7 Endonasal Surgery and Its Current Role in Neurosurgical Paradigms

10.1055/b-0035-104219

7 Endonasal Surgery and Its Current Role in Neurosurgical Paradigms

Michael E. Sughrue and Charles Teo

7.1 Introduction

It is beyond question that endonasal techniques for removal of brain tumors have received well deserved attention in recent years. This book is not about endonasal surgery, as there are countless good resources available on this topic, and to completely address all the nuances of these approaches would significantly increase the heft of this book. However, given that endonasal endoscopic approaches are part of our practice pattern for specific diseases, it is important that we briefly address these approaches, and discuss when we think they are useful.

7.2 A Very Brief Introduction to Endonasal Approaches

The idea of approaching certain skull base pathologies through the nose has been established for some time, and has long been the standard of care for pituitary disease and cerebrospinal fluid (CSF) fistulae, with excellent results and minimal morbidity. Over the past 2 decades, many surgeons have gradually expanded the indications for transnasal surgery to include parasellar disease, including craniopharyngiomas and tumors of the clivus. With improvements in endoscopic technology and surgical instrumentation, essentially any midline or off-midline tumor (intradural or extradural) medial to the cranial nerves can be accessed through the nose, and can be successfully addressed via some approach usually centered on the sphenoid sinus, augmented with techniques borrowed from functional endoscopic sinus surgery. Improved CSF closure techniques have reduced the previously prohibitive problem of dural repair in these patients, although, until the CSF fistula rate is zero, this will always be a consideration.

7.3 Where Do Endonasal Endoscopic Approaches Fit In?

What is clear is that it is possible to remove midline and slightly off-midline pathologies with reasonable results. What is not clear is whether this is the best method for achieving optimal results. These considerations are especially important when the choice is between an endonasal endoscopic approach and keyhole craniotomy.

Firstly, while it is desirable to avoid skin incisions whenever possible, it is clear that endonasal endoscopic surgery as presently practiced is not exactly minimally invasive. Considerable nasal dissection is necessary, often involving turbinectomy, septal mucosa removal (especially if a nasal septal flap is used), sinus manipulation, and extensive bony drilling, which causes some nasal morbidity and requires aggressive nasal care. While these problems are not prohibitive, especially when compared with a large morbid transfacial or transpalatal approach, in many patients they are more challenging for the patient than a well planned keyhole craniotomy. These patients in our experience generally have minimal pain, go home the day after surgery, do not require aggressive postoperative care, and rarely leak CSF. Thus, even as advocates of endonasal endoscopic approaches, it is not clear to us that all endonasal surgery is less invasive than keyhole transcranial surgery; the likelihood is that this depends on the individual situation.

Secondly, while endonasal techniques improved significantly in recent years, it is still easier to perform difficult maneuvers with a microscope through a keyhole than up the nose. For example, in most patients, dissecting small encased arteries out of a moderate-to-large meningioma is easier and safer using transcranial techniques. Without major technological innovation, it is likely to remain that way for some time.

7.4 When Do We Use an Endonasal Approach?

Given our experience with keyhole surgery, we feel that the best situations to use endonasal endoscopic approaches are when the endonasal route provides a specific anatomical advantage over the transcranial route. Specific examples are provided below. A rough guide to when we prefer an endonasal approach versus a transcranial approach is provided in Table 7.1.

**Table 7.1** Decision making for endonasal versus transcranial approaches
Transcranial Better	Endonasal Better	Debatable
CN 7/8 Sphenoid wing or anterior clinoid Lateral temporal bone Tumors which encase vessels Lateral to cranial nerves Need wide margins Needs complex reconstruction for cosmesis/flap Invades facial skin Very bloody/cannot embolize	Sella Clivus Sphenoid sinus/ethmoids involved Pterygopalantine fossa Infratemporal fossa Petrous apex below petrous ICA Medial cavernous sinus Upper dens	Simple olfactory groove tumors Simple Tuberculum tumors Nasal cancer/esthesioneuroblastoma Craniopharyngiomas Meckel cave Petrous apex

7.4.1 Sellar Pathology

This example is obvious to most neurosurgeons, and is provided for completeness. Although most surgeons would favor the endonasal route for purely and slightly suprasellar adenomas, once there is significant extension either into the third ventricle or into the temporal fossae, the criteria for determining the better surgical approach are less clear-cut. We have been pleased with the additional views provided by angled endoscopes and have consequently increased our indications for the transnasal route. Furthermore, other pathologies within the sella, such as meningiomas, that were once felt to be beyond the capabilities of the microsurgical transsphenoidal technique, are now considered appropriate for the endonasal endoscopic approach.

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