Cluster headache (CH) is a primary headache disorder, belonging to the trigeminal autonomic cephalalgias (TACs). As compared to other disorders within the TAC category, patients with cluster headache experience multiple attacks of relatively short-lasting severe headaches. The headaches are characteristically excruciating, unilateral, and commonly involves the first division of the trigeminal nerve, over the peri- and retro-orbital regions and in the temple. The quality of the pain is severe, intense, sharp, and burning and it is commonly described to be worse than childbirth.

Tension-type headache (TTH) is the most common form of headache. It can be categorized into three subtypes. TTH comprises headache attacks with mild to moderate pain intensity and is often described as having a pressing or tightening (nonpulsating) quality. The pain lasts for at least several hours to days and is predominantly felt bilaterally.

Paroxysmal hemicrania (PH) is a primary headache disorder belonging to the group of trigeminal autonomic cephalalgias(TACs). Patients typically experience intense lateralized headaches with pain primarily in the ophthalmic trigeminal distribution (V1) associated with superimposed ipsilateral cranial autonomic features. PH is distinguished from other TACs by an exquisite responsiveness to therapeutic doses of an NSAID. Patients may need to be maintained on indomethacin for several months before trials of reduction can be attempted.

Short‑lasting unilateral neuralgiform headache attacks (SUNHA) is characterized by sudden brief attacks of severe unilateral head pain in orbital, periorbital, or temporal regions, accompanied by ipsilateral cranial autonomic symptoms. There are two subtypes: short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) and short-lasting unilateral neuralgiform headache attacks with cranial autonomic symptoms (SUNA). In SUNCT, the ipsilateral autonomic symptoms must consist of both conjunctival injection and lacrimation.