Cluster Headache

Cluster headache is one of the most painful conditions a person can experience, causing intense attacks of severe, one-sided head pain that can strike multiple times a day for weeks or months at a time.

Table of contents

• What is Cluster Headache?
• Symptoms and Characteristics
• Pattern of Attacks
• What Causes Cluster Headache?
• Who is Affected?
• How is Cluster Headache Diagnosed?
• Treatment Options
• Triggers and Prevention
• Long-term Outlook

What is Cluster Headache?

Cluster headache is a rare and severe type of headache that causes intense pain in or around the eye on one side of the head^[1]. It is considered one of the most painful conditions someone can have^[6]. The condition gets its name from how the headaches occur—they come in clusters or groups of frequent attacks that happen over weeks to months, followed by periods with no headaches at all^[2].

Cluster headache is a primary headache, which means it is a health condition on its own rather than being caused by another illness^[6]. It is typically the most painful type of headache that exists^[1].

Symptoms and Characteristics

A cluster headache begins quickly, usually with no warning, though some people might first experience migraine-like nausea and aura^[1]. When symptoms set in, it usually only takes five to 10 minutes for them to reach their worst^[2].

The pain is typically described as burning, sharp, stabbing, or piercing^[3][2]. It occurs on only one side of the head, most commonly behind or around one eye^[6]. During an attack cycle, the pain usually stays on the same side of the head, although it may switch sides in a different cluster period^[2].

Each individual headache attack lasts between 15 minutes and three hours^[3][2]. The pain can be so severe that people feel restless and unable to sit still—they may pace, rock back and forth, or hold their head^[6]. This restlessness is in contrast to most people with migraine who prefer to remain still during an attack^[6].

On the same side of the head where the pain occurs, people typically experience one or more of these symptoms^[1][3]:

• A red, watering eye
• Drooping or swelling of the eyelid
• A smaller pupil in the affected eye
• Stuffy or runny nostril
• Forehead or facial sweating
• Flushing of the face

Many people report that cluster headaches wake them up an hour or two after going to bed^[2]. They are sometimes called “alarm clock headaches” for this reason, and these nighttime headaches may feel more severe than those during the day^[2].

Pattern of Attacks

People with cluster headache experience multiple headache attacks per day, sometimes as many as eight times daily, though most people have about two attacks per day^[5][6]. These attacks often happen at the same time each day^[3][2].

The headaches occur in bouts or cluster periods that last from weeks to months^[6]. These are followed by periods of remission where the person has no headaches for months or even years^[3][2]. Some people experience cluster headaches seasonally, during the spring or autumn, and at the same time each year^[6].

There are two main types of cluster headache^[6]:

Episodic cluster headache: Bouts last from 7 days to one year, separated by pain-free periods lasting at least 3 months. Most cluster periods usually last between 2 weeks and 3 months. This is the most common form.

Chronic cluster headache: Persistent attacks continue for more than a year without remission, or remission lasts less than three months. Up to 2 in 10 people with cluster headache have chronic cluster headache^[6].

After an attack ends, the pain usually stops suddenly, leaving most people pain-free but exhausted^[6].

What Causes Cluster Headache?

The exact cause of cluster headaches is not known^[3][4]. Researchers believe the condition is linked to a small area at the base of the brain called the hypothalamus^[4][6]. The hypothalamus is part of the brain that is responsible for many bodily functions including body temperature, thirst, sleep cycles, blood pressure, and heart rate^[6].

The headaches appear to be related to the body’s sudden release of histamine (a chemical in the body released during an allergic response) or serotonin (a chemical made by nerve cells) in the area of a nerve in the face called the trigeminal nerve^[4].

Research has shown that during cluster attacks, there is activation of the trigeminovascular complex and the trigeminal-autonomic reflex, which accounts for the severe one-sided headache and the prominent symptoms on the same side of the face^[7]. The unique pattern of attacks occurring at certain times of day and certain times of year is thought to involve the hypothalamus and a structure called the suprachiasmatic nucleus^[7].

Who is Affected?

Cluster headaches are rare, affecting approximately 1 in 1,000 people^[6]. Some estimates suggest the condition affects up to 0.1% of people around the world^[2][7].

The condition is more common in men than women, with a male-to-female ratio of approximately 2.5 to 1^[7]. However, the diagnosis rate among women has been increasing^[9].

Cluster headaches can occur at any age but most commonly start when people are in their 20s through middle age, particularly in their 30s and 40s^[3][4][6]. The typical onset is around age 30^[9].

The condition tends to run in families, suggesting there may be a genetic component^[4][6]. People who smoke are more likely to develop cluster headaches^[6].

How is Cluster Headache Diagnosed?

