Cluster headaches, which occur in cyclical patterns or cluster periods, are one of the most painful types of headache. A cluster headache commonly awakens you in the middle of the night with intense pain in or around one eye on one side of your head.

Bouts of frequent attacks, known as cluster periods, can last from weeks to months, usually followed by remission periods when the headaches stop. During remission, no headaches occur for months and sometimes even years.

Fortunately, cluster headache is rare and not life-threatening. Treatments can make cluster headache attacks shorter and less severe. In addition, medications can reduce the number of cluster headaches you have.

Common signs and symptoms

A cluster headache strikes quickly, usually without warning, although you might first have migraine-like nausea and aura. Common signs and symptoms during a headache include:

• Excruciating pain that is generally situated in, behind or around one eye, but may radiate to other areas of your face, head and neck
• One-sided pain
• Restlessness
• Excessive tearing
• Redness of your eye on the affected side
• Stuffy or runny nose on the affected side
• Forehead or facial sweating on the affected side
• Pale skin (pallor) or flushing on your face
• Swelling around your eye on the affected side
• Drooping eyelid on the affected side

People with cluster headache, unlike those with migraine, are likely to pace or sit and rock back and forth. Some migraine-like symptoms — including sensitivity to light and sound — can occur with a cluster headache, though usually on one side.

Cluster period characteristics

A cluster period generally lasts for several weeks to months. The starting date and the duration of each cluster period might be consistent from period to period. For example, cluster periods can occur seasonally, such as every spring or every fall.

Most people have episodic cluster headaches. In episodic cluster headaches, the headaches occur for one week to a year, followed by a pain-free remission period that can last as long as 12 months before another cluster headache develops.

Chronic cluster periods might continue for more than a year, or pain-free periods might last less than one month.

During a cluster period:

• Headaches usually occur every day, sometimes several times a day
• A single attack can last from 15 minutes to three hours
• The attacks often occur at the same time each day
• Most attacks occur at night, usually 1 to 2 hours after you go to bed

The pain usually ends as suddenly as it began, with rapidly decreasing intensity. After attacks, most people are pain-free but exhausted.

When to see a doctor

See your doctor if you've just started to have cluster headaches to rule out other disorders and to find the most effective treatment.

Headache pain, even when severe, usually isn't the result of an underlying disease. But headaches can occasionally indicate a serious underlying medical condition, such as a brain tumor or rupture of a weakened blood vessel (aneurysm).

Additionally, if you have a history of headaches, see your doctor if the pattern changes or your headaches suddenly feel different.

Seek emergency care if you have any of these signs and symptoms:

• An abrupt, severe headache, often like a thunderclap
• A headache with a fever, nausea or vomiting, a stiff neck, mental confusion, seizures, numbness, or speaking difficulties, which can indicate a number of problems, including a stroke, meningitis, encephalitis or a brain tumor
• A headache after a head injury, even if it's a minor fall or bump, especially if it worsens
• A sudden, severe headache unlike any you've had
• A headache that worsens over days and changes in pattern

The exact cause of cluster headaches is unknown, but cluster headache patterns suggest that abnormalities in the body's biological clock (hypothalamus) play a role.

Unlike migraine and tension headache, cluster headache generally isn't associated with triggers, such as foods, hormonal changes or stress.

Once a cluster period begins, however, drinking alcohol may quickly trigger a splitting headache. For this reason, many people with cluster headache avoid alcohol during a cluster period.

Other possible triggers include the use of medications such as nitroglycerin, a drug used to treat heart disease.

Risk factors for cluster headaches include:

• Sex. Men are more likely to have cluster headaches.
• Age. Most people who develop cluster headaches are between ages 20 and 50, although the condition can develop at any age.
• Smoking. Many people who get cluster headache attacks are smokers. However, quitting smoking usually has no effect on the headaches.
• Alcohol use. If you have cluster headaches, drinking alcohol during a cluster period may increase your risk of an attack.
• A family history. Having a parent or sibling who has had cluster headache might increase your risk.

Cluster headache has a characteristic type of pain and pattern of attacks. A diagnosis depends on your description of the attacks, including your pain, the location and severity of your headaches, and associated symptoms.

How often your headaches occur and how long they last also are important factors.

Your doctor will likely try to pinpoint the type and cause of your headache using certain approaches.

Neurological examination

A neurological examination may help your doctor detect physical signs of a neurological disorder. The exam is usually normal in patients with cluster headaches. Your doctor will use a series of procedures to assess your brain function, including testing your senses, reflexes and nerves.

