Ahead of a forum in Belfast where doctors will study the drug, pentosan polysulphate (PPS), his father, Don, explains how his son's condition has changed.

"What we have noticed in Jonathan has been that his swallow has strengthened. This is something that doesn't normally happen once the swallow starts to fatigue.

Jonathan's condition has stabilised despite doctors' predictions

"He is able to deal with his own saliva, before he would have choked on it. That used to distress him.

"In CJD patients, what happens is they choke on their own saliva, that promotes pneumonia.

"Pneumonia then leads to death. So it's taken part of the risk away.

"There are other small, but significant changes also. His blood pressure has returned to normal, his pulse rate has dropped to normal. His bowels no longer require stimulants.

"When all of these things start with a CJD patient, they remain with that patient.

"We as a family haven't become complacent that Jonathan's illness has completely disappeared. We are just more optimistic, but we're also guarded in that optimism.

"It would appear that one of two things have happened here, although we are still not 100% sure - that is that the disease has been slowing down so significantly or, in fact, PPS is helping it because we see no further signs of deterioration.

Jonathan is being treated at his home

"It's been a roller coaster ride to hell from Jonathan getting the illness.

"At the end of the day, doctors will be given the facts from our own doctors and scientists.

"Those who are still apprehensive - they'll be given a forum in which to address their fears.

"Hopefully those fears will be allayed in that when other families ask for this treatment, they'll not have to jump the hurdles that we did, that they can get the treatment sooner.

"I am angry, but I haven't let that anger blind me. There will be other families who will want this treatment, and if we can help those families, this is what this forum is for."