Evolution and Role of Intraoperative Neurophysiological Monitoring in Intramedullary Spinal Cord Surgery: A 2-Year Series from Saudi Arabia

Abstract

Introduction: Despite recent advances in neuroimaging and microsurgical techniques, surgical resection of spinal cord tumours remains a challenge. However, the evolution with advances and refinement of neurophysiological equipment and methodologies, intra-operative neurophysiolo- gical monitoring (IONM) is now regarded as an essential adjunct to the surgical management of intramedullary spinal cord tumours. This study aims to report our preliminary experience with IONM and emphasise its effective role of achieving maximum tumour resection and minimising neurological injury. Methods: This is a retrospective study performed at our institution between July 2012 and August 2013. It included a cohort of 6 consecutive patients presented with intramedullary spinal cord tumours. Their mean age was 26 years (range, 4 months - 37 years), all were males, and the mean follow up was 11.6 months. Results: We combined the use of somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) in spinal cord surgery. SSEPs are monitored during the incision of the dorsal midline of the spinal cord and this was used in two of our patients and MEPs were used as an essential monitoring during the tumour resection. In addition, we used free-running electromyography (EMG) and muscle MEPs (mMEPs) during tumour resection. Four of our patients (two with ependymoma, one with ganglioglioma, and one with pilocytic astrocytoma) had complete tumour resection and two patients (pilocytic and diffuse astrocytoma) had IONM changes during surgery and had partial tumour resection. At 6-month follow up all our patients had made a good recovery with no new neurological sequelae. Conclusion: This small series and literature review is presented to add and improve the understanding of IONM in intramedullary spinal cord procedures and to reinforce the importance of IONM in optimising tumour resection and neurological outcome. Our series confirm that without D-wave monitoring, free-running EMG and MEP monitoring during tumour resection remain an important adjunct. We also draw attention to the fact that changes in the free-running EMG occur before any changes in the MEPs are noted.