Cluster headache is one of the most severe and unbearable headache types known in neurology. The pain starts suddenly, is short-lived but extremely intense. Many patients describe this pain as “unbearable,” “burning,” or “as if my eye is being gouged out.” Cluster headache is a relatively rare headache disorder seen in approximately 0.1% of the general population. However, cluster headache can seriously affect a person’s daily life, work performance, and sleep pattern. Severe headache attacks that wake one from sleep can cause fatigue, anxiety, and a marked decrease in quality of life. Therefore, cluster headache is considered not just “pain” but a neurological syndrome that turns life upside down.

What is Cluster Headache?

Cluster headache is a neurological syndrome in the primary headache disorders group. It generally manifests itself with very severe pains occurring on one side of the head, around the eye. These pains come in “cluster” periods; that is, they frequently recur during a certain time period, then can disappear for weeks or months. In some patients, it shows seasonal characteristics; attacks can increase in spring and autumn months.

In many patients, these attacks occur at the same times every day — especially intense enough to wake one from sleep at night. Therefore, cluster headache is sometimes also called “alarm clock headache”. The pain is generally felt around the eye, forehead, temple, or on one side of the face.
Patients frequently describe this pain as follows:

“It’s like a hot stick is being stabbed behind my eye.”
“One side of my head is burning, feels like it’s going to explode.”

What Causes Cluster Headache?

Although the cause of cluster headache is not fully known, research shows that this disease is related to dysfunction in the hypothalamus region of the brain. The hypothalamus is the region that controls the body’s biological clock. Therefore, the fact that cluster headache attacks generally repeat at the same times of the day or at the same periods of the year (especially in spring and autumn) is not a coincidence.

In this type of headache, the trigeminal nerve system plays an important role in the occurrence of pain. This nerve carries the pain sensation of the face and when activated, causes severe, unilateral facial and periorbital pain. As a result of this nerve’s close relationship with parasympathetic nervous system fibers, autonomic symptoms such as eye redness, tearing, and nasal congestion may also accompany the headache.

Temporary vasodilation (vessel widening) in brain vessels may be effective in the onset of pain. Additionally, imbalances in brain chemicals such as serotonin, melatonin, and histamine also play a role in both pain and the circadian occurrence of attacks.

Some external factors can also trigger this biological sensitivity:

• Alcohol, especially when consumed during the attack period, can immediately trigger pain.
• Smoking can increase disease risk and attack frequency.
• Sleep irregularities, stress, and sudden environmental changes (e.g., pressure difference, temperature change) can also be triggers.

In summary, cluster headache is a neurological disease resulting from complex interaction between the brain, vascular system, and nerve networks. Therefore, its treatment also requires a combination of multifaceted, biological, and behavioral approaches.

Risk Factors in Cluster Headache

Although it is not fully known why cluster headache occurs in some people, research shows that some risk factors facilitate disease development.

Gender

Cluster headache is seen 3-4 times more frequently in men than in women.
Although this condition was thought to be more common in men for many years, recent studies show that diagnosis rates in women are increasing and the gender difference is gradually decreasing.
Hormonal factors and lifestyle differences are thought to play a role in this difference.

Age

The disease generally starts between ages 20 and 40 and is most commonly seen in early 30s.
However, it can also start at an earlier age or advanced age in some patients.
This age range suggests that changes in brain chemicals and biological rhythm may be effective.

Smoking and Alcohol Use

A large portion of cluster headache patients are individuals who smoke.
Smoking can facilitate attacks by affecting brain vascular structure and oxygenation.
Additionally, alcohol, especially when consumed during cluster periods, is one of the strongest external factors that can immediately trigger attacks.
Therefore, patients are advised to stay completely away from alcohol, especially during attack periods.

Genetics and Family History

Genetic predisposition also plays a role in cluster headache.
In people who have this disease in their family, the risk is 5 to 10 times higher than in the general population.
Research shows that genetic factors may be 5-20% effective in disease development.

What Are the Symptoms of Cluster Headache?

