INTRAOPERATIVE MOTOR AND SENSORY MONITORING OF THE CAUDA-EQUINA

A SET OF standard techniques to monitor the motor and sensory function of the cauda equina is proposed for surgery in the lumbosacral spinal canal for the release of a tethered cord or the removal of a neoplasm . Continuous loudspeaker-controlled recording of electromyographic act ivity in four leg muscles of both sides supplied the surgeon with imme diate feedback on injury to any of the motor roots from the second lum bar to the fourth sacral segment. Continuous recording of tibial nerve somatosensory evoked potentials yielded information about the functio nal state of parts of the lumbosacral sensory pathways. Motor roots co uld be identified by electrical stimulation in the operating field wit h bipolar stimulation forceps and recording of compound muscle action potentials from the leg muscles. Sensory nerve roots could be identifi ed by nerve root somatosensory evoked potentials recorded from the sca lp after the electrical stimulation of the exposed nerve. This set-up is a combination of previously developed monitoring techniques and pro vides the surgeon with functional information: 1) continuous feedback on the state of the endangered motor and sensory function of the cauda equina; and 2) rapid anatomical identification of nerve roots and the ir distinction from fibrous or neoplastic structures.