Noelle Pikus-Pace has revealed that she was suffering with concussion-like symptoms in the build-up to the 2014 Winter Olympics.
The 31-year-old American finished second in the women's skeleton event in Sochi on Friday.
"I felt fine and safe sliding, but my vision has been going in and out of being able to focus, which slows my reaction time," The AP quotes her as saying.
"It has been an extremely difficult week, but my family, coaches, and prayers of many allowed me to come out and compete the best I can given the situation."
Great Britain's Lizzy Yarnold won gold in the event.
Germany
Switzerland
Hungary
Scotland
