Endoscopic Sphenoidotomy

The paired sphenoid sinuses are the most posteriorly positioned of the paranasal sinuses. Due to this location, endoscopic approaches to the sphenoid sinus are preferred to address most pathology that may arise in this location. The pathology may be isolated within the sphenoid sinus or may be part of inflammatory sinonasal disease involving the ethmoid or other paranasal sinuses. The sphenoid sinus is also the gateway to many extended endonasal procedures, including approaches to pituitary lesions, other sellar and parasellar lesions, and petroclival lesions amenable to an endonasal approach.

The two main endoscopic pathways to the sphenoid sinus are the transseptal and transethmoid approaches. Both require identification of the natural sphenoid ostium medial to the superior turbinate (ST) and enlargement of this ostium for endoscopic access. These approaches may be combined with a posterior septectomy for simultaneous access to both sphenoid sinuses, most commonly indicated for extended endonasal approaches ( Figs 110.1 and 110.2 ).

Fig. 110.1, Endoscopic view of right sphenoid ostium medial to superior turbinate (retracted laterally in this image). Previous total ethmoidectomy and maxillary antrostomy have been performed.

Fig. 110.2, Right sphenoid ostium is visible following resection of the inferior one-third of the superior turbinate.

The transseptal approach proceeds through the sphenoethmoidal recess, in the geometrically narrow airspace between the nasal septum medially and the middle turbinate laterally. This corridor rarely requires ethmoid dissection or resection of the ST and thus has the advantage of a simpler dissection with preservation of olfactory fibers. This is the most direct endoscopic approach and is most commonly used for isolated sphenoid pathology and for access to the sphenoid sinus for extended endoscopic approaches in the sagittal plane.

The transethmoid approach to the sphenoid sinus proceeds lateral to the middle turbinate and requires dissection of the uncinate process, anterior and posterior ethmoid sinus labyrinths, and typically resection of the inferior one-fifth to one-third of the ST. The approach affords a larger corridor for improved endoscopic visualization and instrumentation and provides for early identification of the skull base and lamina papyracea landmarks prior to enlarging the sphenoid ostium and taking down the rostrum. This approach is most commonly used as part of functional sinus surgery in the management of chronic sinusitis.

In some patients, the sphenoid sinus may have pneumatization of a lateral recess between the vidian and trigeminal nerves, and selected lesions in this part of the sphenoid, such as a meningoencephalocele, may be approached endoscopically with the addition of a transpterygoid dissection. The latter approach requires a transethmoid corridor to the sphenoid sinus, combined with a wide maxillary antrostomy with posterior maxillary wall/pterygopalatine fossa dissection to allow unobstructed endoscopic access to the lateral recess of the sphenoid sinus.

Key Operative Learning Points

1.
The two main endoscopic approaches to the sphenoid sinus are transnasal and transethmoid.
2.
The preferred point of entry to the sphenoid sinus is through the natural ostium, always located medial to the ST and just lateral to the articulation of the nasal septum into the face of the sphenoid sinus/sphenoid rostrum.
3.
The sphenoid sinus is in close proximity to critical structures, including the internal carotid artery, optic nerve, orbital apex and intraconal musculature, posterior ethmoid artery, pituitary gland, and skull base, any of which may be injured during endoscopic surgery.

