Objectives To emphasise the importance of motor evoked potential (MEP) recordings from a simple urethral sphincter electrode along with routine use of bulbocavernosus reflex recordings, anal sphincter and other lower limb muscle free running and stimulated EMG and MEP’s, and SEP techniques for sphincter preservation.
Design Case report.
Subjects Patients with conus or other spinal lesions at risk of postoperative sphincter disturbance.
Methods Transcranial ‘train of 5’ stimulation (5 pulses, interstimulus interval 4msec, 200 µsec pulse width) was applied, with recordings from the urethral sphincter (small electrode taped to Foley catheter to lie just inside the urethra, referred to nearby needle anteriorly in mons pubis) and anal sphincter (paired needle electrodes in both left and right sides of external sphincter).
Results Intraoperative stimuli of structures during dissection at one point gave a motor response confined to the urethral sphincter suggesting that these fibres may have been considered non-functional and cut had these not been assessed separately. Urethral sphincter MEP’s during the dissection confirmed that these motor fibres remained in continuity throughout.. The patient was intact after tumour removal.
Conclusions This is an avant-garde technique by which we managed to save the nerve supply to the urethral sphincter and eventually urinary continence which would have been compromised if separate urethral monitoring was not attempted along with usual intraoperative nerve monitoring. We believe its first in the UK.
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