Thomas, five, has pioneering implant to help stimulate brain

Thomas Melville-Ross is the smallest patient to be given the device to stimulate his brain and help stop involuntary muscle contractions and movements caused by his severe disabilities.

Weighing just two stones, he was operated on at the Evelina Children's Hospital in south London in an attempt to help the severe dystonia he suffers. It was the first time the device had been used by British surgeons.

Thomas and his twin sister Alice were born at just 24 weeks and have suffered severe complications as a result.

Dystonia affects the brain's ability to control movements, leading to muscle spasms. Thomas is profoundly deaf.

Surgeons at Evelina placed four electrodes deep inside Thomas's brain to deliver electric pulses to the affected area, so he will eventually be able to control his movements enough to work an electric wheelchair and learn to communicate through a laptop. After the four-hour operation, which involved drilling holes in the skull, the electrodes were attached to a battery pack which sits under the skin on Thomas's chest.

The operation was carried out just before the New Year and the early signs are promising.

Alice is due to have an implant fitted in three months. It can be left in place for up to 10 years, whereas previously a child of Thomas's size and age would need surgery to replace the battery pack, which is fitted on the chest, every two years.

Without the new implant he would have had to wait several years before he was big enough to have one of the older devices fitted, by which time his condition may have deteriorated.

The twins' parents, James and Georgie, both 36, from Aylesbury, Buckinghamshire, said they wanted the children to have a better quality of life. Mr Melville-Ross, a PR consultant, said: "We did a lot of soul searching before deciding to go ahead with the operation for Thomas and potentially it could make a big difference to him."

Jean-Pierre Lin, consultant paediatric neurologist at Guy's and St Thomas', said: "Premature babies like Thomas are often affected by dystonia but because they develop smaller physically, it has been impossible to give them early treatment.

"As a result, they have gone on to suffer a poor quality of life and a number of knock-on problems such as spinal and hip injuries.

"This new device means we can try and help manage their conditions from a far earlier age. This should also benefit patients suffering from Parkinson's and essential tremor."

Mr Richard Selway, consultant functional neurosurgeon at King's College Hospital, said: "In addition to being smaller, the fact the new device is rechargeable is a massive benefit. Previously, I would have had to [replace the device] every two years. This offers exciting possibilities and we anticipate being able to treat a lot more children in the coming years."