Intraoperative neurophysiology in tethered cord surgery:Techniques and results

©AANS, 2017. OBJECTIVE The aim of this study was to establish optimal electric stimulation parameters for intraoperatively monitoring the bulbocavernosus reflexes (BCRs) in infants. METHODS The authors retrospectively reviewed the medical records of all infants (age < 24 months) who had undergone an untethering operation for tethered cord syndrome between May 2013 and February 2014 at a single institution and whose baseline BCR had been elicited during surgery. Using different combinati ons of stimulation parameters-number of stimulation pulses: 4 or 8 pulses, interpulse interval: 1, 2, or 5 msec, and polarity of stimulation: biphasic or monophasic-the authors compared the relative mean amplitude of 10 BCR responses (rmaBCRs) to each combination of parameters. RESULTS The rmaBCRs were larger with the 8-pulse stimulations than with the 4-pulse stimulations (p < 0.0001). There was a tendency, though not statistically significant, for larger rmaBCRs to be obtained with the longer interpulse interval in the 8-pulse stimulation (p = 0.1289). The biphasic stimulation produced larger rmaBCRs than the monophasic stimulation (p = 0.0005). CONCLUSIONS Biphasic 8-pulse stimulations with 5-msec or 2-msec intervals yield the largest BCR responses. Considering that an 8-pulse stimulation with 5-msec intervals may overlap the onset of the BCR, a biphasic 8-pulse stimulation with 2-msec intervals is recommended as the optimal stimulation paradigm to monitor intraoperative BCRs in infants