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Introduction

  • There has been an evolution in the theories of pathogenesis and clinical management of sinonasal inflammatory disease that has revolutionized the practice of otolaryngologists.

  • Diseases previously managed with open procedures are now widely managed with endoscopic approaches as the technology too has greatly improved.

  • Further, the advancement of topical therapies and in-office procedures has created opportunities to manage disease, while creating cost-saving techniques and possibly improving patient safety.

  • However, the variability of the anatomy and their critical relationship with the sinonasal cavities still remain true and a detailed knowledge of the embryology, and anatomy of the paranasal sinuses is necessary to avoid potentially disastrous surgical complications.

Embryology of Paranasal Sinuses

Ethmoturbinals

  • Development heralded by the appearance of a series of ridges or folds on the lateral nasal wall at approximately the eighth week (Figure 33-1).

  • Six to seven folds emerge initially but eventually only three to four ridges persist.

  • Persistant ridges are referred to as ethmoturbinals from an ethmoid origin:

    • First ethmoturbinal—rudimentary and incomplete in humans

      • – Ascending portion forms the agger nasi.

      • – Descending portion forms the uncinate process.

    • Second ethmoturbinal—forms the middle turbinate

    • Third ethmoturbinal—forms the superior turbinate

    • Fourth and fifth ethmoturbinals—fuse to form the supreme turbinate

  • Furrows form between the ethmoturbinals and ultimately establish the primordial nasal meati and recesses.

    • First furrow (between the first and second ethmoturbinals)

      • – Descending aspect forms the ethmoidal infundibulum, hiatus semilunaris, and middle meatus.

        • The primordial maxillary sinus develops from the inferior aspect of the ethmoid infundibulum.

      • – Ascending aspect contributes to the frontal recess.

    • Second furrow (between the second and third ethmoturbinals) forms the superior meatus.

    • Third furrow (between the third and fourth ethmoturbinals) forms the supreme meatus.

Figure 33-1

Fetal cartilaginous capsule at 9 to 12 weeks.

Contemporary Sinus Embryology Theory

  • In addition to the traditional ridge and furrow concept of development, a cartilaginous capsule surrounds the developing nasal cavity and plays a role in sinonasal development.

  • At 8 weeks, three soft-tissue elevations or preturbinates are seen that correlate to the future inferior, middle, and superior turbinates.

  • At 9 to 10 weeks a soft-tissue elevation and underlying cartilaginous bud emerges that corresponds to the future uncinate process.

  • By 13 to 14 weeks a space develops lateral to the uncinate anlagen that corresponds to the ethmoidal infundibulum.

  • By 16 weeks, the future maxillary sinus begins to develop from the inferior aspect of the infundibulum.

  • All three turbinates and each paranasal sinus arise from the cartilaginous nasal capsule which resorb or ossify over time.

Anatomic Considerations in Endoscopic Sinus Surgery (ESS)

The Lamellae

  • The basal or ground lamella of the middle turbinate divides the anterior and posterior ethmoid air cells.

  • The frontal, maxillary, and anterior ethmoids cells ...

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