Burkholder said Thursday that Patterson is undergoing further tests. The 27-year-old Patterson was hospitalized after suffering a seizure Wednesday morning at training camp at Lehigh University.
"What they did determine through some of the testing is that Mike has a congenital tangle of blood vessels right outside his brain that is called arteriovenous malformation, or what we refer to as AVM," Burkholder said. "I'm pretty sure that's what caused the seizure. We're pretty sure it was not football related."
Patterson's agent, J.R. Rickert, disputed the definite diagnosis of AVM. He said it's too early to say the 6-foot-1, 300-pound Patterson has the condition. Rickert spoke with Patterson and his wife, Bianca, Thursday morning. He had a conversation with Burkholder on Wednesday.
"Rick spoke to one doctor who evaluated Mike that's leaning toward the diagnosis of AVM," Rickert told The Associated Press. "Two other doctors are not leaning toward AVM. They haven't ruled it out, but they're not leaning in that direction at all. They're saying it's premature to diagnose him in that capacity.
"We're going to take Mike to a fourth specialist to get an opinion. After we get that opinion, Mike and Bianca will get together and make a decision about the best course of action based on which opinion they want to follow."
Burkholder refused to discuss treatment options.
"With today's medicine, there is just a ton of options and everyone wants to jump right in to surgery because that's what been happening, not just with this particular case but with anything," Burkholder said. "There are so many other avenues out there, so it'd be foolish for me to even speculate what's going to happen with Mike. We handle football injuries all the time, but this is a neurological problem."
The trainer said Patterson is on medication to prevent another seizure, and anticipates he'll be released from the hospital Thursday.
It's unknown when or if Patterson will return to the Eagles.
On Wednesday, Patterson dropped to the ground between drills during a morning practice, and the player began violently shaking. He was immediately tended to by Burkholder and his staff, with assistance from rookie Danny Watkins, a trained firefighter, and taken by ambulance to Lehigh Valley Hospital.
"It just so happened at football practice," Burkholder said. "It could've happened anywhere."
AVMs are malformations or tangles of arteries and veins that alter blood flow. The cause isn't known, but they are usually present at birth. They can form anywhere, but are more common in the brain or spinal cord.
About 300,000 Americans are thought to be affected by AVMs of the brain or spinal cord. Most people don't experience any symptoms, and aren't aware of the malformation until symptoms arise, usually in their 20s, 30s and 40s. Common symptoms are headaches and seizures. The biggest risk is bleeding.
Treatments include medications, surgery or radiation and vary depending on the size and location.
Players around the NFL expressed their concern for Patterson on Twitter.
"Prayers go out 2 Mike Patterson. Great college teammate n even better person!" wrote Green Bay Packers All-Pro linebacker Clay Matthews, who played with Patterson at Southern California.