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PAIN WITHOUT A CAUSE: HEADACHE

You may reasonably be annoyed that I place headache in a chapter on pains without a cause if you know that your own headaches are caused by irritation, anxiety, fatigue, alcohol and so on. You are quite right, but we need to understand why those conditions set off some mechanism in the head which makes a head ache.

There are many types of headache without any structural lesion to explain the cause. Migraine and tension headaches are very common, while others are rare but devastating, such as cluster headaches, or even very rare such as ice-cream headache or headache triggered by sexual activity. Migraine occurs in about 15 per cent of any population studied. Environment can hardly be considered a deep cause because rates are found to be the same in country and city dwellers, graduates of Oxford and long-term prisoners. Rates are higher in women, especially after puberty, but men have identical types of attack. Before an attack, there may be hours or days of vague premonitory symptoms such as mood changes, yawning or craving for special foods. This may be followed by an aura, most commonly visual with shimmering lights and patterns, which then proceeds to a headache on one side (the word migraine comes from the French demi-craine, which means half the head). This pain grows, often with pounding and tenderness accompanied by a dislike of light and sounds, and leads to vomiting and sleep. Once the attack is over, patients are relatively normal although subtle changes remain that could be due to medicines taken or to the fear of the next attack.

These headaches are called vascular headaches because of the throbbing which times with the heartbeat. It is obvious that such a complex suite of signs and symptoms can hardly all have a single cause. There is no evidence that the early phase of the aura has a vascular origin but there are many changes in the brain. If there are vascular changes, they appear late in the attack and may well be secondary to central changes. In spite of this, the rationale for the treatment of migraine has focused on the blood vessels. Drugs directed at the blood vessels include the older remedies derived from ergot and the more recent drug sumatriptan. The success of these compounds in arresting a migraine attack should not be taken as proof that the pain originates from the blood vessels. They have central actions and the vascular effects may be secondary to these.

Tension headache is the type of headache with which we are all too familiar. It can last from half an hour to seven days. It has a pressing, tightening, non-pulsating quality on both sides and does not usually stop everyday activity. It is clearly different from most migraine attacks. It has been called a tension headache because it feels as though the muscles of the head are tense. Unfortunately for this belief, there is not a scrap of evidence that the muscles are overactive.

So there is no evidence that either blood vessels in spasm or muscles in cramp cause headaches. Doctors are therefore once again driven away from the peripheral tissues where the pain seems to exist and need to search the brain for the cause. We do not yet have the ability to study brain mechanisms in sufficient detail to pin down a central cause, if it exists.

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Pain Relief