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Every night, at the moment she started to fall asleep, a 77-year-old woman felt a sledgehammer pounding inside her head. It did not hurt. It jolted her awake and left her anxious, so she built a routine around avoiding it: stay awake on purpose until she was exhausted enough that the sledgehammer could no longer wake her. Her usual sleep onset drifted to around 4 a.m. Once she was finally asleep, she reported averaging about seven hours.

She had done this for 15 years.

The case was presented at the 40th annual meeting of the Associated Professional Sleep Societies in Baltimore and published as an abstract in the journal SLEEP by Darian Aboubakare, Qaiser Patel, and Nader Mina of Corewell Health East in Michigan. A conference abstract does not go through the full peer review a journal article receives, and the report is deliberately brief. What it documents is a diagnosis that took a decade and a half to arrive and then required no medication at all.

The Noise Is Real to the Brain and Absent from the Room

Exploding head syndrome is classified in the International Classification of Sleep Disorders, third edition, under Other Parasomnias. The defining feature is a sudden loud noise or a sensation of explosion inside the head at the transition into or out of sleep, with no external source and, critically, no pain.

Descriptions in the literature run to thunder, blasts, gunshots, and electrical crackling. A case series in Case Reports in Neurology covering six patients ranging in age from 13 to 77 listed sounds ranging from a firecracker to a gunshot, mostly experienced as happening inside the skull.

A sledgehammer is a less common metaphor than most, which may be part of why the diagnosis was slow. The phenomenon itself has been recognized for a long time. American neurologist Silas Weir Mitchell wrote up two patients with what he called sensory discharges in 1876, according to a reference summary maintained by the National Library of Medicine, and the current name was coined by British neurologist J.M.S. Pearce more than a century later.

Fifteen Years of Normal Scans

Her medical history included headache, anxiety, chronic insomnia, and obesity. Over the 15 years, she had multiple brain imaging studies. All were negative for stroke or any acute process. She was under neurology care for what the abstract calls her painless head explosions, and was prescribed a series of headache medications. Only gabapentin reduced the severity.

None of that is unusual. The same case series found that five of its six patients had come to a sleep clinic for complaints other than exploding head syndrome, and the authors note that patients rarely seek medical attention for the symptom alone, partly because it is hard to phrase as a complaint.

The consequences in this case were not trivial. She was not distressed by pain, because there was none. She was distressed by the interruption, and her adaptation to it, deliberately deferring sleep for years, is what turned a benign parasomnia into severe chronic insomnia.

How Common It Is Depends Entirely on How You Ask

The prevalence figures in this literature diverge wildly, and the reason is methodological rather than biological.

When Brian Sharpless interviewed 211 undergraduate students using semi-structured diagnostic interviews, 18% reported lifetime exploding head syndrome and 16.6% met criteria for recurrent episodes. Only 2.8% experienced it severely enough to be associated with clinically significant distress or impairment. That finding challenged a long-standing assumption that the condition was rare and mainly a problem after age 50.

Screening questionnaires land in a similar broad range. A validation study of one parasomnia screening tool, described in the same case series, put the figure near 13.8% among psychiatric patients, 10.0% among patients with sleep disorders, and 10.7% among healthy controls. But when researchers applied strict criteria to a Japanese working population of 1,843 government employees, 46 respondents, or 2.49%, reported sudden noises or explosion sensations, and only 23, or 1.25%, met full diagnostic criteria. That study also found the condition related to depression, anxiety, insomnia and fatigue measures after adjusting for age, sex, body mass index and sleep duration.

The gap between 18% and 1.25% is not a contradiction. It is the difference between ever having experienced the sensation and having a disorder by formal criteria. It also explains why something genuinely common in the population is genuinely uncommon in clinic.

She Slept Better in the Lab Than She Had in a Decade

Her doctors ordered polysomnography, an overnight sleep study, to evaluate for obstructive sleep apnea and parasomnias. She told them she doubted she could fall asleep before 4 a.m.

She fell asleep at 11:10 p.m. Her sleep latency that night was 74 minutes, against a habitual latency of more than 360 minutes at home. The study was diagnostic for mild obstructive sleep apnea, with an apnea-hypopnea index of 11.49 events per hour at the 3% desaturation threshold. She reported sleeping better than she did at home and had no exploding head syndrome episodes during the recording.

The intervention that preceded this was counseling and reassurance. Once she was told what the sensation was, that it was a recognized parasomnia, that it was not a stroke or a tumor, and that it was not a sign of brain damage, the avoidance behavior that had structured her nights for 15 years began to loosen.

That is the standard first-line approach. Education and reassurance about the harmless nature of the episodes often produce improvement on their own, and drug treatment is generally reserved for people with significant distress or functional impairment. The authors' conclusion is about the cost of delay: despite repeated evaluations, the parasomnia was missed for a decade and a half, and naming it was most of the treatment.

Anyone experiencing frightening sensations around sleep onset, or persistent insomnia they have reorganized their life around, should raise it with a clinician rather than assuming nothing can be done.

Key Questions Answered

What is exploding head syndrome?

A parasomnia in which a person perceives a sudden loud noise or a sense of explosion inside the head at the transition into or out of sleep, with no external sound and no pain.

Is it dangerous?

The episodes themselves are not considered harmful. The harm in this case came from the patient's avoidance of sleep, which produced years of severe insomnia.

Why did it take 15 years to diagnose?

She was evaluated repeatedly with brain imaging that found nothing acute and was treated for headache. The abstract's authors describe the parasomnia as having been missed despite multiple evaluations.

How common is it?

Estimates range from 18% lifetime in an interviewed student sample down to 1.25% meeting full diagnostic criteria in a Japanese working population, depending on how strictly the condition is defined.

How is it treated?

Reassurance and education are first line. Medication is generally reserved for people with significant distress or functional impairment.

Does it require a sleep study?

Not to diagnose the parasomnia itself, which rests on the patient's description. Here, polysomnography was used to check for sleep apnea and other parasomnias, and it found mild obstructive sleep apnea.

Originally published on Medical Daily