This is a guest post by Monty Rothermere.
Things that go bang in the dark
Exploding head syndrome (EHS) is surely one of strangest and least well-understood parasomnias (and certainly the most dramatically named). Despite its ominous title, this sleep disorder is not physically harmful and it certainly won’t involve expulsion of your cerebrum! Nonetheless, for those who suffer from EHS, it can be an extremely frightening experience, even more so if they are unaware that their experience is shared by others.
The condition was first described in 1920, yet was not clinically characterized in any depth until 1989 by S.M. Pearce. In this paper, 50 patients presenting EHS described their symptoms, which were characterized by a sense of explosion within the head in the twilight hours of sleep.
According to various accounts, the phenomenon usually occurs at night when first falling asleep or when falling asleep after having woken during the night.The main symptoms are an extremely loud noise or sense of explosion within the head, sometimes accompanied by flashes of light. The experience is never painful as such, but often terrifying- this much is clear from patients descriptions of the symptoms. One account described a ‘noise as if head will burst open’, others include ‘shotgun or thunderclap’ !
There are a number of unpleasant sensations which seem to go hand in hand with the attacks, although these are probably related to the sense of fear and anxiety which EHS induces. Almost all patients report fear, terror,palpitations/forceful heartbeats and others report tinnitus and a sensation of falling.
The onset of the syndrome may occur at many different ages, although it most commonly starts in middle to late age. The frequency of attacks is also variable, often with numerous episodes in succession followed by longer periods of remission, although some may experience mild attacks quite in-frequently.
Although EHS is not usually associated with other conditions, one woman reported symptoms of EHS accompanied by sleep paralysis as a symptom of migraine aura . This combination, however, seems to be more the exception than the rule, most are just stand-alone cases.
I suffered from EHS from my early childhood to my latter teenage years.My experience of it was different to most people’s. It would always occur1when falling asleep after waking up in the middle of the night. I never experienced an explosion like sound, but instead an extremely loud low frequency oscillation (which would put Dubstep to shame!). At the same time I was paralyzed and felt a strong shaking sensation, which disappeared as soon as the noise did. On one particularly intense occasion bright blue intense flashes of light accompanied the attack.
It was extremely frightening to say the least, but after a few attacks I just came to accept it as normal and stopped worrying about it. This seems to be generally the case, people feel much more comfortable with the experience once they know that they aren’t alone and that it cannot do them any harm.
The cause of EHS is not understood; some tentative explanations have been put forward involving the inner ear, but there is nothing convincing that I’m aware of. There is a coincidental report of a one person experiencing remission from symptoms whilst taking topiramate, an anti-convulsive drug used in the treatment of epilepsy. The attacks did not decrease in frequency but did decrease in intensity to the point where they became barely noticeable. Electroencephalograms taken during attacks, have however eliminated epileptic seizures as a cause  and the recommended treatment for EHS is reassurance of its benevolence rather than a course of drugs.
I suspect that exploding head syndrome is probably far more common than is currently though. The peculiarity of the experience might discourage people from reporting it to their GP for fear of being thought insane! However the more people do report their experiences, the better understood it will become, so it should be positively encouraged!
 R. W. Evans and J. Pearce, “Exploding head syndrome,” Headache: The Journal of Head and Face Pain, vol. 41, no. 6, pp. 602–603, 2001.
 S. M. Pearce, “Exploding head syndrome,” Journal of Neurology, Neurosurgery, and Psychiatry, vol. 52, pp. 907–910, 1989.
 G. M. Palikh and V. BV, “Topiramate responsive exploding head syndrome,” J Clin Sleep Med, vol. 6, no. 4, pp. 382–383, 2010.
 C. Sachs and E. Svanborg, “The exploding head syndrome: polysomno-2graphic recordings and therapeutic suggestions,” Sleep, vol. 14, no. 3,pp. 263–266, 1991.