14 June 2012 Last updated at 10:45 ET By Pallab Ghosh Science correspondent, BBC News

Doctors in Scotland have said five stroke patients involved in an experimental stem cell treatment have shown signs of slight improvement.

They have stressed that it is too soon to tell whether the improvement is due to the therapy.

The medical team has talked about the first results of the treatment at a conference in Japan.

The procedure is controversial as brain cells from a foetus were originally used to create the stem cells.

A team, from Glasgow's Southern General Hospital, has been injecting the stem cells into the brains of stroke patients.

The trial began in November 2010. The participants are all men over the age of 60 who have been severely disabled by a stroke and have shown no sign of improvement for at least a year.

We hope to tease out over the next 18 months whether the improvement is due to the treatment

The doctors hope that the treatment will repair their damaged brain tissue and restore some of their movement and ability to speak.

The trail is at an early stage, and doctors are primarily looking to see that the treatment is safe. But they have found that five of the six patients treated so far have shown some slight signs of improvement.

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Stem cell stroke trial promising