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Sudden unexpected death: a rare event in a large community based prospective cohort with newly diagnosed epilepsy and high remission rates
  1. S D LHATOO,
  2. Y LANGAN,
  3. B K MACDONALD,
  4. S ZEIDAN,
  5. J W A S SANDER
  1. Epilepsy Research Group and Neuroepidemiology Unit, Institute of Neurology and the National Hospital for Neurology and Neurosurgery, 33 Queen Square, London, UK
  1. Dr S D Lhatoo, Epilepsy Research Group and Neuroepidemiology Unit, Institute of Neurology and the National Hospital for Neurology and Neurosurgery, 33 Queen Square, London WC1N 3BG, UK

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It is now accepted that mortality in epilepsy is significantly increased, with standard mortality ratios raised twofold or threefold. Early deaths are usually attributable to the underlying cause of epilepsy and mortality in chronic cases is commonly due to the epilepsy itself.1 Of the deaths that are directly related to epilepsy, the commonest category is sudden unexpected death in epilepsy (SUDEP). This is widely defined as a sudden unexpected, non-traumatic and non-drowning death in a person with epilepsy with or without evidence of a seizure and excluding documented status epilepticus in which postmortem examination does not disclose a cause of death. Less common causes are status epilepticus, accidents due to seizures, drowning, and aspiration. The National General Practice Study of Epilepsy (NGPSE) is a prospective, population based, observational study of 792 patients with newly diagnosed epilepsy (564 definite cases and 228 probable cases)2 followed up for 8000 patient-years and has provided valuable insights into the prognosis and mortality of epilepsy. Fifty per cent of the definite cases were between the ages of 15 and 59 years—encompassing the age band in which the phenomenon of SUDEP is most commonly found. The overall standardised mortality ratio among patients with definite epilepsy in this cohort was 3.0 (95% confidence interval (95% CI) 2.5–3.7).1

The true incidence of SUDEP is not precisely known. Studies have varied in their methodology and study populations have ranged from those in death certificates and coroners’ registers (more community based) to epilepsy surgery cohorts and institutionalised patients (patients with chronic epilepsy).3 Figures derived from community based prospective studies indicate numbers of up to 1:1100.4Patients with chronic epilepsy seem to have a much higher incidence of SUDEP and a tertiary clinic based population with chronic epilepsy in the United Kingdom had an estimated incidence of 1:200 patients.5 This is in some contrast with the two SUDEP deaths in 5000 patient years reported by the MRC Anti-epileptic Withdrawal Study Group for patients in remission from epilepsy.6

We report the first sudden unexpected death in epilepsy in the NGPSE. A 42 year old man known to have poorly controlled idiopathic generalised epilepsy treated with phenytoin and sodium valproate, was found dead in bed, having been well in the hours and days preceding death. He was known to misuse alcohol and was questionably compliant with medication, both factors thought to increase the risk of sudden death. A necropsy did not disclose any relevant pathology—consistent with the definition of SUDEP.

Mortality has been studied in detail in this large cohort1and it was only in the 13th year of follow up (8000 patient-years) that the first SUDEP was reported. This could falsely give the impression that SUDEP is a rare occurrence and it must be borne in mind that in large community based cohorts such as the NGPSE, most patients enter remission from seizures and it is the patients who continue to have epilepsy that are most at risk from sudden death. Indeed in this cohort, the number of patients who still have active epilepsy, using International League Against Epilepsy criteria for remission (no seizures for 5 years or more with or without medication) and on follow up are 111 from an original 792 who had definite or probable epilepsy. On its own, therefore, it does not provide a true indication of the incidence of SUDEP but it is nevertheless an interesting finding on the prognosis of epilepsy in a large, community based cohort.

Acknowledgments

Financial support and sources of funding for the NGPSE were the National Hospital for Neurology and Neurosurgery, Brain Research Trust, and the National Society for Epilepsy.

References

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