Take head injury, for example. If a child is known to have cut her head falling in the playground, and then has her first seizure two weeks later, many parents will link the two events, and attribute the onset of epilepsy to this minor head injury on no basis other than coincidence in time. A minor head injury at work followed some weeks later by a first seizure unfortunately may lead to litigation between employer and employee, as the latter holds that he ‘was perfectly all right before the accident’. The association of events in time is, however, no evidence of cause. Severe head injuries may, however, result in the development of epilepsy, so-called

post-traumatic epilepsy. Somewhere in the continuum of mild to moderate to severe head injuries there must be a zone where there is reasonable doubt as to whether epilepsy was or was not caused by the injury.

The same arguments apply when assessing the effects of a difficult birth and the possible relationship of that to the subsequent development of epilepsy. There is no doubt that a very difficult labour, especially if the baby is small, may cause significant brain damage, severe learning difficulties, cerebral palsy, and epilepsy may result. However, after many difficult or prolonged labours the child develops perfectly normally and twins are no more likely to develop seizures than single births. It used to be thought that forceps or breech deliveries might be blamed for the subsequent development of epilepsy. However, a follow-up study of all children born in one week showed that epilepsy was no more likely to develop after such births than after normal unassisted deliveries. It is now known that in many children born with cerebral palsy or severe learning difficulties there are problems in cerebral development that precede birth. Although sometimes these may be visible on scanning, in other cases the abnormality is no more than a subtle disorder of organization of the developing nerve cells visible only microscopically in tissue obtained at surgical operation or after death. These may, however, be sufficient to cause seizures.

Having given these warnings against uncritically linking life events and the development of epilepsy, what are the factors which can be said, with a fair degree of confidence, to cause epilepsy? The causes are different at different ages. Some causes, such as a structural congenital brain abnormality may cause seizures in the neonatal period, and the abnormally organized brain may cause seizures throughout life, as is indicated by the long continuing arrow. Other causes occur only at one age, and their effect then ceases. Metabolic disturbances in the neonatal period, such as hypoglycaemia, are examples of this.

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