Endoscopic trans-nasal craniotomy

Abstract

The ventral skull base presents a unique surgical challenge. Disease is often closely associated with critical structures and morbidity from therapy can be high. The main stay of anterior skull base approaches were combined trans-facial incisions with craniotomy. Skull base surgery is a dynamic subspecialty and the last decade has witnessed the application of endoscopic techniques to the ventral skull base using an endonasal corridor. The transition from external approaches to an endonasal corridor has not been without controversy. This thesis addresses several critical issues in managing skull base pathologies via an endoscopic trans-nasal craniotomy. The ability of the surgeon to remain orientated amongst a surgical field, which at first appears without landmarks, is critical. The orbital floor or maxillary line defines the skull base. This landmark is robust and provides safe passage in endoscopic surgery. The nasoseptal flap has revolutionised the ability to reliably reconstruct large skull base defects. However, data was lacking and a systematic review of the published outcomes from both free and vascularised skull base operations demonstrate the superiority of vascularised reconstructive tissue. The implications of nasoseptal harvest for subsequent sinonasal function were assessed using validated outcomes for patients, having had tumour surgery, with and without a nasoseptal flap. Sino-nasal function is not impaired long-term. The ability to modify the nasoseptal flap to reconstruct even small defects from pituitary surgery, without adversely affecting sino-nasal function, and particularly smell, was a critical step in refinement. Finally, a multi-centre study on endoscopic versus open surgical outcomes from the management of olfactory neuroblastoma was performed. This study demonstrated that even the most advanced tumours were being managed via endoscopic techniques with as good or better outcomes to traditional approaches. The ability to define the tumour site and achieve clear surgical resection margins may account for this observation. The endoscopic trans-nasal craniotomy has evolved dramatically in the past decade. The ability of the surgeon to locate the skull base, robustly reconstruct the defect, retain sino-nasal function and preserve smell are key advances. These evolutions have shifted the approach to difficult tumours, such as olfactory neuroblastoma and have improved the outcomes for patients with skull base pathologies.