The Clinical Utility of Neuromonitoring in Endoscopic Endonasal Pituitary Surgery

Background: Somatosensory evoked potentials (SSEPs) and extraocular muscle electromyography (EMG) are neuromonitoring modalities often used during endoscopic endonasal pituitary surgery. The utility and necessity of electrophysiological monitoring for para-sellar surgery is not well documented.

Objective: To analyze the clinical effectiveness of SSEPs and EMG in endoscopic endonasal pituitary surgery. Our institution transitioned away from routine neuromonitoring to a more selective protocol for neuromonitoring use during the study period, and we sought to identify if this selective use led to negative outcomes or increased rate of utility due to better patient selection.

Methods: We retrospectively reviewed 311 patients who underwent endoscopic endonasal pituitary surgery between January 2013 and July 2018 at our institution by a single neurosurgeon. Nonsellar pathology and extended endonasal approaches other than transsellar or transcavernous were excluded. Variables collected included demographics and patient symptoms, pathological diagnosis, tumor characteristics (hormone profile, invasion of local structures, size, and recurrence), neuromonitoring modality, evidence of monitoring utility, and clinical outcomes.

Results: The patients included had a mean age of 51 (SD = 16.6 years) and 55.6% were female. Of the 311 cases, 215 (69.1%) were monitored by SSEPs, 84 (27.0%) were monitored by SSEPs and EMG, and 96 (30.9%) cases utilized no monitoring. There were 12 cases where SSEP changes were falsely positive. No SSEP change fit criteria for exhibiting utility (i.e., SSEP showing a true positive change or evidence of the surgeon relying on the monitoring during surgery). Extraocular muscle EMG showed activity during seven cases with five true positive and two false-positive results. EMG fit utility criteria for 20 cases overall, including the 5 true positive changes and 15 other cases where EMG was useful to ensure no free-run activity during tumor dissection (true negative). EMG demonstrated significantly more utility than did SSEP (χ ², p < 0.001). All EMG cases demonstrating clinical utility were in patients with a tumor invading the cavernous sinus space. By the end of the study period, neuromonitoring was used in 41% of patients as opposed to 87% of patients before the protocol change. There was no change in patient outcomes over this period, as measured by new neurological deficit after surgery, (χ ², p = 0.93).

Conclusion: We did not find any cases where SSEP monitoring demonstrated a true positive change in EEA for pituitary surgery. SSEPs show little clinical utility within endoscopic endonasal pituitary surgery and surgeons should reevaluate the need for SSEP monitoring in these cases. EMG neuromonitoring should be utilized in cases demonstrating cavernous sinus invasion due to its utility both for positive findings (warning) and negative findings (assurance).

Publication History

Publication Date:
12 February 2021 (online)