Case study 136 - Concussion A concussion is a mild traumatic brain injury that affects brain function. Effects are often short term and can include headaches and trouble with concentration, memory, balance, mood and sleep.Concussions usually are caused by an impact to the head or body that is associated with a change in brain function. Not everyone who experiences a blow to the body or head has a concussion.The symptoms of a concussion can be subtle and may not occur right away. Symptoms can las