The patient states that he has been having the same type of headaches for 4- or 5-years duration “on and off”. There is no history of trauma. They are worsened by stress, weather changes or may come on for “no reason”. He has used Excedrin for pain relief. When he gets a headache, he needs to lie down and close his eyes. Pain is described as throbbing, “dull and massive”, pounding, aching, with nausea toward the end of the headache cycle. The location of the pain was described as “behind the eyes and all the way around” the head. Neck pain is described as achy and stiff and worsens when he has a headache. A diagnosis of Migraine Headaches was made at Barrows Neurological Institute 6 months ago. Treatment there was unsuccessful.

Question: Based on this clinical history, what are some of the differential diagnoses you are considering?