By observing these warning criteria, surgery can be safely carried out if changes of signal amplitudes are within the threshold boundary. Future studies should aim to validate and refine the "warning criteria" for intraoperative neurophysiologic monitoring in different surgery. / During stable anesthesia, experiments were completed in 31 pigs. A decrease in SEP amplitude > 25% and / or TceMEP amplitude > 65% was associated with substantial risk of postoperative motor deficit. In addition, rapid deterioration of signal within 5 min of an event, and / or a lack of signal recovery within 30 min after the initial deterioration were also predictors of postoperative paraplegia or weakness. These findings also correlated well with radiological changes in the spinal cord. The sensitivity and specificity for TceMEP to predict adverse neurologic outcome were 100% and 90.5%, respectively. / In a porcine model of direct compression and distraction of the exposed spinal cord, we measured the perioperative changes in SEP and TceMEP. This was correlated with postoperative motor function using the modified Tarlov scale. Magnetic resonance diffusion tensor imaging of the spinal cord was also performed to assess the anatomical extent of injury three days after surgery. / The spinal cord is at risk of injury during complex operations of the spine or aorta, and may result in catastrophic long term disability. Intraoperative monitoring with somatosensory evoked potential (SEP) and transcranial electric motor evoked potential (TceMEP) are commonly performed to assess the integrity of the sensory and motor pathways, respectively. The purpose of this study was to identify the minimum changes in signal amplitudes, beyond which postoperative neurologic deficit may occur. / Liu, Quanmeng. / Adviser: Matthew Tu Chan. / Source: Dissertation Abstracts International, Volume: 73-02, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 87-103). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.