Attention has recently been drawn to a condition termed the exploding head 
syndrome, which is characterized by unpleasant, even terrifying sensations of 
flashing lights and/or sounds during reported sleep. Nine patients complaining 
of sensations of explosions in the head during sleep or drowsiness were 
investigated with polysomnographic recordings. None of them had any neurological 
disorder. Five patients reported explosions during the recording sessions. 
According to the recordings, the attacks always took place when the patients 
were awake and relaxed. In two cases abrupt electroencephalographic (EEG) and 
electromyographic changes indicating increasing alertness were recorded at the 
time of the reported attacks. In the remaining three cases no EEG changes were 
seen. Thus, there were no indications of an epileptic etiology to the condition. 
In all patients the symptoms ameliorated spontaneously with time. The severity 
of the symptoms was reduced by reassurance of the harmlessness of the condition. 
Clomipramine was prescribed to three patients who all reported immediate relief 
of symptoms. It is concluded that symptoms of this type are probably not true 
hypnagogic phenomena but may be an expression of emotional stress in the awake 
state.