Simultaneous combination of electromagnetic navigation with visual evoked potential in endoscopic transsphenoidal surgery: clinical experience and technical considerations

Objective: The combination of electromagnetic navigation with continuous monitoring techniques allows for the best available anatomic and real-time functional intraoperative monitoring. Methodological aspects and technical adaptations for this combination of methods and the results from 19 patients with tumors in the pituitary region are reported. Methods: We retrospectively identified 19 patients who were treated with transsphenoidal surgery using high-resolution endoscopy (eTSS) at our hospital between June 2015 and June 2016. All patients underwent surgery under electromagnetic navigation with visual evoked potential (VEP) monitoring. The cases were reviewed for information on disease, and the distance between the patient tracker and emitter was measured. Results: In 19 patients, 17 had pituitary adenomas, 1 had a Rathke cleft cyst, and 1 had an arachnoid cyst. The optimal distance between the patient tracker and emitter was 20–25 cm. VEP monitoring could be performed with unaffected recording quality under electromagnetic navigation. Also we were able to perform the registration and eTSS at this distance using both navigation and VEP monitoring. Conclusions: We performed eTSS for pituitary tumor by simultaneously using electromagnetic navigation and VEP. The optimal distance between the emitter and tracker minimizes VEP monitoring noise and allows accurate electromagnetic navigation.