This large retrospective interrogation of the International Cardiac Arrest Registry aimed to evaluate the outcomes of cardiac arrest survivors with myoclonus receiving modern postresuscitation care. (1)
Of the 2532 patients studied who sustained cardiac arrest between 2002-2012, 88% underwent therapeutic hypothermia and 18% exhibited myoclonus (471 patients). Good outcome (defined as cerebral performance category 1-2 at hospital discharge) was noted in 9% patients with myoclonus. Perhaps predictably, the patients with myoclonus with good outcome as opposed to poor outcome were younger (53.7yrs vs 62.7yrs), had more VF/VT as presenting rhythm (81% vs 46%), shorter ischaemic time (18.9 vs 26.4 minutes), less other epileptiform activity on EEG (2% and 15%) and, interestingly, received more neuromuscular blockade (93.5% vs 72%). The authors also provide the prevalence of other EEG abnormalities in the patients with myoclonus with different neurologic outcomes, something that may well aid in prognostication.
In this study, 9% patients with myoclonus after cardiac arrest showed a good neurological outcome, suggesting that myoclonic jerks in isolation should not be considered a sign of futility.
The incidence of myoclonus found in this study is lower (18%) than studies from the pre-TTM era. The findings run contrary to two widely cited large cases of patients with myoclonic status in whom no survivors were identified (2, 3)
Study Strengths & Limitations
The large size and international provenance of this study renders its findings widely generalisable. It highlights the importance of ensuring that all patients who exhibit clinical myoclonus undergo EEG testing for prognostication.
The retrospective nature of the study means that the cohort and the survival data, as well as group proportions, may skewed by withdrawal of care on 62% patients with myoclonus overall received. The negative implications of myoclonus may have driven earlier discontinuation of treatment in these groups and it is possible to conjecture that some of these patients may have made a good recovery.
The database provenance of the data does not allow differentiation between myoclonic status and myoclonic jerks, evaluation of the timing of the myoclonus (e.g. intention or action myoclonus typically occurs during recovery and carries a better prognosis). Future studies should do so.
Recent articles have called for delayed prognostication in outcome prediction after cardiac arrest. This study suggests that myoclonic jerks do not inevitably portend a poor outcome. Future prospective studies should clarify the importance of myoclonus of different types and timings to allow reliable identification of patients with a better neurological prognosis.
- This study compels the intensivist to re-evaluate the significance of isolated myoclonus after cardiac arrest, as it should not be independently interpreted as a sign of futility.
- It underlines the importance of using and correctly interpreting EEG in patients with myoclonus after cardiac arrest
- It highlights the urgent need for further prospective studies to clarify the importance of myoclonus to allow for reliable assessment of a patient’s neurological outcome.
This article review was submitted by ESICM NEXT Committee member Katie Lane.
1. Seder DB et al. Neurological Outcomes and Postresuscitation Care of Patients with Myoclonus following Cardiac Arrest. Critical Care Medicine, 2015. 43 (5) pp 965-972 10.1097/CCM.0000000000000880
2. Wijdicks EF et al. Prognostic value of myoclonus status in comatose survivors of cardiac arrest. Ann Neurol 1994; 35:239-243.
3. Young GB et al. The significance of myoclonic status epilepticus in postanoxic coma. Neurology 1990; 40:1943-1948.