HEALTH / Common Complaints: Brain tumours

Neurotic New Yorkers portrayed by Woody Allen are not the only ones who fear they might have a brain tumour. Many people who have bad headaches worry that this might be the first symptom of cancer inside the skull. The anxiety may be intense, combining as it does fear of cancer, fear of brain disease, and fear of mental illness. Such worries are almost invariably groundless: neurologists are agreed that a headache which has persisted for a year with no other symptoms is unlikely to be due to a brain tumour.

Brain tumours, cancers and other growths are fairly rare; the number of new cases in Britain each year is between 3,000 and 3,500. About two-thirds of these eventually prove fatal, but they account for less than 2 per cent of all cancer deaths. Brain cancers are, however, the second most common cancer in childhood (after leukaemia), occurring most often in children aged two to eight. Tumours are rare in teenagers and young adults; the peak age in adults is 50-60 years.

These are generalisations. There are a dozen or more types of brain tumour. Some originate in the brain itself, but tumours may also grow in the membranes covering the brain (meningiomas), in the nerves leading from it, and in the pituitary gland behind the eyes. Some tumours are cancerous. Even those that aren't can be dangerous: an expanding growth will cause problems as it raises the pressure within the skull.

The early symptoms are, indeed, often those of raised intracranial pressure: headache, often worse on waking, vomiting, failing vision, and eventually drowsiness. Sometimes the first symptoms are due to pressure on a nerve or nerve centre - a squint, unsteadiness and clumsiness, vertigo, or weakness in a group of muscles.

If the tumour is at the front of the skull, the first symptoms may be a change in personality. The third common way for brain tumours to show themselves is by causing epileptic attacks. All of these symptoms, however, have other possible causes; for example, only 10 per cent of people aged over 25 who develop epilepsy will be found to have brain tumours.

During the past 20 years, advances in X- ray and other investigations have made it far easier for doctors to get accurate pictures of the brain without risk to the patient; CT scanning and magnetic resonance imaging produce clear cross-sectional images in which even small tumours show up clearly. In the United States, where fear of litigation promotes over-investigation, virtually every person with a persistent headache has tests of this kind - expensive, time-consuming, and sometimes upsetting for the patient.

Early diagnosis improves the chances of succesful treatment, but cancerous tumours deep within the brain have a poor outlook; the most malignant may be fatal within a few weeks of the first symptoms. The results of treatment are continuing to improve, but there remains one huge defect in our knowledge: no preventive strategy is possible, because the cause of brain tumours is unknown. A link between tumours and exposure to electromagnetic radiation from high- voltage power cables, radar installations and the like has been suggested but not proved. Brain tumours remain mysterious; we are fortunate that they are not more common.