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.
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.