Marcellino C, Wijdicks EF. Posthypoxic action myoclonus (the Lance Adams syndrome). BMJ Case Rep. 2020 Apr 16;13(4):e234332.

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• Action myoclonus is exceptionally rare (less than 0.5% in a series of patients who have a cardiac arrest).
• Myoclonus occurring after hypoxic brain injury from cardiac arrest, characterised by abrupt irregular muscle contractions. (1)
  • Acute: starting within 48 hours after the arrest (when isolated, sometimes terms acute Lance-Adams syndrome). (2)
  • Chronic: Lance-Adams syndrome, which may start from days to weeks after arrest and progressively worsen, with or without other neurological symptoms.
• Potentially confused with myoclonus status in a comatose patient, yet the examination, imaging, degree of disability and prognosis are very divergent.
• Typically, no EEG seizure correlates.

Aicua Rapun I, et al. Early Lance-Adams syndrome after cardiac arrest: Prevalence, time to return to awareness, and outcome in a large cohort. Resuscitation. 2017 Jun;115:169-172.

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Results: Among 458 consecutive patients, 7 (1.5%) developed early LAS (4 women, median age 59 years). Within 72h after CA, in normothemia and off sedation, all showed preserved brainstem reflexes and localized pain. All patients were initially treated with valproate, levetiracetam and clonazepam; additional agents, including propofol and midazolam, were prescribed in the majority. First signs of awareness occurred after 3-23 days (median 11.8); 3/7 reached a good outcome at 3 months.

Conclusion: Early after CA, myoclonus together with a reactive, epileptiform EEG, preserved evoked potentials and brainstem reflexes suggests LAS. This condition was managed with a combination of highly dosed, large spectrum antiepileptic agents including propofol and midazolam. Even if awakening was at times delayed, good outcome occurred in a substantial proportion of patients.

English WA, Giffin NJ, Nolan JP. Myoclonus after cardiac arrest: pitfalls in diagnosis and prognosis. Anaesthesia. 2009 Aug;64(8):908-11.

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