The seizure lasted four minutes, Burkholder said. Doctors had yet to determine a cause, but after a magnetic resonance image, bleeding on the brain was ruled out. Patterson was under the care of Lehigh Valley's neurological unit, and his wife was with him by the afternoon.
Burkholder said that dehydration could have contributed to the seizure. Temperatures weren't especially high when Patterson fell at approximately 9:35 a.m., but the sun was shining and players were sluggish.
"I don't want to speculate that it's heat, but [camp] is an ongoing event day after day," Burkholder said. "And your tank can empty slowly and then it can catch up to you."
Twenty minutes after Patterson started to convulse, he left in an ambulance. They were a tense 20 minutes, as defensive and offensive linemen reacted emotionally to Patterson's seizure and fans realized what was going on.
"It was a scary situation," Eagles guard Todd Herremans said.
After walking from one field to an area designated for one-on-one drills, Patterson started shaking violently. Eagles coach Andy Reid was nearby, saw what happened immediately, and started screaming for the team's medical staff. Burkholder was assisted by Jeremy Ng, an emergency-room physician the team retains, and assistant trainer Chris Peduzzi.
Patterson briefly lost consciousness, Burkholder said. He also bit his tongue and started to bleed profusely from the mouth. A few players were visibly upset. Defensive end Trent Cole threw his helmet to the turf.
"It wasn't bad enough to require any treatment," Burkholder said. "It's just that your mouth bleeds like crazy, so it's a scary situation."
After Patterson was stabilized, he started to move his extremities. Teammates circled around him and held up towels and their helmets to shield him from the sun.
Guard Danny Watkins, a former firefighter who was trained as an emergency medical technician, initially tried to assist the Eagles medical staff, but Reid held him back. However, when the ambulance arrived, Watkins helped unload the stretcher and transfer Patterson onto the spine board.
There is no timetable for Patterson's return.
"It's not like hamstring strains," Burkholder said. "We don't see tons of seizures in our sport, so that's why I have a whole team of physicians, and Lehigh Valley Hospital has a great neuro department.
"So we're allowing them to handle the case now, and then we'll get him to see our docs down at the Pennsylvania Hospital eventually."
With Patterson out, Trevor Laws sidelined with a hip flexor injury, free-agent signee Cullen Jenkins still not allowed to practice, and Brodrick Bunkley traded to Denver, the Eagles are short on defensive tackles.
Defensive end Victor Abiamiri had been playing some inside, but he was on crutches with a boot on his right leg later Wednesday.
"Do I have a concern about the shortage of defensive tackles? Yeah, I do," Reid said. "Realistically, we're short."
Patterson, 27, is entering his seventh season and has played in the most games (95) of any current Eagle. He was the Eagles' No. 1 pick in 2005 out of Southern California. The 6-foot-1, 300-pounder has never missed a game because of injury.
He's also one of the most-liked players in the locker room. He texted a few players not long after the incident to say he was OK, and called his brethren on the defensive line.
"He called to say he was doing well," defensive tackle Antonio Dixon said. "He was alert and said to the D-line don't worry about him, he's doing good."
Contact staff writer Jeff McLane at 215-854-4745, firstname.lastname@example.org, or @Jeff_McLane on Twitter.