What are cluster headaches?
Cluster headaches are episodes of frequently severe headaches which involve the area of the forehead and eye. They are usually one-sided. Cluster headaches most frequently affect males in early to mid adulthood. We do not know exactly what causes cluster headaches.

What are the symptoms of cluster headaches?
Each attack occurs suddenly, often without any warning. Pain is typically experienced mainly in or around one eye or temple, and may spread to other regions on the same side of the head.

In addition to the headache component described above, episodes of cluster headaches frequently include eye watering (lacrimation), nasal congestion or runny nose, a ‘bloodshot’ eye (‘scleral injection’), swelling around the eye, a droopy eye, constricted (small) pupil, and facial sweating.

As suggested by their name, cluster headaches typically occur in clusters over several days or weeks, and then disappear for a variable period of time. Each attack most commonly lasts 45-90 minutes. Attacks may occur from once every couple of days, up to eight times per day. They usually occur at the same time of the day, and patients frequently say they could ‘set their clock’ by the onset of the headache. A fairly typical scenario is for a cluster to last 1-3 months once every year or two, and for them to occur at about the same time of the year.

Who gets cluster headaches?
Cluster headaches are very uncommon, affecting 1 in 1000 people. Men are five times more frequently affected than women. The first cluster typically develops between the ages of 20-40 years, but it can start earlier or later.

What causes cluster headaches?
It is known that the part of the brain called the hypothalamus becomes overactive during each attack, and as a result it may release chemicals (neurotransmitters) which stimulate the brain to cause the pain and other symptoms. It is unclear exactly what causes this overactivity.

Heredity (genetic factors) may play a role. In 5% of cases, cluster headaches also occur in a close relative.

Most cluster headaches occur for no obvious reason. Some people do find that certain activities or environmental factors may 'trigger' a headache.

Trigger factors in some people include:

• Alcohol
• Hot temperatures
• Strong smelling substances such as perfumes, petrol, etc.

How is the diagnosis made?
There are no special tests to diagnose cluster headaches. The diagnosis is based on the typical symptoms and signs. Investigations are usually done if the diagnosis is unclear in order to exclude other causes of headache.

How are cluster headaches prevented?
A number of medications may be used to try and prevent cluster headaches from occurring. These include:

• Verapamil
• Corticosteroids, given at the beginning of a cluster. This may prevent further headaches
• Lithium
• Methysergide
  

How are cluster headaches treated?
Cluster headaches may be treated with a variety of medical therapies, including anti-migraine agents, lithium, and breathing pure (100%) oxygen. Most cases are able to be controlled with such measures. The treatment of cluster headaches is usually coordinated by a neurologist.

Standard painkillers do not work, and even if they do they usually take so long to work that the headache may have gone before the pain-relief takes effect.

Sumatriptan is the most widely used medication to 'abort' a cluster headache. This is injected (usually by the patient) just under the skin, and works within 5-10 minutes. A nasal spray for of this drug is also available.

Where cluster headaches become unresponsive to conventional medical therapies, and are severe enough to cause a significant degradation in the person’s quality of life, surgical intervention may be considered.

Surgical approaches to the treatment of this frequently devastating condition have involved:

• Percutaneous interference with the trigeminal or sphenopalatine ganglion by balloon compression, heating, or glycerol injection. The success rate of these strategies does appear low, although some practitioners report reasonable results.
• Occipital and frontal peripheral nerve stimulation. This technique has low risks and may offer substantial benefit to a small number of patients.
• Deep brain stimulation. Following the observation of metabolic changes within a discrete region of the brain (the posterior hypothalamus) during cluster headaches, deep brain stimulation has emerged as a promising way to treat these individuals.

What is deep brain stimulation for cluster headaches?
Deep brain stimulation for cluster headaches involves the placement of an electrode (a wire) in the posterior hypothalamus on the same side of the brain as the headaches. This permits the delivery of a high frequency current to inactivate this area.

In small groups of patients with greater than 12 months follow-up after surgery, approximately two-thirds of patients have been rendered pain-free, and around half have been able to cease pharmacological treatment. These results are extremely encouraging, however confirmation that these benefits persist for several years will be required before deep brain stimulation for cluster headaches becomes a standard therapy. Nevertheless, in patients with no other alternatives, it is a technique worth contemplating at present.