Power 1 Walnut - an illegal sex-enhancement drug that has caused the deaths of 10 this year - was found by the National Neuroscience Institute (NNI) to cause severe brain damage.

Singapore researchers using magnetic resonance imaging (MRI) confirmed the finding after studying the brains of eight men who took it.

Straits Times reported that the researchers found lesions and plaque build-up in parts of the brain which control short-term memory, and the part that links the right brain and the left.

Of the eight patients in the study, seven were found to have damages in the forebrain that controls short-term memory and spatial navigation and three had unusual damage in one side of the brain.

The drugs contain glibenclamide, which is used to treat high sugar in diabetic patients, resulting in severe low blood sugar.

As many as 220 cases of strong adverse drug reaction had been reported in 2008, with a total of 10 deaths.

The 10, aged between 35 and 84, were comatose when they died from complications such as infections and major organ failure.

The findings is published in this month's Radiology, a peer review journal and represents one of the largest series of hypoglycaemic brain damage in the world.

Hypoglycaemic brain damage or brain damage resulting from severely low blood sugar is a rare condition.