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Sphenoidotomy: Operative Technique

Anesthesia

Sphenoidotomy can be performed under local or general anesthesia depending on the patient's preference, the surgeon's experience, the health and age of the patient, and the severity of the sinus problem.

Operative Technique

As previously described for ethmoidectomy and antrostomy, surgery begins with a careful examination of the nose. 

 Saggital Section - Anterior Wall - Sphenoid Sinus

Saggital cadaver section shows exposure of the anterior wall of the sphenoid sinus (SS) by performing a total ethmoidectomy. Alternately, the posterior-inferior half of the middle turbinate can be removed to expose the sinus and the sphenoid ostium (SO, white circle).

In those patients with isolated sphenoid sinusitis, sphenoidotomy can be performed with or without ethmoidectomy. Most patients have both ethmoid and sphenoid sinusitis, and we recommend first performing the ethmoidectomy to enhance visualization of the sphenoid sinus.

 Endoscopic Photograph - Sphenoid Sinus Ostium

Endoscopic photograph showing the approximate location of the sphenoid sinus ostium (opening of the sphenoid sinus into the nose) relative to the middle turbinate (mt) and the lateral nasal wall. One more anterior lateral nasal wall structures is the uncinate process (up), which is the most anterior element of the osteomeatal complex (or middle meatus) or primary drainage site of the ethmoid, maxillary and frontal sinuses. The sphenoid sinus drains independently of the middle meatus, and medial to the posterior insertion of the middle turbinate.

 Saggital Section - Sinuses

Saggital cadaver section illustrating the relationship of the sphenoid sinus (SS) ostium (black arrow) to the middle turbinate (mt), the posterior tip of the middle turbinate (white arrow), ethmoid sinus (ES) and pituitary gland (pg).

Ideally, the sphenoid sinus is entered by enlarging the ostium of this sinus. The ostium lies approximately inferior to the lower border of the superior turbinate, and between the nasal septum and the middle turbinate. When the sphenoid ostium cannot be identified, the sinus is best entered in the medial and inferior quadrant of the anterior wall of the sinus.

This site is the safest location to enter the sphenoid sinus because the carotid artery, optic nerve and other important cranial nerves are located within the lateral wall of the sinus. The superior medial quadrant is not by us recommended as the site of entry due its proximity to the anterior cranial fossa floor. 

Further, posterior ethmoid cells can pneumatize or extend into the sphenoid bone lying above the sphenoid sinus. During "sphenoidotomy" these posterior ethmoid cells can be confused with the sphenoid sinus, and the sphenoid sinus inadvertently left intact.

 Measurement of Sphenoid Sinus Ostium

As reported by Harris Mosher, the average distance of the sphenoid sinus ostium is 7 cm from the anterior nasal spine to the face of the sinus at an angle of 30 degrees from the floor of the nose (Mosher, 1929). As this measurement is frequently cited, it is important to remember that Mosher was reporting an average and that there is significant variation between patients.

After entering the sphenoid sinus, the anterior wall should be carefully removed. This is best performed by removing the anterior wall from medial to lateral, and inferior to superior. This technique permits the surgeon to widely expose the surgical field; that is, the contents of the sphenoid sinus as progressing from the least to most important anatomy. The bony partions between ethmoid cells extending into the sphenoid bone and the sphenoid sinus, should be removed to permit complete drainage of these sinuses.

 Removal of Anterior Wall of Sphenoid Sinus

Approximate removal of anterior wall of sphenoid sinus is illustrated (white arrow, outlined in white).

References

Mosher HP. 1929 The surgical anatomy of the ethmoidal labyrinth. Ann Otolaryngol, 38:869-901.

Schaefer, S.D.1998 An anatomic approach to endoscopic intranasal ethmoidectomy. Laryngoscope, 108:1628-1634.

Stammberger, H. 1986 Endoscopic endonasal surgery-concepts in the treatment of recurring rhinosinusitis: Part II. Surgical technique. Otolaryngol. Head Neck Surg., 94:147-156.

Wigand, M.E., Steiner, W. and Jaumann, M.P. 1978 Endonasal sinus surgery with endoscopical control: From radical operation to rehabilitation of the mucosa. Endoscopy, 10:255-260.

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