[Neurophysiological monitoring in spine surgery. Spinal cord stimulation]

Neurophysiological monitoring in spine surgery can be performed by a number of methods, although there is no general agreement about which is the best.

The aim of this study was to evaluate our experiences using the method of spinal cord stimulation with recording carried out on the peripheral nerve.

We studied 51 patients with scoliosis who were submitted to surgical correction. Stimuli were administered with the cathode located in the dorsal epidural space, two levels above the curve to be corrected, and recording was performed on the posterior tibial nerve in the popliteal fossa.

Potential was obtained in 78% of cases, with a very low number of averages and the maximum reduction in the amplitude of the potential was found to be 33%. Spinal cord stimulation evokes muscular responses in several muscles and sensory responses in the sural nerve. None of the patients who were monitored using this method presented postoperative neurological deficits added to their previous pathology.

The neurogenic potentials obtained by epidural spinal cord stimulation are very useful for monitoring spine surgery because they are very stable, they can be obtained quickly, they avoid the need to interfere with the anaesthetist's field and because, albeit to a small extent, they may contain information about motor pathways. The main drawback is that it is not always possible to place the electrode and that in 22% of cases we have not managed to obtain the motor component and we have therefore had to be cautious in evaluating it, since its disappearance would only give rise to a partial reduction in the potential.