DESCRIPTION

• A primary headache disorder characterized by circadian and circannual episodes consisting of multiple attacks of severe, unilateral sharp, searing, or piercing pain typically localized to the periorbital and/or temporal areas
• It is the most common headache among trigeminal autonomic cephalgias (TACs)
• Accompanied by signs of ipsilateral parasympathetic autonomic activation as well as restlessness or agitation
• Autonomic symptoms: signs of parasympathetic hyperactivity (ipsilateral lacrimation, eye redness, nasal congestion) and sympathetic hypoactivity (ipsilateral ptosis and miosis)
• Individual attacks occur from once every other day up to 8 times per day and can last 15 to 180 minutes per day if untreated.
• Attacks usually occur in series (cluster periods) that are often seasonal, lasting for weeks or months, and are separated by remission periods usually lasting months to years.
• About 10–15% of patients have chronic symptoms without remission periods (i.e., chronic cluster headache [cCH]).

EPIDEMIOLOGY

ETIOLOGY AND PATHOPHYSIOLOGY

Complex and incompletely understood, possible mechanisms include the following:

• Activation of the trigeminovascular system which leads to the release of vasodilatory peptides including substance P, neurokinin, and calcitonin gene-related peptide (CGRP)
• Posterior hypothalamus activation and the hypothalamic-brainstem-cerebellar interconnections may trigger an attack by activating trigeminal nociceptive pathways through increased parasympathetic outflow.
• Alterations in the descending pain modulation network and disordered pain modulation during cluster periods

RISK FACTORS

• Age: 70% onset before age 30 years
• Cigarette smoking or childhood exposure to cigarette smoke
• History of head trauma

COMMONLY ASSOCIATED CONDITIONS

• Depression (24%) with increased risk of suicide
• History of migraine, frequently in female patients; medication-overuse headache
• Asthma (9%)
• Sleep apnea (30–80%)