Neurophysiologic intraoperative monitoring during surgery for tethered cord syndrome.

Tethered cord syndrome (TCS) occurs when the distal spinal cord is adherent to inelastic tissue. This results in sensorimotor deficits in the lower extremities, bowel and bladder dysfunction, and musculoskeletal deformities. Tethered cord syndrome is often found in childhood, but may be first noticed in adults as well. The symptoms are usually progressive unless halted by surgical correction of the spinal cord tethering. Surgery for TCS can be complicated by inadvertent injury to nerves that are either embedded in the tether or in close proximity to it. In an attempt to reduce this iatrogenic injury, neurophysiologic intraoperative monitoring is used to identify neural structures in the surgical field and reduce the risk of injury. Many neurophysiologic intraoperative monitoring paradigms have been used in TCS surgery, including free running and stimulated electromyography of the muscles of the lower extremities, external anal and external urethral sphincter electromyography, tibial, clitoral, and dorsal penile somatosensory evoked potentials, and bulbocavernosus reflex testing. It is widely believed that neurophysiologic intraoperative monitoring helps reduce morbidity of TCS surgery, but data supporting this are limited. This article will review the various neurophysiologic intraoperative monitoring paradigms that can be used in TCS surgery and discuss the data supporting the use of these paradigms.