Spinal cord and nerve root monitoring during surgical treatment of lumbar stenosis

The author describes application of intraoperative neurophysiologic monitor ing to surgical treatment of lumbar stenosis. Benefits of somatosensory and motor evoked potential studies during surgical correction of spinal deform ity are well known and documented. Free-running and evoked electromyographi c studies during pedicle screw implantation is an accepted practice at many institutions. However, the functional integrity of spinal cord, cauda equi na, and nerve roots should be monitored throughout every stage of surgery i ncluding exposure and decompression. Somatosensory evoked potentials monito r overall spinal cord function. Intraoperative electromyography provides co ntinuous assessment of motor root function in response to direct and indire ct surgical manipulation. Electromyographic activities observed during expo sure and decompression of the lumbosacral spine included complex patterns o f bursting and neurotonic discharge. In addition, electromyographic activit ies at distal musculature were elicited by impacting a surgical instrument or graft plug against bony elements of the spine. All electromyographic eve nts provided direct feedback to the surgical team and were regarded as a ca use for concern. Simultaneously monitored evoked potential and electromyogr aphic studies protect spinal cord and nerve roots during seemingly low-risk phases of a surgical procedure when neurologic injury may occur and the pa tient is placed at risk for postoperative myelopathy or radiculopathy.