For most of the day Sam Goddard looks like anyone else with severe brain damage.

He sits virtually motionless, face contorted, eyes open and moaning but unable to talk.

Then his fiancee gives him a sleeping pill, and within minutes the 25-year-old springs to life.

"How do you feel?" she asked Sam not long after this astonishing "awakening" happened for the first time.

"F***ing great," he replied.

"It's a miracle. For 15 months I was trapped in my own body. I could not communicate verbally at all and now I can."

That heartwarming moment was caught by a camera crew from an Australian TV documentary last month.

Like dozens of similar cases around the world, Sam's recovery has baffled medical experts.

The sports-mad accountant collapsed following a game of soccer on Valentine's Day last year, just three months before he was due to marry his university sweetheart, Sally Nielsen.

After suffering massive strokes, doctors at the Royal Brisbane Hospital told his his devastated wife-to-be and family he would probably die. At best he would end up a "vegetable".

For the next 45 days Sam lay in a coma.

"Pretty much every day they said he would die," says Sally. "After about two weeks he contracted pneumonia and at that point they gave him a one per cent chance of survival."

Against all odds, almost 18 months on the cheeky, funny man she fell in love with is back.

Sam's vocal cords have recovered to the point where he not only sounds like his old self, he regularly breaks into song as well.

But the dramatic transformation lasts for only a couple of hours each day. Paradoxically, the sleeping pill that brings Sam back to life like clockwork wears off just as quickly.

"It's really hard because Sam has a degree of short term memory loss," says Sally. "So sometimes, because he can't remember, he doesn't understand why he's suddenly losing the ability to speak. It's really frightening because he panics and gets upset."

Like many medical discoveries, the benefits of Sam's so-called "Lazarus pill" were stumbled on by accident.

Twelve years ago the mother of a man who had been comatose for five years after being hit by a truck asked South African GP Wally Nel to prescribe her son a sedative. She was worried involuntary spasms in his arm were making him uncomfortable.

But just minutes after taking Stilnox, Louis Viljoen said: "Hello, mummy."

Nel went on to pioneer the use of the drug for brain injuries and says he has since witnessed hundreds of similar cases.

Last year he helped run a small clinical trial in which 10 of 23 patients given Stilnox showed an increase in brain function ranging from 10 to 40 per cent.

His British-based colleague Ralf Clauss, a nuclear medicine specialist, has conducted brain scans that suggest the drug's active ingredient - zolpidem - temporarily activates damaged brain cells, resulting in some patients recovering the ability to talk.

Sam's road back to full consciousness was a consequence of sheer desperation on the part of his fiancee and parents, John and Leslie Goddard.

In the weeks following the strokes, as doctors predicted the worst, Sally clung to the smallest signs of hope; a rise in blood pressure when she kissed Sam, the slightest flicker of his eye lashes, his finger twitching when she held his hand.

Slowly but surely he began to move his hands and arms. After more than a year of painful rehabilitation he was able to walk again and write short notes.

But progress slowed and Sally turned to the internet in a frantic search for a "miracle cure".

Enthused by the discovery of the Stilnox stories, she pleaded with doctors in Brisbane to prescribe the drug for Sam.

"Over a five month period we got a firm 'no' to use it for what we wanted to use it for," she says.

"It was really frustrating because we felt like we'd gone down every avenue possible to aid Sam's recovery. We felt it held the key."

In late May Sally finally gained access to a drug with a controversial reputation. A string of users have complained it caused them to engage in erratic behaviours - from fighting to driving and self-harm - while still fast asleep.

Although Sam's levels of alertness improved, Sally initially thought Stilnox had limited effect.

So she increased the daily dose.

"I'm not a doctor but I thought 'let's just take a risk here, what's the worst that can happen'," she said.

"And we were just chatting with friends and he suddenly just chimed in on the conversation.

"I had to record it on my phone. I was in a state of shock. I thought I was dreaming.

"It wasn't until I played it back that I believed he was talking. And it was like the whole world had just opened up to us. It was just the most amazing feeling. And he told me he loved me."

Sam, who was only allowed home from hospital two months ago, has continued to improve.

"I'm really hoping he can time his physical, occupational and speech therapy around the time when he's on Stilnox, because when he is most alert he can participate more and get more out of it," says Sally.
But there are also significant financial challenges.

The couple, who bought a three-storey townhouse just before Sam's accident, have now moved in with his parents. Sally has temporarily quit her job as a wedding planner to look after him.

If she returns to work, the cost of Sam's daily therapies will be 50 per cent more than her daily wage.

The goal of finding a wheelchair accessible house seems a distant dream.

"We are struggling financially," she says. "We're coming to the point in the next couple of months where we'll have to sell our house just to survive."

Despite the challenges, Sally remains optimistic and totally committed to a man she still hopes to marry.

"I feel like we're only halfway through the story in a way," she says. "There's so much more to come."