he's not here. >> 12-year-old parker barnes, and 4-year-old alexia baier, have been suffering debilitatings like these for months. >> get away! get away! >> reporter: parker missed nearly a full grade of school and at one point stopped talking for four months. >> i would liken it mostly to an abduction. something came in the window and stole our child, but it's not our kid. our kid is gone. like, gone. >> after so much uncertainty, both families now have the same diagnosis, that disorder called pandas. some doctors believe pandas works like this. when anybody gets sick, the immune system makes antibodies to fight off the drugs, but those travel to the brain causing it to swell. they say that swelling can trigger a wide variety of neurological issues like ticks, rages, depression, or obsessive compulsive behavior. >> traditional onset ocd is gradual. comes over a period of days or weeks. pandas ocd comes on overnight. it's lightning-like onset where the child is struck down. >> reporter: doctors say pandas is triggered by strep. pans is triggered by other common childhood illnesses like wal

parker's a very severe case. and that he's gonna need the biggest punch that we can find. >> reporter: natalie and brian barnes hadxtreme treatment dr. latimer had suggested -- plasmapheresis, scary cleansing of his immune system. >> parker suffers every day. he has no childhood right now. it's like, if you had a child that was told they had leukemia. and they had to be hospitalized to get chemotherapy. you would not hesitate. >> reporter: but remember that diagnosis -- p.a.n.d.a.s. -- is controversial. and that treatment for it -- unconventional. not all doctors accept it, including, as the barnes were shocked to find out, their local immunologist. >> he said, "i will not participate on any level with your son if you give him that treatment." "i don't agree with it. and i won't touch him." >> reporter: and with that, plasmapheresis was out. >> it just wasn't possible. it just didn't happen. >> the logistical problem of trying to get it arranged was confounding. >> reporter: so now what? >> there's a million ways. and i think it depends on what your doctor considers serious, what they're comfortable ordering. >> r