Cranial Nerve Monitoring and Intraoperative Cranial Computer Tomography for Safe Resection of Intra- and Periorbital Tumors

Background: During surgery for intra- or periorbital tumors, we recorded evoked compound muscle action potentials (ECMAPs) from the extraocular and intraocular muscles. Intraoperative cranial computer tomography (iCCT) allows on the one hand resection control during surgery and on the other hand location control of intraocular needles. Methods: We analyzed patients with sphenoorbital and orbital tumors for safe and complete resection from January, 2012 to October, 2013. The ECMAPs were recorded through a surface electrode and/or intraorbital needle electrodes. For further neuromonitoring control and resection control, we performed iCCT. Results: We analyzed 15 patients with sphenoorbital tumors: 11 meningiomas, 3 fibrous dysplasias, 1 metastasis. For 15 patients, ECMAPs were successfully recorded from the intraocular muscles. Five patients were recorded by extraocular surface muscle monitoring. Ten patients did not exhibit any postoperative deterioration of oculomotor nerve function. Three patients exhibited a temporary deterioration of oculomotor nerve function immediately after surgery. Two patients had a preoperative permanent functional deficit. In 12 patients tumor were completely resected and in 3 patients small tumor rest was revealed by iCCT. Conclusion: ECMAP recordings from the intraocular muscles precisely indicated the locations of cranial nerves better than surface electrodes. The iCCT enable tumor resection control and neuromonitoring control for intraorbital neuromonitoring.