Intraoperative study of afferent and efferent connections in the upper lumbar spinal cord - Part 2: genitoinguinal...

To describe spinal reflex responses mediated by the upper lumbar spinal cord in humans and observed intraoperatively under general anesthesia.

Thirty-one participants undergoing spinal surgery were enrolled. Reflex responses were recorded from the iliopsoas, adductor magnus, and rectus femoris muscles following electrical stimulation of the cutaneous territory innervated by the genitofemoral and ilioinguinal nerves using a multipulse train paradigm.

Reflex responses were obtained in the iliopsoas, adductor magnus, and rectus femoris muscles, with distinct recordability rates and neurophysiological characteristics. The most robust and consistently reproducible responses were recorded in the iliopsoas muscle; this response pattern was termed the Genitoinguinal Reflex (GNIR).

GNIR components can be reliably elicited in humans under general anesthesia. Stimulation frequently produced proximal thigh movement, which may interfere with surgery and therefore necessitates intermittent application when safe.

The identification of these reflex responses expands current knowledge of human spinal cord circuitry. Moreover, GNIR recording may represent a useful intraoperative neurophysiological technique for monitoring the integrity of the upper lumbar spinal cord, L1-L2 nerve roots, and the genitofemoral, ilioinguinal, and femoral nerves.