Sphenoethmoidal air cell
Citation, DOI & article data
Sphenoethmoidal air cell, also commonly known as the Onodi air cell, is an anatomical variant of the paranasal sinuses, important due to its close proximity to the optic nerve and internal carotid artery.
The sphenoethmoidal air cell is generally defined as the posteriormost ethmoidal air cell, that extends posteriorly to lie superolateral to the sphenoid sinus and thus in close proximity to the optic nerve and internal carotid artery 5,8. It often extends into the anterior clinoid process; importantly, aeration of the anterior clinoid process does not imply presence of an Onodi cell, as frequently such aeration is due to rescesses of the sphenoid sinus 9.
Rarely, it may lie superiorly to the sphenoid sinus and is then called a central Onodi air cell 4.
The incidence of sphenoethmoidal air cells is variable, reported in 3.4 to 60% of individuals 1,8; the discrepancy of these rates of incidence likely results from variability in definition rather than true incidence 8.
Onodi air cells are usually asymptomatic, unless complicated by sinus disease (e.g. mucocoeles, squamous cell carcinoma, and acute sinusitis, which have all been reported in sphenoethmoidal air cells), leading to early optic nerve involvement.
The importance of these air cells stems primarily from their location adjacent to the optic nerve and internal carotid artery, with as little as 0.03 mm (median 0.08 mm) of bone separating them 1.
Potential damage to these critical structures occurs when attempts to enter the sphenoid sinus endoscopically are made by passing through the posterior wall of the sphenoethmoidal air cell expecting to enter the sphenoid sinus 5.
History and etymology
The importance and variability of the posteriormost ethmoidal air cells was described by the Hungarian laryngologist Adolf Ónodi (1857-1920) in 1904 6,7.
- 1. Thanaviratananich S, Chaisiwamongkol K, Kraitrakul S et-al. The prevalence of an Onodi cell in adult Thai cadavers. Ear Nose Throat J. 2003;82 (3): 200-4. - Pubmed citation
- 2. Lim CC, Dillon WP, Mcdermott MW. Mucocele involving the anterior clinoid process: MR and CT findings. AJNR Am J Neuroradiol. 1999;20 (2): 287-90. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 3. Jones NS, Strobl A, Holland I. A study of the CT findings in 100 patients with rhinosinusitis and 100 controls. Clin Otolaryngol Allied Sci. 1997;22 (1): 47-51. - Pubmed citation
- 4. Cherla DV, Tomovic S, Liu JK et-al. The central Onodi cell: A previously unreported anatomic variation. Allergy Rhinol (Providence). 2013;4 (1): e49-51. doi:10.2500/ar.2013.4.0047 - Free text at pubmed - Pubmed citation
- 5. Kennedy DW, Bolger WE, Zinreich SJ. Diseases of the Sinuses. pmph usa. (2001) ISBN:1550090453. Read it at Google Books - Find it at Amazon
- 6. Onodi A, Die Sehstörungen und Erblindung nasalen Ursprunges, bedingt durch Erkrankungen der hinteren Nebenhöhlen. Ophthalmologica 1904;12:23-46
- 7. Forbis PTL. Stedman's Medical Eponyms. Lippincott Williams & Wilkins. (2005) ISBN:0781754437. Read it at Google Books - Find it at Amazon
- 8. Matti Anniko, Manuel Bernal-Sprekelsen, Victor Bonkowsky, Patrick Bradley, Salvatore Iurato. Otorhinolaryngology, Head and Neck Surgery. Springer (2010). ISBN:3540689400. Read it at Google Books - Find it at Amazon
- 9. Lim CC, Dillon WP, McDermott MW. Mucocele involving the anterior clinoid process: MR and CT findings. AJNR Am J Neuroradiol. 1999;20 (2): 287-90. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 10. William T. O’Brien, Sr, Stefan Hamelin, Erik K. Weitzel. The Preoperative Sinus CT: Avoiding a “CLOSE” Call with Surgical Complications. (2016) Radiology. 281 (1): 10-21. doi:10.1148/radiol.2016152230 - Pubmed