The inner-ear disorder is causing a nerve on his right side to be less response than his left side. The impacted nerve, Cosart says, affects "balance and gravity."
Being able to pinpoint the issue has been a relief for the Texas native, who is confident his recovery shouldn't be a long process.
Currently on the Minor League disabled list, Cosart is taking medications, and he's been throwing in recent days. He says he, "feels great."
Doctors believe Cosart has been dealing with the condition all season.
After seeing the specialist in Chicago, Cosart will have a better idea of when he may return to game action. Foremost, he is striving to get "back to normal."
It's been a rough year for Cosart, who dealt with a blister in Spring Training, and opened the season as Miami's fifth starter. But on May 19, he went on the disabled list with vertigo, and returned on June 25.
On the mound, he's never settled into a rhythm. In nine games (eight starts), Cosart is 1-4 with a 5.36 ERA.
Cosart still projects to be part of Miami's rotation in the future. The club this week traded veteran right-handers Mat Latos to the Dodgers and Dan Haren to the Cubs.
Once Cosart gets healthy and he shows improvement on the mound, he could be an option to start for the Marlins later this month or in September.
"We need him to come back healthy and ready," manager Dan Jennings said. "Glad they were able to identify the problem."
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter @JoeFrisaro and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.