Olfactory outcomes after endonasal skull base surgery: a systematic review

For the last two decades, endonasal approach has been regularly applied to treat skull base lesions. However, postoperative olfactory dysfunction remains an unsolved problem. This systematic review aimed to identify factors that might affect postoperative olfactory prognosis of patients undergoing endonasal surgery for resection of sellar/parasellar lesions. The literature search was conducted comprehensively to exhaust studies which focused on patients' olfaction with objective olfactory assessments after endonasal skull base surgery. We sought to characterize the potential factors that might affect postoperative olfactory outcomes. Nineteen articles met inclusion criteria. We found that (1) endoscopic surgery was beneficial to patients' olfactory prognosis than microscopic surgery (incidence of postoperative decreased olfactory function: 18.48% (39/211) for the endoscopic group and 36.88% (52/141) for the microscopic group, P < 0.01); meta-analysis for single rate, 20% (95% CI 9-30%) for the endoscopic group and 35% (95% CI 0-72%) for the microscopic group); (2) harvesting septal flaps was an unfavorable factor for olfactory recovery and the rescue flap technique should be preferred compared with the HB flap; (3) no evidence showed that resection of the middle turbinate was detrimental to recovery of olfaction. Patients undergoing endoscopic endonasal surgery may have better olfactory outcomes than those undergoing microscopic endonasal surgery for resection of sellar/parasellar lesions. Special attention should be paid when using septal flaps is planned and the rescue flap technique should be the preferred choice. After resecting the middle turbinate, patients' olfaction still has a great chance of returning to the baseline. More homogeneous and high-quality studies are needed for further assessment.