Cluster headache is diagnosed by a doctor based on the description of the pain, where it occurs, how severe it is, and other accompanying symptoms^[14]. How often headaches happen and how long they last are also important factors^[14].

There are no specific tests to diagnose cluster headaches^[3][6]. A doctor will typically make a diagnosis by^[6]:

• Asking about symptoms and medical history
• Performing a physical examination
• Conducting a neurological examination

It can be helpful to keep a headache diary detailing symptoms to share with your doctor^[6].

Because other conditions can have similar symptoms to cluster headaches, a doctor may refer you to a specialist called a neurologist (a doctor who specializes in conditions affecting the brain and nervous system)^[14]. The specialist may order a brain scan to rule out other possible causes of the symptoms^[3][6]. Tests might include an MRI (magnetic resonance imaging) scan or a CT (computed tomography) scan^[14].

Cluster headache is often confused with other common types of headaches such as migraine, sinus headache, and tension headache^[4]. Unfortunately, many people are not properly diagnosed, and even when they are, the journey to diagnosis can be challenging^[5].

Treatment Options

There is no cure for cluster headaches, but treatments can help ease and prevent symptoms^[3][6]. Treatment is divided into two categories: acute (or abortive) treatments that aim to stop or reduce the severity of an attack when it happens, and preventive (or prophylactic) treatments that reduce the frequency and intensity of headache attacks^[10].

Regular painkillers such as paracetamol and ibuprofen do not work for cluster headaches because they take too long to act^[3][4].

Treatments for Stopping an Attack

If a cluster headache has already started, the main treatments include^[3][6]:

Oxygen therapy: Breathing 100% (pure) oxygen through a mask is one of the first-line treatments. It should be used with a flow of at least 12 liters per minute for 15 minutes^[10]. This can be effective in about 75% of patients with cluster headache^[5].

Triptan medicines: These are given as an injection or a nasal spray^[3]. Sumatriptan is the most studied triptan for cluster headache^[10]. A typical dose is 6 mg given as a subcutaneous injection, which can be effective because of the rapid onset^[10]. Nasal spray (20 mg) may also be used^[10].

Other acute treatments may include medicines such as dihydroergotamine^[4].

Some people may be offered a device that gives mild electrical pulses to the back of the neck^[3].

Preventive Treatments

Your doctor may prescribe medicines that can help prevent cluster headaches before they start. The preventive regimen should start at the onset of a cluster period and continue until the patient has been headache-free for at least 2 weeks, then may be tapered slowly to prevent recurrences^[10].

Common preventive medicines include^[3][6]:

• Verapamil (a calcium channel blocker that relaxes blood vessels) – this is considered the cornerstone of prevention^[10]
• Corticosteroids such as prednisone (which reduce inflammation and swelling)
• Lithium

Surgical Options

Rarely, when other treatments have not worked, you may be offered surgery^[3][6]. This involves implanting a small device called a neurostimulator to help treat headaches. This device delivers tiny electrical signals to certain nerves such as the occipital nerve in the scalp^[4].

Triggers and Prevention

Some people find that certain triggers can cause cluster headaches. Common triggers include^[3][4]:

• Smoking
• Drinking alcohol
• Perfume or strong smells (such as paint, nail varnish, or petrol)
• Physical exertion or exercise
• High altitudes (trekking and air travel)
• Bright light (including sunlight)
• Heat (hot weather or hot baths)
• Foods high in nitrites (bacon and preserved meats)
• Certain medicines
• Cocaine

Keeping a headache diary may help you understand your personal triggers^[3][4]. Write down when a headache begins, how long it lasts, and what might have triggered it^[4].

Some lifestyle approaches may help manage symptoms^[16]:

• Adopt a consistent sleep schedule to regularize the body’s rhythms
• Get regular exercise to improve sleep, boost blood circulation to the brain, and reduce stress
• Practice deep breathing exercises to relieve stress
• Consider yoga, which combines breathing techniques with stretching

Long-term Outlook

The prognosis of cluster headache remains difficult to predict^[7]. Patients with episodic cluster headache can shift to chronic cluster headache and vice versa^[7].

The good news is that cluster headache tends to improve with age. Over time, people typically have less frequent bouts and more prolonged periods of remission between cluster periods^[6][7].

Cluster headaches can have a real impact on life, affecting quality of life, mental health, and productivity^[9]. Because the pain is so severe, some people may experience thoughts of suicide—if you are having an attack and feel suicidal, it is crucial to seek immediate help by calling emergency services or a suicide prevention helpline^[5].

With proper diagnosis and treatment, many people with cluster headache can manage their condition effectively. Finding the right healthcare providers who understand the condition and are willing to work with you to find effective treatments is key to managing cluster headache successfully^[18].