Key points
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Preoperative assessment of the imaging is crucial to identify sites of potential complications and to create a roadmap of the surgical plan.
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The maxillary sinus ostium is never anterior to the middle turbinate.
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The orbital floor is a great landmark, because the skull base is always superior to it.
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Beware of Onodi cells and atelectatic maxillary sinuses.
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Meticulous dissection and mucosal preservation techniques are key in preventing postoperative synechiae and fibrosis.
| CSF | Cerebrospinal fluid |
| CT | Computed tomography |
| LP | Lamina papyracea |
| NLD | Nasolacrimal duct |
| SPA | Sphenopalatine artery |
| UP | Uncinate process |
Introduction or overview: nature of the problem
Complications can occur at any point during or after a procedure. Knowledge of anatomy of the sinuses, their variations, and their surrounding structures should be well understood. To prevent complications, areas of potential hazard are assessed preoperatively using diagnostic imaging.
Introduction or overview: nature of the problem
Complications can occur at any point during or after a procedure. Knowledge of anatomy of the sinuses, their variations, and their surrounding structures should be well understood. To prevent complications, areas of potential hazard are assessed preoperatively using diagnostic imaging.
Safe sinus surgery: sinus anatomy
Safe sinus surgery is predicated on knowledge of anatomy and the potential complications that lie therein. The paranasal sinuses are bordered by critical vascular and neurologic structures, including the brain, eye, nerves, carotid artery, and cavernous sinus.
Complications can be categorized in many ways: intraoperative versus postoperative, early versus late, by severity, or by anatomic site. In this article, the anatomy and potential complications are described as they relate and are seen during the stepwise process of a typical endoscopic sinus surgery. Therefore, numerous pearls are mentioned to alert the reader to the potential complication at the relevant step.
Middle Turbinate
The middle turbinate is often the first structure encountered in performing endoscopic sinus surgery. Its position, size, shape, and potential pneumatization may cause unwanted obstruction in the surgical visual field. Improper handling of the middle turbinate may lead to postoperative synechiae or lateralization, change in olfaction, and even cerebrospinal fluid (CSF) leak. The middle turbinate has 4 attachment sites. Its attachment anteriorly to the aggar nasi region forms the anterior buttress. It is attached vertically in the sagittal plane to the cribriform plate, laterally in the coronal plane to the lateral nasal wall, and laterally in the axial (or horizontal) plane to the lateral nasal wall. One of the most common minor complications is postoperative synechiae. Therefore, maneuvers and techniques have been developed to minimize this complication. A relaxing incision of the basal lamella is made at the junction of the coronal and sagittal planes of the middle turbinate. This strategy allows for a more stable medialization of the middle turbinate. Removing the horizontal portion of the basal lamella weakens the stability and may result in lateralization; therefore, this should be avoided.
Postoperative hyposmia is certainly one of the risks of sinus surgery and should be discussed as part of the informed consent. Olfactory fibers descend from the olfactory cleft onto the superior turbinate and septum and occupy a space between 2 and 10 cm. The incidence of postoperative hyposmia has been studied in various circumstances and using various techniques, including removal of the inferior portion of the superior turbinate, removing the middle turbinate entirely or in part, and also when septal deviation is corrected. In all circumstances, the incidence is low and may be related either to the removal of olfactory neuroepithelium or by altering the flow of air. In addition to olfactory injury, dissection medial to the middle turbinate may result in a CSF leak and thus should be avoided or performed with extreme caution.
When an obstructive concha bullosa is present, it may be advantageous to remove the lateral half of it. Not only does this procedure facilitate dissection of the sinuses, it is important for postoperative debridement as well as to prevent synechiae. There are numerous techniques in the surgical management of the concha bullosa. One must avoid destabilizing the middle turbinate if puncturing the concha bullosa. Because the concha bullosa is lined with functional mucosa on the inside, one must be careful to preserve the portion on the remnant middle turbinate for functional purposes.
