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-concussion syndrome
If another blow to the head occurs after a concussion but before its symptoms have gone away, there is a slight risk of developing the serious second-impact syndrome (SIS). In SIS, the brain rapidly swells, greatly increasing intracranial pressure. People who have repeated mild head injuries over a prolonged period, such as boxers and Gridiron football players, are at risk for chronic traumatic encephalopathy (or the related variant dementia pugilistica), a severe, chronic disorder involving a decline in mental and physical abilities.