Exploding head syndrome is a form of hypnagogic auditory hallucination and is a rare and relatively undocumented parasomnia event in which the subject experiences a loud bang in their head similar to a bomb exploding, a gun going off, a clash of cymbals, ringing, an earthquake, or any other form of loud, indecipherable noise that seems to originate from inside the head.
This noise usually happens at the onset of sleep or within an hour or two of falling asleep, but is not necessarily the result of a dream. Although the sound is perceived as extremely loud, it is usually not accompanied by pain. Attacks appear to change in number over time, with several attacks happening in a space of days or weeks, followed by months of remission. Sufferers often feel a sense of fear and anxiety before and after an attack, accompanied by elevated heart rate.
Attacks may also be accompanied by perceived flashes of light (when perceived on their own, known as a "visual sleep start") or difficulty in breathing. The condition is also known as "auditory sleep starts". The associated symptoms are varied, but the benign nature of the condition is emphasized and neither extensive investigation nor treatment are indicated. Sufferers may experience an inability to vocalize any sound, or mild forms of sleep paralysis during an attack. There is no known treatment.
I got that from Wikipedia.
Apparently this is part of a Writing Challenge. To see more, go to www.WeWorkForCheese.com . Today's theme is "And then my brain exploded".