Your worst nightmare

Friends told Birbiglia that he ought to see a doctor but he resisted - until something happened that almost killed him. He was in a second-floor hotel room in Washington when he dreamt he was in a war zone and that his room had been targeted by a guided missile. Terrified, he jumped from bed and leapt through the window, only to wake up on the lawn below, bleeding and confused. He received 33 stitches in his head and legs and counts himself lucky that he hadn't taken a room on the 10th floor.

Birbiglia, who has now written a book about his experiences, titled Sleepwalk with Me, is one of the many people who suffer from parasomnias, a broad category of sleep disorders that includes bruxism, or teeth grinding, restless-leg syndrome and a sleep-related eating disorder that causes people to binge while asleep, often on bizarre combinations of things: buttered cigarettes, raw bacon, tubs of margarine. But the best known of all parasomnias is sleepwalking, which occurs in 4 per cent of adults and, according to a paper from the Monash Medical Centre, will be experienced by up to 45 per cent of children.

''Sleepwalking, sleep talking and night terrors are all part of the same phenomenon,'' says a sleep specialist at The Children's Hospital at Westmead, Dr Chris Seton. ''All are caused by the same electrical triggers in the brain, called hypersynchronous slow-wave activity. When the young brain gets the trigger, it usually results in night terrors. At early school it shows up as sleep talking and in later childhood it's sleepwalking.''

Most sleepwalking occurs in the first third of the night, when people are progressing from non-rapid eye movement (or deep) sleep to lighter sleep. Sleepwalkers become stuck in this ''mixed state'', in which different parts of the brain are in effect awake (the part responsible for movement, for instance) while other parts (those responsible for memory) remain asleep. This is why sleepwalkers can get up and rearrange the furniture or have sex but have no recollection of it the morning after.

Most people sleepwalk for only five minutes to 20 minutes but some episodes can last considerably longer and involve complex behaviour, such as text messaging, driving a car or even climbing to the top of a 50-metre crane and crawling out on its exposed arm (as a 15-year-old London girl did in 2005).

Sleepwalkers can, occasionally, be violent, even murderous. In his 1632 publication, Thautomatographia naturalis, Polish physician Jan Jonston described the case of a Paris man who, while asleep, got up, took his sword, swam across the river Seine and killed a man before swimming back home and hopping into bed, all without waking.

These days, homicidal somnambulism is a recognised phenomenon, so much so that some courts consider it a legitimate defence for murder. Last year, prosecutors in England dropped a murder case against then 59-year-old father-of-two Brian Thomas, who killed his wife in his sleep while the couple were on a campervan holiday in Wales. Believing their van had been broken into, Thomas attacked and strangled his wife before making a desperate call to emergency services.

But the most famous case of homicidal somnambulism involved a Toronto man, Kenneth Parks. In the early hours of May 23, 1987, Parks got up in his sleep, drove 23 kilometres to his in-laws' home, broke in, assaulted his father-in-law and stabbed his mother-in-law to death. He then drove himself to a police station, where he told officers: ''I think I have killed some people with my bare hands.'' Following testimony from sleep specialists, a jury acquitted Parks, deciding that he was indeed sleepwalking and thus not responsible for his actions.

But the Parks case remains a line in the sand for some sleep specialists.

''I knew someone who walked off a second-floor building at Sydney University and broke both legs and another person who went out and chopped wood in their sleep,'' says a professor in sleep medicine at Sydney's Woolcock Institute of Medical Research, Dr Ron Grunstein.

''But I find it hard to believe the complex brain behaviour that Parks demonstrated could occur with the cortex of the brain asleep.''

Studying sleepwalking is notoriously difficult. ''Putting someone into a foreign clinical environment seems to reduce slow-wave sleep, when most sleepwalking happens,'' says Grunstein, who has studied sleep disorders for 25 years. ''We often get patients who sleepwalk every night but they come into the lab and don't sleepwalk at all. And you can't put them into a PET scanner because they get up to walk and bang their head.''

The main advance has been in understanding that the sleeping brain is not ''an all-or-nothing proposition''. ''We now know that we are all in some kind of mixed state when we sleep but for some people, the differences are more distinct,'' Grunstein says.

Because of their zombie-like appearance - open-eyed, yet unresponsive - sleepwalkers have always inspired trepidation. In the 1800s, night terrors and other disorders were thought to be a sign of demonic possession. (Indeed, in 1991, Seton saw a boy who suffered night terrors and whose parents had arranged an exorcism with their local priest: ''I had to ring the priest and ask him not to do it.'') After World War 1, doctors realised the problem was medical; until the 1960s, however, sleepwalking was commonly thought to be connected to psychiatric illness.

''This is completely wrong,'' Seton says. ''Twenty years ago, researchers in California studied thousands of kids with and without psychological conditions and found that terrors and sleepwalking occurred equally.''

Despite this, many sleepwalkers still feel stigmatised. ''When I start telling people about my sleepwalking, they always look a bit wary,'' says a northern beaches woman who did not want to be identified. ''I have a business up here and I wouldn't want people thinking I was mad.''

The woman, now 45, first sleepwalked at the age of 11, when living close to Victoria Road in Rydalmere.

''Mum heard the door go in the middle of the night and eventually found me 20 metres up the street, in my pyjamas, standing on the kerb about to wander across Victoria Road,'' she says.

Whenever her cousin slept over, the two girls, while asleep, would engage in long conversations, the contents of which neither could remember in the morning. Later, while holidaying in Hawaii, she dreamt the hotel was on fire and ran to the balcony. ''I was ready to jump when a friend came out to see what I was doing,'' she says.

Though she no longer sleepwalks, her dreams (and nightmares) remain particularly vivid. ''I wake up and tell my husband all about them in great detail and he says, 'Wow, I can't even remember my dreams.' He reckons I'm lucky,'' she says. ''I'm not so sure.''

TREATMENT AND PREVENTION

Sleepwalking can be exacerbated by stress, sleep deprivation or disruption, obstructive sleep apnoea or fever. Sometimes it can occur as a side effect of alcohol or sedatives such as Stilnox. In most cases, doctors will recommend improved ''sleep hygiene'': maintaining regular sleep cycles and avoiding disturbances. In severe cases, minor tranquillisers such as diazepam and temazepam have been useful, as has the anti-epileptic drug clonazepam. (Next year the Woolcock Institute plans a multi-centre, placebo-controlled trial of clonazepam for sleepwalking/night terrors.) For children's night terrors, which often occur at the same time each night, try waking your child for 10 nights in a row, 15 minutes before the episode usually happens.

LIKE FATHER, LIKE SON

In 2002, Dr Chris Seton saw a 12-year-old boy who had walked, in his sleep, from his home in Killara, on Sydney's north shore, to the Harbour Bridge, where he fell asleep at the base of one of the northern pylons. ''The boy had no memory of how he got there,'' Seton says. ''He'd walked 12 kilometres down the Pacific Highway - a cab driver later reported seeing him - and would have negotiated several traffic lights.'' The boy's parents initially suspected that he had sneaked out to play. ''But he was still in his pyjamas and footy socks, which he always wore to bed in winter, and they were worn through,'' Seton says. ''There were also cuts and abrasions on the soles of his feet. However, the giveaway was that his dad turned out to be a chronic sleepwalker and one thing we do know is sleepwalking is hereditary.''

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