OXNARD, Calif. -- Dallas Cowboys defensive tackle Amobi Okoye was cleared by doctors Thursday for full football activities 13 months after being placed in a medically induced coma at a Houston hospital to stabilize recurring seizures.

Okoye was diagnosed in March 2013 with anti-NMDA receptor encephalitis, a potentially lethal brain injury that includes seizures and memory issues.

He is the first football player to attempt to come back from the disease.

Cowboys DT Amobi Okoye is the first football player to attempt to come back from anti-NMDA receptor encephalitis, a potentially lethal brain injury that includes seizures and memory issues. AP Photo/Ringo H.W. Chiu

He was cleared by Dr. Imo Aisiku after a trip to Boston and will rejoin the Cowboys in Dallas. The disease is relatively new, discovered in 2007. In order to begin practicing, Okoye will have to be removed from the non-football illness list.

"I'm listening to the doctors and what they're saying and we're kind of working through this together because it is new," head athletic trainer Jim Maurer said. "It's not been done, so it will be a work in progress.

The Cowboys will work him in slowly, but owner and general manager Jerry Jones said he did not expect Okoye to practice Monday.

According to Okoye's agent, Ian Greengross, the 310-pound Okoye lost close to 90 pounds while in recovery and needed to rebuild his brain function over time with physical and occupational therapy. The Cowboys had interest in signing Okoye in 2013 in part because of then-defensive line coach Rod Marinelli, who is now the defensive coordinator. Marinelli coached Okoye for two years with the Chicago Bears.

"The easy way to think of it is it's like a virus putting a tent on your brain," Greengross said. "It's like a football field with a tarp on it. You can't play on it but the field is still there. Once it's lifted it comes back to normal, but it just takes time."

Because no player has dealt with this situation before, there is no way to quantify how the brain will react to repetitive blows. Maurer said the Cowboys have taken baseline tests with Okoye and will be in constant communication with him regarding how he feels once he returns to practice.

"We hope he doesn't get hit, but you try to be prepared for if something does happen or if there's a deterioration in some way whether it's headaches or something else," Maurer said.

A first-round pick in 2007 by the Houston Texans, Okoye has started 59 of 87 games in his career and has 16 sacks.

"I just think like anything else he's been working on the side doing his conditioning, but we've got to work him back in slowly like we've done with some other guys and just monitor and see how he's doing and take it day by day," coach Jason Garrett said. "It's exciting news for us. He's a good football player when he's healthy and playing in this league. He knows our scheme. It's the reason we got him and I think our patience has paid off up to this point, so it will be fun to see him out on the practice field, see what kind of progress he can make."