The Expanded Endonasal Approach to Skull Base Meningiomas

Abstract

Classic approaches to the skull base have involved either anterior, middle, or posterior fossa craniotomies, with retraction of the brain to expose the relevant intracranial anatomy, often with separate approaches from the midface or temporal bone to expose the relevant extracranial anatomy. The expanded endonasal approach (EEA) to skull base tumors was introduced as an alternative minimally invasive strategy for selected tumors in the late 1990s/early 2000s [3, 11, 12]. It offered some significant advantages in selected tumors, including the elimination of the need for skin incisions, the elimination of brain retraction, and the addition of excellent visualization of critical structures. In the early part of the experience with EEA, there was significant controversy about its safety, with critics of the approach citing the risk of infection and the possibility of cerebrospinal fluid leakage as a consequence of the procedure. However, early experience showed the safety of the procedure, especially relative to traditional skull base approaches, in selected tumors. We reported our experience in 800 consecutive patients performed by a single neurosurgeon over a decade and demonstrated the safety of the procedure for a broad range of pathologies [15]. Since then, the procedure has been adopted worldwide and has been made safer by advances in technology and reconstructive techniques. Since our original description of a modular anatomical classification system [25], expansion of the anatomic limits of the procedure has continued to increase the number of skull base tumors accessible by this approach. In this chapter, we will describe the use of EEA for skull base meningiomas, focusing on the anatomic limits of the use of EEA for these tumors, the advantages and disadvantages of EEA, and the technical nuances of the use of EEA for meningiomas.