43
CHAPTER
Sudden Unexpected Death in Epilepsy
Abeer J. Hani and Rodney A. Radtke
Mortality in people with epilepsy can be attributed to one of three causes: epilepsy-related causes, causes related to the underlying etiology of the epilepsy, and causes unrelated to the epilepsy or its underlying etiology. The epilepsy-related deaths include seizure-related deaths, treatment-related deaths, status epilepticus, and sudden unexpected death (SUDEP). Among these causes, SUDEP remains an important cause of premature death in epilepsy patients. The reported incidence of SUDEP has varied widely depending on cohorts included. A systemic review (1) of available studies yielded the following statistics. Assuming an overall epilepsy prevalence of 7.1 per 100,000 population, the crude annual incidence of SUDEP is estimated at 1.16 per 1,000 persons with epilepsy. Epilepsy onset at the age of 1 year incurs a lifetime risk of SUDEP of 8% by 70 years of age, whereas epilepsy onset at the age of 30 years yields a corresponding risk of 4.6%. The lowest incidence of SUDEP is reported in population-based incidence cohorts with higher incidence noted in those with refractory epilepsy (2). The risk among patients with presumably chronic and often refractory epilepsy has been reported as 1.1–5.9 per 1,000 person-years. The highest risk has been reported among epilepsy surgery candidates or patients who continue to have seizures after surgery with estimated risk of 6.3–9.3 per 1,000 person-years. In the MORTality in Epilepsy Monitoring Unit Study (MORTEMUS), the risk of SUDEP was 1.2 per 10,000 video EEG (vEEG) monitorings (3).
Despite the desire to improve the understanding of SUDEP, the discussion of SUDEP in the clinical setting continues to be a great challenge to physicians and patients alike. In this chapter, an overview of the definition of SUDEP, mechanisms involved and risk factors of SUDEP will be provided. This is then followed by a discussion of the possible methods to prevent SUDEP. Finally, an approach to counseling patients about SUDEP will be suggested.
DEFINITION AND CLASSIFICATION OF SUDEP
The classification and diagnosis of SUDEP is a challenging task, given the unpredictable occurrence, often in unwitnessed settings, and often with lack of complete autopsy examinations. As such, there has been an effort to improve and standardize the definition of SUDEP. In 1997, two complementary definitions of SUDEP were proposed (Table 43.1) (4,5). The classic definition of SUDEP has been a “sudden, unexpected, witnessed or unwitnessed, nontraumatic and nondrowning death in patients with epilepsy, with or without evidence for a seizure and excluding documented status epilepticus, in which postmortem examination does not reveal a toxicologic or anatomic cause of death (4).” If a postmortem examination finds no other causes of death, the case would be considered a definite SUDEP. If autopsy were not performed, it would be considered a probable SUDEP.
In 2012, a unified definition and classification of SUDEP was suggested (Table 43.2) (6). The aim of the unified definition was to expand the definition of SUDEP and to clarify some of the definitions as well as to provide a framework to define SUDEP even in the absence of all the data surrounding the circumstances of death in epilepsy. The updated definition of SUDEP now is a “sudden, unexpected, witnessed or unwitnessed, nontraumatic and nondrowning death, occurring in benign circumstances, in an individual with epilepsy, with or without evidence for a seizure and excluding documented status epilepticus (seizure duration ≥30 minute or seizures without recovery in between), in which postmortem examination does not reveal a cause of death.” The concept of SUDEP plus has been introduced also to identify situations whereby evidence indicated that a preexisting condition could have contributed to the death in addition to SUDEP. An example of a SUDEP plus case would be the unwitnessed sudden death in an epilepsy patient with known long QT-syndrome and with negative postmortem examination. Different categories of SUDEP have been suggested, including definite SUDEP/SUDEP plus, probable SUDEP/SUDEP plus, possible SUDEP, near- SUDEP/SUDEP plus, not SUDEP and unclassified. Selected examples of each of these types can be found in Table 43.2.
MECHANISMS UNDERLYING SUDEP
The putative mechanisms underlying SUDEP continue to be a subject of evaluation and research. Periictal alteration of respiratory function, cardiac arrhythmias, and alterations in sleep and autonomic function as well as various genetic factors have been implicated in the mechanisms underlying SUDEP (Figure 43.1). Knowledge of these mechanisms will help guide the development of strategies to prevent SUDEP.
TABLE 43.1 The 1997 Definitions of SUDEP
NASHEF 1997 DEFINITION OF SUDEP | ANNEGERS 1997 DEFINITION OF SUDEP |
Sudden, unexpected, witnessed or unwitnessed, nontraumatic and nondrowning death in patients with epilepsy, with or without evidence for a seizure and excluding documented status epilepticus, in which postmortem examination does not reveal a toxicologic or anatomic cause of death. | Criteria for diagnosis of SUDEP:
|
| Classification of SUDEP:
|
Source: Adapted from Refs. (4) and (5).
TABLE 43.2 Unified 2012 Definition and Classification of SUDEP
SUDEP TYPE | DEFINITION | EXAMPLES |
Definite SUDEPa | Sudden, unexpected, witnessed or unwitnessed, nontraumatic and nondrowning death, occurring in benign circumstances, in an individual with epilepsy, with or without evidence for a seizure and excluding documented status epilepticus (seizure duration ≥ 30 minute or seizures without recovery in between), in which postmortem examination does not reveal a cause of death | Witnessed sudden death in sleep or during activity including exercise in an epilepsy patient, no seizure; negative postmortem examination |
Definite SUDEP Plusa | Satisfying the definition of Definite SUDEP, if a concomitant condition other than epilepsy is identified before or after death, if the death may have been due to the combined effect of both conditions, and if autopsy or direct observations/recordings of terminal event did not prove the concomitant condition to be the cause of death | Cardiorespiratory arrest after habitual seizure in an epilepsy patient; postmortem examination shows coronary artery atheroma but no evidence of myocardial infarction |
Probable SUDEP/Probable SUDEP Plusa | Same as Definite SUDEP but without autopsy. The victim should have died unexpectedly while in a reasonable state of health, during normal activities, and in benign circumstances, without a known structural cause of death | Epilepsy patient, no other relevant preexisting conditions; dead in bed in the morning, benign circumstances; no postmortem examination |
Possible SUDEPa | A competing cause of death is present | Epilepsy patient, no other relevant preexisting conditions; dead in water but not submersed, benign circumstances; postmortem examination |
Near-SUDEP/Near-SUDEP Plus | A patient with epilepsy survives resuscitation for more than 1 hour after a cardiorespiratory arrest that has no structural cause identified after investigation | Epilepsy patient; cardiorespiratory arrest after witnessed seizure, resuscitated but dies within a few days or weeks; negative postmortem examination |
A clear cause of death is known | Epilepsy patient; cardiorespiratory arrest after habitual seizure, resuscitated but dies after 5 days; postmortem examination shows large myocardial infarction | |
Unclassified | Incomplete information available; not possible to classify | — |
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