Post-concussion syndrome
Though no universally accepted definition of postconcussive syndrome exists, most of the literature defines the syndrome as the development of at least 3 of the following symptoms: headache, dizziness, fatigue, irritability, impaired memory and concentration, insomnia, and lowered tolerance for noise and light. One complication in diagnosis is that symptoms of PCS also occur in people who have no history of head injury, but who have other medical and psychological complaints. In one study 64% of people with TBI, 11% of those with brain injuries, and 7% of those with other injuries met the DSM-IV criteria for post-concussion syndrome. Many of these PCS sufferers were misdiagnosed as having other unrelated conditions due to commonality of symptoms. (see diagnosis, below).
Concussions in American football
On September 30, 2014, researchers with Boston University announced that in autopsies of 79 brains of former NFL players, 76 had tested positive for CTE. As of January 2017, that number had grown to 90 out of 94. A study published in "The Journal of the American Medical Association" in July 2017 showed that 110 of 111 former NFL players whose brains were examined were found to have suffered from CTE.