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
As way of comparison, a collision of 80g is a big hit in a college football game of which there might be only six per game. And the range of 80, 90, or 100g is generally where risk of acute injury and concussion begins to occur (concussion being symptoms such as feeling foggy or woozy and not necessarily loss of consciousness). An example of a lesser force of 40g is heading a soccer ball, and even with blows in this 30 to 40g range, it is not known whether these pose a cumulative risk of injury.