in recent years to ensure more thorough clinical assessment of the athlete with suspected concussion and to enforce guidelines around management of the concussed athlete. All sporting organisations should ensure that medical and support staff covering sporting events have adequate education and training in immediate and long-term management of concussion.