Although largely neglected in earlier literature, sudden unexpected death in epilepsy (SUDEP) is the most important epilepsy-related mode of death, and is the leading cause of death in people with chronic uncontrolled epilepsy. Research during the past two to three decades has shown that incidence varies substantially depending on the epilepsy population studied, ranging from 0.09 per 1000 patient-years in newly diagnosed patients to 9 per 1000 patient-years in candidates for epilepsy surgery. Risk profiles have been delineated in case-control studies. These and other studies indicate that SUDEP mainly occurs in the context of a generalised tonic-clonic seizure. However, it remains unclear why a seizure becomes fatal in a person that might have had many similar seizures in the past. Here, we review SUDEP rates, risk factors, triggers, and proposed mechanisms, and critically assess potential preventive strategies. Gaps in knowledge are discussed and ways forward are suggested.

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Sudden unexpected death in epilepsy: current knowledge and future directions.

Objective: To determine incidence of and risk factors for sudden unexpected death in epilepsy (SUDEP). Methods: Three epilepsy centers enrolled 4,578 patients and prospectively followed these patients for 16,463 patient-years. The cohort was screened for death annually. Deaths were investigated to determine whether SUDEP occurred. Potential risk factors were compared in SUDEP cases and in controls enrolled contemporaneously at the same center. Results: Incidence of SUDEP was 1.21/1,000 patient-years and was higher among women (1.45/1,000) than men (0.98/1,000). SUDEP accounted for 18% of all deaths. Occurrence of tonic-clonic seizures, treatment with more than two anticonvulsant medications, and full-scale IQ less than 70 were independent risk factors for SUDEP. The number of tonic-clonic seizures was a risk factor only in women. The presence of cerebral structural lesions and use of psychotropic drugs at the last visit were not risk factors for SUDEP in this cohort. Subtherapeutic anticonvulsant levels at the last visit were equally common in the two groups. No particular anticonvulsant appeared to be associated with SUDEP. Conclusions: These results support the idea that tonic-clonic seizures are an important proximate cause of SUDEP. This information creates a risk profile for SUDEP that may help direct preventative efforts.

Incidence and risk factors in sudden unexpected death in epilepsy: A prospective cohort study

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(98)05114-9.pdf

Risk factors for sudden unexpected death in epilepsy: a case control study

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(11)60176-1.pdf

Sudden unexpected death in epilepsy

Objective: To examine the influence of various factors on the risk of sudden unexpected death in epilepsy (SUDEP). Methods: The authors investigated 154 cases in which a postmortem examination was performed. Each case had four controls with epilepsy from the community, matched for age and geographic location. Backward stepwise conditional logistic regression analysis was performed and odds ratios for risk and protection were determined. Results: The risk of SUDEP was increased with a history of generalized tonic-clonic seizures in the previous 3 months (odds ratio [OR]: 13.8, 95% CI: 6.6 to 29.1). The presence of supervision at night was found to be protective (OR: 0.4, 95% CI: 0.2 to 0.8) when a supervising individual shared the same bedroom or when special precautions such as a listening device were employed (OR: 0.1, 95% CI: 0.0 to 0.3). Conclusion: This work lends support to the view that SUDEP is a seizure-related phenomenon and that control of tonic-clonic seizures is important in its prevention. Nocturnal supervision seems to protect against SUDEP.

Case-control study of SUDEP

Unexpected sudden death is a common event in otherwise healthy epileptics, though its etiology has remained unclear. Many authors have suggested cardiac arrhythmias as the cause, and limited data in humans and animal studies have supported this. However, autopsy series in humans have shown pulmonary edema, a phenomenon not compatible with a sudden arrhythmic death, as a possible cause. We developed a model of status epilepticus in unanesthetized, chronically instrumented sheep in which sudden death and pulmonary edema occur. Catecholamine levels and seizure type and duration did not differ between animals dying suddenly and those surviving. Benign arrhythmias were generated in all animals; in no case did an arrhythmia account for the death of an animal. Striking hypoventilation was demonstrated in the sudden death group but not in the surviving animals. Differences in peak left atrial and pulmonary artery pressures, and in extravascular lung water were also demonstrated; pulmonary edema did not account for the demise of the sudden death animals. Thus, our model of epileptic sudden death supports a role of central hypoventilation in the etiology of sudden unexpected death and confirms the association with pulmonary edema. The importance of arrhythmia in its pathogenesis is not confirmed.

John Valente

Papers

The role of hypoventilation in a sheep model of epileptic sudden death