Thank you to our friends and partners at the Epilepsy Therapy Project/epilepsy.com, the Epilepsy Foundation of America, and Canada’s SUDEP Aware for their tireless and determined pursuit of current and relevant information pertaining to the facts of SUDEP. What follows is gleaned from the efforts of these organizations and shared here with great thanks, gratitude, and honor to be working with groups so committed to working toward the same goals as the Danny Did Foundation.
People who live with epilepsy or with a loved one who has epilepsy should be aware that epilepsy occasionally can be fatal. This uncomfortable truth often is hidden or ignored because it is relatively rare and so hard to discuss. Some doctors argue: don’t inform patients, because it will be too frightening. Others think that doctors should provide factual information and let patients and families decide how they best can deal with the information.
Sudden Unexpected Death in Epilepsy (SUDEP), is an almost self-explanatory term: it applies to a sudden death in someone known to have epilepsy, in the absence of an obvious cause for the death. Although most instances are presumed to occur during seizures, not all do and a seizure at the time of death is not a requirement for diagnosis of SUDEP. A widely accepted definition of SUDEP was proposed by Nashef in 1997: “the sudden, unexpected, witnessed or unwitnessed, non-traumatic, and non-drowning death of patients with epilepsy with or without evidence of a seizure, excluding documented status epilepticus, and in whom post-mortem examination does not reveal a structural or toxicological cause for death.”
The number of people dying from SUDEP is difficult to determine. There is no central national or regional registry with long-term follow-up data to track such deaths, although several are being formed, particularly in Europe, Canada and the United States. Information from county and state mortality registries is incomplete and incorrect. Mortality statistics are based largely on diagnoses written on death certificates by treating physicians. Many physicians are unfamiliar with SUDEP, and so would not list SUDEP on a death certificate. County Medical Examiners, who often sign off on cases of otherwise unexplained or suspicious deaths, are more likely to have heard of SUDEP. Still, their diagnosis might make no mention of SUDEP, referring only to “epilepsy” or “seizure.”
SUDEP has been estimated to account for 15-20% of all cases of death in people with epilepsy (Pedley and Hauser 2002). SUDEP is more likely in people with uncontrolled tonic-clonic (grand mal) seizures, those who are having seizures but not taking adequate doses of antiepileptic medications. Those who take multiple antiepileptic drugs are at higher risk, but this may be because many who are taking multiple medications are having more frequent or more severe seizures, and that is the real risk factor. Seizures that occur during sleep may increase the risk. Males and African-Americans may be higher risk. Many other risk factors have been considered, but not yet proven. Among people with uncontrolled epilepsy, SUDEP is not rare, emphasizing the urgent need for better diagnosis, prevention and treatment of uncontrolled epilepsy.
The cause of SUDEP is not entirely known, although there are several plausible theories, most of which focus on breathing (respiration), heart rhythms, and brain function.
A pause in breathing, called apnea, is common during or after a seizure. Studies during video-EEG monitoring (O’Regan and Brown 2005) have shown breathing pauses longer than 15 seconds in 30% of partial seizures. Such pauses can be associated with significant drops in blood oxygen levels (Blum et al. 2000). Normal oxygen saturation in blood is above 98%, and significant problems can occur with saturations less than about 85% in people unaccustomed to such low oxygen blood levels. A study monitoring oxygen levels during seizures (Bateman and Seyal 2009) showed oxygen levels below 90% in 33% of seizures, below 80% in 10% of seizures and below 70% in 4% of seizures.
Apnea can be caused by obstruction in the pharynx or throat blocking air passages, or by loss of breathing signals normally directed by the brainstem to the respiratory muscles. Brain failure of breathing signals is called central apnea, and it seems to be the type of apnea seen during seizures. However, some authors have argued that post-seizure apnea can also be from throat obstruction.
Autopsies after SUDEP and laboratory experiments in models of SUDEP sometimes show lung tissue filled with water, a condition called pulmonary edema. The water component of blood leaks from lung capillaries into lung tissue, because the capillary fluid is under high pressure. During seizures, this high capillary pressure results from seizure-induced constriction of the veins draining blood from the lungs. With water in the lung tissue, blood oxygenation drops. Pulmonary edema can add to the oxygenation problems produced by apnea. A few published cases have documented prolonged apnea in conjunction with SUDEP.
How often apnea is the mechanism for SUDEP cannot be known. At what point in a seizure-related respiratory pause would it make sense to give oxygen or artificial respiration? The answers are not known. Standard seizure precautions for a patient hospitalized with seizures include delivery of oxygen by mask or nasal prongs during and after a seizure. Yet, oxygen therapy rarely is prescribed for home use. The reason for this discrepancy is unknown.
Heart rhythm problems likely account for some instance of SUDEP. During seizures, changes in heart rate are common, the usual change being an increase of heart rate during a seizure, but other serious arrhythmias can occur (Nei et al. 2000). More serious are very high rates that interfere with the heart filling with blood, or pauses in the heart rate.
Brain dysfunction is another category of possible causes for SUDEP. Blood flow to brain increases markedly during a seizure to keep up with the demands of the increased electrical activity. The increased brain blood flow raises pressure inside the closed head. If the pressure becomes too high, then brain tissue can be compressed and injured, resulting in a stroke-like picture or possibly even death. This is extremely rare. Short of compression, seizures might cause the vital centers in the brainstem that control blood pressure and respiration to temporarily malfunction.
Mixed causes: SUDEP probably results from a variety of causes, related to problems with heartbeat, breathing and brain function. Different people may have different causes and more research will be needed to clarify the most important causes.
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