Olfactory outcomes after transsphenoidal endonasal surgery

Background: The endonasal approach is the gold standard for the resection of pituitary tumours, with either microscopic endonasal transsphenoidal (MET) or endoscopic endonasal transsphenoidal (EET) technique. Advantages and disadvantages of both techniques have been widely described in the literature, although limited attention has been paid to its impact on the sense of smell. Objective: The present study aims to quantify the effect of transnasal surgery on pituitary patients and examine olfactory outcomes. Methods: A prospective cohort study assessing the sense of smell of 20 patients (10 MET and 10 EET) pre-operatively. Olfactory function was re-assessed 6 months after surgery, using the University of Pennsylvania Smell Identification Test (Sensonics Inc., Haddon Heights, NJ). Results: The UPSIT (Sensonics Inc.) results showed a median pre-operative score of 33 (IQR 31-37.5) (normosmia). The median post-operative result was 25 (IQR 19.5-32), consistent with moderate microsmia. Twenty percent of the patients had normal olfactory function post-operatively, all of whom were from the EET group. Twenty percent had mild microsmia, equally divided in MET and EET subgroups. Seven patients had severe microsmia. Four patients were completely anosmic at 6 months follow-up. Conclusions: Patients undergoing a transsphenoidal procedure are at risk of olfactory disturbance post-operatively, which may include loss of the sense of smell. This information is relevant to the patients' perioperative experience, and should be incorporated into counselling with regards to outcomes and expectations. Although the study size is small, the study results suggest the ETS technique may be less traumatic for the olfactory function. A larger study powered to fully examine potential differences in olfactory outcomes following ETS and MTS is warranted.