Abstracts

Rationale: Post-anoxic myoclonus is historically considered a strong predictor of poor prognostic after cardiac arrest (CA). Although recent studies suggested that a subset of these patients may improve towards a good outcome, identifying these patients has been difficult. We examined the prognostic ability of EEG and MRI in combination to identify patients with good outcome in a multi-centric retrospective study. Methods: Adults with post-anoxic myoclonus who had an MRI within 15 days after CA were retrospectively identified in four prospective CA registries. Primary functional measure of good outcome was assessed as sufficient recovery to follow command at discharge. Clinical exam consisted of pupillary and corneal reflexes, and motor exam of flexion or better vs posturing/no movement. EEG was assessed by local certified neurophysiologists for continuity, reactivity, presence of epileptiform activity, and burst suppression with identical bursts (BSIB). MRI was assessed by local neuroradiologists for presence of diffusion restriction and/or FLAIR changes consistent with anoxic brain injury diffusely, in the cortex, subcortical region, or deep structures. A combined EEG/MRI variable was assessed; it was deemed “anoxic” if either best EEG background was discontinuous or MRI revealed anoxic brain injury (or both), and “non-anoxic” otherwise. Results: There were 78 patients (median 56 years; 37% women); of these, 61 (78%) died, 11 (14%) followed commands at discharge, and 7 (9 %) presented good outcome at three months. All 11 patients who followed commands had intact pupillary and corneal reflexes, and 9 (82%) had motor response of flexion or better whereas these were present in 44 (66%), 30 (45%), and 5 (7.5%), respectively patients who did not recover.EEG was continuous in 23 patients (29%), reactive in 18 (23%), and in 73 (94%) showed epileptiform patterns. In patients who followed commands, EEG was continuous in all, reactive in 8 (72.7%), and epileptiform in 9 (81.8%); no patients showed BSIB. In patients who did not follow commands, EEG was continuous in 12 (18%, p<0.001 as compared to following commands), reactive in 10 (15%, p<0.001), epileptiform in 65 (95.5%, p=0.093), and had BSIB in 38 (57%, p=0.001).MRI revealed anoxic brain injury in 61 patients (78%). In patients who followed commands, anoxic injury was present in 1, with subtle changes in the corona radiata. In patients who did not recover to follow commands, anoxic changes were seen in 60 (89%, p<0.001); cortical in 35 (52%), subcortical in 1 (1%), deep structures in 27 (40%), and diffusely in 23 (34%). The combined EEG/MRI variable to identify good outcome revealed a sensitivity of 91%, specificity of 99%, positive value of 91%, and a negative predictive value of 99%. In patients who had continuous EEGs, all patients who did not have anoxic brain injury on MRI improved to following commands, whereas 1 of 12 patients with injury on MRI did. Conclusions: EEG and MRI are complementary in determining outcome in patients with postanoxic myoclonus; combining them demonstrates extremely accuracy in identifying both good and poor outcome. Patients who exhibit a continuous EEG and do not exhibit anoxic brain injury on MRI have universally good outcome in our cohort. Funding: No funding