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Nonictal Near Sudden Unexpected Death in Epilepsy

      To the Editor
      The presence of epileptiform discharges and seizures is routinely monitored by electroencephalography (EEG) during Wada testing. Spontaneous cardiac arrhythmias are unexpected.
      • Ahern G.L.
      • Sollers J.J.
      • Lane R.D.
      • et al.
      Heart rate and heart rate variability changes in the intracarotid sodium amobarbital test.
      Malignant cardiac arrhythmias, including asystole, are rare complications that occur in patients with focal seizures and have been implicated in sudden unexpected death in epilepsy (SUDEP).
      • Lanz M.
      • Oehl B.
      • Brandt A.
      • Schulze-Bonhage A.
      Seizure induced cardiac asystole in epilepsy patients undergoing long term video-EEG monitoring.
      We report a case of nonictal near-SUDEP.

      Report of a Case

      A 30-year-old man with drug-resistant, localization-related epilepsy underwent an evaluation for surgical treatment. Recurrent focal seizures with dyscognitive features and focal seizures evolving to convulsions had continued despite a trial of 4 antiseizure drugs. Video-EEG monitoring captured 3 left temporal seizures characterizing the localization during a presurgical evaluation. Electrocardiography (ECG) revealed normal sinus rhythm with sinus tachycardia during the seizures. An initial Wada test was invalid because of oversedation from amobarbital. During preparation for a repeated study and prior to catheterization, bradycardia and subsequent asystole occurred with generalized tonic stiffening that was first suspected to represent a seizure. Subsequent review of the ECG confirmed asystole causing convulsive syncope. A precordial thump prompted immediate resolution (after 64 seconds) without the need for antiarrhythmic medication. Outpatient Holter monitoring subsequently recorded a 33-second episode of spontaneous asystole. This episode resolved without clinical signs, and a permanent cardiac pacemaker was implanted without recurrence.

      Discussion

      This patient with drug-resistant focal seizures exhibited spontaneous cardiac asystole undetected during seizure monitoring. Had the Wada test not revealed in-hospital cardiac asystole, sudden cardiac death may have occurred without intervention. Cardiorespiratory disturbances are normally controlled by the autonomic nervous system and in many cases are associated with seizures.
      • Ryvlin P.
      • Nashef L.
      • Lhatoo S.D.
      • et al.
      Incidence and mechanisms of cardiorespiratory arrests in epilepsy monitoring units (MORTEMUS): a retrospective study.
      A disturbed cerebral-cardiac relationship from brainstem dysregulation of cardiac sympathetic-parasympathetic activity may be the foundation for near death from a malignant arrhythmia in some patients with epilepsy. However, without EEG and ECG monitoring, it would have been difficult during Wada testing to conclude that the witnessed event was nonepileptic. An event misdiagnosed as an epileptic seizure would have been disastrous because of a missed treatment of a malignant cardiac arrhythmia.
      Cardiac arrhythmias may account for a substantial number of cases of SUDEP. The underlying pathophysiology is incompletely understood, although neurogenic cardiac asystole is believed to contribute to SUDEP.
      • Rugg-Gunn F.J.
      • Simister R.J.
      • Squirrell M.
      • Holdright D.R.
      • Duncan J.S.
      Cardiac arrhythmias in focal epilepsy: a prospective long-term study.
      SUDEP is reported to occur in about 1.8 per 1000 patients with epilepsy and is increased in patients who have persistent seizures despite antiseizure drugs.
      • Rugg-Gunn F.J.
      • Simister R.J.
      • Squirrell M.
      • Holdright D.R.
      • Duncan J.S.
      Cardiac arrhythmias in focal epilepsy: a prospective long-term study.
      Before we are able to prevent SUDEP,
      • Hirsch L.J.
      • Hauser W.A.
      Can sudden unexplained death in epilepsy be prevented?.
      we must learn the mechanism or mechanisms that underlie its occurrence. Rather than a single mechanism, our case supports observational findings of nonictal near-SUDEP as a mechanism that may occur independent of seizures. We support recommendations to maintain a heightened suspicion for spontaneous malignant arrhythmias in patients with uncontrolled seizures. Despite the absence of ECG abnormalities during ictal recordings, we recommend combined ECG and EEG monitoring during Wada testing and continued cardiac vigilance in patients with drug-resistant focal epilepsy.

      Acknowledgment

      We thank Kirsten H. Yelvington, REEGT, CLTM, for her help in patient diagnostics and data review as well as the Mayo Clinic Division of Cardiovascular Diseases for their excellent patient care. We thank Ms Gabrielle Petito (clinical research intern) for her help with review, writing, and formatting the submitted manuscript and Ms Kelly Viola, ELS, and Ms Alison Dowdell for their help in manuscript preparation and submission.

      References

        • Ahern G.L.
        • Sollers J.J.
        • Lane R.D.
        • et al.
        Heart rate and heart rate variability changes in the intracarotid sodium amobarbital test.
        Epilepsia. 2001; 42: 912-921
        • Lanz M.
        • Oehl B.
        • Brandt A.
        • Schulze-Bonhage A.
        Seizure induced cardiac asystole in epilepsy patients undergoing long term video-EEG monitoring.
        Seizure. 2011; 20: 167-172
        • Ryvlin P.
        • Nashef L.
        • Lhatoo S.D.
        • et al.
        Incidence and mechanisms of cardiorespiratory arrests in epilepsy monitoring units (MORTEMUS): a retrospective study.
        Lancet Neurol. 2013; 12: 966-977
        • Rugg-Gunn F.J.
        • Simister R.J.
        • Squirrell M.
        • Holdright D.R.
        • Duncan J.S.
        Cardiac arrhythmias in focal epilepsy: a prospective long-term study.
        Lancet. 2004; 364: 2212-2219
        • Hirsch L.J.
        • Hauser W.A.
        Can sudden unexplained death in epilepsy be prevented?.
        Lancet. 2004; 364: 2157-2158