Cluster headache is a relatively rare condition of extremely severe headache, affecting less than 1% of the population. The typical symptoms are so unusual that it cannot be confused with anything else.

The pain of cluster headache is excruciatingly severe and localised to behind one eye (i.e. it is much more localised than migraine). Patients often can point to the lower area with one finger. The attacks are ALWAYS on the same side. The attacks start very quickly building up from no pain up to maximum pain often within seconds to minutes. The typical attack duration can be as little as 20 to 30 minutes but can go on for some hours. The name “cluster headache” comes from the pattern in which typically patients will get several attacks in one day, often around 3 every day for several weeks or months and then they may have a gap for months or even years. Sometimes attacks occur at the same time of the year or season. At the end of the run the attacks will just spontaneously settle down leaving the patient exhausted and fearful when the next run will start. In addition to the pain, the eye usually waters, is red, the pupil is small and the eyelid droops. It is usual for attacks to occur between 1 and 3 in the morning waking people from sleep and so a number of patients during the cluster run are often afraid to go to bed. The pain is non-pulsatile, unlike migraine, and excruciatingly severe. I have known patients to try and knock themselves out to end the suffering of an attack. Unlike migraine, cluster headache is much more common in men than in women and it is uncommon for this condition to come on in a person who is not a smoker. We do not know why this is the case but unfortunately stopping smoking doesn’t get rid of the problem. The typical age of onset is also in middle age.

As with most of the other headache conditions, we don’t know the cause of cluster headache but genetic factors appear to be much less likely than in migraine. Occasionally the condition can be caused by an artery pressing on a nerve at the base of the brain and so a high-resolution MRI scan is often performed in patients to see whether this is the case. If so, the condition may be helped by surgical moving of the artery.

Treatment for the Attack

In general, because the pain is so severe and comes on so quickly, general painkilling drugs taken by mouth, although may be taken in desperation, are rarely adequately effective.

Despite cluster headache been quite a different condition to migraine, the triptans are probably even more effective in cluster than in migraine. Because of the very rapid onset, intranasal or injected formulations may be better because of the fast onset than tablets.

At high concentrations, oxygen constricts blood vessels in the head and this may be why it works in cluster headache. The problem is the standard oxygen masks given for patients with lung disease only give a slight enrichment of oxygen because in those patients giving them too much can be harmful. This means there is no standard system for giving high flow oxygen to patients with cluster headache. We need to use a resuscitation type mask which is tight fitting and a method to make sure that the oxygen your breathing is not piloted by your exhaled breath. Oxygen can only be supplied on a doctor’s prescription and you need to buy the equipment yourself. The cylinders are rented, however.

To make sure patients only go to the trouble of getting the gear if it is likely to be effective, we often bring patients into our clinic for a test of oxygen. Generally, we trigger an attack either using wine (which of course the patient has to supply) or glyceryl trinitrate tablets that are generally used in the treatment of heart disease.

Preventative Treatment

Because of the severe nature of the pain, few patients rely only on treatment for the attack and generally try to suppress the attacks using preventative treatment.

Verapamil is a calcium antagonist used in the treatment of high blood pressure and heart disease. It is the first line treatment for the suppression of cluster headache attacks. However, the maximum licensed dose for heart disease is 480 mg daily. Verapamil does not penetrate the brain very well and experience from cluster experts is that the dose may need to go considerably higher up to double the recommended maximum dose or even higher again with a maximum of 1200 mg daily. Clearly such use is “off-label” and going beyond the maximum recommended dose should only be done under specialist supervision.The particular concern is that verapamil causes a slowing of communication between the pacemaker part of the heart and the main pumping chambers. We can easily measure this on the ECG. If the effect is too much it could cause a loss of communication between the pacemaker part of the heart and the pumping chambers resulting in a very slow heart rate. This is not a heart attack or cardiac arrest but would not be desirable. In practice this means we generally fairly quickly get patients up to 480 mg daily using a controlled-release formulation. Further increases are only done after an assessment of the patient and a review of the ECG. You should only conclude that verapamil has failed once you have got to either the maximum dose listed above, the ECG suggests we should not go higher or the patient otherwise has unacceptable side-effects. However, verapamil is generally very well tolerated with usually the only symptom of concern being constipation.

Topiramate may be effective in cluster headache and it is used as for migraine.

Most patients can get temporary control of the episode of cluster using high-dose prednisolone. My experience is that in any individual patient there is particular dose which completely controls the symptoms and even a small reduction below that leads to complete loss of control. In other words, it seems to be an “all-or-none” effect. Unfortunately doses that need to be used are often very high between 25 and 75 mg daily. These are not safe for long-term use and can cause major long-term problems but for a week or two are probably not too much of a problem. The main concern is brain stimulation and excitation with sleeplessness. There can be serious weight gain with these drugs. Their best use is as a very short-term stopgap whilst getting other treatments on board.

Lithium is normally only used for the prevention of attack of flare-ups of manic depression. There is some evidence that it is effective in cluster. It has a narrow safety margin which means that dosage is adjusted according to blood levels. It can cause a number of side effects on mood and concentration and with prolonged use can be damaging to the kidneys.

There is evidence that this is effective in cluster headache. This is discussed in the section on migraine.