FOR most people, 10 hours of sleep a day is plenty.

For assistant sales manager Damian Ng, 29, however, a snooze can sometimes last three weeks.

He would only wake up to eat or shower.

But being a real life Rip Van Winkle is hardly a happy fairy tale.

Said Mr Ng: "I would feel really lethargic and really tired. I would be out of sync with the world and everything would look fuzzy and blur to me."

Doctors, when told of his symptoms, reckon he could be suffering from the rare neurological condition called Kleine-Levin Syndrome (KLS), which is also known as Sleeping Beauty Syndrome.

Those with this condition live, sleep and behave normally for weeks or months - and suddenly end up sleeping for days or weeks at a stretch. They can wake up during that period but would be groggy and disoriented until the episode passes.

For Mr Ng, these episodes used to occur once a year. They started when he was 13.

"People like us who have such episodes throughout our lives can find it a barrier to live normal lives," he said.

It has been two years since his last attack and - as he ritually rapped his desk with his knuckles - he hopes it will not return.

His first episode occurred when he was in Secondary 1, on a school trip to Johor. During the return journey on the coach, he started feeling like he was dreaming. It was a "spacey feeling".

When he got home, he said he rested on his mother's lap and cried.

Fortunately, it was the December holidays. He spent three to four weeks in a slumber, he said.

His younger sister, Miss Cerenna Ng, 28, a teacher, said she felt quite helpless when it happened.

She said: "If you see his state, see him sleep for so long, you would feel uncomfortable as well."

He looked normal but dazed and unable to focus whenever she woke him.

She said the family had to take care of him. Even their grandmother had to travel from Clementi to their Jurong West home to cook for him.

It also led to some friction between his parents.

His father is a taxi driver and his mum is a technical administration assistant.

Said Mr Ng: "My father thought I was possessed while my mum thought it was a medical problem."

He said he visited doctors to get medical leave and they often thought he was faking.

One doctor even speculated to his mother that he may be suffering from relationship problems and was trying to avoid school.

But he said his teachers were sympathetic when his mother called to explain his absence. His classmates would also help him.