The researchers who developed the technique say the procedure has been performed on seven patients.

The brain cells used for the treatment originate from human tumour tissue composed of embryonic-like cells.

Scientists have manipulated these cells to produce fully differentiated, non-dividing neurons - potentially usable brain cells.

Treatment success

Scientists at the University of Pittsburgh Medical Centre reported results from their research at the 24th American Heart Association International Conference on Stroke and Cerebral Circulation.

Professor Douglas Kondziolka, lead author of the study, said: "We're trying to evaluate if it's feasible to put these cells into the brain and whether the process is safe.

"To this date, it has been safe and there have been no problems noted. That's been encouraging and the most important thing is hopefully this will lead to a larger second study."

Hospital care and rehabilitation is the current treatment

Of the seven patients treated, all have been able to leave hospital within 24 hours and three have reported small improvements in motor skills, Professor Kondziolka said.

The first patient to receive a transplant - a 62-year-old woman who suffered a major stroke in autumn 1997 - has felt well over the first seven months and has had slight improvements in speech, he added.

"An important part of the research is that this is setting the foundation for a possible future treatment.

"It's like in baseball - you don't walk up to bat your first time and try to hit a home run. If you can walk, and get on base, you can set the stage for something bigger later."

Ongoing research

The researchers are studying patients aged 40 to 75 who have had a stroke in the previous six months to six years.

They want to determine whether or not they can get motor skills to return through transplantation.

The only treatment option at the moment is intensive rehabilitation in order to recover lost motor skills.

The scientists hope the transplanted cells will link with other cells in the same area to help restore speech and movement.

The therapy involves two to six million cells being transplanted in and around stroke-damaged areas of the brain.

The brain cells used for the treatment are provided by a company known as Layton Bioscience, and are known as LBS-neurons.

The surgeons use a computed tomography (CT) scan of the patient's brain to identify three or more sites to inject the lab-grown cells.

Professor Kondziolka said the research was only just beginning.

"It's difficult to say whether the functional gains some patients have described are due to what we've done or something else.