The symptoms of cluster headache are quite characteristic and can generally be distinguished from other headaches at first glance. Pain during the cluster period (can last up to 12 weeks) is felt in each attack on one side of the head (usually the same side), mostly around the eye, temple, or forehead. The severity of pain is extremely high — patients often describe this as “like a hot stick is being inserted behind my eye” or “unbearable burning and piercing pain”.

Attacks generally last between 15 minutes and 3 hours and can repeat more than once per day (1-8 attacks). These attacks generally tend to occur at the same times of the day. Cluster headache attacks mostly wake the patient from sleep at the same time every night, suggesting the disease is related to the “biological clock.”

Pain is generally accompanied by autonomic symptoms:

• Eye redness and tearing on the painful side,
• Nasal congestion or discharge,
• Sweating on forehead and face,
• Drooping eyelid (ptosis) and pupil constriction (miosis),
• Facial flushing,
• Marked restlessness or inability to stay still

Cluster headache can be differentiated from migraine by questioning patients’ behavior patterns during headache attacks.
While migraine patients generally want to lie down in a quiet environment, people with cluster headache are generally in motion, pacing in the room, holding their head, or leaning against the wall. They may even engage in self-harming behaviors due to the severity of pain.

Although this headache type is short-lived, it is one of the most severe pain types and is sometimes also called “suicide headache” in patients.

What Are Attack Periods and Cluster Periods in Cluster Headache?

Cluster headache takes its name from “attacks occurring in clusters.”
In this disease, pains are in the form of intensely recurring attacks during certain periods, followed by completely pain-free periods lasting months or even years.

Cluster Period (Active Period)

The cluster period is the period when the disease is active and pain attacks are frequently experienced.

• This period generally lasts 6 to 12 weeks.
• Patients can experience headache attacks every day, even several times a day during this process.
• Attacks mostly occur at the same times of the day (especially at night, usually a few hours after sleep).
• During the cluster period, situations such as drinking alcohol, smoking, high altitude, or oxygen deficiency can easily trigger attacks.

Out-of-Cluster Period (Remission)

During these periods, patients are completely pain-free.

• The remission period can generally last for months, sometimes years.
• However, in some patients, cluster periods recur seasonally during the year. It is frequently seen that attacks restart especially in spring and autumn months.
• Seasonal recurrences are an important finding supporting the role of the hypothalamus that directs the brain’s biological clock.

Chronic Cluster Headache

In some patients, pain-free periods are not seen or last very short.
In this case, chronic cluster headache diagnosis is made.
The chronic form constitutes approximately 10-15% of the total patient group and may be more resistant in treatment.

International Classification of Headache Disorders, 3rd Edition (ICHD-3) Diagnostic Criteria

The diagnosis of cluster headache is made according to International Classification of Headache Disorders, 3rd Edition (ICHD-3) criteria. These criteria are clinically accepted as gold standard for both research and daily practice diagnosis.

General Definition

Cluster headache is a type of trigeminal autonomic cephalalgia that progresses with severe or very severe pains occurring on one side of the head, usually in the orbital, supraorbital, or temporal region. Pain is generally accompanied by autonomic symptoms on the same side (e.g., eye tearing, nasal discharge, sweating).

International Classification of Headache Disorders (ICHD-3) Diagnostic Criteria – 3.1. Cluster Headache

3.1.1. Episodic Cluster Headache

Diagnostic Criteria:

1. At least 5 attacks
   B. Severe or very severe, unilateral orbital, supraorbital and/or temporal pain; if untreated, lasts 15-180 minutes
   C. Pain is accompanied by at least one of the following on the same side:
2. Eye redness and/or tearing
3. Nasal congestion and/or nasal discharge
4. Forehead and facial sweating
5. Eyelid edema
6. Eyelid drooping (ptosis) and/or pupil constriction (miosis)
7. Restlessness or agitation
   Attack frequency: Up to 1 attack per day (rarely up to 8)
   E. Attacks occur in cluster periods (7 days – 1 year); between these periods there is a pain-free (remission) period of at least 3 months.

3.1.2. Chronic Cluster Headache

Diagnostic Criteria:

1. Attacks meeting cluster headache criteria (A-D)
   B. Cluster periods last longer than 1 year and remission period is shorter than 3 months,
   or there is no remission period.

