Sphenoidotomy
Richard R. Orlandi
INTRODUCTION
Endoscopic sphenoidotomy is typically performed for inflammatory disease of the sphenoid sinus. The sphenoid sinus is located deep within the skull base area, and its adjacency to the pituitary gland, optic nerve, cavernous sinus, and internal carotid artery makes surgery in this area challenging. Various techniques have been developed for accessing and identifying the sphenoid sinus, including the following:
Staying medial to the middle and superior turbinates
Using a strictly transnasal, rather than transethmoid, approach can facilitate identification of the sphenoid ostium within the sphenoethmoidal recess. However, when combined with surgery lateral to the middle turbinate, operating medial to the turbinate as well can lead to its destabilization.
Measuring from the anterior nose
The face of the sphenoid is typically 7 cm from the nasal sill. Unfortunately, this technique does not typically differentiate a sphenoethmoidal (Onodi) cell from the sphenoid sinus.
Inability to see the floor of the sphenoid sinus
The floor of the sphenoid sinus typically cannot be seen with a zero-degree nasal telescope. This finding differentiates the sphenoid sinus from posterior ethmoid cells, especially sphenoethmoidal (Onodi) cells. Significant hypoplasia of the sphenoid sinus, as can be seen in cystic fibrosis, or severe edema that can effectively raise the mucosal floor of the sphenoid sinus may alter this finding.
Image-guided surgery (IGS)
IGS can be very helpful in confirming the position of instruments within the sinuses, especially in the sphenoid sinus. IGS confirms the anatomy of the face of the sphenoid sinus and can ensure appropriate entry into and opening of the sphenoid sinus, thereby assuring treatment of this sinus. It is, however, not foolproof and is meant to be used as a tool to confirm anatomy, not determine it. IGS is not a substitute for anatomic knowledge and surgical teaching.
Use of the superior turbinate as a landmark
The superior turbinate has been shown to be a reliable landmark to the natural ostium of the sphenoid sinus, whether through a transethmoid or a transnasal approach.
HISTORY
Inflammation of the sphenoid sinus is the primary indication for surgery. Acute and chronic sphenoid sinusitis can present with pain in the temporal, occipital, or retro-orbital regions. Chronic inflammation of the sphenoid sinus is most often seen in conjunction with other affected sinuses so that sphenoid symptoms may not stand out. Involvement of the sphenoid sinus by inflammation is best assessed using a CT scan following a trial of medical therapy.
PHYSICAL EXAMINATION
Because of the deep location of the sphenoid sinus, findings of uncomplicated sphenoid inflammation are confined to those seen during nasal endoscopy. Edema, polyps, and abnormal secretions in the sphenoethmoidal recess can all be seen during nasal endoscopy. Complications of sphenoid inflammation affecting the eye or cavernous sinus can manifest as orbital findings.
INDICATIONS
Indications for endoscopic sphenoidotomy are as follows:
Acute sphenoid sinusitis unresponsive to medical therapy.
Chronic sphenoid sinusitis unresponsive to medical therapy.
Acute or chronic sphenoid sinusitis with an orbital or intracranial complication.
Sphenoid sinus mucocele.
Cerebrospinal fluid leak of the sphenoid sinus. Leaks involving the lateral pterygoid recesses of a well-pneumatized sinus may require addition of a transpterygopalatine fossa approach.
Tumors involving the sphenoid sinus or medial middle cranial fossa, especially the sella turcica.
CONTRAINDICATIONS
Sphenoid sinus surgery is contraindicated when insufficient instrumentation or an inexperienced surgeon is encountered. The patients general fitness for surgery including cardiovascular, pulmonary, and coagulation considerations applies to sphenoid surgery as well.
PREOPERATIVE PLANNING
Surgery should follow a thorough assessment and trial of medical therapy for inflammatory disease, or where other indications are present. Once surgery has been decided upon, the patient’s individual anatomy must be assessed on the preoperative CT study. Items to be considered are the following:
Size of the sphenoid sinuses. The sinus can be hypoplastic, especially in cases of cystic fibrosis. This anomaly must be recognized preoperatively in order to determine how large an opening can be created in the anterior face of the sphenoid sinus.
Deviation of the intersinus septum. The intersinus septum may severely deviate to one side, making for one large and one small sphenoid sinus. Again, the relative size of the sinus dictates how large an opening can be made. In cases where the intersinus septum is to be removed, as in pituitary surgery, great care should be taken with a severely deviated partition as it may terminate laterally in the internal carotid artery. Avulsing this posterolateral termination could lead to an injury to the internal carotid artery.
Degree of inflammation. In nearly all cases of sphenoid sinus surgery, the floor of the sinus cannot be seen with a zero-degree nasal telescope. This is one clue to determining position within the sphenoid sinus, as opposed to a large posterior ethmoid cell. In cases where there is severe edema or opacification of the sinus, the mucosa of the floor of the sphenoid sinus may be so edematous as to make it visible with a zero-degree telescope. Such conditions should be identified preoperatively.
Anatomic variations. Extensive pneumatization of the posterior ethmoid sinus can result in expansion into the sphenoid bone. This occurs as the sphenoid sinus is developing at the same time. The result is that two sinuses pneumatize the sphenoid bone: a sphenoethmoidal (Onodi) cell and the true sphenoid sinus. In this variation, the sphenoethmoidal cell is superior to the sphenoid sinus. On coronal CT imaging, a horizontal bone partition is seen dividing the sphenoid sinus below from the sphenoethmoidal cell above.
SURGICAL TECHNIQUE
Hemostatic Measures
For procedures that involve the posterior ethmoid or sphenoid sinuses, an injection of the sphenopalatine artery is performed as it enters the nose through the sphenopalatine foramen. This injection provides vasoconstriction and also limits stimulation, allowing for decreased systemic anesthetic. The injection can be performed through a transpalatal or transnasal route.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
