Optimising motor evoked potentials for spinal cord monitoring

During complex surgery, during which the nervous system is at risk, intraoperative neurophysiological monitoring (IONM) is used to detect and prevent neurologic injury. Surgical procedures during which IONM is used range from intramedullary tumour resection to scoliosis correction and endovascular aneurysm repair to vestibular schwannoma resection. The goals of IONM can be divided into 'mapping' and 'monitoring' of the nervous system. During 'mapping' the goal is to localise anatomical structures during surgery. The goal of 'monitoring' is to (continuously) monitor neurological functions. For monitoring of the spinal cord, the motor tracts can be monitored using muscle motor evoked potentials (mTc-MEPs) and spinal motor evoked potentials (D-waves) elicited by transcranial electrical stimulation. For monitoring of the sensory tracts, somatosensory evoked potentials (SSEPs) can be used. It is recommended that both sensory tracts and motor tracts are monitored during surgical procedures where the spinal cord is at risk.IONM is increasingly used worldwide. The amount of clinical evidence demonstrating the added value of IONM is increasing. It is generally accepted that IONM can predict the post-operative neurological outcome, but whether the use of IONM can also help to prevent post-operative neurological damage has still to be proven. The primary aim of this thesis is to optimise motor evoked potentials for spinal cord monitoring by optimising elicitation and recording of mTc-MEPs (Part 1) and investigating the effects of physiological and pharmacological parameters on mTc-MEPs (Part 2). Furthermore, the clinical applications of spinal cord monitoring were explored (Part 3)