TONIC-CLONIC STATUS EPILEPTICUS

The annual incidence of tonic-clonic status is estimated to be 18–28 cases per 100 000 persons. It occurs most commonly in children, the mentally handicapped, and in those with structural cerebral pathology especially in the frontal lobes. Most episodes of status develop without a prior history of epilepsy, and these are almost always caused by acute cerebral disturbances; common causes are cerebral infection, trauma, cerebrovascular disease, cerebral tumour, acute toxic or metabolic disturbances, or childhood febrile illness. In patients with pre-existing epilepsy, status can be precipitated by drug withdrawal, intercurrent illness or metabolic disturbance, or the progression of the underlying disease, and is more common in symptomatic than in idiopathic epilepsy. About 5% of all adult patients attending an epilepsy clinic will have at least one episode of status in the course of their epilepsy; in children the proportion is between 10–25%.

The physiological changes in status can be divided into two phases, the transition from phase 1 to 2 occurring after about 30–60 minutes of continuous seizures (table 2, fig 1). In phase 1, compensatory mechanisms prevent cerebral damage. In phase 2, however, these mechanisms break down, and there is an increasing risk of cerebral damage as the status progresses. The cerebral damage in status is caused by systemic and metabolic disturbance (for example, hypoxia, hypoglycaemia, raised intracranial pressure) and also by the direct excitotoxic effect of …