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).
Post-traumatic seizure
PTS is associated with a generally good prognosis. It is unknown exactly how long after a TBI a person is at higher risk for seizures than the rest of the population, but estimates have suggested lengths of 10 to over 15 years. For most people with TBI, seizures do not occur after three months, and only 20–25% of people who suffer TBI have PTS more than two years after the injury. However, moderate and severe TBI still confer a high risk for PTS for up to five years after the injury.