Intraoperative EMG monitoring in surgery of tumor in the floor of the fourth ventricle

Objective To analyze the protective role of intraoperative EMG monitoring in surgical removal of tumors related to the floor of the fourth ventricle and its influencing factors.Methods Intraoperative EMG monitoring was performed during the surgical removal of 32 patients with brain tumor, admitted to our hospital from January 2007 to December 2010; among these 32patients, 11 was conformed as having medulloblastoma, 9 ependymoma, 6 brain stem cavernous hemangioma, 4 brain stem exogenous glioma and 2 hemangioblastoma of the dorsal brain stem. The influencing factors of intraoperative EMG monitoring and the possible damage of cranial nerve nuclei caused by these surgical procedures were analyzed.Results Twenty-one patients enjoyed total removal, 9 sub-total removal and 2 partial removal. Good function protection of patient's posterior cranial nerves was noted in 9 patients, mild impairment in 18 patients, and moderate dysfunction in 5 patients.The influencing factors of EMG monitoring included leaking electric current caused by bipolar coagulation, excessive use of muscle relaxant drugs, changes in depth of anesthesia, and rapid changes of patient′s temperature, saline temperature and blood pressure. Conclusion The intraoperative EMG monitoring can provide evidence about the location of the cranial motor nuclei during the surgical removal of the tumor related to the floor of the fourth ventricle and the function protection of patient’s posterior cranial nerves. Key words: Brain stem neoplasm;  Cranial motor nuclei;  Intraoperative EMG monitoring