Abstract
The skull base is a beautiful landscape of compartments, bony ridges and prominences, winding sutures, scattered foramina, and dural folds. This exquisite complexity is multiplied by relationships with cranial nerves, brainstem surfaces, posterior circulation arteries, and veins. It is a daunting task to describe this anatomy while focusing on details relevant to neurosurgeons, but this chapter is our attempt. We hope this chapter will serve as a guide to deepen the understanding of the surgical anatomy of the skull base; however, there is no substitute for time spent in the cadaver laboratory with a scalpel, a drill, and microscissors peering through an operating microscope at the magnified and illuminated landscape of the brainstem. This habit transforms learning into mastery.
Our collective knowledge of skull base anatomy appears to be dwindling in this era of digital learning, surgical subspecialization, and minimally invasive surgery. Computer-generated atlases and three-dimensional videos are replacing cadaver laboratories and eliminating hands-on dissection. Neurosurgeons are partnering with neurotologists who make the temporal bone and all of its complex anatomy their domain. Although this partnership enhances the expertise of the skull base team, it diminishes neurosurgical familiarity with this anatomy. Endoscopy is changing our management of skull base lesions and decreasing the number of skull base operations. Advances in stereotactic radiosurgery and endovascular intervention are similarly reducing case volumes of tumors, arteriovenous malformations, and aneurysms. The result is diminished expertise in skull base surgery and diminished knowledge of skull base anatomy. It is easy to wonder whether skull base anatomy is clinically relevant to modern neurosurgical practice.
We think that knowledge of skull base anatomy is a cornerstone of the surgeon’s skill. Many consider manual dexterity to be the most important quality in a skillful neurosurgeon, but knowledge of anatomy guides the hands and gives the neurosurgeon the confidence to explore the surgical field. Mastery of anatomy is the cognitive skill that informs the neurosurgeon regarding where to work, what to see, how to maneuver better, and what to protect. Comfort in the anatomic arena around the skull base translates to confidence in executing the surgical strategy designed for the patient’s pathology. Analyzing anatomic relationships, practicing surgical steps, and learning from mistakes in bloodless cadavers translate to better surgical outcomes in live patients.
In this chapter we review the anatomy of the skull base as it relates to five approaches used frequently in skull base surgery: the far lateral approach, the retrosigmoid approach, the transpetrosal approaches, the orbitozygomatic approach, and the endoscopic endonasal approach. We present the bone anatomy, surgical technique, and important anatomy encountered within the surgical corridor. This information is intended to facilitate, rather than replace, hands-on learning in cadaveric dissection and will be more valuable if read in this context.