Intraoperative study of afferent and efferent connections in the upper lumbar spinal cord - Part 1: Cremasteric reflex.

OBJECTIVE

To evaluate the feasibility, neurophysiological characteristics, and stimulation and recording parameters of the cremasteric reflex (CMR) in males under general anesthesia.

METHODS

Fifteen male patients undergoing spinal surgery with intraoperative neurophysiological monitoring were enrolled. CMR responses triggered using a multipulse train stimulation paradigm were recorded intraoperatively from the cremaster muscle following electrical stimulation of the upper medial thigh.

RESULTS

Following ipsilateral upper medial thigh stimulation, CMR responses were recorded in 23 of 30 cremaster muscles across 15 participants, yielding an overall recordability rate of 76%. Mean onset latency was 26.3 ms, and mean peak-to-peak amplitude was 20.0 µV. Recordability was lower in participants with a body mass index greater than 25 kg/m2.

CONCLUSIONS

CMR responses can be elicited in males under general anesthesia using multipulse train stimulation. Higher BMI appears to negatively affect response recordability. Electrical stimulation frequently induced proximal thigh movement, which may interfere with the surgical field; therefore, recordings should be performed intermittently and only when surgically safe.

SIGNIFICANCE: This study provides the first demonstration of intraoperative CMR elicitation in humans under general anesthesia. This technique may represent a novel adjunct for monitoring the functional integrity of the upper lumbar spinal cord, L1-L2 nerve roots, and the genitofemoral and ilioinguinal nerves.