The trend in IONM usage in the current literature, which may be a direct consequence of improved efficacy of the procedure, and the development of optimized treatment algorithm [6]. Nevertheless, it is well known that the use of somatosensory evoked potentials (SEPs) alone may be ineffective in detecting a motor tract deficit [7, 8]. As a result, various methods for monitoring the motor tract of the spinal cord have been developed. The most commonly used stimulation technique is transcranial electric stimulation (TES) of the primary motor cortex by corkscrew electrodes placed in the scalp, to produce myogenic motor evoked potential[9]. The combination of SEPs and TES-MEPs provides global monitoring coverage of spinal cord function [10]. Based on the available evidence, it is recommended that the use of multimodality neuromonitoring be considered in complex spine surgery where the spinal cord or nerve roots are deemed to be at risk [11].
Iatrogenic spinal cord injury is the most feared complication of complex spine surgery. The incidence of neurological complications for spinal deformity surgery has been estimated by the Scoliosis Research Society as 1%, except when a combined approach is used, where the rate increases to 1.87% [1]. Intraoperative neuromonitoring (IONM) techniques are usually implemented during spine surgery to avoid nefarious abuse of the nervous system, which can cause postoperative problem [2].~In 1992 a Scoliosis Research Society study concluded that the use of intraoperative spinal cord neurophysiological monitoring during operative procedures including instrumentation should be considered ''a viable alternative as well as an adjunct to the use of the wake-up test during spinal surgery'' [5]. The benefit of using neuromonitoring has been validated by numerous studies involving scoliosis correction, revision surgeries and vertebral osteotomies.