Bilaterally exposed carotid arteries after drainage of a sphenoid sinus mucocele.

A 27-year-old man presented with a several-month history of headaches. Magnetic resonance imaging (MRI) revealed the presence of a 3.7 x 3.9 x 4.2-cm mass within an expanded sphenoid sinus. The mass was mildly hyperintense on T1-weighted imaging, hypointense on T2-weighted imaging, and did not enhance with gadolinium administration. Bone was noted to be thinned but not invaded, the pituitary gland was displaced superiorly, and the anterior brainstem was flattened. The mass, which was consistent with a mucocele, surrounded the carotid arteries.

Accordingly, the patient was taken to the operating room, where he underwent image-guided sphenoidotomy with drainage and marsupialization of the mucocele. The sphenoid face was eroded, no intersinus septum was seen in the massively expanded sinus cavity, and dura was exposed throughout the sphenoid. Pathology was consistent with chronic sinusitis.

Computed tomography (CT) performed 2 weeks postoperatively revealed an expanded sphenoid sinus but no evidence of recurrence of the mucocele (figure 1). The patient was returned to the operating room at that time for thorough sinonasal debridement and endoscopy of the sphenoid sinus. Both of his carotid arteries were dehiscent of bone in their cavernous sinus segments and clearly visible within the sphenoid sinus (figure 2).

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Mucoceles are the most common space-occupying lesions of the sphenoid sinus. (1) Infected mucoceles are known as mucopyoceles. They are either primary from expansion of a mucous retention cyst or secondary from obstructed sinus ostia, although an obvious etiology is not always found in the patient's history. Mucoceles can remain clinically silent for years and then become symptomatic as they expand to involve surrounding structures while remodeling and expanding bone. Approximately 90% involve the frontal and ethmoid sinuses, while the remainder arise in the maxillary sinus. Mucoceles isolated to the sphenoid sinus are rare.

When they do occur, mucoceles isolated to the sphenoid sinus cause symptoms related to surrounding structures that are vulnerable to compression, including the pituitary gland, optic nerve, chiasma, and the structures found within the cavernous sinus. (2) CT and MRI are appropriate for diagnosis. MRI findings are often similar to those seen in the case described here, but they can vary depending on the water and protein content.

Conservative drainage and marsupialization are adequate for the treatment of mucoceles that are lined by pseudostratified, ciliated, columnar epithelium. Radical extirpation has been less commonly advocated since the advent of endoscopic and image-guided surgery. (3,4) Allowing for continued sinus drainage is central to preventing a recurrence.

The carotid artery is located in the midposterior portion of the lateral sphenoid sinus. It may be readily apparent endoscopically, and the overlying bony covering has been reported to be less than 0.5 mm thick in nearly 88% of patients and entirely dehiscent in up to 8%. (5) In a study of 500 consecutive high-resolution CT scans, the parasphenoidal carotid artery was noted to be "at risk" in 31.4% of patients and had no bony covering in 14.4%. (6)

Our case underscores the importance of a thorough understanding of sinonasal anatomy and the critical structures surrounding the operative field. While intraoperative avoidance of these structures has improved with superior imaging, endoscopic techniques, and image-guidance techniques, there is no substitute for an intimate knowledge of anatomy and respect for the potential dangers of surgery.

References

(1.) Weiss RL, Jr., Bailey BJ. Approaches to the sphenoidal sinus. In: Bailey BJ, ed. Head and Neck Surgery--Otolaryngology. Philadelphia: Lippincott Williams and Wilkins, 2001:383-92.

(2.) Hantzakos AG, Dowley AL, Yung MW. Sphenoid sinus mucocele: Late complication of sphenoidotomy. J Laryngol Otol 2003;117: 561-3.

(3.) Har-El G. Endoscopic management of 108 sinus mucoceles. Laryngoscope 2001;111:2131-4.

(4.) Kennedy DW, Josephson JS, Zinreich SJ, et al. Endoscopic sinus surgery for mucoceles: A viable alternative. Laryngoscope 1989;99: 885-95.

(5.) Kingdom TT, Delgaudio JM. Endoscopic approach to lesions of the sphenoid sinus, orbital apex, and clivus. Am J Otolaryngol 2003;24:317-22.

(6.) Johnson DM, Hopkins RJ, Hanafee WN, Fisk JD. The unprotected parasphenoidal carotid artery studied by high-resolution computed tomography. Radiology 1985;155:137-41.

From the Department of Otolaryngology--Head and Neck Surgery, Thomas Jefferson University Hospital, Philadelphia.