Additional Notes

• Pains frequently wake one from sleep at night (especially during REM sleep).
• Typically occurs at the same time every day, supporting the hypothalamic “biological clock” connection.
• Can be confused with migraine, but in cluster headache patients are generally restless and in motion, while migraine patients prefer to rest in a dark environment.

When Should You Consult a Neurology Specialist?

Headache is a condition everyone experiences from time to time, but cluster headache is not an ordinary pain.
In the following situations, you definitely need to consult a neurology specialist:

• If you have severe and recurring headaches,
• If your pains are clustering during certain periods and occurring at the same times every day,
• If symptoms such as eye redness, tearing, nasal congestion, or sweating occur along with pain,
• If your pains are waking you from sleep or seriously affecting your daily life,

these may be typical findings of cluster headache and neurological evaluation is essential for correct diagnosis.

Additionally, emergency medical help should be sought in the following situations:

• If you have pain that you describe as suddenly starting and the most severe headache of your life,
• If the headache is accompanied by fever, nausea, neck stiffness, vision disorder, speech difficulty, or clouded consciousness,
• If the headache started after trauma (fall, impact).

Early diagnosis and appropriate treatment both reduce the frequency of pains and significantly increase your quality of life.

How is Cluster Headache Diagnosed?

The diagnosis of cluster headache is based on the patient’s history and clinical findings.
For diagnosis, ICHD-3 diagnostic criteria published by the International Headache Society (IHS) are taken as basis. These criteria clarify the diagnosis according to the duration, frequency, and accompanying symptoms of pain.

What is Done in the Diagnostic Process?

1. Detailed Patient History:
   The doctor asks detailed questions about the onset time, duration, frequency, severity of pain, and accompanying symptoms.
   Findings such as pain recurring at the same times of the day, eye redness, or nasal congestion are guiding in diagnosis.
2. Neurological Examination:
   Detailed examination is done to exclude other neurological diseases.
   Examination findings are generally normal, allowing diagnosis to be based on clinical features.
3. Imaging Methods:
   Cluster headache diagnosis is made clinically, but other causes (e.g., tumor, aneurysm, sinus diseases) are ruled out with brain MRI or CT scan.
   MRI is especially recommended in a patient being considered for cluster headache for the first time.
4. Pain Diary:
   Patients are asked to keep a pain diary.
   When the time, duration, severity of attacks, and accompanying symptoms are written, both diagnostic accuracy increases and treatment planning becomes easier.

Differential Diagnosis (To Distinguish from Other Diseases)

Cluster headache can be confused with the following conditions:

• Trigeminal Neuralgia: Generally seconds-long, electric shock-like pains are seen.
• Temporal Arteritis: Especially in elderly patients, progresses with chewing pain and high sedimentation.
• Sinusitis: More dull, pressure-type pains and usually seen with nasal congestion.
• Migraine: Longer lasting pains accompanied by light and sound sensitivity.

After this detailed evaluation, the diagnosis is confirmed and a personalized treatment plan is prepared.

Can Cluster Headache Be Diagnosed Immediately?

Although cluster headache has clinically distinct features, unfortunately, its diagnosis is often delayed. This situation leads both to patients being exposed to unnecessary treatments for a long time and to serious deterioration in quality of life.

Extent of Diagnostic Delay

• In a comprehensive meta-analysis conducted by Van Obberghen et al. in 2025, the average diagnostic delay in cluster headache was reported as 10.4 years (95% CI [9.1-11.8]) [The Journal of Headache and Pain, 2025].
• In a study by Kim et al. on 235 patients in 2022, it was stated that diagnostic delay lasted longer than 7 years in 36.4% of patients, and this rate showed a decreasing trend in the last 10 years (Frontiers in Neurology, 2022).
• According to Frederiksen et al.‘s Danish Cluster Headache Survey data, although diagnosis time has significantly shortened in each decade from the 1950s to 2010, it is still around an average of 5-6 years (Cephalalgia, 2020).
• In older literature, Voiticovschi-Iosob et al. (The Journal of Headache and Pain, 2014) reported average diagnostic delay as 5.3 ± 6.4 years.

