Adverse events during transcranial muscle evoked potential monitoring

BACKGROUND: Transcranial muscle evoked potential (TC-MsEP) monitoring is available to assess spinal cord motor tract function for preventing paralysis in spine surgery. Recently, the quality of monitoring has improved. However, adverse events such as torn tracheal tube, bitten tongue, and mandibular fracture are reported. METHODS: We reviewed retrospectively adverse events with TC-MsEP monitoring by Multipulse D-185 (Digitimer Ltd., the U.K.) during spine surgery in our hospital. In addition, we compared the number of cases with transformed tracheal tubes in cases using Multipulse D-185 and in cases using the other stimulation device. RESULTS: Since June 2007, Multipulse D-185 is applied as a stimulating device of TC-MsEP, and we experienced two adverse events of lasceration of tongue and teeth dislocation. There was a significant difference (P=0.02) in the number of transformed tracheal tube between Multipulse D-185 (11 of 20) and the other stimulation device (2 of 19). CONCLUSIONS: It seems that two adverse events were due to excessive masseter muscles contraction with TC-MsEP monitoring. Prevention for bite injury and ventilation strategy for tube occlusion or stenosis using Multipulse D-185 for TC-MsEP are necessary.