Significant Underreporting of Preoperative Hyposmia in Patients Undergoing Endoscopic Skull Base Surgery: Discrepancies Between Subjective and Objective Measurements.

The assessment of baseline olfactory function before endoscopic skull base surgery (ESBS) has been relatively limited compared with analysis before functional endoscopic sinus surgery (FESS). Our study addresses this knowledge gap, assessing preoperative olfactory function in ESBS and FESS and elucidating any differences.  We conducted a retrospective review of patients undergoing anterior ESBS or FESS at a single institution between 2021 and 2022. We included 171 patients and compared their reported and measured preoperative olfactory function using the Sino-Nasal Outcome Test questionnaire and the 40-item University of Pennsylvania Smell Identification Test.  Of the 171 patients included in this study, 30% of patients underwent ESBS and 70% underwent FESS. Of all patients, only 57% correctly reported their objective preoperative olfactory function. Of the 36 ESBS patients with measured preoperative hyposmia, only 31% correctly reported hyposmia, while 69% incorrectly reported normosmia. This distribution significantly differs (  < 0.0001) from the FESS subset (89 patients), with 64% correctly reporting hyposmia and 36% incorrectly reporting normosmia.  Our analysis demonstrates higher than anticipated underreporting of preoperative hyposmia in patients undergoing ESBS as well as discrepancies between subjective and objective olfactory functions in the FESS population. The results highlight several gaps in knowledge regarding perioperative olfactory function that would be best examined with more thorough pre- and postoperative objective olfactory testing. This analysis demonstrates significant prognostic uncertainty for patients and providers and creates significant medicolegal uncertainty regarding the appropriate attribution of postoperative olfactory loss in cases without objective preoperative testing.