Status epilepticus: classification and pathophysiology

Abstract

© Cambridge University Press 2012. Introduction. Seizures are, for the most part, self-terminating, but on occasions they can persist, leading to status epilepticus. The first definitions of status epilepticus were restricted to tonic-clonic seizures, but at the Marseilles Colloquium in 1962 status epilepticus was redefined so that it depended on the persistence of the seizure rather than its form. The definition was ‘a condition characterized by epileptic seizures that are sufficiently prolonged or repeated at sufficiently brief intervals so as to produce an unvarying and enduring epileptic condition’. This definition introduces two aspects that remain contentious, first the duration of a seizure before it becomes ‘enduring’ and second the concept of status epilepticus as ‘unvarying’. Although the length of time that a seizure or series of seizures have to continue before being classified as status epilepticus is to an extent arbitrary, most would accept a limit of 30 minutes. Treatment, however, should begin at an earlier time point to prevent the progression to established status epilepticus (see Chapter 96: ‘Status epilepticus: diagnosis and management’). More importantly, as will become apparent, status epilepticus is anything but an ‘unvarying’ condition, and is perhaps best considered a condition with a number of distinct physiological and pharmacological stages. Epidemiology. Status epilepticus is a common condition with an incidence of 10 to 60 per 100 000 person-years, depending on the population studied (the higher incidence is in people from poorer socioeconomic background). Over half the cases of status epilepticus occur in people without a prior history of epilepsy and it is critical to identify the underlying cause. Infections with fever are the most common cause of status epilepticus in children, whilst in adults cerebrovascular accidents, hypoxia, metabolic causes and alcohol are the main acute causes. In people with epilepsy, status epilepticus is commonly precipitated by drug withdrawal, and reintroduction of the withdrawn drug can lead to a rapid resolution of the episode. Status epilepticus is recurrent in over 10% of people, emphasizing the need to have a protocol in place to prevent further episodes of status epilepticus. The prognosis of status epilepticus is related to aetiology; however, the prognosis of certain conditions such as stroke is worse if associated with status epilepticus. The mortality for status epilepticus is 10–20% and is higher in the elderly. If people prove resistant to first-line therapies the mortality increases to approximately 50%.