Myoclonus no longer a show-stopper

In comatose survivors of cardiac arrest, myoclonus is considered a grave prognostic sign. The American Academy of Neurology stated in 20061 that:
After cardiac arrest, the following clinical findings accurately predict poor outcome;

  • myoclonus status epilepticus within the first 24 hours in patients with primary circulatory arrest
  • absence of pupillary responses within days 1 to 3 after CPR
  • absent corneal reflexes within days 1 to 3 after CPR
  • and absent or extensor motor responses after 3 days.

However in the age of targeted temperature management the presence and/or timing of these signs needs to be re-evaluated. It has been suggested that therapeutic hypothermia and sedation required for induced cooling might delay recovery of motor reactions up to 5–6 days after cardiac arrest. Now a series of three survivors of cardiac arrest who had massive myoclonus in the first four hours after return of spontaneous circulation (ROSC) is reported2, all of whom were treated with TTM and experienced good neurologic outcomes.

Early myoclonus in comatose survivors of cardiac arrest, even when it is not myoclonic status epilepticus (MSE), is considered a sign of severe global brain ischemia and has been associated with high rates of mortality and poor neurologic outcomes. We report on three survivors of primary circulatory cardiac arrests who had good neurologic outcomes (two patients with a CPC score=1 and one patient with a CPC score=2) after mild therapeutic hypothermia, despite exhibiting massive myoclonus within the first four hours after return of spontaneous circulation. The concept that early myoclonus heralds a uniformly poor prognosis may need to be reconsidered in the era of post-cardiac arrest mild therapeutic hypothermia.

1. Practice Parameter: Prediction of outcome in comatose survivors after cardiopulmonary resuscitation (an evidence-based review): Report of the Quality Standards Subcommittee of the American Academy of Neurology
Neurology. 2006 Jul 25;67(2):203-10 Full Text
2. Neurologic Recovery After Therapeutic Hypothermia in Patients with Post-Cardiac Arrest Myoclonus
Resuscitation published on line 03 October 2011

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