In 1868 Bacon, an eminent physician, noted the occurrence of ‘sudden death in a fit’ and almost 40 years later Spratling, one of the earliest American neurologists, recognised epilepsy as ‘a disease which destroys life suddenly and without warning through a single brief attack.’ Despite this, in the 1960’s it was suggested that ‘there is no reason why …someone with epilepsy… should not live as long as he would if he did not have epilepsy’ (Livingstone 1963). SUDEP is sudden unexpected death in someone with epilepsy, who was otherwise well, and in whom no other cause for death can be found, despite thorough post mortem examination and blood tests. The definition excludes people dying in status epilepticus and those who drown.

Awareness of SUDEP has increased over recent years, yet in many countries the medical profession has been reluctant to consider SUDEP. Indeed, there is little information on the number of cases in different countries. It has been estimated that the risk of sudden death is almost 24 times higher than for someone without epilepsy. Most people with newly diagnosed epilepsy will stop having seizures, and SUDEP is very rare amongst them. Searching for risk factors in this group would require meticulous follow up of large numbers of people. Studies of SUDEP have therefore usually been conducted in groups of people with more severe forms of epilepsy, such as specialist clinic populations, hospital inpatients or residential groups. The risk of SUDEP is elevated in these populations. It is estimated as between 1:500 and 1:1000 patient-years in community based populations with epilepsy, and even higher in people considered for surgery.

The cause of death in SUDEP is currently, by definition, unknown, but various risk factors have been suggested. These include young adulthood, presence of convulsive attacks, poor seizure control and poor adherence with antiepileptic drugs (AEDs). Other suggested risk factors are male gender, use of more than one AED, frequent changes of dose or type of AED, alcohol abuse and certain epilepsy syndromes.

Studies of age at death in SUDEP can be problematic because its definition requires negative findings at post mortem examination. Many elderly people have evidence of vascular disease and it is often difficult to exclude this as a cause of death. Most studies have found young adults as the group at higher risk. The age of onset of seizures is lower in people with epilepsy who died of SUDEP than in those dying of other causes.

SUDEP is usually unwitnessed but, when witnessed, often follows a convulsion. Evidence for a seizure prior to death is frequently, but not always, found at post mortem examination. Studies have found that most cases of SUDEP in whom the seizure type was known, had a history of convulsions. Many people dying of SUDEP are found in or near the bed. A recent study found that supervision at night appears to be protective.

Higher rates of SUDEP are found in studies of people with severe epilepsy, suggesting that people with frequent, severe seizures are most at risk. Some authors have suggested that seizure frequency is not a risk factor but a recent study found it to be the most significant risk factor.

There is conflicting evidence concerning the use of more than one AED as a risk factor. One study which showed increased risk associated with multiple AEDs suggested this may be because these people have more severe seizures, while another found the increased risk associated with more than two AEDs was still significant after adjusting for seizure frequency. Other studies have not found any association.

People have debated whether SUDEP is more likely in men than women, but a recent study found the rate of SUDEP to be identical in men and women.

Written by: Gail Bell & Ley Sander
Institute of Neurology, Queen Square, London, UK.

Reprinted with the permission of Epilepsy Australia-the national coalition of Australia epilepsy associations and Epilepsy Bereaved UK.