Have you ever been woken up suddenly by an extremely loud noise, but upon investigation you’re unable to find any cause or evidence that the sound actually happened?
It can be extremely distressing to find that this startling experience was all in your head. Rest assured you’re not alone, and this bizarre phenomenon has a name: Exploding head syndrome.
But what is exploding head syndrome? And why do some people experience these nighttime attacks?
What Is Exploding Head Syndrome?
Exploding head syndrome (EHS) is a parasomnia that causes you to perceive loud noises as you are falling asleep, or upon awakening. The perhaps misleading name is an attempt to describe the sudden, almost violent nature of the noise -- which is often likened to a bomb exploding.
The first description of this bizarre phenomenon appeared in a paper published in the Virginia Medical Monthly back in 1876. The author, a doctor by the name of Silas Weir Mitchell, wrote in detail about the experiences of one of his patients -- Mr. V -- who complained of “a noise in my head, which is sometimes like the sound of a bell, which has been struck once … or else I hear a loud noise, which is most like that of a guitar string, rudely struck, and which breaks with a twang.” 
Later on, in the early 1900s, Welsh psychiatrist Sir Robert Armstrong-Jones documented several patients with nighttime “snapping of the brain.” But it wasn’t until 1988 that the name exploding head syndrome was coined by neurologist John M.S. Pearce in his Lancet article.
To date there are dozens of examples of studies investigating this bizarre phenomenon, but even now science has failed to pinpoint the mechanism behind exploding head syndrome.
What Are The Symptoms Exploding Head Syndrome?
While the perception of a sudden loud noise is the hallmark of EHS, this is often accompanied by a variety of other symptoms. Some people have an attack only once, or on very rare occasions; for others, EHS can be a nightly experience.
Many of those with recurring EHS report that the attacks tend to come in clusters -- occurring regularly over the span of a few days, then going dormant for weeks or months before beginning again.
During an exploding head syndrome attack you may experience the following:
1. Attack occurs as you’re falling asleep or upon waking up
EHS always happens at either one of two times:
- As you’re drifting off to sleep.
- As you’re waking up.
However, it’s less likely to happen when waking up in the morning -- rather, it occurs if you wake up during the night.
2. Perception of a sudden loud noise
While everyone who has EHS perceives a loud noise, everyone describes what they hear slightly differently. People have compared it to:
- A bomb exploding.
- A gun being fired.
- Symbols clashing.
- A door slamming.
- People screaming or shouting.
- A buzzing noise.
3. Usually not associated with pain
While startling, EHS is typically not accompanied by any painful sensations. However, some people report feeling hot or feeling as if an electric current is running from their lower torso into their head.
4. Occasionally accompanied by a flash of light
At the same moment you perceive the sound, you may also see a flash of light. This can either fill your entire visual field or appear more like lightning.
5. May have trouble breathing
Some people find that their attacks make it difficult to breathe, causing them to gasp for air. This is most likely due to the startling nature of the experience and the nervous system response it elicits.
6. May raise your heart rate
Along with difficulty breathing, you may experience a sudden increase in your heart rate (tachycardia) or heart palpitations. This is also believed to be caused by anxiety.
7. Sometimes associated with sleep paralysis
EHS often appears in tandem with another parasomnia: Sleep paralysis. Sleep paralysis is likewise associated with the switch between sleeping and waking states and results in you being paralysed while fully conscious.
8. Lasts a few seconds to minutes long
The duration of an EHS attack varies from person to person. Usually they are very short -- lasting only a few seconds; however, people do report attacks that linger for minutes after waking.
9. Makes you feel frightened, anxious or distressed
EHS attacks understandably cause a lot of fear and distress. You may feel as if you are in danger, or that you are suffering a medical emergency such as a stroke.
How Common Is Exploding Head Syndrome?
Exploding head syndrome was once thought to be an exceedingly rare disorder. As the bizarre phenomenon gained attention -- both by the scientific community and mainstream media -- more and more people started sharing their personal experiences.
Today, the actual prevalence of the disorder remains unknown, but it appears EHS may be much more common than once thought.
Generally it’s estimated that approximately 10% of the population is affected by EHS; and women have a slightly greater risk of experiencing the parasomnia than men. While the average age of onset is reported to be 58 years old, physicians have treated patients as young as 10.
However, new research conducted by Brian Sharpless at the Washington State University in 2015 suggests that even these numbers are shy of reality. The largest study of its kind, Sharples interviewed 211 undergraduate students and discovered that 18% had experienced EHS in their lifetime -- with 16.60% reporting that they had attacks on a regular basis. 
