Post-concussion syndrome
About 10% of people with PCS develop sensitivity to light or noise, about 5% experience a decreased sense of taste or smell, and about 14% report blurred vision. People may also have double vision or ringing in the ears, also called tinnitus. PCS may cause insomnia, fatigue, or other problems with sleep.
Second-impact syndrome
The condition was first described in 1973 by R.C. Schneider, and the term second-impact syndrome was coined in 1984. In 1984, R.L. Saunders described the death of a football player who had died after a second, unremarkable concussion and hypothesized that the second blow caused a catastrophic rise in ICP, possibly through loss of vasomotor tone, because the brain was in a vulnerable state. Between 1984 and 1991, only four cases were documented. Between 1992 and 1998, reports of the condition began to be made more frequently than they had before, a fact is thought to be due to wider recognition of the syndrome by clinicians. In 1991, J.P. Kelly and others reported another football death after repeated concussions and coined the term "vascular congestion syndrome".