Limbaugh said on his radio show Tuesday that Fox's jerky movements in a commercial for Missouri Senate challenger Claire McCaskill were just "an act," USA Today reported Wednesday.
Limbaugh said that Fox has mentioned that he sometimes passes on taking his medication in order to illustrate Parkinson's severe physical effects.
Limbaugh said later in his show, "If this was not an act then I apologize."
The "Back to the Future" star's spokesman, John Rogers, said that Limbaugh's remarks were "shameful."
"It's an appalling, sad statement," Rogers said. "Anybody who understands Parkinson's disease knows it's because of the medicine that one experiences" jumpy body movements like those seen in the ad.
Fox has had Parkinson's disease for 15 years and is supporting candidates who would vote to expand stem cell research using human embryos.