In the first double blind controlled trial of botulinum toxin, a teaspoonful of which would be enough to kill 100,000 people, doctors in Leeds are using the poison to treat children with cerebral palsy, to help them to walk.
The toxin causes a dangerous form of food poisoning known as botulism, a creeping paralysis whose first signs are difficulty in swallowing and speaking. Even with prompt treatment with an antitoxin, it kills one in four of those affected.
It works by blocking nerve transmission which weakens or paralyses muscles with unusually long-lasting effects. As a lethal, tasteless, potent poison it attracted the interest of chemical warfare experts.
Doctors discovered that the same effect could be put to medical use, and have experimented over the last 10 years with the injection of tiny amounts of the toxin to ease a range of disorders caused by involuntary contraction of the muscles. Examples include squinting, blepharospasm, in which the eyes are repeatedly screwed up, and torticollis, in which the head is pulled over to one side.
Until now, however, the treatment has only been tried on individual patients and it has been impossible to tell whether the improvement noted in them has been due to the placebo effect - the patient's belief that a treatment will bring improvement.
Researchers at St James's University Hospital in Leeds have selected 50 children with cerebral palsy - half of whom will be given injections of the toxin and half injections of an inert substance. The injections will be coded so that neither the children, nor their parents, nor the doctors administering them know which is which.
After three months, the code will be broken and the toxin offered to those children not getting it. Dr Tim Ubhi, who is co- ordinating the study, said: "It is the most lethal toxin around, yet its potential is amazing. It is probably the biggest advance in the treatment of cerebral palsy for decades. People have been using it ad hoc for some time, but we have no firm evidence that it works."
Dr Ubhi said a pilot trial in Leeds, involving 20 children, found that 18 improved with the injection and none deteriorated. Doctors in London and Belfast have also used it successfully.
Children whose legs are affected by cerebral palsy suffer contracture of the muscles, which causes the limbs to twist, making walking difficult or impossible. The injection allows the muscles to relax and stretch to a more normal length, which may also increase the child's growth.
"We think that once we have proved it works, it will be used by district hospitals very quickly. It looks that good," Dr Ubhi said.
Richard Parnell, research officer at Scope, the charity for people with cerebral palsy, said the toxin was not a licensed drug and required further tests on its long-term effects. "The evidence is that it works on selected children but it is not a catch-all solution. It is potentially a very exciting treatment but we have to be cautious."
CASE STUDY: 'Now she can do what her friends do. She is just so happy': Francesca Capitano has worn splints on her legs for much of her short life. She was a premature baby and suffered bleeding into her brain when she was five-days-old, which left her with brain damage. Now aged nine, it is mainly her legs that are affected, and she has always hated wearing splints, because they made her feel different from other children.
When doctors offered her a new treatment, her parents, Christine and Tony, of Penders Fields, Leeds, did not hesitate. Christine said: "I knew it was toxic but the dose was minimal and I could always take her to the hospital if there were problems. I have a lot of faith in the doctors."
Francesca had two injections of botulinum toxin, followed by two more, six months later, at St James's Hospital. Christine noticed the difference within days. "I didn't dare say anything because I was afraid to believe it. The doctors told us nothing because they didn't want to raise our hopes. Then others in the family and at her school started noticing she was walking better."
By relaxing the muscles in her twisted legs, the injections not only made it easier for her to walk, they relaxed her whole body. Suddenly, a whole range of activities, from skipping to swiming to riding a bicycle became possible for her. Since last October she has only worn her splints at night.
Christine said: "We used to have tears when she couldn't ride a bike. Francesca is a very determined child and she would keep a brave face at school, but when she came home she would be in floods of tears. Now she can do what other children do. She is just so happy that she can keep up with her friends. It has given her confidence a real boost."Reuse content