Effectiveness of intraoperative monitoring of the bulbocavernosus reflex for predicting postoperative pelvic disorders in the surgical treatment of distal spine tumors

The study evaluated the diagnostic effectiveness of changes in the parameters of the bulbocavernous reflex during intraoperative neurophysiological monitoring in the surgical treatment of caudal spinal cord tumors. The study was performed during examinations and neurosurgical treatment of 58 patients suffering from intradural extramedullary and intramedullary tumors of the caudal spinal cord. In 23 (39.7%) patients, the tumors were localized at the level of the lower thoracic–lumbar spine (Th11–L1), and in 35 (60.3%) patients, they were at the level of the lumbosacral spine (L2–S2). Pelvic organ dysfunction was assessed based on the extent of neurogenic bladder symptoms before surgery, 10–14 days after surgery, and a year later. The bulbocavernous reflex was recorded in response to genital nerve stimulation, with a series of three pulses lasting 0.5 ms each, and the repetition rate of the series was 2 Hz. The intensity of the stimulation current was 75% of the maximum intensity. The bulbocavernous reflex was registered from the external anal sphincter muscles. During intraoperative monitoring, the bulbocavernous reflex remained stable in 49 patients. In this group, pelvic dysfunction was not observed immediately or 12 months after surgery. Persistent changes in motor response parameters were registered in nine patients; seven and eight cases of dysuric disorders were observed immediately after surgery and 12 months after surgery, respectively. Persistent changes in the bulbocavernous reflex during intraoperative monitoring were significantly more often associated with pelvic organ dysfunction immediately after surgery (χ² = 36,323; p < 0.001) and 12 months after surgery (χ² = 32,284; p < 0.001). The sensitivity and specificity of intraoperative monitoring of the bulbocavernous reflex in assessing the risk of pelvic dysfunction in the postoperative period were 96.1% and 100%, respectively. In general, postoperative pelvic organ dysfunction is a frequent cause of neurological complications following surgical treatment of caudal spine tumors. Therefore, during surgery, neurophysiological monitoring is implemented to control pelvic organ functions, including the registration of the bulbocavernous reflex.