The concussion diagnosis that prevented Will Power from starting the season-opener in St Petersburg was incorrect, IndyCar has announced.
Power crashed his Team Penske Dallara-Chevrolet in the event's first practice session last Friday, but was cleared to continue driving and took pole position next day.
He suffered nausea after qualifying and underwent further tests that concluded he had sustained concussion in the practice crash, ruling him out of the race.
But subsequent tests with the University of Miami's concussion programme have now revealed this diagnosis was most likely incorrect.
An IndyCar statement said Power "passed the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) test and a MRI/DVI study was normal in all parameters. Power was evaluated by a team of physicians specialising in concussions".
IndyCar safety consultant Dr Terry Trammell said the university doctors believed the symptoms Power displayed on Saturday were related to "a lingering inner-ear infection for which he was being treated".
Penske team president Tim Cindric had already suggested that illness had complicated the St Petersburg diagnosis.
Trammell said the university physicians "conducted a week's worth of testing in one day" and "concluded definitively that Will had not sustained recent head trauma."
Sunday's concussion judgement came after Power failed a Sports Concussion Assessment Tool test.
"Given the nature of his inner-ear infection, it would have been extremely difficult for Will to pass the SCAT," said Trammell.
He said the findings backed up IndyCar medical director Dr Geoffrey Billows' original decision to clear Power to drive again after his Friday accident.
"There is no evidence that he sustained a concussion in the crash on Friday, which is consistent with his ear accelerometer data and the mandatory screening evaluation conducted after his crash," Trammell said.
The new diagnosis means Power is immediately clear to drive again and removes any doubt over his participation in the next round at Phoenix International Raceway in early April.
Oriol Servia was called up to stand in for Power in the St Petersburg race but finished only 18th after being caught up in a mid-race pile-up.
Team-mates Juan Pablo Montoya, Simon Pagenaud and Helio Castroneves finished first, second and fourth respectively.