Cluster headaches are often considered one of the most painful human experiences.  They are short (lasting usually 15-180 minutes), frequent (up to 8 a day), unilateral headaches behind or around the eye often with ipsilateral autonomic symptoms and restlessness.  While migraines and tension headaches are seen frequently in the emergency department, cluster headaches are much less frequently seen and often are harder to identify as a result.  There are certain points to remember with patients that are experiencing cluster headaches and we list 10 of them here.