Mathis was pulled from the game after trying to tackle Chicago running back Matt Forte in the first quarter. He laid on the ground for a short amount of time before walking off slowly under his own power.
"I passed all the tests," said Mathis, who did not return to the game. "Their doctors said they thought I went out and their doctors were the first ones that arrived to me.
"Memory and all of the other signs are great. I passed the test twice."
Mathis made one tackle before being injured Sunday. He was replaced by rookie Darius Slay, who had seven tackles and a pass defended.
Detroit coach Jim Schwartz said that the Lions' other starting cornerback, Chris Houston, left the game with a leg injury in the fourth quarter.