Atlas of Imaging of the Paranasal Sinuses, Second Edition

Lalitha Shankar, Kathryn Evans, Lalitha Shankar, Kathryn Evans

• Publisher: CRC Press
• Year: 2021
• Print ISBN: 9780367390723
• eBook ISBN: 9781000162103
• Topic: Medicine
• Subtopic: Radiology, Radiotherapy & Nuclear Medicine

With color illustrations, the Second Edition of this best-selling guide concentrates on the advances in technology that are now available to the clinical otolaryngologist. This reinforces the book's position as a classic guide, especially to the problems associated with endoscopic sinus surgery.

6 Anatomical variants of the ostiomeatal complex in the paranasal sinuses

DOI: 10.1201/9781003076438-6

Messerklinger demonstrated that ventilation and drainage of the anterior ethmoid sinus, the maxillary sinus, and the frontal sinus are dependent upon the patency of the ostiomeatal complex through which these sinuses connect into the nasal cavity.

Most sinus infections are rhinogenic in origin and spread from the ostiomeatal complex to secondarily involve the frontal and maxillary sinuses. The small clefts of the ostiomeatal complex in the lateral nasal wall are easily narrowed or occluded by mucosal edema, resulting in impaired ventilation, failure of mucociliary clearance, and the stagnation of mucus and/or pus in the larger paranasal sinuses.

This process is usually reversible, and once the ostiomeatal complex is reopened, the secondary disease within the larger maxillary and frontal sinuses usually resolves spontaneously. If, however, there is an anatomical variant that narrows these key ethmoid clefts, then a minimal amount of mucosal edema may predispose the patient to recurrent infections and may result in chronic inflammatory changes in the mucosa.

Previously, surgical procedures to alleviate recurrent or chronic inflammatory episodes have been directed at the larger paranasal sinuses. The ventilation of these sinuses was improved by creating new and theoretically effective alternative drainage pathways. The alternative drainage procedures, such as an inferior meatal antrostomy, are now known not to redirect the flow of mucus through the newly created opening (antrostomy), but only to act as ‘drains’ when the mucociliary system is overwhelmed by mucus and pus. The persistence of symptoms following these procedures is usually secondary to persistent disease in the anterior ethmoid affecting the natural ostia and the ostiomeatal complex. When ostiomeatal complex disease is present, recurrent sinus infections may also occur despite there being a widely patent natural accessory ostium.

Functional endoscopic sinus surgery is directed at the natural drainage pathways. The limited surgical resection of tissue that widens these natural clefts and improves sinus ventilation usually leads to a reversal of the mucosal disease in the larger paranasal sinuses. Direct endoscopic examination and visualization of the small clefts of the ostiomeatal complex are not possible, and consequently computed tomography (CT), especially in the coronal plane, is essential for the assessment of the patient with recurrent or persistent sinusitis. Coronal CT allows the radiologist to determine the site and extent of disease in the paranasal sinuses and in the surrounding soft tissues and to identify those anatomical variants that may predispose the individual to sinusitis. Although it is recognized that anatomical variations occur in individuals with no history of rhinosinusitis, variations of the size or position of the normal structures in the lateral nasal wall can impede optimal sinus drainage and occur alongside recurrent sinusitis. Important anatomical variants in the sinuses and the nasal cavity of which surgeons must be aware prior to any intervention are discussed in this chapter.

These important anatomical variants are listed in Table 6.1.

Table 6.1 Important anatomical structures of the ostiomeatal complex and their variations

Variations in the structures of the ostiomeatal complex Large agger nasi cells When present and enlarged, agger nasi cells can obstruct the frontal recess Uncinate process Aplasia or hypoplasia Medial or lateral deflection Pneumatization Hypertrophy Accessory middle turbinate Middle turbinate Paradoxically bent middle turbinate Secondary middle turbinates Lateralization of middle turbinate Aplasia or hypoplasia Hypertrophy Soft tissue and bony hypertrophy of middle turbinate Concha bullosa Ethmoid bulla Large: Protrudes into middle meatus Overhangs hiatus semilunaris Obstructs ethmoid infundibulum Obstructs frontal recess Hypoplasia Large Haller’s cells When present and enlarged, a Haller’s cell can obstruct the natural ostium of the maxillary sinus and the infundibulum Nasal septum Deviation of nasal septum and septal spurs Other variants to note before surgery Dehiscence of lamina papyracea Dehiscence of orbital floor Low-lying fovea ethmoidalis Dehiscence of optic nerve canal Dehiscence of internal carotid artery bony wall Hypoplasia of maxillary sinus Ethmomaxillary sinus Ethmosphenoid sinus Unilateral atresia of nasal cavity

AGGER NASI CELLS (Figures 6.1–6.5)

Figure 6.1 Large agger nasi cell. CT scan demonstrating a large right agger nasi cell (A) occluding the frontal recess (arrow) and resulting in frontal recess disease, normal lacrimal fossae. Note the erosion of the lateral wall of the orbit on the left side (open arrow).

Figure 6.2 Multiseptate agger nasi cell. CT scan demonstrating a multiseptate agger nasi cell (A) on the left side.

Figure 6.3 Agger nasi cell and frontal recess disease. Inflammatory disease can be seen in the large agger nasi cells and the left frontal recess (arrow). The large agger nasi cells (A) encroach on the neck of the middle turbinate. The larger the agger nasi cell, the greater the encroachment on the neck of the middle turbinate (M), resulting in a restricted frontal recess. The medial wall of the orbit is extremely thin and inflammation may spread through the wall to involve the orbit or the lacrimal sac.

Figure 6.4 Agger nasi cell and encroachment on neck of middle turbinate. Anterior CT scan showing a large agger nasi (A) cell encroaching on the waist of the middle turbinate and compromising the frontal recess (arrow) on the left side.

Figure 6.5 Agger nasi cell and encroachment on neck of middle turbinate. A large agger nasi cell (A) is against the vertical plate of the middle turbinate (M) associated with appositional changes in the frontal recess very close to the lamina lateralis of the cr...

Table of contents

• Cover Page
• Half-Title Page
• Title Page
• Copyright Page
• Table of Contents
• Contributors
• Acknowledgments
• Introduction
• Nasal physiology
• Gross and sectional anatomy of the nasal cavity and paranasal sinuses
• Computed tomography of the paranasal sinuses
• The normal anatomy of the paranasal sinuses as seen with computed tomography and magnetic resonance imaging
• Anatomical variants of the ostiomeatal complex in the paranasal sinuses
• The radiological features of benign inflammatory paranasal sinus diseases
• Complications of sinusitis
• Tumors and tumor-like conditions of the sinonasal cavity
• The postoperative appearances of the paranasal sinuses
• Congenital facial and paranasal sinus abnormalities
• Imaging of midface and paranasal sinus trauma
• Bibliography