Description

• A primary headache disorder characterized by multiple attacks of unilateral, excruciating, sharp, searing, or piercing pain; typically localized in the periorbital area and temple accompanied by signs of ipsilateral parasympathetic autonomic features, along with restlessness and agitation
• Autonomic symptoms: parasympathetic hyperactivity signs (ipsilateral lacrimation, eye redness, nasal congestion) and sympathetic hypoactivity (ipsilateral ptosis and miosis)
• Patients often pace the floor during an acute attack because lying down seems to exacerbate the pain.
• Symptoms usually remain on the same side during a single cluster attack.
• Individual attacks last 15 to 180 minutes if untreated and occur once every other day to 8 times per day.
• Attacks usually occur in series (cluster periods) that are often seasonal, lasting for weeks or months, separated by remission periods usually lasting months or years.
• About 10–15% of patients have chronic symptoms without remissions (i.e., chronic cluster headache [cCH]).

Epidemiology

Incidence
1-year incidence: 2 to 10/100,000

• Lifetime prevalence: 124/100,000
• Predominant sex: male > female; 2.1:1 overall
• Women often develop earlier in life (20s)
• Mean age of onset: 30 years
• Episodic/chronic ratio: 6:1

Etiology and Pathophysiology

• Complex and incompletely understood
• Possible mechanisms include the following:
  • Posterior hypothalamus activation may trigger an attack by activating trigeminal nociceptive pathways through perivascular activation and increased parasympathetic outflow
  • Alterations in the descending pain modulation network and disordered pain modulation during cluster periods

• Usually sporadic: autosomal dominant in 5% of cases; autosomal recessive or multifactorial in other families
• Evidence varies: First-degree relatives carry 5- to 8-fold and second degree 1- to 3-fold increased relative risk of disease.
• >50% with migraine and 18% with CH in family history

Risk Factors

• Male gender
• Age: 70% onset before age 30 years
• Cigarette smoking or childhood exposure to cigarette smoke
• Family history of CH
• Personal history of head trauma

Commonly Associated Conditions

• Depression (24%)
• Increased risk of suicide secondary to the extreme nature of the pain
• Medication-overuse headache
• Asthma (9%)
• History of migraine, frequently in female patients
• Sleep apnea (30–80%)