Cluster headache is a neurological condition characterized by intensely painful headache attacks that occur in cyclical patterns. It is considered one of the most severe pain conditions a person can experience. The headaches appear in groups or “clusters,” where an individual might have frequent attacks for weeks or months, followed by periods of remission that can last for months or even years. This cyclical nature, combined with the intensity of the pain, distinguishes it from other headache disorders like migraines.
Identifying Cluster Headache Attacks
The pain of a cluster headache attack is severe with a rapid onset, described as a piercing, burning, or boring sensation. It is strictly unilateral, affecting only one side of the head in, behind, or around one eye. The pain can radiate to the forehead, temple, and cheek on the affected side. An attack lasts from 15 minutes to three hours if untreated and can strike with little warning.
Accompanying the pain are distinct autonomic symptoms on the same side of the head. These include a red and tearing eye, a runny or stuffy nostril, a drooping or swollen eyelid, and facial sweating.
A defining behavioral characteristic is a sense of restlessness or agitation. Unlike individuals with a migraine who prefer to lie still, those with a cluster headache are more likely to pace or rock back and forth. This compulsion to move is a response to the pain’s severity.
The timing of attacks is a hallmark of the condition, occurring in cycles called cluster periods that last for weeks or months. During these periods, attacks can happen from once every other day to eight times a day. The condition is episodic when cluster periods are separated by pain-free remission of three months or longer. It is chronic when attacks occur for over a year with remission periods lasting less than three months.
Suspected Causes and Common Triggers
The precise cause of cluster headaches is under investigation, but evidence points to the hypothalamus. This deep brain structure acts as the body’s internal biological clock, regulating sleep-wake cycles. Its dysfunction is linked to the cyclical nature and predictable timing of attacks, which often occur at the same time each day or night.
The pain is generated through the trigeminal nerve pathway. During an attack, this nerve, responsible for facial sensation, becomes activated. This activation causes the severe pain around the eye and triggers the associated autonomic symptoms like tearing and nasal congestion.
Certain factors can provoke attacks, but only when a person is in an active cluster period. The consumption of alcohol is a well-documented trigger that can bring on a headache quickly. Other potential triggers include strong odors from substances like perfume or gasoline, and the medication nitroglycerin. These factors do not cause attacks during remission.
The Diagnostic Process
The diagnosis of cluster headache is based on a detailed patient history. A doctor relies on the person’s description of the attacks, as the specific symptoms, timing, and associated behaviors are key diagnostic criteria.
A neurological examination is also performed to assess the function of the brain and nervous system. This involves tests for vision, coordination, reflexes, and sensation to help rule out other causes.
Imaging tests are ordered to exclude other conditions that could mimic the symptoms. An MRI or CT scan of the brain is used to look for underlying structural problems, such as a tumor or an aneurysm. While these scans cannot visualize a cluster headache, they are an important step in confirming the diagnosis.
Treatment and Management Options
Treatment for cluster headache has two main approaches: acute therapies to stop an ongoing attack and preventative strategies to reduce attack frequency during a cluster period. These are often used in combination.
To stop an ongoing attack, the inhalation of 100% oxygen is a highly effective treatment, providing relief within 15 minutes for many. Another primary acute treatment involves medications called triptans. Injectable or nasal spray versions are preferred over oral tablets because they work much faster.
Preventative treatments are started at the onset of a cluster period to decrease the severity and frequency of attacks. The most common first-line medication is the calcium channel blocker verapamil, though it can take time to reach its full effect. A short course of corticosteroids, such as prednisone, may be prescribed to quickly break the attack cycle.
Other preventative options include medications like lithium or newer injectable therapies that target the CGRP protein, which is involved in pain signaling. These treatments are tailored to the individual’s specific situation and pattern of attacks.