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
Second-impact syndrome shares all the risk factors of concussion; that is, those who are at increased risk for concussion are also at higher risk for SIS. Thus, people who participate in sports such as boxing, soccer, American football, baseball, rugby, basketball, ice hockey, pro wrestling, and skiing (especially Alpine) are at increased risk. The condition most commonly occurs in American football.