Slow and steady breathing. Eyes heavy and gritty. The resting mind drifts off to the floating, semi-conscious state between wakefulness and sleep.
All of a sudden, you're awake. A sound — something like an explosion or a gunshot — has fully aroused the body, tingling with alertness. Surely this noise or sensation that struck so abruptly wasn't real. Or was it?
An experience like the phenomenon described is provocatively called "exploding head syndrome." Brian Sharpless, a researcher with Washington State University's Department of Psychology, is trying to find out more on the long-known but mysterious condition.
People who've had an episode of exploding head syndrome, or EHS, experience the perception of a loud noise during transitions in and out of sleep. The theorized cause of these symptoms, Sharpless explains, is a misfiring of neural activity in the brain as it's preparing for the sleep state. Although it's not harmful, and not usually associated with any pain, it can be frightening for those who've had it happen and don't know why.
"Some people might think it's caused by a non-natural process," Sharpless explains. "It's really scary, and if you don't know what something is and it's dramatic, you think it's more severe. Some people think they're having a seizure or hemorrhage."
Sharpless recently completed the largest study of its kind on exploding head syndrome, interviewing 211 undergraduates at WSU. The results were surprising. Of those interviewed, 18 percent of students said they'd experienced EHS at least once, and 16.6 percent had experienced it on multiple occasions. A very small number of participants, less than 3 percent, reported EHS was causing problems in their lives.
In a paper on the study's results published online by the Journal of Sleep Research earlier this year, Sharpless notes that contrary to a previous belief that EHS was mainly seen in older adults, this study shows it's relatively common in younger populations. Sharpless hypothesizes this could be because the college-age population typically has more disrupted sleep patterns than the rest of us.
Another finding of the diagnostic interviews conducted for the study is that more than a third of students who'd experienced EHS also reported experiencing another related sleep disorder called isolated sleep paralysis. Sharpless has also studied sleep paralysis, and is writing a book on the subject for publication this summer. ISP, as it's known, refers to a period as a person is falling asleep or waking up during which voluntary muscle movement is incapacitated, but that person can see and move their eyes. Sharpless thinks there may be a common underlying factor between EHS and ISP, but more research is needed.
Niels Nielsen was 11 years old the first time he experienced an episode of exploding head syndrome.
"I remember being about to fall asleep, and then having this sensation there was a shot of lightning inside of my head," Nielsen describes. "It was pretty startling and jarring, and it only lasted a second or so. I wasn't scared... and it didn't seem to be anything bad or dangerous."
Nielsen, now 37, a psychiatrist at WSU's student Health & Wellness Services, wasn't part of Sharpless' study, but found out about it through an email update about university research projects.
"The title 'exploding head syndrome' caught my attention and immediately I thought, 'I wonder if that is this thing I have,'" he recalls. "So I sent him an email and he sent me a copy of the paper, and it seemed to fit what I had experienced."
Nielsen has never been so disturbed by his experiences to feel the need to reach out to a doctor, and having also experienced ISP and myoclonic jerks (sudden muscle twitches) in his sleep, he assumed the episodes were related.
Sharpless' take is that, like Nielsen, many others who've experienced EHS aren't mentioning it to their health care providers. At the same time, there isn't a lot of empirical data on just how prevalent EHS is.
"I don't think it's widely known in the field yet, so it might be misdiagnosed," he says. "My sense is that patients aren't reporting it and are afraid of being misperceived as crazy or strange, and providers aren't asking because it's believed to be so rare."
Exploding head syndrome was described in medical literature as early as 1876, then referred to as "sensory discharges," and as "snapping of the brain" in a 1920 report.
Coinciding with a lack of data on the prevalence of EHS, there aren't any well-established treatments that have been researched in clinical trials. But Sharpless says there are indications that simply telling people who have EHS that it's not harmful to them can help reduce the frequency of episodes.
"We haven't tested that, but it seems reasonable. It makes you feel reassured when you find out you're not the only person having it. You're less anxious to go to bed and less likely to worry," he says.
The next step in Sharpless' research on exploding head syndrome? Finding out what differentiates people who've experienced EHS from those who haven't. ♦