Effects of partial neuromuscular blockade on lateral spread response monitoring during microvascular decompression surgery

•The efficacy of partial neuromuscular blockade (NMB) for intraoperative monitoring of lateral spread responses (LSRs) has not been established yet.•The successful intraoperative LSR monitoring can be achieved under partial NMB with train-of-four and T1 amplitude monitoring.•The spontaneous free-run facial EMG occurred less frequently in patients with partial NMB.

ObjectiveWe evaluated the effect of partial neuromuscular blockade (NMB) and no NMB on successful intraoperative monitoring of the lateral spread response (LSR) during microvascular decompression (MVD) surgery.MethodsPatients were randomly allocated into one of three groups: the TOF group, the NMB was targeted to maintain two counts of train-of-four (TOF); the T1 group, maintain the T1/Tc (T1: amplitude of first twitch, Tc: amplitude of baseline twitch) ratio at 50%; and the N group, no relaxants after tracheal intubation. Successful LSR monitoring was defined as effective baseline establishment and maintenance of the LSR until dural opening.ResultsThe success rate of LSR monitoring was significantly lower in the TOF group. But, there was no significant difference between T1 and N. The detection rate of spontaneous free-run electromyography (EMG) activity was significantly higher in the N group compared with the TOF and T1 groups.ConclusionsPartial NMB with a target of T1/Tc ratio at 50% allows good recording of LSR with same outcome as surgery without NMB, and reduced spontaneous EMG activity.SignificanceWe suggested the availability of partial NMB for intraoperative LSR monitoring.