"The problem for Michael was not the hit, but the mounting of the GoPro camera that he had on his helmet that injured his brain," Jean-Louis Moncet told radio station Europe 1 over the weekend.
Moncet was reported to have spoken to Schumacher's son, Mick, but the journalist denied this in a tweet later.
Schumacher, a seven-time Formula 1 champion, suffered severe head injuries in a skiing accident in Meribel in the French Alps on Dec. 29. Schumacher emerged from a medically induced coma in June. He has been receiving treatment at home since September.
"We are trying to get more information about the original report from Jean Louis Moncet. His tweet this morning suggests the comments didn't come from a family member," GoPro spokesman Jeff Brown wrote in an emailed response to Reuters.
The company's shares ended down 9.8 percent at $76.67 on the Nasdaq on Monday. Up to Friday's close, the stock had nearly quadrupled in value since the company listed on June 26.
Shares of other wearable camera makers also fell, with Digital Ally Inc closing 12.9 percent lower at $10.41 and Taser International Inc ending 3.2 percent down at $13.61.
© Thomson Reuters 2014
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