Uncinate
A proper uncinectomy is key for good visualization during endoscopic ethmoidectomy, maxillary antrostomy, and when approaching the frontal sinus. Therefore, an incomplete uncinectomy is often the reason for failure of sinus surgery. Knowledge of its anatomy and sites for potential failure are important in order to avoid them. The uncinate is a crescent-shaped bone that develops from the first ethmoturbinal in close relation with the aggar nasi region. It is a thin bone the free edge of which runs almost sagittally from anterior-superior to posterior-inferior. Its superior attachment is variable and may attach laterally to the lamina papyracea (LP), superiorly to the skull base or medially to the middle turbinate. The superior attachment dictates the frontal sinus drainage pathway. The most common configuration encountered regarding the superior attachment of the uncinate is a lateral attachment to the orbit forming a terminal recess (recessus terminalis). In this configuration, the frontal sinus drains medial to the uncinate process (UP) into the middle meatus. However, if the uncinate attaches more medially, to the skull base or middle turbinate, then the frontal recess drains lateral to the UP into the ethmoid infundibulum. The maxillary line is the lateral attachment site of the UP and must not be mistaken for the free edge of the UP itself. Palpating the suspected structure reveals its identity, with the UP being mobile, whereas the maxillary line is firm. The maxillary line is also the posterior border of the nasolacrimal duct (NLD), which corresponds to the suture line between the UP and the lacrimal bone. Therefore, the maxillary line is the landmark used for the safe anterior extent of an uncinectomy.
Studying the uncinate architecture on the computed tomography (CT) scan is key in the preoperative preparation. It is important to identify a hypoplastic maxillary sinus ( Fig. 1 ). This feature can be easily recognized on the CT scan. In this setting, risk of orbital injury is higher when performing an uncinectomy, because the UP lies in a more lateral position and the orbital floor is pulled inferiorly, as seen in Fig. 1 . One must recognize this preoperatively and perform the uncinectomy with the utmost care in order not to penetrate the orbit or injure the infraorbital nerve.
Maxillary Antrostomy
The maxillary sinus is the largest of the pneumatized paranasal sinuses. Its anterior wall makes up the face of the maxilla. Superiorly is the orbital floor. The maxillary sinus drains medially via the natural ostium into the ethmoid infundibulum. The ostium can be found lateral to the UP, typically at the level of the lower portion of the middle turbinate. The ostium is located in the superior aspect of the medial maxillary sinus wall or immediately superior to the inferior turbinate. The true ostium is elliptical or teardrop in shape. An accessory or false ostium can be found in the posterior fontanelle in 10% to 20% of patients and is usually more round. If the accessory ostium is not conjoined with the true ostium, recirculation of mucus may occur. The NLD is located anterior to the maxillary sinus ostium by a distance of 0.5 to 1.8 mm. An important relationship to remember is that the ostium is never anterior to the anterior free edge of the middle turbinate. Therefore, keeping the middle turbinate in view while performing an uncinectomy and maxillary antrostomy may help in avoiding injury to the NLD. Injury to the NLD may result in postoperative epiphora. Care must be taken while enlarging the maxillary antrostomy posteriorly, because one may run into bleeding by encountering a branch of the sphenopalatine artery (SPA). The SPA exits the pterygopalatine fossa, which is located posterior to the maxillary sinus, and further lateral is the infratemporal fossa. The SPA exits via the sphenopalatine foramen, which is located immediately posterior to the crista ethmoidalis, the attachment site of the middle turbinate. There are typically multiple branches that run submucosally from which are the feeders to the lateral nasal wall. The infraorbital nerve courses along the inferior orbital floor and can be seen indenting into the maxillary sinus and in some cases can be suspended into the maxillary sinus ( Fig. 2 ). Haller cells, also referred to as infraorbital ethmoid cells, are ethmoid cells in origin, which pneumatize into the maxillary sinus ( Fig. 3 ). These cells should be identified preoperatively, because they pose a potential for failure to create an adequate drainage pathway. Related to the maxillary sinus, the maxillary ostium serves as an excellent, consistent, and reliable landmark for the sphenoid ostium, which lies at the same level, as discussed later.