Imaging tests

If you have unusual or complicated headaches or an abnormal neurological examination, your doctor might recommend other tests to rule out other serious causes of head pain, such as a tumor or an aneurysm. Common brain imaging tests include:

• MRI. This uses a powerful magnetic field and radio waves to produce detailed images of your brain and blood vessels.
• CT scan. This uses a series of X-rays to create detailed cross-sectional images of your brain.

There's no cure for cluster headaches. The goal of treatment is to decrease the severity of pain, shorten the headache period and prevent the attacks.

Because the pain of a cluster headache comes on suddenly and might subside within a short time, cluster headache can be difficult to evaluate and treat, as it requires fast-acting medications.

Some types of acute medication can provide some pain relief quickly. The therapies listed below have proved to be most effective for acute and preventive treatment of cluster headache.

Acute treatments

Fast-acting treatments available from your doctor include:

• Oxygen. Briefly inhaling pure oxygen through a mask provides dramatic relief for most who use it. The effects of this safe, inexpensive procedure can be felt within 15 minutes.

  Oxygen is generally safe and without side effects. The major drawback of oxygen is the need to carry an oxygen cylinder and regulator with you, which can make the treatment inconvenient and inaccessible at times. Small, portable units are available, but some people still find them impractical.

• Triptans. The injectable form of sumatriptan (Imitrex), which is commonly used to treat migraine, is also an effective treatment for acute cluster headache.

  The first injection may be given while under medical observation. Some people may benefit from using sumatriptan in nasal spray form, but for most people this isn't as effective as an injection and it may take longer to work. Sumatriptan isn't recommended if you have uncontrolled high blood pressure or heart disease.

  Another triptan medication, zolmitriptan (Zomig), can be taken in nasal spray form for relief of cluster headache. This medication may be an option if you can't tolerate other forms of fast-acting treatments.

  Oral medications are relatively slow to act and are often not useful for acute treatment of cluster headaches.

• Octreotide. Octreotide (Sandostatin), an injectable synthetic version of the brain hormone somatostatin, is an effective treatment for cluster headache for some people. But overall, it's less effective and acts less quickly to relieve pain than triptans.
• Local anesthetics. The numbing effect of local anesthetics, such as lidocaine, may be effective against cluster headache pain in some people when given through the nose (intranasal).
• Dihydroergotamine. The injectable form of dihydroergotamine (D.H.E. 45) may be an effective pain reliever for some people with cluster headache. This medication is also available in an inhaled (intranasal) form, but this form hasn't been proved to be effective for cluster headache.

Preventive treatments

Preventive therapy starts at the onset of the cluster episode with the goal of suppressing attacks.

Determining which medicine to use often depends on the length and regularity of your episodes. Under the guidance of your doctor, you can taper off the drugs once the expected length of the cluster episode ends.

• Calcium channel blockers. The calcium channel blocking agent verapamil (Calan SR, Verelan) is often the first choice for preventing cluster headache. Verapamil may be used with other medications. Occasionally, longer term use is needed to manage chronic cluster headache.

  Side effects may include constipation, nausea, fatigue, swelling of the ankles and low blood pressure.

• Corticosteroids. Inflammation-suppressing drugs called corticosteroids, such as prednisone (Prednisone Intensol, Rayos), are fast-acting preventive medications that may be effective for many people with cluster headaches.

  Your doctor may prescribe corticosteroids if your cluster headache condition has started recently or if you have a pattern of brief cluster periods and long remissions.

  Although corticosteroids might be a good option to use for several days, serious side effects such as diabetes, hypertension and cataracts make them inappropriate for long-term use.

• Lithium carbonate. Lithium carbonate (Lithobid), which is used to treat bipolar disorder, may be effective in preventing chronic cluster headache if other medications haven't prevented cluster headaches.

  Side effects include tremor, increased thirst and diarrhea. Your doctor can adjust the dosage to minimize side effects.

  While you're taking this medication, your blood will be checked regularly for the development of more-serious side effects, such as kidney damage.

• Noninvasive vagus nerve stimulation (VNS). VNS uses a hand-held controller to deliver electrical stimulation to the vagus nerve through the skin. Although more research is needed, some studies found that VNS helped reduce the frequency of cluster headaches.

• Nerve block. Injecting a numbing agent (anesthetic) and corticosteroid into the area around the occipital nerve, situated at the back of your head, might improve chronic cluster headaches.

  An occipital nerve block may be useful for temporary relief until long-term preventive medications take effect. It's often used in combination with verapamil.

Other preventive medications used for cluster headache include anti-seizure medications, such as topiramate (Topamax, Qudexy XR).

