Sometimes difficult. "vascular" headaches are associated with neurologic symptoms, aura, throbbing, unilateral. Tension headache often generalized, worse in pm's, no aura or neurologic sx. Cluster ha tend to be excruciating / lancinating, brief and asssociated with ocular sx. Tension and vascular headache can overlap - more of a spectrum rather than binary division. Response to medications is sometimes helpful.