"They said it is relatively common and now I have had it I keep hearing from other people they have had it, too. But it was a real shock."
Butt says many of the symptoms have now cleared, with the return of his balance the next and most important step. "It is getting better but I am still not driving work at home.
"The stipes [stewards] know and they have told me I have to get a clearance from the doctor on Friday to be able to drive on Saturday.
"The strange part is the doctors can't tell me exactly what has gone wrong. The two most likely reasons are a head knock or a virus of some type and I haven't had any head knocks, so the virus sounds the most likely reason.
"If that has caused it the doctors said I could have had it for a while lying dormant."
Butt has two scheduled Jewels drives with Wilma's Mate the second favourite for the $100,000 4-year-old trot after drawing the ace.
"I'd love to drive her because I really think she can win but obviously I won't be driving her if I'm not right. So the doctors will tell me on Friday but it has improved quite a lot the last few days."
For all his success, Butt has driven just one Jewels winner, One Over Da Moon, at Ashburton in 2013 for Wilma's Mate's trainers Paul Nairn.
Should he not be able to take the reins on Saturday his son Bob would seem the most likely replacement as he won races on Wilma's Mate last season.
Wilma's Mate is the $4 second favourite for her division on Saturday, with Southland mare Dark Horse still at $2.50 with the New Zealand TAB, though she opened $4.50 with Australian bookmakers post-draw last Friday.
The big shortener in that market has been Marcoola, with last season's champion 3-year-old trotter into $4.20 after looking more aggressive at the Ashburton workouts on Saturday.