Temporal dynamics of EEG patterns associated with generalized myoclonus after cardiopulmonary resuscitation

Introduction: There is only limited knowledge on the temporal dynamics of EEG patterns associated with generalized myoclonus (GM) after cardiopulmonary resuscitation (CPR).

Methods: We examined 100 consecutive comatose survivors of CPR with GM occurring within 24 hours, when the first EEG was done (=day 1). Subsequent EEGs were recorded in all surviving patients at day 2, and between days 3 and 4, days 5 and 6, and days 7 and 8.

Results: GM was mainly associated with a burst-suppression EEG (BS-EEG) (n=67), or continuous generalized epileptiform discharges (CGED) (n=21). The remaining patients had areactive alpha- or theta coma EEG, delta EEG, or a flat (<20µV) recordings. Surviving patients showed highly variable EEG sequences composed of these patterns with often subtle transitions, especially between between BS-EEG and CGED. About ((frac13)) of patients also had coexistence of different EEG-patterns in the same recording, mainly BS-EEG with trains of CGED. In general, different EEG-sequences ended as flat or isoelectric recordings.

Conclusion: GM after CPR is mainly associated with BS-EEG or CGED. All postanoxic EEG-patterns are transient and followed by a variety of EEG sequences finally leading to flat or isoelectric recordings. Different EEG-sequences were composed of a number of EEG patterns each of which is recognized as an unfavourable sign, i.e. BS-EEG, CGED, areactive alpha- or theta coma EEG, flat or isoelectric recordings. Different EEG-patterns in anoxic encephalopathy may reflect different forms of neocortical dysfunction, which occur at different stages of a dynamic process finally leading to severe neuronal loss.