Muscle relaxant use during intraoperative neurophysiologic monitoring.

Neuromuscular blocking agents have generally been avoided during intraoperative neurophysiological monitoring (IOM) where muscle responses to nerve stimulation or transcranial stimulation are monitored. However, a variety of studies and clinical experience indicate partial neuromuscular blockade is compatible with monitoring in some patients. This review presents these experiences after reviewing the currently used agents and the methods used to assess the blockade. A review was conducted of the published literature regarding neuromuscular blockade during IOM. A variety of articles have been published that give insight into the use of partial pharmacological paralysis during monitoring. Responses have been recorded from facial muscles, vocalis muscles, and peripheral nerve muscles from transcranial or neural stimulation with neuromuscular blockade measured in the muscle tested or in the thenar muscles from ulnar nerve stimulation. Preconditioning of the nervous system with tetanic or sensory stimulation has been used. In patients without neuromuscular pathology intraoperative monitoring using peripheral muscle responses from neural stimulation is possible with partial neuromuscular blockade. Monitoring of muscle responses from cranial nerve stimulation may require a higher degree of stimulation and less neuromuscular blockade. The role of tetanic or sensory conditioning of the nervous system is not fully characterized. The impact of neuromuscular pathology or the effect of partial blockade on monitoring muscle responses from spontaneous neural activity or mechanical nerve stimulation has not been described.