OVERVIEW

What is cluster headache?

Headache is one of the most common symptoms in neurology clinics.

When headaches are caused by other diseases, they are referred to as "secondary headaches." If no specific cause can be identified, they are called primary headaches. These primary headaches are further classified based on their characteristics, and cluster headache is one of them.

Cluster headaches have the following features:

• They occur in clusters, meaning the headaches happen repeatedly over a period (cluster period) followed by a pain-free interval (remission period), and this cycle repeats.
• The pain is usually concentrated around the eye, almost always on one side. It rarely alternates sides (as migraines sometimes do) or occurs bilaterally (as tension-type headaches often do).
• Each headache episode can last from 15 minutes to 3 hours (without medication).
• During an attack, symptoms such as tearing, conjunctival redness, nasal congestion, runny nose, restlessness, or agitation may occur on the same side as the pain.

Are cluster headaches common?

No.

The prevalence of cluster headache is <0.1%. According to a 2006 epidemiological survey in China, the prevalence was only 4.8 per 100,000 people, while international data suggest it may reach up to 0.4%. Cluster headache is a relatively rare primary headache disorder.

SYMPTOMS

Why is cluster headache called "suicide headache"?

During a cluster headache attack, the pain can be extremely intense and often unbearable for patients, hence it is also referred to as "suicide headache." Compared to tension-type headaches and migraines, cluster headaches are the most severe type of headache.

Why is cluster headache called "alarm clock headache"?

Cluster headache is also known as "alarm clock headache" because its attacks occur at relatively fixed times. This is mainly reflected in two aspects:

• The headache often occurs at a specific time each day, more commonly in the afternoon or at night.

• Some patients experience attacks during specific seasons each year, such as spring or autumn.

Research suggests that the hypothalamus plays a key role in triggering cluster headache attacks. The periodic nature of the headaches may be related to the suprachiasmatic nucleus, which regulates the body's circadian rhythm.

What accompanying symptoms may occur during a cluster headache attack?

• Eye symptoms: such as eyelid swelling, drooping eyelids, conjunctival redness, tearing, and constricted pupils.

• Nasal symptoms: such as nasal congestion or runny nose.

• Forehead or facial symptoms: such as sweating or flushing on the forehead or face.

• Ear symptoms: such as a feeling of fullness.

• Mood changes: restlessness or agitation.

As evident, cluster headache patients may inevitably experience some emotional fluctuations.

If you suffer from cluster headaches, while managing symptoms, you can improve your emotional state through lifestyle changes like meditation or exercise, or seek counseling to overcome emotional distress. If someone around you has cluster headaches, offer them understanding and care.

CAUSES

Who is commonly affected by cluster headaches?

Cluster headaches predominantly occur in young adults aged 20–40, with men being 4–5 times more likely to develop them than women. There is typically no family history of the condition.

Are there triggers for cluster headache attacks?

Cluster headaches can be triggered by the following factors, which should be avoided whenever possible:

• Irregular lifestyle habits;

• Alcohol consumption;

• Oxygen deprivation, particularly in patients with sleep apnea syndrome;

• Use of medications such as nitroglycerin.

Why do cluster headache patients experience difficulty opening their eyes or eyelid drooping?

Cluster headache patients exhibit dysfunction in two neural pathways: one is the trigeminovascular pathway, which causes headache pain, and the other is the autonomic nervous pathway (including sympathetic and parasympathetic nerve fibers), responsible for accompanying symptoms such as tearing, conjunctival redness, nasal congestion, and runny nose.

Eyelid drooping (ptosis) results from impaired sympathetic nerves controlling the upper eyelid muscles. Patients may also experience a smaller palpebral fissure, sunken eyeball (enophthalmos), and constricted pupil (miosis) on the affected side.

DIAGNOSIS

Can cluster headaches be self-diagnosed?

Generally, patients cannot determine it themselves.

If headaches occur repeatedly or are severe, a doctor should be consulted. Based on the consultation, the doctor will decide whether tests are needed to rule out secondary headaches. If tests are normal, the type of primary headache must be identified based on its characteristics before targeted treatment can be administered.

Many patients take painkillers on their own or repeatedly request multiple tests from doctors, neither of which is advisable.