Diagnostic Delay in Cluster Headache in Turkey

One of the most comprehensive data on cluster headache in Turkey was presented in a multicenter study conducted by Yalınay Dikmen P. et al. (2022) (Cluster Analysis Revealed Two Hidden Phenotypes of Cluster Headache). In this study, the average diagnostic delay in diagnosing Cluster Headache patients in Turkey was found to be 4.9 ± 6.8 years. A significant portion of patients were followed before diagnosis with diagnoses of migraine (41%) or sinusitis (27%). Researchers stated that this delay can be shortened thanks to increased awareness of cluster headache and early referral to neurology centers specialized in headache.

Reasons for Delay in Cluster Headache

1. Misdiagnosis
   Cluster headache is frequently confused with sinusitis, migraine, or trigeminal neuralgia.
   Especially symptoms such as periorbital pain and nasal congestion can lead to sinusitis diagnosis.
2. Rarity of the disease
   Since it is encountered less in the community compared to migraine, many patients cannot reach the correct specialty for a long time.
3. Patients’ late application to the healthcare system
   The periodic nature of attacks and the presence of long pain-free intervals between cluster periods lead patients to apply late with the thought of “it passed on its own.”
4. Atypical course of pain characteristics
   Classic autonomic symptoms (eye tearing, nasal discharge, etc.) may be weak in some patients; this makes diagnosis difficult.

Consequences of Diagnostic Delay

• Unnecessary tooth extractions, sinusitis surgeries, or migraine treatments may be applied.
• Late start of appropriate treatment (e.g., oxygen, triptan, verapamil) can lead to chronification of attacks and development of depression/anxiety.
• A new analysis published in Frontiers in Pain Research (2024) reported that diagnostic delay shows positive correlation with attack frequency and pain severity.

To Reduce Diagnostic Delay

• Increasing awareness of cluster headache in the community and among healthcare professionals
• Primary care physicians (especially otolaryngology, dentistry, emergency physicians) recognizing the typical features of this disease is of critical importance in terms of early referral to neurology.

How is Cluster Headache Treated?

Cluster headache treatment is planned in three stages to rapidly terminate pain attacks and prevent the occurrence of new attacks:

1. Acute Attack Treatment (intervention at the moment of attack)
2. Bridge (Transition) Treatment
3. Preventive (Prophylactic) Treatment

1. Acute Attack Treatment

Cluster headache attacks are very severe and reach peak within minutes.
Therefore, effective treatment should be done with fast-acting methods.

a. Subcutaneous Sumatriptan (Imigran®)

Most effective medication in attack treatment.

• 6 mg subcutaneous (under the skin) injection form is used.
• Generally significantly reduces or completely stops pain within 10 minutes.
• A maximum of two doses can be used daily.
• Tablet form is not preferred in attack treatment because it acts slowly.

b. High-Flow Oxygen Therapy

Oxygen is one of the safest and most effective acute treatment methods in cluster headache.

• Applied at 12-15 L/min with non-rebreather mask.
• Taking high-flow oxygen for 10-15 minutes can completely stop pain in many patients.
• Can be prescribed for home use with appropriate equipment.
• Starting early increases treatment success.

Oxygen therapy is the first choice especially for patients who cannot use sumatriptan.

Alternatives

Methods such as nasal zolmitriptan spray or intranasal lidocaine may help in some patients but have lower effectiveness.

2. Bridge (Transition) Treatment

Before the preventive treatment takes effect, short-term “interim” treatment is needed.
The goal during this period is to reduce pain frequency and pass through the cluster period more lightly.

a. Corticosteroids (Prednisone or Methylprednisolone)

• Started at high dose (e.g., 60-80 mg/day) for 7-10 days, then gradually reduced.
• Generally stops attacks within a few days.
• Long-term use is not recommended because side effects (blood sugar, blood pressure, weight gain, etc.) may occur.

b. Nerve Blocks

• Occipital nerve block is done with steroid or local anesthetic injection.
• Can reduce attack frequency and severity during the cluster period.
• Quite effective as bridge treatment in recurring attacks.

