Chapter 3 Endoscopic Lateral Nasal Wall and Anterior and Posterior Ethmoid Sinus Dissection
Introduction
The aim of this chapter is to share basic information of the anatomy of the lateral nasal wall and the anterior and posterior ethmoid sinus in a step-by-step manner. One of the keys to learn endoscopic sinus surgery is to acquire knowledge of the anatomy of the nose and the paranasal sinuses. Before performing an endoscopic dissection, it is important to develop an understanding of the gross anatomy of the lateral nasal wall ( Figs. 3.1 and 3.2 ). This chapter describes sequential steps for performing the anterior and posterior ethmoid sinus dissection and offers tips on instrument handling techniques.
3.1 Indications for Ethmoid Sinus Surgery
Inflammatory diseases:
Chronic rhinosinusitis with or without nasal polyposis refractory to medical therapy.
Sinus mucoceles.
Allergic fungal sinusitis.
Neurorhinologic disorders:
Rhinopathic headaches resistant to medical therapy.
Orbital indications:
Severe exophthalmos.
Nasolacrimal duct obstruction.
Restorative indications:
Cerebrospinal fluid leak.
Severe posterior epistaxis.
Severe anterior epistaxis.
Choanal atresia/stenosis.
Neoplastic diseases:
Benign tumors.
Malignant tumors.
Skull base surgery:
Transnasal surgical approaches for skull base lesions.
3.2 Surgical Steps
The order of these steps is presented in an anteroposterior procedure. They may be changed or performed differently, depending on the anatomy, the experience of the surgeon, the intraoperative bleeding, etc. Detailed approaches to the frontal and sphenoid sinuses can be checked in Chapters 4 and 5, respectively.
3.3 Infundibulotomy
It involves removal of the uncinate process. The uncinate process is classically described as the first ethmoidal lamellae ( Fig. 3.3 ).
3.3.1 Technique
Gently medialize the middle turbinate with a ball-tipped probe or a backbiter. The Freer elevator can be used to palpate the maxillary line (hard bone) and the uncinate process (bounces back when pushed laterally). It allows identifying the insertion of the uncinate process to the maxillary line. Uncinectomy can be performed in two fashions: anteroposterior and retrograde technique.
3.3.2 The Anteroposterior Approach
It is performed through an initial vertical incision through the uncinate process. A sickle knife or a Freer′s elevator is used to incise the uncinate process at the level of its middle and inferior third; then the incision is extended inferiorly and posteriorly along its horizontal aspect. Once it is made sure that there is enough distance to the papyracea, enlarge the incision superiorly (if indicated) to open the infundibulum toward the frontal outflow tract. Remaining superior and inferior attachments of the uncinate can be cut with a through-cutting forceps. Alternatively, one may insert a straight-forward Blakesley to grasp the superior attachment and then rotate it clockwise (on the left side) and counterclock-wise (on the left side) at its inferior attachment to avoid peeling the mucosa off the lateral nasal wall and inferior turbinate, respectively. On the right side of the patients, rotation of the instrument goes the other way round ( Fig. 3.4a ).
Then, identify the natural ostium of the maxillary sinus, the recessus terminalis, if any, and the frontal recess ( Fig. 3.4b ).
The natural ostium of the maxillary sinus cannot be inspected before the uncinectomy with a 0 or a 30- degree lens, in particular cases with a 45 or a 70- degree endoscope.
3.3.3 Indications
Uncinectomy is the first and often the most important step in most procedures for the ostiomeatal complex.
An infundibulotomy (also with just a partial resection of the uncinate) as a sole procedure can be performed for isolated purulent maxillary sinusitis refractory to medical treatment.
Removal of irreversibly diseased mucosa (polyposis) of the infundibulum.
Access to the maxillary, anterior and posterior ethmoid, and frontal sinuses.
The anteroposterior approach has a higher risk of orbital penetration. Exposed orbital fat should be left alone and should not be manipulated.1–4
3.3.4 Posteroanterior Approach
A small backbiter (with branch closed) is introduced into the middle meatus. The instrument is rotated so that the biting blade is opened upward, in the vertical plane of the meatus. The open blade is then rotated horizontally to engage the posterior free edge of the uncinate process. Try to luxate the uncinate medially along its entire length so as to facilitate resection. The backbiting forceps can now cut the luxated aspect of the uncinate within the middle meatus through its entire thickness without stripping mucosa of the lateral wall. The upper uncinate process can now be mobilized with a ball probe and gently dissected downwards with a curved J-curette. A 45-degree Blakesley-Weil forceps can now be used to grasp the mobilized uncinate ( Fig. 3.4c ).
This approach is safer as one moves away from the orbit when dissecting, and thus the risk of inadvertently entering the orbit is reduced.5–8
3.3.5 Tips and Tricks
Avoid too deep penetration of the tip of the sickle knife during uncinectomy because it may injure the lamina papyracea.
Check the distance between the uncinate and the orbit in a coronal section of the computed tomography (CT) scan to avoid orbital penetration.
While dissection, displace the uncinate process away from the orbit.
Palpate the eye softly from outside while working near the lamina papyracea to check for bony dehiscences of the papyracea (particularly in a revision case) or even possible herniation of orbital fat.
When addressing the frontal outflow tract, it is important to remove the uncinate process in its most superior extension to adequately visualize the frontal outflow tract.
Avoid using the backbiter just biting anteriorly toward the lacrimal sac/duct (the bony resistance will increase here): medialize the uncinate before biting.
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