A possible case of two Onodi cells in a single patient.

A 57-year-old woman was referred for evaluation of an 8-month history of persistent sinus symptoms that had not responded to treatment with numerous medications. She described her problem as "a cold." Computed tomography (CT) of her sinuses revealed chronic ethmoid sinusitis and an unusual anatomic configuration in the left posterior ethmoid and sphenoid sinuses (figure, A).

The patient underwent endoscopic sinus surgery. Dissection of the left posterior ethmoid cells revealed the presence of a superior Onodi cell (sphenoethmoid cell) above the sphenoid sinus (figure, B). After a very large posterior ethmoid cell was cleaned out, a second posterior ethmoid cell was found lateral and posterior to the left sphenoid sinus (figure, C). This cell was completely separate from the Onodi cell. On close-up examination of the Onodi cell, it was evident that a bony bulging of the optic nerve was present along the superior portion of its posterior wall (figure, D). A bony bulging of the internal carotid artery was also noted inferomedially in the posterior wall. Just below the optic nerve bulge, there appeared to be a bony depression called the infraoptic recess (figure, D). Sphenoethmoidectomy was completed, and the patient did well postoperatively.

The Onodi cell was first described in 1903 by Prof. Adolf Onodi (1857-1919), a professor of laryngology at the University of Budapest. (1) The reported incidence of Onodi cells varies widely (3.5 to 51%), a consequence of the different criteria used to define it. (2-7) Posterior ethmoid cells that are intimately proximal to the optic nerve are considered to be Onodi cells. They may extend posteriorly beyond the anterior part of the sphenoid sinus, either superiorly or superolaterally. (2-7) Kainz and Stammberger wrote that these cells may or may not contain tuberculum nervi optici (the bulging of the optic canal into the wall of the Onodi cell).2 According to this theory, our patient may have had two Onodi cells.

In a typical case of Onodi cell, one should look for a bulging of the optic nerve, which should run transversely along the superior portion of the posterior wall of the Onodi cell (figure, D). One should also notice an infraoptic recess. Bulging of the internal carotid artery may be present inferomedially.

The presence of multiple posterior ethmoid cells that extend beyond the anterior part of the sphenoid sinus superiorly or laterally has not often been described. This report describes such a case.

Awareness of the presence of an Onodi cell or multiple Onodi cells is important prior to dissection in the sphenoethmoid area (7) The sphenoid sinus is normally situated behind the posterior end of the posterior ethmoid sinus. Merely assuming that the posterior wall of the Onodi cell will lead into the sphenoid sinus might result in an adverse event if the posterior wall is penetrated. Awareness and knowledge of the surgical anatomy of each individual patient prior to surgery are of utmost importance.

References

(1.) Onodi A. Des rapports entre le nerf optique et le sinus sphenoidal. La cellule ethtnoidale posterieure en particulier. Revue Hebd Laryng d'Otol Rhinol 1903;25:72-140.

(2.) Kainz J, Stammberger H. Danger areas of the posterior rhinobasis. An endoscopic and anatomical-surgical study. Acta Otolaryngol 1992;12:852-61.

(3.) Yeoh KH, Tan KK. The optic nerve in the posterior ethmoid in Asians. Acta Otolaryngol 1994;114:329-36.

(4.) Dixon FW. A comparative study of the sphenoid sinus: A study of 1600 skulls. Ann Otol Rhinol Laryngol 1937;46:687-98.

(5.) Weinberger DG, Anand VK, AL-Rawi M, et al. Surgical anatomy and variations of the Onodi cell. Am J Rhinol 1996; 10:365-70.

(6.) Stammberger HR, Kennedy DW. Paranasal sinuses: Anatomic terminology and nomenclature. The Anatomic Terminology Group. Ann Otol Rhinol Laryngol Suppl 1995;167:7-16.

(7.) Yanagisawa E, Weaver EM, Ashikawa R. The Onodi (sphenoethmoid) cell. Ear Nose Throat J 1998;77:578-80.

From the Department of Otolaryngology, University of South Florida College of Medicine, Tampa, and the Halifax Medical Center, Daytona Beach, Fla. (Dr. Christmas and Dr. Mirante); and the Southern New England Ear, Nose, Throat, and Facial Plastic Surgery Group, New Haven, Conn., the Section of Otolaryngology, Hospital of St. Raphael, New Haven, and the Section of Otolaryngology, Yale University School of Medicine, New Haven (Dr. Yanagisawa).