US doctors are trying to find out why a severely brain-damaged man has suddenly started to speak after nearly 10 years.
Herbert (left) has lived in a nursing home for more than seven years.
Donald Herbert, 43, a firefighter, was badly injured in a house fire in 1995 and was deprived of oxygen for several minutes before being rescued.
He was in a coma for more than two months, and since then he has been blind, barely able to speak and unable to recognise family and friends.
But at the weekend he spoke lucidly with his wife and family for 14 hours.
He has since maintained his recovery.
Medical experts say it is almost unheard of for patients to recover from such severe brain injuries after so many years.
Michael Powel, a neurosurgeon at the National Hospital for Neurology and Neurosurgery, in London told the BBC he had not seen anything similar in his 25 years working in the specialty.
A news conference on Mr Herbert's condition is scheduled for Wednesday.
The firefighter was injured when the roof of a burning house collapsed on him in December 1995. He was left without oxygen for several minutes.
He has been in a nursing home in the city of Buffalo, in New York state, for more than seven years.
But on Saturday he suddenly asked for his wife Linda and chatted with her, his four sons and other family until he fell asleep on Sunday morning.
His uncle, Simon Manka, told AP news agency he thought he had only been away for three months.
Not like Schiavo
Experts say there are several possible reasons for the change.
His brain may have been impaired by some condition, other than the injury itself, which was successfully dealt with.
A change in medication might also have brought about an improvement.
There have been several other similar cases of brain recovery in the US.
Arkansas car accident victim Terry Wallis woke up two years ago after 19 years in a coma and began speaking to his family.
And Tennessee police officer Gary Dockery, paralysed and mute after a shooting in 1988, started speaking again eight years later. He died of a blood clot on the lung in 1997.
None of the victims was in a persistent vegetative state like Terri Schiavo, the brain-damaged woman who died last month after her feeding tube was removed.