These findings indicate that not only is EHS not that rare, but it’s also not a disorder reserved for those of middle-age. Which made sense to Sharpless who had failed to see a biological reason for these restrictions in the first place. Instead, he attributes the previous faulty numbers to the fact that many people simply do not talk about their symptoms, possibly out of embarrassment.
What Causes Exploding Head Syndrome?
The cause of exploding head syndrome remains a mystery; however, several theories have been proposed to account for the bizarre symptoms.
Some believe that EHS is the result of a minor seizure in the temporal lobe, which is in charge of sensory processing. But EEG testing of neuronal activity has not provided any evidence to bolster this claim. Other researchers think the cause lies in a sudden shift in the tiny structures that make up the middle ear, or an issue with calcium signalling between neurons.
The prevailing theory at this time is that EHS is caused by a dysfunction in the neurons of the brainstem -- the area of the brain in charge of sensory-motor reflexes and making the transition between sleep and waking states.
Sharples draws the comparison between this transition period and shutting down a computer, suggesting that an EHS attack occurs when our sensory neurons (particularly auditory in this case) do not shut down smoothly and instead fire simultaneously. 
While it’s difficult to determine what triggers a disorder that is so poorly understood, research suggests that there are several factors that put you at a greater risk for experiencing an EHS attack:
- Emotional Distress
- Sleep Deprivation
- Age 50+
Additionally, Simon Sherwood at the University College Northampton in the UK found that belief in the supernatural is associated with a greater likelihood of suffering from EHS. Although others believe this may just be due to the fact that these individuals are more likely to freely discuss their symptoms. 
There are other conditions that can cause you to perceive a sound that is does not have an environmental cause, such as:
- Other sleep disorders
- Certain medications
- Mental health conditions
- Headache syndrome
- Substance abuse
- Medical conditions affecting the brain
Diagnosis: How Is Exploding Head Syndrome Diagnosed?
Exploding head syndrome is a benign condition that poses no direct risk to your health; however, when it happens frequently it can cause significant sleep disruption and anxiety. If EHS attacks are affecting your quality of life you should discuss your condition with your doctor.
You will be asked to give a detailed account of your symptoms: When did they start? How often do they happen? How long do they last? You may want to prepare for your appointment by keeping a sleep diary to record your EHS attacks in detail.
Your doctor will also want to know your medical history, what medications and supplements you are taking, and any substance use. They may also ask you questions about your family, such as if any of your relatives suffer from sleep disorders (including EHS).
There’s no specific test that can be used to diagnose EHS, but you may be asked to complete a sleep study in order to check for other sleep disorders. This test can also provide your doctor with a greater understanding of your symptoms and how they’re affecting your sleep patterns.
Treatments & Remedies: What Can You Do To Treat Exploding Head Syndrome?
If you’re able to identify what is triggering your episodes of exploding head syndrome then you can make specific changes in your lifestyle to treat your symptoms. For the majority of people reducing stress and relieving sleep deprivation.
- Stress: Take some time to relax, especially right before bedtime. What activity you choose is completely up to you: reading, taking a short walk, relaxing in a hot bath are all great stress relievers. The most important thing is that you choose something that works for you.
Avoid alcohol and watching TV as a form of stress relief -- both of these have a negative impact on your circadian rhythms and may exacerbate your symptoms.
Additionally, practicing yoga, tai chi and meditation can help prevent stress before it happens; and therefore may help keep your EHS at bay.
- Sleep Deprivation: Practicing good sleep hygiene can help you get more and better quality sleep. Remember: adults need to get between 6 to 8 hours of sleep every day.
While exploding head syndrome does not typically require medical treatment, if your symptoms are particularly severe your doctor may prescribe a medication. When taken at low doses, tricyclic antidepressants (such as clomipramine) help regulate the stages of sleep -- this medication is also used to treat sleep paralysis. Other drug treatments include calcium channel blockers.
Knowledge Is Comfort
A 2013 study conducted by neurologist Gauntam Ganguly at the University of Southern California’s Keck School of Medicine revealed that there may be a very simple treatment for exploding head syndrome: knowledge.
Ganguly found that reassuring patients that their scary symptoms are not caused by a serious life-threatening illness often is enough for them to experience relief from the disorder. This is further supported by many personal accounts that report similar recovery after discovering that what they were experiencing has a name and that they’re not alone.