THE CAUSES OF EPILEPSY: TUMOURS
A tumour arising within the brain understandably causes great anxiety-perhaps more so than with tumours elsewhere in the body, as a brain tumour may appear to strike at the very centre of one’s soul and being. Many people with simple headaches due to anxiety or stress believe that they have a brain tumour which is causing their headache. However, the incidence of primary tumour is very low (10 per 100 000 per year). It is, however, true that tumours can cause epilepsy. This is much more likely to happen in adults than in children.
Brain tumours are either primary or secondary. A secondary tumour is one that has been carried in the blood to the brain from another site. Cancers of the lung (bronchus) or breast are by far the most common of these. Usually the site of the original cancer is known, and the appearance of seizures in such a patient is an ominous sign indicating that a secondary tumour has arisen within the brain. Sometimes, however, the original cancer has not been discovered at the time of the first seizure, and a careful clinical examination will reveal a small tell-tale lump in the breast, or the lung cancer will be seen on a chest X-ray.
Primary tumours of the brain do not arise in nerve cells. They either arise in the supporting cells between nerve cells which play an active role in their nutrition (glial cells) or in the meninges, the covering membranes of the brain. These tumours are called gliomas and meningiomas. There are other types of primary cerebral tumours, such as those arising from the cells lining the cavities of the brain, or from blood vessels, but these are rare.
Primary brain tumours are not like cancer of the breast, or bowel, or bronchus. They show no tendency to develop blood-borne secondary deposits in other organs. This is fortunate, but there are other characteristics which hinder effective treatment. The gliomas infiltrate normal brain extensively, so there is no apparent margin beyond which one can be quite certain that no abnormal cells have reached. This makes recurrence after surgical excision very likely. Meningiomas, however, are encapsulated tumours, and can often be removed completely, with a good chance of complete eradication. However, meningiomas often have an extensive blood supply, so complete removal may be technically very difficult.
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