Primary Headache Disorders

A primary headache disorder is the illness itself, not pain caused by another disorder. The major groups are migraine, tension-type headache, trigeminal autonomic cephalalgias such as cluster headache, and several less common syndromes. Migraine is a disorder of the trigeminovascular system. Trigeminal sensory fibres release calcitonin gene-related peptide (CGRP), which contributes to vasodilation, neurogenic inflammation, and sensitization of central pain pathways. Sensitization helps explain why light, sound, touch, movement, and routine activity can become intolerable during an attack. CGRP-targeting therapies work because they interrupt a fundamental migraine pathway. The phenotype matters. A person with migraine often withdraws to a dark, quiet room because movement worsens pain. A person with cluster headache is more often visibly distressed, restless, and pacing. That behavioural contrast can be diagnostically useful before the formal criteria are even applied.