You’re in bed. The chatter of the mind and thoughts of the day are slowly dissolving as you’re drifting off to sleep. Suddenly the tranquility is shattered by a loud explosion sound like a cymbal crash radiates from your head and through your body, resonating for a few seconds and fading into nothingness. As the adrenaline wears off and the phenomenon dissipates as quickly as it arrived, you realize that the sound came from nowhere but inside your own mind. You lay back, relax and continue on to sleep.

If this sounds familiar, then congratulations, you may have experienced Exploding Head Syndrome.

Though it sounds like a possible Monty Python skit or B-movie plot, the phenomenon itself is much more benign. It is a “parasomnia”, a sleep disorder, characterized by a sudden loud noise, much like an explosion, gunshot or cymbal crash emanating from inside of your head suddenly and without warning, when on the border between sleep and waking life; the state of consciousness known as hypnagogia.

The phenomenon was first described by Silas Weir Mitchell as “Sensory discharges” in 1876, and came to be known as “Exploding Head Syndrome” in a paper by J M Pearce in 1989. It is a surprisingly common phenomenon, affecting approximately 27% of students and 10% to 18% of the general population. Despite this relative commonality, it remains a mysterious and relatively understudied phenomenon.

Many possible causes have been identified including partial temporal lobe seizures, ear dysfunction and calcium channel dysfunction. Though the most up to date working theory is that it is caused by a dysfunction of the reticular formation in the brain, an evolutionarily ancient brain stem network which plays a crucial role in mediating arousal and consciousness. Each night, when our bodies begin to shut down, sleep paralysis kicks in, to make sure we don’t become a safety hazard to ourselves and others, attempting to act out our dreams. It is hypothesized that a glitch in the reticular formation results in a delayed shutdown of some brain areas, which then causes a surge of neural activity in areas of the brain responsible for sound perception.

Others have described it as “a high tension cable snapping”, “my entire body feels like it’s being jolted by electricity, just no pain. I’ll be right on the verge of sleep and then BAM, mini-seizured right back to full awareness”, “similar to if someone were to dump an entire bucket of freezing water on you, unexpectedly just as you’re on the verge of sleep, that little in between space”. Some have heard neighbors shouting, a bark, gunshots, car crashes or what sounds like people breaking in.

Sleep paralysis problems appears to accompany anecdotal reports which, along with hypnagogic hallucinations, could go some way in explaining many reports of alien abductions and other paranormal phenomena.

I would describe it as though reality is a string and it is suddenly plucked. Like your body is a old CRT monitor and someone just hit the degauss button. A fizzling electric brain buzz that crescendos to an explosion and fizzling out through the rest of your body. A sudden crash and reboot. A roaring vibration traveling inwards from all points. Sometimes accompanied by a flash of light and brief bodily sensations. It not an unpleasant experience, in fact it can be somewhat exhilarating. Gets the blood pumping. In my experience it is a rare event that occurs roughly once every few months, peaked in university and has been less frequent since.

I find it is likely after stress and consistent nights of sleep deprivation. I can feel when it is likely. The world feels a bit fuzzier. It is often accompanied by strong migraines and, when falling asleep, a strong impulse to tense upper body muscles that is hard to resist. Once it happens it can feel like a pressure release and is almost always followed by a deep, dreamless and incredibly restful sleep.

“What is the treatment?”, you may ask. The treatment is as mysterious as the disease in this case. One effective substance is the antidepressant Clomipramine whose mechanism of action is unknown. It also has can some pretty intense side effects so in this case, the best medicine may be good old fashioned healthy living and stress management.

As neurosciencentific progress marches forward, improved understanding of the brain and underlying mechanisms of sleep may elucidate what’s really going on in the mysterious gray area between normal wakeful consciousness and sleep where our heads sometime explode.

Maybe one day we’ll know why are heads are exploding.

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