Surgery

Rarely, doctors may recommend surgery for people with chronic cluster headaches who don't find relief with aggressive treatment or who can't tolerate the medications or their side effects.

Sphenopalatine ganglion stimulation involves surgery to implant a neurostimulator that's operated by a hand-held controller. Some research showed quick pain relief and a lower frequency of headaches, but more studies are needed.

Several small studies found that occipital nerve stimulation on one or both sides may be beneficial. This involves implanting an electrode next to one or both occipital nerves.

Some surgical procedures for cluster headache attempt to damage the nerve pathways thought to be responsible for pain, most commonly the trigeminal nerve that serves the area behind and around your eye.

However, the long-term benefits of destructive procedures are disputed. Also, because of the possible complications — including muscle weakness in your jaw or sensory loss in certain areas of your face and head — it's rarely considered.

Potential future treatments

Researchers are studying several potential treatments for cluster headache.

• Occipital nerve stimulation. In this procedure, your surgeon implants electrodes in the back of your head and connects them to a small pacemaker-like device (generator). The electrodes send impulses to stimulate the area of the occipital nerve, which may block or relieve your pain signals.

  Several small studies of occipital nerve stimulation found that the procedure reduced pain and frequency of headaches in some people with chronic cluster headaches.

• Deep brain stimulation. Deep brain stimulation is a promising but as yet unproven treatment for cluster headaches that don't respond to other treatments.

  In this procedure, doctors implant an electrode in the hypothalamus, the area of your brain associated with the timing of cluster periods. Your surgeon connects the electrode to a generator that changes your brain's electrical impulses and may help relieve your pain.

  Because this involves placing an electrode deep in the brain, there are significant risks, such as an infection or hemorrhage.

  Deep brain stimulation of the hypothalamus may provide relief for people with severe, chronic cluster headaches that haven't been successfully treated with medications.

The following measures may help you avoid a cluster headache attack during a cluster cycle:

• Stick to a regular sleep schedule. Cluster periods can begin when there are changes in your normal sleep schedule. During a cluster period, follow your usual sleep routine.
• Avoid alcohol. Alcohol consumption, including beer and wine, can quickly trigger a headache during a cluster period.

Because cluster headaches can be so painful, you may want to try alternative or complementary therapies to relieve your pain.

Melatonin has shown modest effectiveness in treating nighttime attacks. There's also some evidence that capsaicin, used inside your nose (intranasally), might reduce the frequency and severity of cluster headache attacks.

Living with cluster headache can be frightening and difficult. The attacks can seem unbearable and make you feel anxious and depressed. Ultimately, they can affect your relationships, your work and the quality of your life.

Talking to a counselor or therapist might help you cope with the effects of cluster headaches. And joining a headache support group can connect you with others with similar experiences and provide information. Your doctor might be able to recommend a therapist or a support group in your area.

You're likely to start by seeing your primary care doctor. However, you may be referred to a doctor trained in treating brain and nervous system disorders (neurologist).

Here's some information to help you get ready for your appointment.

What you can do

When you make the appointment, ask if there's anything you need to do in advance, such as fasting for a specific test.

Keep a headache diary

One of the most helpful things you can do is keep a headache diary. Each time you get a headache, jot down these details that might help your doctor determine your type of headache and discover possible headache triggers.

• Date. Charting the date and time of each headache can help you recognize patterns.
• Duration. How long does each headache last?
• Intensity. Rate your headache pain on a scale from 1 to 10, with 10 being the most severe.
• Triggers. List possible triggers that might have caused your headache, such as certain foods, sounds, odors, physical activity or oversleeping.
• Symptoms. Did you have any symptoms before the headache, such as aura?
• Medications. List all drugs, vitamins and supplements, including dosages, even if they're unrelated to your headache.
• Relief. Have you had any pain relief, from complete pain relief to none?

Take a family member or friend to your appointment, if possible, to help you remember the information you receive.

List questions to ask your doctor. For cluster headaches, basic questions include:

• What's likely causing my symptoms?
• What other possible causes are there?
• What tests do I need?
• Is my condition likely temporary or chronic?
• What treatment do you recommend?
• What other treatments are there?
• I have other health conditions. How can I best manage them together?
• Are there restrictions I need to follow?
• Should I see a specialist?
• Are there brochures or other printed material I can have? What websites do you recommend?

Don't hesitate to ask other questions.

What to expect from your doctor

Your doctor is likely to ask you questions, such as:

• When did your symptoms begin?
• Have your symptoms been continuous or occasional?
• Do your symptoms tend to occur at the same time of day? Do they occur during the same season each year?
• Does alcohol appear to cause your symptoms?
• How severe are your symptoms?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?