what type of headache is in the back of your head?
1 THUNDERCLAP HEADACHE, a sudden severe headache in the back of the head, reaching its peak in less than a minute. Causes include: 2  BRAIN ANEURYSM â a widening of one of the brain arteries.  Bleeding between the brain and membranes covering the brain (subarachnoid hemorrhage), usualy from a RUPTURED ANEURYSM.