History

1.
History of present illness
- a.
  The nature, severity, and duration of symptoms related to sphenoid pathology should be obtained. In chronic rhinosinusitis, this may include cardinal symptoms of nasal obstruction, postnasal drip or chronic drainage, loss of the sense of smell, or facial pain. Sphenoid sinusitis classically, though not reliably, produces headaches felt at the scalp vertex and/or deep-seated retro-orbital pain.
- b.
  Determine if there are associated symptoms, especially if noninflammatory disease is suspected. This may include ophthalmologic deficits such as visual loss, decreased color vision, diplopia, or xerophthalmia. Look for signs of orbital apex syndrome (decreased vision, ophthalmoplegia, proptosis) or superior orbital fissure syndrome (ophthalmoplegia, proptosis). Evaluate any neurologic complaints, including changes in mental status, facial numbness, and severe headache.
- c.
  For chronic sinusitis, the history should include recent requirements for antibiotic or oral steroid therapy, current use of topical nasal medications including saline lavage, clinical response to these medications, previous medications trialed for control of symptoms, and any associated asthma, allergies, aspirin sensitivity, or immunodeficiency.
- d.
  Additional questions may be tailored to the suspected pathology. For example, for sphenoid sinus meningocele, whether there is any antecedent history of unilateral rhinorrhea, or history of meningitis, assess for risk factors for chronic invasive fungal sinusitis, including immunocompromise, history of diabetes, and country of origin.
2.
Past medical history
- a.
  Determine the patient’s current level of general health, including the history of major systemic disease, history of cardiopulmonary disease, and fitness for general anesthesia.
- b.
  Survey for systemic disease that may present with sinonasal complaints. These include granulomatosis with polyangiitis (formerly known as Wegener’s granulomatosis), sarcoidosis, Churg-Strauss disease, aspirin-exacerbated respiratory disease (Samter’s triad), and/or cystic fibrosis.
- c.
  Elicit any history of previous sinus, nasal, or skull base procedures, and whether there were any associated complications with these procedures. Revision endoscopic surgery often proceeds through distorted anatomy which increases the complexity of the procedure.
- d.
  Family history: History of coagulopathy or atopy
- e.
  Medications:
  - 1)
    Antiplatelet drugs
  - 2)
    Herbal products such as garlic, ginseng, and gingko

Physical Examination

1.
A complete examination of the head and neck should be performed on all patients.
2.
Preoperative, diagnostic nasal endoscopy should be performed on all patients undergoing endoscopic sphenoidotomy. The nose should be prepared with topical anesthetic with decongestant. Endoscopic visualization of the sphenoethmoid recess in the unoperated nose is best tolerated with a 30-degree endoscope angled superiorly and passed posterior along the floor of the nose, following the course of the inferior turbinate. In the setting of ongoing inflammation, is sometimes not possible to visualize the sphenoid ostium without manipulation of the turbinates. A trail of purulence arising from the sphenoid sinus and/or posterior ethmoid complex can sometimes be seen in this recess.

Imaging

Computed Tomography Imaging

Computed tomography imaging (CT) best defines the pneumatization and bony confines of the sphenoid sinus, including the presence of dehiscent bone of the optic nerve canal, internal carotid artery canal, and/or skull base. A deviated septum, ethmoid disease, and the lateral recess that may be encountered during an endonasal approach may be identified preoperatively. CT may be paired with a computer-assisted intraoperative navigation system for assistance in endoscopic identification of landmarks, including the natural ostium. The sphenoid sinus should be evaluated on axial, coronal, and sagittal views, preferably with cuts of less than 1 mm. Bone windowing is useful, and, in the case of opacification, soft tissue-windowing should be studied to evaluate the contents of the sinus. Heterogeneous opacification of the sphenoid sinus could signal the presence of a fungal ball, eosinophilic mucin, or a sinonasal tumor.

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is indicated in select cases to further characterize the internal contents of the opacified sphenoid sinus or soft tissue lesions found in this cavity or to identify extrasinus extension of disease. This includes suspected neoplasm, encephalocele or meningocele, and complicated rhinosinusitis.

Indications

1.
Chronic, symptomatic sphenoid sinusitis after failure of a trial/several trials of maximal medical therapy
2.
Neoplasm involving the sphenoid sinus, for biopsy and/or definitive management
3.
Cerebrospinal fluid leak, with or without associated meningoencephalocele, for endoscopic repair of the skull base
4.
Access for expanded endonasal approaches to the cranial base or orbit

Contraindications

1.
Not medically fit for surgery
2.
Largely dehiscent carotid artery (relative)

Preoperative Preparation

1.
A course of oral steroids and antibiotics may be considered for 3 to 5 days prior to surgery to reduce inflammation and bleeding and to improve endoscopic visualization.
2.
Preoperative medical clearance, if necessary
3.
Reverse/manage anticoagulation, if necessary
4.
Obtain consent for surgery, including discussion of possible risks, benefits, and alternatives to surgery.

Operative Period

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Introduction