Abstract
Constant-voltage and constant-current stimulators may be used for transcranial electrical stimulation of motor evoked potentials (TES-MEP). However, no previous report has determined whether the two monophasic stimulation methods lead to similar responses during intra-operative monitoring. We studied differences in the lateralities of compound muscle action potentials (CMAPs) during intra-operative spinal cord monitoring via TES-MEP using monophasic constant-current and constant-voltage stimulations. CMAPs were bilaterally recorded from the upper and lower limb muscles in 95 patients who underwent elective spine and spinal cord surgery. We used two monophasic stimulation patterns: pattern 1, right anode and left cathode; pattern 2, right cathode and left anode. There were no statistically significant differences between the right and left sides with respect to success rates, wave amplitudes, and efficiencies, with constant-voltage stimulation, however, there were statistically significant differences between the right and left sides with constant-current stimulation. In case of our stimulation condition, there were no statistically significant differences between the right and left sides with respect to CMAPs with constant-voltage stimulation; constant-current stimulation was influenced by the type of monophasic stimulation, which necessitates the switch the polarity of the stimulation to bilaterally record CMAPs.
Highlights
Iatrogenic spinal cord injury is the most serious complication in spine surgery
When comparing the success rates obtained with the constant-current stimulator to those obtained with the constant-voltage stimulator in pattern 1, we found no significant differences in the left-side muscles, except for the left abductor hallucis (p = 0.03), where we observed a significantly higher success rate with the constant-voltage stimulator
When comparing the success rates obtained with the constant-current stimulator to those obtained with the constant-voltage stimulator in pattern 2, we found no significant differences in the right-side muscles, except for the right deltoid (p = 0.03), abductor hallucis (p = 0.001), and quadriceps (p = 0.03), where we observed a significantly higher success rate with the constant-voltage stimulator
Summary
Iatrogenic spinal cord injury is the most serious complication in spine surgery. Transcranial electrical stimulation of motor-evoked potentials (TES-MEP), an intraoperative spinal cord monitoring technique, is an essential tool used to avoid iatrogenic spinal cord injury during risky surgeries, such as scoliosis surgery, spinal cord tumour surgery as well as severe spinal canal stenosis due to degenerative spondylotic changes. We have found that, in several instances, constant-voltage stimulation proves better than constant-current stimulation in terms of successfully evoking CMAPs5. Transcranial stimulation involves an anode and a cathode placed on opposite sides of the body It predominantly stimulates the brain on the anode side and evokes large potentials in contralateral muscles[4,7,8]. 2 msec 50 μsec stimulation in terms of successfully evoking CMAPs, no previous study has reported whether the methods generate responses equivalent to monophasic stimulation during intraoperative monitoring. This information is important for surgeons, providing knowledge of the weak point on intraoperative spinal cord monitoring
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