Image caption Clots block the flow of blood, starving the brain of oxygen

It may be possible to use a drug to prevent some of the lasting and crippling damage caused by a stroke, according to doctors in the US and Canada.

A safety trial, published in the Lancet Neurology medical journal, suggested the chemical NA-1 was safe to use.

The study on 185 people also hinted that patients given the drug developed fewer regions of damaged brain tissue.

The Stroke Association said that it was promising, but needed more research.

Tests in primates had suggested NA-1 prevented brain cells dying when a stroke starved them of oxygen.

A small trial was set up at 14 hospitals in the US and Canada.

Patients who took part were having an operation to repair a brain aneurysm, a weakened blood vessel which could rupture, are at increased risk of a stroke.

Ninety-two people had the drug injected into a vein, while another 93 were injected with salty water.

'Safe'

The doctors concluded that NA-1 was safe, with only two patients having mild side effects.

However, brain scans also showed that fewer brain lesions, damaged areas of tissue, formed in patients given the drug.

The doctors involved said the study provided evidence that "neuroprotection is achievable" but said that "a larger trial is necessary to investigate the robustness of the effect".

Prof Markku Kaste, from Helsinki University Central Hospital, said: "Age is the greatest risk factor for stroke. Because of the global population ageing, the number and burden of strokes will increase."

He said previous trials to use drugs to protect the brain had resulted in failure. His said this drug still need to be assessed in much larger clinical trials before its effectiveness was known.

Dr Peter Coleman, from the Stroke Association charity said: "We welcome any treatment that could protect brain cells after a stroke and limit the amount of brain damage. This potential treatment appears promising, but a lot more research is needed."

The trial was funded by the biopharmaceutical companies NoNO and Arbor Vita.