What tests are needed for cluster headaches?

Clinically, rare headaches (prevalence <1%) require relevant tests to exclude secondary causes. Various intracranial organic diseases, such as tumors, inflammation, multiple sclerosis, and vascular diseases, can mimic cluster headaches. Therefore, patients must undergo CT or MRI scans to rule out these conditions.

What types of cluster headaches are there?

There are two types of cluster headaches:

• Episodic cluster headaches: Headache-free intervals last more than 1 month.
• Chronic cluster headaches: Headaches persist for over 1 year, or remission periods last less than 1 month.

Which headache disorders resemble cluster headaches?

Paroxysmal hemicrania, hemicrania continua, and SUNCT (short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing) are similar to cluster headaches but differ in presentation and require differentiation for proper treatment.

• Paroxysmal hemicrania: Similar to cluster headaches, it is a rare primary headache. Compared to cluster headaches, its attacks are shorter (typically 2–30 minutes), more frequent (over 5 times daily), and respond poorly to standard cluster headache treatments. Indomethacin is effective.

• Hemicrania continua: If paroxysmal hemicrania occurs daily for over 3 months, it is termed hemicrania continua. Indomethacin is effective.

• SUNCT: Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing. Attacks are extremely brief (average 1 minute) and highly frequent (average 28 times daily). SUNCT does not respond to indomethacin but may improve with newer antiepileptic drugs.

• SUNA: Short-lasting unilateral neuralgiform headache attacks with cranial autonomic symptoms. Unlike SUNCT, SUNA presents with only one or neither of conjunctival injection or tearing. Treatment is similar.

TREATMENT

How to Quickly Relieve Pain During a Cluster Headache Attack?

Cluster headache attacks are sudden and brief, so only medications or methods that act quickly are effective. Drugs that work for migraines often fail for cluster headaches because they don't act fast enough.

Currently, treatments proven to stop cluster headache attacks include inhaling pure oxygen through the nose, nasal administration of sumatriptan or zolmitriptan, and subcutaneous injection of sumatriptan.

Triptans are a specific class of pain-relief drugs that act on the trigeminovascular pathway.

This family of drugs includes zolmitriptan, sumatriptan, rizatriptan, naratriptan, almotriptan, frovatriptan, and eletriptan. Most are oral formulations, while a few are available as subcutaneous injections or nasal sprays.

How to Use Medication During the Cluster Period of Cluster Headaches?

During the cluster period, daily medication is required until the headaches disappear, followed by tapering off over at least two weeks before stopping. Do not discontinue abruptly. Repeat this process when the next cluster period begins.

Preventive medications are the mainstay during the cluster period, including ergotamine, verapamil, lithium carbonate, corticosteroids, methysergide, and valproate (also called transitional therapy). These drugs help prevent headache attacks.

How to Use Medication During the Intermission of Cluster Headaches?

The intermission is a symptom-free period. Apart from tapering off cluster-period medications, no additional treatment is needed. For patients with long intermissions, there may be extended drug-free periods.

Can Cluster Headaches Be Cured or Resolve on Their Own?

Cluster headaches may have long symptom-free intervals (intermissions), during which no extra medication is needed, but this does not mean the condition is cured.

During cluster periods, standardized transitional therapy is still required to prevent attacks.

If transitional therapy is stopped abruptly without medical guidance, some episodic cluster headaches may progress to chronic cluster headaches, making the condition harder to treat.

DIET & LIFESTYLE

What is good to eat for cluster headaches? Are there any dietary restrictions?

Like other primary headache disorders, patients with cluster headaches should pay attention to a reasonable diet:

• Avoid allergenic medications, spicy and irritating foods, fried foods, and foods high in tyramine that may trigger headaches, such as chocolate, cheese, citrus fruits, and alcoholic foods.
• Consume more foods rich in vitamin B1, such as grains, legumes, fresh fruits, and vegetables.
• Quit smoking and alcohol.

PREVENTION

How can cluster headache patients prevent headache attacks?

Avoid using sensitizing medications and certain spicy, irritating foods, fried foods, as well as foods high in tyramine that may trigger headaches, such as chocolate, cheese, citrus, and alcoholic beverages. Quit smoking and alcohol.