In this study, the research team will investigate the incidence and etiology of olfactory dysfunction following endoscopic endonasal skull base surgery, by combining clinical assessments with histomolecular analysis.

The incidence of olfactory dysfunction following endoscopic endonasal skull base surgery remains unclear in current research, and the results vary widely. Additionally, the pathophysiology of this postoperative olfactory dysfunction and the impact of this surgery on the trigeminal system has not been investigated to date. In this study, the investigators developed a state-of-the-art clinical pipeline with olfactory and trigeminal assessments, prior to and following endoscopic endonasal skull base surgery. Furthermore, the investigators will collect surgical waste tissue from the posterior septal mucosa, which is removed during this procedure to gain access to the sphenoid sinus and the (para)sellar region. By performing histomolecular analysis, the research group aims to elucidate the pathophysiology of olfactory dysfunction following this surgery.

Inclusion Criteria:

• Adult patients scheduled for endoscopic endonasal skull base surgery

Exclusion Criteria:

• Pre-existing anosmia
• Patients has a history of previous endoscopic endonasal skull base surgery

All patients presenting with an indication for endoscopic endonasal skull base surgery for lesions in the anterior skull base (the parasellar region)