The Benefit of Neuromuscular Blockade in Patients with Postanoxic Myoclonus Otherwise Obscuring Continuous Electroencephalography (CEEG)

Abstract

Introduction. Myoclonus status epilepticus is independently associated with poor outcome in coma patients after cardiac arrest. Determining if myoclonus is of cortical origin on continuous electroencephalography (CEEG) can be difficult secondary to the muscle artifact obscuring the underlying CEEG. The use of a neuromuscular blocker can be useful in these cases. Methods. Retrospective review of CEEG in patients with postanoxic myoclonus who received cisatracurium while being monitored. Results. Twelve patients (mean age: 53.3 years; 58.3% male) met inclusion criteria of clinical postanoxic myoclonus. The initial CEEG patterns immediately prior to neuromuscular blockade showed myoclonic artifact with continuous slowing (50%), burst suppression with myoclonic artifact (41.7%), and continuous myogenic artifact obscuring CEEG (8.3%). After intravenous administration of cisatracurium (0.1 mg-2 mg), reduction in artifact improved quality of CEEG recordings in 9/12 (75%), revealing previously unrecognized patterns: continuous EEG seizures (33.3%), lateralizing slowing (16.7%), burst suppression (16.7%), generalized periodic discharges (8.3%), and, in the patient who had an initially uninterpretable CEEG from myogenic artifact, continuous slowing. Conclusion. Short-acting neuromuscular blockade is useful in determining background cerebral activity on CEEG otherwise partially or completely obscured by muscle artifact in patients with postanoxic myoclonus. Fully understanding background cerebral activity is important in prognostication and treatment, particularly when there are underlying EEG seizures.

Figure 1

Effect of cisatracurium on continuous electroencephalography (CEEG). (a) The CEEG is completely obscured by myogenic artifact. After neuromuscular blockade, generalized continuous slowing is seen. (b) Myogenic artifact obscured the CEEG. After neuromuscular blockade, generalized slowing along with lateralized right slowing is seen. (c) Rhythmic myogenic artifact partially obscured the CEEG. After neuromuscular blockade, 3 Hz generalized periodic discharges were seen consistent with nonconvulsive status epilepticus.

Figure 2

Effect of filtering continuous electroencephalography (CEEG) compared to cisatracurium. CEEG is partially obscured by myogenic artifact filtered at (a) 70 Hz, (b) 50 Hz, (c) 30 Hz, (d) 15 Hz, and (e) 5 Hz compared to neuromuscular blockade (f). This patient had asymmetric burst suppression (decreased left hemisphere).