Endoscopic Anatomy for Transnasal Transsphenoidal Pituitary Surgery in the Presence of a Persistent Trigeminal Artery

Abstract

Endoscopic procedures are becoming increasingly important for transnasal transsphenoidal approaches to the skull base and particularly for pituitary surgery. A persistent trigeminal artery (PTA) is rare. Its presence, if it goes unnoticed or if the surgeon is not aware of such a variant, may endanger the success of surgery. During an endoscopic inspection using a supraorbital approach in a fresh cadaveric specimen in which the arteries had been injected with latex glue, the presence of an anomalous intracranial artery, suggestive for PTA, was disclosed. The specimen was then fixed and a CT scan with 3D reconstruction of the circle of Willis was done to evaluate the imaging of such an anatomical variation. Thereafter an endoscopic transsphenoidal approach to the pituitary fossa was performed, to verify the endoscopic anatomy. The performed CT scan allowed visualization of the entire course of the anomalous vessel, confirming a PTA. During the endoscopic transsphenoidal approach, the presence of the vascular anomaly, altering the bony bulging of the internal carotid artery on the lateral side of the sphenoidal roof, was disclosed. The parasellar course of the PTA could be exposed by drilling the overhanging bone. The presence of the anatomical variant did not interfere with surgical manoeuvres and the procedure, simulating a transsphenoidal approach to the pituitary, could be safely completed. Variants such as PTA are rare and routine preoperative imaging for pituitary procedures does not always include studies to detect this vascular anomaly. The occasional intraoperative detection of a PTA during an endoscopic transsphenoidal procedure can be managed; almost any surgical manipulation is possible and pituitary surgery can be successfully completed, provided the surgeon is aware of the possible existence of this variant and its irregular anatomical course. However, the presence of a PTA may have dramatic consequences if surgery is directed to the lateral parasellar region, as for intracavernous lesions; in these cases a complete neuroradiological study including MRI-angiography and possibly CT-angiography is advised.