Abstracts

Rationale: Myoclonic status epilepticus is often seen after cardiac arrest. Previous studies reported almost uniformly fatal outcome in such patients. However, there is emerging evidence for functional recovery in some of these patients. Recent studies have reported that poor outcomes are associated with early onset myoclonus (considered early onset if seen within 24h of arrest), attenuation of background EEG activity, lack of EEG reactivity and when the myoclonus is associated with epileptiform discharges. Few studies have examined the electrographic and clinical characteristics systematically. We examined the clinical and EEG characteristics as well as the prognostic significance of post anoxic myoclonus. Methods: Single-center retrospective chart review was performed for all cardiac arrest patients who developed myoclonus within the first 72 hours and underwent continuous EEG monitoring (CEEG) as part of routine clinical care between 2011- 2015. Relevant clinical variables were identified including time of onset, semiology of myoclonus and details of cardiac arrest. Outcomes were assessed using Glasgow- Pittsburgh Cerebral Performance Categories (CPC) and categorized as good (CPC 1-3) vs bad (CPC 4-5) outcome. EEG findings including background, reactivity, presence of epileptiform discharges and presence of EEG correlate to myoclonus were reviewed at 6, 12, 24, 48 and 72 hours after the return of spontaneous circulation (ROSC). Available video (N=15) was used to identify the semiology and confirm the electro-clinical correlation. Results: 43 patients were included in the study, of which 34 (79%) underwent therapeutic hypothermia. The majority of patients (78%) had early myoclonus: 48% with onset prior to initiation of hypothermia and 30% during the cooling phase. The most common semiology was multi-focal myoclonus followed by facial/ocular myoclonus. Out of the 43 patients, 6 patients survived, of whom 5 had good functional outcome. All 5 patients with good outcome had a sustained continuous EEG background at all times (3 as early as 12 hours), with or without epileptiform discharges. Myoclonus was early onset in 4 of these 5 patients (1 prior to hypothermia, 2 during cooling and 1 did not undergo hypothermia) with good outcome, and EEG correlate was seen in 4/4 (data not available for the 5th). Out the 15 patients for whom video was available, 3 had myoclonus time locked with epileptiform discharges, 7 had myoclonus associated with highly epileptiform bursts of suppression burst (SB) pattern, 3 had no EEG correlate (suppressed portion of SB/diffuse suppression) and 2 correlated with non-epileptiform bursts of SB pattern. Conclusions: Early onset (within 24 hours) multi-focal myoclonus is the most common pattern seen in cardiac arrest patients. Preliminary findings suggest that despite early onset myoclonus, the distinct EEG finding of continuous background, irrespective of presence of epileptiform discharges/patterns or EEG correlate to myoclonus, may suggest the possibility of good functional outcome. The ongoing study with a larger patient population will further clarify these findings. Funding: None