A Cadaveric Study to Evaluate the Reaches of Far Lateral and Expanded Endonasal Endoscopic Approaches to the Brainstem: Does a Combined Approach Result in Better Visualization versus either Approach Alone?

Objective: A cadaveric study to evaluate the reaches of far lateral and expanded endonasal endoscopic approaches to the brainstem. Does a combined approach result in better visualization versus either approach alone?

Introduction: The far lateral is a well-known approach that allows access to lesions posterior, lateral and anterior to the brainstem. More recently, endoscopic endonasal approaches have become a widely used approach to the midline skull base. Continued advances have expanded the midline approach from the crista galli to the craniocervical junction. Many continue to push the envelope and have ventured out laterally with their endoscopic approaches. For example, Avella et al, described an endonasal approach with an anterior petrosectomy and medial condylectomy that provided a wide corridor exposing the ventrolateral surface of the brainstem. Being at an institution where we are very familiar with expanded endoscopic endonasal skull base approaches, we wanted to determine whether the combination of both approaches would result in better visualization versus either approach alone.

Methods: This is a cadaveric feasibility study where 5 heads were used and measurements were taken to determine the anterior extent of a far-lateral approach and the lateral extent of an endonasal endoscopic approach to the brainstem. We also commented on the location of vital structures such as perforating vessels and cranial nerves and if they were restricting/obstructing in any way. The endonasal approaches would be limited to standard expanded midline technique without lateral bony removal or exposure. The far lateral approach was done in standard fashion.

Results: We discovered that the combined approach allowed significantly improved visualization around the brainstem. This allowed us to work safely around the brainstem with less concern about traction on the brainstem and avoiding perforators off the basilar artery and its branches.

Conclusion: This combined approach demonstrated superior visualization of the brainstem and surrounding structures. This gave us the ability to work more safely around delicate structures and seemed to minimize injury to the brainstem and its surrounding cranial nerves and blood vessels. Doing a combined approach would also allow you to stage a procedure if necessary (i.e., a large epidermoid cyst) to avoid surgeon fatigue and to decrease patient time under anesthesia. More studies would need to be done to determine if this actually reduces patient morbidity.