Exploding head syndrome 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 or any other form of loud, indecipherable noise that seems to originate from inside the head. Contrary to the name, exploding head syndrome has no elements of pain, swelling or any other physical trait associated with it. They may be perceived as having bright flashes of light accompanying them, or result in shortness of breath, though this is likely caused by the increased heart rate of the subject after experiencing it. It most often occurs just before deep sleep, and sometimes upon coming out of deep sleep.
Attacks can increase or decrease with time, and can disappear for long stretches at a time, or entirely, of their own volition. Subjects often feel fear or distress after the incident.
http://www.sleepassociation.org/index.php?p=explodingheadsyndromeWho knew?? Does insurance cover it??