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The first patients to take part in a clinical trial of a stem cell treatment for stroke have seen reductions in their disability, according to doctors.

Six patients in the west of Scotland had human stem cells inserted close to the damaged part of their brain.

After receiving the treatment, they saw improvements in the limb weakness they suffered as a result of their stroke.

Howeve, doctors have cautioned against reading too much into the early results of the clinical trial.

It is the world's first trial of a neural stem cell therapy for stroke.

Stroke is the third largest cause of death and the single largest cause of adult disability in the developed world.

The trial is being conducted at the Institute of Neurological Sciences at the Southern General Hospital in Glasgow, and is being led by Glasgow University neurologist Professor Keith Muir.

He said: "So far we've seen no evidence of any harmful effects. We're dealing with a group of people a long time after a stroke with significant disability and we don't really expect these patients to show any change over time.

"So it's interesting to see that in all the patients so far they have improved slightly over the course of their involvement in the study."

All six patients suffered a stroke six months to five years before they were recruited to the trial, and all had been left with limb weakness.

The patients were assessed using the National Institutes of Health Stroke Scale.

Prior to the study, the first five patients had a median score of eight. Three months after treatment their median score had fallen to four.

The sixth patient was treated less than three months ago. Six further patients will be treated as part of this Phase 1 trial.

Professor Muir said he was "intrigued" by the early results.

He added: "We know that if you're involved in a trial you are going to see patients change in behaviour, particularly if you're doing something invasive, so we need to be very cautious indeed in interpreting these results.

"However, that said, it is not something we'd anticipated seeing in this group of patients."

Further trials are needed to establish whether stem cells actually help the brain repair damaged tissue.

Michael Hunt, chief executive officer of the company developing the treatment, ReNeuron, said: "The clinical trial is primarily a safety study and we must therefore treat any of the observed early indications of functional benefit with considerable caution at this stage.

"That said, we remain encouraged by the results seen in the study to date and we look forward to providing further updates."