exploding head syndrome

   Also known as auditory sleep start. The term exploding head syndrome was introduced in or shortly before 1988 by the British neurologist John M.S. Pearce (b. 1936) to denote an abrupt and exceptionally loud "akoasm (i.e. a nonverbal auditory hallucination) typically reported as sounding like an explosion, a roar, or a ringing noise deep inside the head. This akoasm is usually reported as occurring within an hour or two after falling asleep. Although it is not usually accompanied by a headache, affected individuals may be so overwhelmed by the experience that they do describe it in terms of a headache. After waking up, the individual may experience a sense of anxiety, accompanied by a tachycardia. The exploding head syndrome may occur once only, or repeatedly (albeit irregularly) over a time span of months or even years. It has occasionally been reported as being accompanied by a perceived flash of light. This flash of light is referred to as "visual sleep start. By analogy, the exploding head syndrome has been designated as an auditory sleep start. The etiology and pathophysiol-ogy of the exploding head syndrome are basically unknown. As Pearce speculates, "The syndrome is entirely benign, and I suspect common and underreported. The cause of the bomb-like noise remains a mystery: no known vascular or hydrodynamic changes in the brain, labyrinths, or cerebrospinal fluid would cause such a symptom, although a momentary (almost ictal) disinhibition of the cochlea or its central connections in the temporal lobes, or a sudden involuntary movement of the tympanum or tensor tympani, might be the explanation."

   References

   Blom, J.D., Sommer, I.E.C. (2009). Auditory hallucinations. Cognitive and Behavioral Neurology (in press).

   Pearce, J.M. (1988). Exploding head syndrome. Lancet, 2, 270-271.