This presentation describes anatomy of paranasal sinuses

1. Anatomy of Para nasal sinuses Dr. T. Balasubramanian M.S. D.L.O.

3. These sacs surround the nasal cavity

4. They are paired

5. Four in number

6. They include frontal, maxillary, ethmoidal and sphenoid sinuses

8. Maxillary sinus - Boundaries Medial wall – This is the base of the pyramidal shaped maxillary sinus. This corresponds to the lateral wall of the nasal cavity. This wall has its convexity towards the maxillary sinus. The central portion of this wall is very thin and could even be membranous in places. The natural ostium is present in this wall. The natural ostium is present closer to the roof of the sinus. Anterior wall – Corresponds to the cheek area of the face. This portion also constitutes the lateral wall of the maxilla. Hence it would be appropriate to call it as antero lateral wall. The most important feature of this wall is the canine fossa. Roof – Forms the floor of the orbit. This wall is thin. It is through this wall the infraorbital vessels and nerve traverses. Floor – Is formed by the alveolar process of maxilla and the hard palate. The roots of the first and second molars may reach up to the floor of the sinus. Posterior wall – Formed by temporal surface of maxilla and is very thick

10. Inferiorly – Bounded by alveolar ridge

11. Laterally – Bounded by canine eminence

12. Superiorly – Infraorbital foramen

13. Medially – Pyriform aperture

15. Roof of maxillary sinus is weakened by the presence of infraorbital canal and infraorbital foramen

16. In children the floor of the maxillary sinus lie at the same level as that of the nasal cavity, in adults it lies about 5 – 10 mm below the level of nasal cavity

17. Dental infections involving the first and second molars may involve the maxillary sinus, because the bone is thin in this area.

19. It is shaped more or less shaped like L

20. Posterior wall – Related to the anterior cranial fossa

21. Floor – Is formed by the upper part of orbit

22. Drains into the anterior part of middle meatus via the frontonasal duct

24. It is composed of complex bony labyrinth with thin walls

25. There may be 6 – 10 ethmoid cells present in adults

26. Common sinus infections in children involve Ethmoidal sinuses

27. Because of its close proximity to orbit and skull base infection involving this group of sinus is more prone for complications.

28. Ethmoidal sinus anatomically have been divided into anterior, middle and posterior groups according to their drainage pattern. Anterior and middle group drain into the middle meatus while the posterior group drain into the superior meatus

29. With the advent of FESS the study of Ethmoidal sinuses have gained importance.

32. Large aggernasi air cell can impede frontal sinus drainage due to its close proximity to the frontal sinus drainage pathway.

33. Pneumatized middle turbinate is known as concha bullosa. Inflammed concha bullosa of middle turbinate may block middle meatus drainage channels.

34. Haller cells belong to the anterior ethmoidal group of air cells. These cells are also known as infra orbital cells. Enlargement of this cell may block drainage of the maxillary sinus.

36. Pneumatization of this sinus begins during the 4th year of childhood and gets completed by the 17th year of life.

37. It varies in size and may be asymmetric.

39. Lateral wall – Optic nerve and internal carotid artery

40. Floor – Nerve of pterygoid canal