Neuvirth collapsed prior to a neutral-zone faceoff 7:37 into the first period of the Flyers' 3-0 win against the New Jersey Devils at Wells Fargo Center on Saturday. He was removed from the ice on a stretcher and taken to the hospital.
"My understanding is that his sinus was clogged up and that has something to do with it," Hextall said prior to the Flyers game against the New York Rangers at Madison Square Garden on Sunday (7:30 p.m. ET; NBCSN, NHL.TV).
Hextall added that dehydration might have played a role.
"I'm sure there are a few things related," Hextall said. "Dehydration is always something that affects the body in funny ways, so I'm sure when you're sick hydration is usually an issue so hydration is probably tied in there."
Neuvirth is expected to make a full recovery.
"I'm not a doctor, but all the tests came back normal and that's pretty much what you're looking for," Hextall said. "Other than that, something freak happened and health-wise everything is good."
The Flyers medical staff was aware of Neuvirth's sinus issue, but Hextall said there were no indications before the game that he was susceptible to losing consciousness and passing out.
"He was feeling fine, but he felt this way for I don't know how long," Hextall said. "It wasn't the first day."
Hextall said Neuvirth did not remember collapsing.
"He just said neutral zone faceoff and then I got a little dizzy and that was it," Hextall said.
Anthony Stolarz replaced Neuvirth and made 26 saves. Stolarz had been recalled from Lehigh Valley of the American Hockey League earlier Saturday after Steve Mason was too ill to play because of a stomach illness.
Stolarz arrived just before the game started and had no warmups before entering.
"Real good composure on his part coming into that situation," Flyers coach Dave Hakstol said. "Not easy on any level, but he did a real good job. Guys in front of him I thought did a real good job allowing him to work into the game, but he had some work right away and he did a good job settling himself in."
Stolarz will start against the Rangers. Mason will dress as the backup.
"Our medical people, like I said [Saturday] night after the game, full commendation to them," Flyers coach Dave Hakstol said. "We take every precaution."