3. Preventive (Prophylactic) Treatment

The purpose of preventive treatment is to prevent the recurrence of attacks and lighten cluster periods.
These treatments are applied with the start of the attack period and generally continue for several weeks.

a. Verapamil

• First-line preventive treatment in cluster headache
• Can be used in 240-960 mg/day dose range (gradually increased).
• Its effectiveness is high, but regular monitoring with ECG is required due to effects on heart rhythm.

b. Lithium

• Especially used in chronic cluster headache.
• Serum level monitoring is required (between 0.6-1.2 mmol/L).
• Kidney, thyroid functions, and electrolytes should be checked at regular intervals.

c. CGRP Monoclonal Antibodies (Galcanezumab)

• Recent studies have shown that galcanezumab can reduce attack frequency in episodic cluster headache.
• It is in subcutaneous injection form.
• Although not yet approved in all countries, it has potential to be an important option in preventive treatment in the future.

Lifestyle and Supportive Approaches

• Alcohol is a strong trigger especially during cluster periods; should be completely avoided.
• Smoking increases disease risk; quitting is recommended.
• Regular sleep, stress management, avoiding caffeine and excessive fatigue can reduce attack frequency.
• If there are accompanying conditions such as sleep apnea or depression, they must definitely be treated.

Treatment in Cluster Headache Should Be Personalized

Cluster headache is a disease that progresses differently in each patient and shows individual characteristics.
Therefore, the treatment plan should definitely be made personally by a neurology specialist, taking into account the patient’s age, accompanying diseases, and general health status.

With regular follow-up and the right treatment combination, significant reduction in attack frequency and severity can be achieved in the vast majority of patients.

Frequently Asked Questions About Cluster Headache

1. Why is cluster headache seen more frequently in men?

Cluster headache was 3-5 times more common in men than in women in the past. Hormonal differences, lifestyle (especially smoking and alcohol use), and biological rhythm differences were shown as reasons for this.
However, recent studies show that this disease is increasingly being diagnosed in women, and the gender difference is decreasing.

What should be done: It should not be forgotten that cluster headache can also occur in women; if typical symptoms exist, a neurology specialist should be consulted without delay.

2. How is cluster headache distinguished from migraine?

Cluster headache progresses with very short but extremely severe attacks (15 minutes-3 hours). Pain is generally unilateral, felt around the eye; eye tearing, nasal discharge, and facial flushing accompany.
Migraine pain generally lasts longer (4-72 hours), is throbbing in character, and occurs with light, sound sensitivity. While migraine patients generally prefer lying in a quiet environment, cluster headache patients feel the need to move during pain.

What should be done: If attacks are short but very severe and especially around the eye, it may be cluster headache, not migraine.

3. Can cluster headache completely heal?

There is no definitive cure for cluster headache, but with correct treatment, the disease can be completely controlled.
100% oxygen therapy and sumatriptan injection during attack are the most effective methods.
Verapamil is the first choice medication for preventing cluster periods; lithium can be used in chronic cases.
Among new generation treatments, CGRP-targeted drugs (e.g., galcanezumab) also show promising results.

What should be done: Treatment should definitely be planned personally by a neurology specialist.

4. Why are alcohol and smoking such effective triggers in cluster headache?

Most cluster headache patients are smokers and alcohol, especially during cluster periods, can trigger the attack within minutes.
Alcohol dilates blood vessels and increases histamine release. Smoking affects brain chemistry by disrupting the balance mechanisms of the hypothalamus.

What should be done: During the cluster period, alcohol should be completely avoided, and smoking should definitely be quit.

5. Why does cluster headache usually start at night?

Cluster headache generally occurs between 1-3 AM at night. This results from rhythm disorder in the hypothalamus region that directs the brain’s “biological clock.”
When falling asleep, melatonin and serotonin levels change, causing the trigeminal nerve system to become sensitized.
Attacks generally start during REM sleep and therefore patients wake with pain.

What should be done: Establishing regular sleep habits and keeping night oxygen therapy ready can reduce attack frequency.