Voges, who was captaining Middlesex against Hampshire at Southampton's Rose Bowl, was felled when hit in the back of the head by the ball which was thrown from the boundary and misjudged by wicketkeeper John Simpson.
The West Australian was helped off the field by two physios after a short break in play and then transported to a hospital as a precautionary measure after showing signs of concussion.
He was released hours later, reportedly suffering headaches.
"The feeling from the physio Peter Waxman is that it is a concussion but that will be shown up later," said Middlesex director of cricket Angus Fraser soon after the incident.
"He wasn't feeling very well in the dressing room so we decided to get him to the hospital to get him checked over.
"It was a freak injury but you wonder why when a cricket ball which gets thrown around the field as much as it does it doesn't happen as often. A cricket ball is a hard thing."
