Scottish experts have discovered that Bell's Palsy, a syndrome which causes the muscles on one side of the face to become paralysed, can now be cured by a new steroid treatment.
Bell's Palsy affects the facial nerve which enables people to smile and close their eyes.
The researchers at Dundee University found that treating the condition early on with prednisolone completely cured some people in three months and offered a 95 per cent chance of complete recovery after nine months.
Bell's Palsy affects one in 60 people during their lifetime and can strike almost anyone at any age; it more commonly affects pregnant women and people with diabetes, flu, colds and other upper respiratory ailments.
The cause of the condition remains a mystery, but it is widely treated with expensive anti-viral drugs.
The new study says that the relatively cheap steroid prednisolone was the "best treatment" and offered "significantly" better recovery rates than the anti-viral agent acyclovir, which they say "has little benefit".
Professor Frank Sullivan, the director of the Scottish School of Primary Care at the university, and his team examined about 500 sufferers and he says the new treatment offers a significant improvement in how Bell's Palsy is dealt with and will make a real difference to patients.
Professor Sullivan says the study gives clear-cut evidence that early treatment with steroids offers by far the best results for complete recovery.
The study was led by Dundee University, with support from other Scottish universities at Aberdeen, Edinburgh and Glasgow and GP services around the country.
The findings have been published in the New England Journal of Medicine.