Epidemiology & Definition Cluster headaches are one of the most painful types of headache. More common in men than women, often starting between ages 20 and 40. Clinical Presentation Characterised by recurrent, severe, unilateral (around the eye) headache attacks. Episodes typically last between 15 minutes and 3 hours. Associated symptoms include: Conjunctival injection (redness). Nasal congestion or rhinorrhoea. Forehead and facial sweating. Miosis (pupil constriction) or ptosis (drooping eyelid). Restlessness or agitation. Attack frequency can range from one every other day to up to eight times per day. Typically, episodes occur in clusters or bouts lasting several weeks or months, separated by remission periods. Aetiology & Pathophysiology Exact cause is unclear but may be related to abnormalities in the hypothalamus. Triggers can include alcohol, strong smells, and changes in sleep pattern. Investigations Diagnosis is largely clinical based on characteristic symptoms. Neuroimaging (MRI) may be done to rule out other causes if presentation is atypical. Management Acute attacks: High-flow oxygen and sumatriptan injections or nasal spray. Prevention: Verapamil is the mainstay of prophylaxis. Other options include lithium and corticosteroids. Prognosis Condition is chronic with acute episodic bouts. However, pain-free intervals can last months to years.