Endoscopic Transethmoid Sphenoidotomy
Peter H. Hwang
INTRODUCTION
Prior to the era of endoscopic sinus surgery, surgical approaches to the sphenoid sinus often required accessory incisions to visualize and dissect the posterior aspects of the nasal cavity. Collateral tissue removal was required of these external approaches, including a transmaxillary technique via a sublabial transantral approach and a transethmoid technique via an external Lynch incision or lateral nasal “keyhole” incision. Midline approaches to the sphenoid included open rhinoplasty, sublabial, or transnasal microscopic techniques. Despite transnasal microscopic approaches being relatively tissue sparing, all midline approaches still required dislocation or manipulation of the septum in order to access the sphenoid. Contemporary management of disease in the sphenoid sinus uses an endoscopic transethmoid approach to the sphenoid sinus that preserves tissue and function and is safe and efficacious.
HISTORY
Patients with sphenoid sinus pathology may present with a wide range of complaints from no symptoms at all to debilitating headache and prostration. Acute sphenoid sinusitis can be a medical emergency, with patients appearing toxic and classically complaining of severe vertex or retro-orbital headache. Patients with chronic sphenoid sinusitis may present with more subtle symptoms of retro-orbital pressure, nasal or ear fullness, hyposmia, and postnasal discharge. Sphenoid sinus fungus ball may be asymptomatic, presenting incidentally on imaging of the head for nonsinus indications. Benign tumors, when confined to the sphenoid cavity, may likewise cause no symptoms. However, malignant tumors involving the sphenoid sinus may present with cranial neuropathies if the bony boundaries of the sphenoid have been transgressed. Specifically, cranial nerves II, III, IV, V, and VI may be affected, presenting as impaired visual acuity, diplopia, or facial numbness.
PHYSICAL EXAMINATION
Patients with uncomplicated pathology in the sphenoid should have no abnormal physical findings on external examination. Abnormalities on physical examination should therefore alert the clinician to the possibility of a complication of sphenoid disease. Patients with acute sphenoid sinusitis with or without meningitis may present with vital signs suggestive of sepsis. In neutropenic or otherwise immunocompromised patients, a detailed examination of the cranial nerves is essential to rule out an invasive infectious process such as acute invasive fungal sinusitis. Evaluation of cranial nerve function is also important in patients with suspected neoplasms of the sphenoid. Neoplasms originating from the sellar and parasellar regions may be associated with diminished visual acuity or impaired visual fields. Abnormalities of cranial nerves III to VI suggest involvement of the cavernous sinus or the apex of the orbit.
Diagnostic nasal endoscopy is imperative for evaluation of all patients with suspected sphenoid sinus disease. In patients with suspected sphenoid sinusitis, the sphenoethmoid (SE) recess and superior meatus should be examined for edema and purulent discharge, which can be sampled and cultured to guide antimicrobial therapy. The nasal mucosa should also be examined for crusting or necrosis, which may indicate an underlying granulomatous or ischemic etiology. Nasal polyps or neoplasms protruding from the sphenoid sinus may be visible in the SE recess. Biopsy of nasal masses in the office setting can be considered on a case by case basis and approached with caution after careful review of the radiologic and endoscopic findings.
INDICATIONS
There are two primary endoscopic approaches to the sphenoid sinus: transnasal, via the medial nasal cavity to the SE recess, and transethmoid, via the anterior ethmoid sinus and superior meatus to the SE recess. Both approaches reach the natural ostium of the sphenoid sinus, but the techniques differ in the amount of tissue removed and the subsequent exposure and visualization achieved.
Transnasal sphenoidotomy provides faster access to the sphenoid ostium than a transethmoid approach because of its more direct nature, but it may not offer sufficient access to the sphenoid when tissue removal or access to the lateral sphenoid is required. Conversely, the transethmoid approach is indicated when a larger sphenoidotomy is desired; the posterior ethmoidectomy cavity can accommodate enlargement of the sphenoidotomy laterally toward the medial wall of the orbit. The transethmoid approach is also indicated when ethmoid sinus disease exists concurrently with sphenoid sinus disease, and a surgical approach addressing both sites is indicated. One significant advantage of the transethmoid approach over the transnasal approach is that it involves minimal mobilization of the middle turbinate, which can destabilize the turbinate and make it prone to lateralization.
CONTRAINDICATIONS
There are relatively few contraindications to endoscopic transethmoid sphenoidotomy. In cases of revision surgery, contraction of the ethmoid sinus from neo-osteogenesis or from lateralization of the middle turbinate may make the transethmoid approach more complex. Prolapse of orbital or intracranial contents through dehiscences of either the lamina papyracea or ethmoid skull base, respectively, can impede transethmoid access to the sphenoid sinus and place the patient at greater risk for surgical complications. Unrecognized bony dehiscences of the optic or carotid canals within the sphenoid sinus may predispose to inadvertent injury of these vital structures.
Medical comorbidities rarely serve as absolute contraindications to surgery except in severe cardiopulmonary compromise, but bleeding diatheses or blood dyscrasias such as thrombocytopenia can adversely affect endoscopic visualization and potentially increase the difficulty of performing the sphenoidotomy. In such cases, the surgeon should anticipate the need for transfusion of blood products in order to maintain an optimal surgical field.
PREOPERATIVE PLANNING
Preoperative Imaging
Preoperative review of thin-section noncontrast computed tomography (CT) of the ethmoid and sphenoid sinuses is essential prior to beginning surgery. A checklist of anatomic landmarks and variants should be reviewed, including the presence of Onodi (sphenoethmoid) cells; integrity of the bony medial orbital wall and orbital apex; integrity of the ethmoid and sphenoid skull base and of the bony optic and carotid canals; size and pneumatization pattern of the sphenoid sinus; and patency of the SE recess. While most of these landmarks can be recognized on coronal images, the axial and sagittal images can provide important supplemental anatomic perspectives. For example, the ostium of the sphenoid sinus is best seen on axial images (Fig. 15.1), and knowledge of a more medial or lateral position of the ostium as noted on the axial image can facilitate identification of the sphenoid ostium. In addition, sagittal images of the sphenoid can readily demonstrate Onodi cells by revealing “stacking” of the Onodi cell above the sphenoid sinus within the pneumatized sphenoid bone.
SURGICAL TECHNIQUE
The patient is positioned supine with the head elevated 15 to 30 degrees, which helps to reduce bleeding in the operative field. Total intravenous anesthesia facilitates an optimized surgical field with respect to control of bleeding. The eyes are taped or covered with an occlusive dressing, taking care to still allow palpation and
inspection of the orbits as needed during the case. The mucosa of the nasal cavity is decongested with a topical decongestant. To reduce bleeding from the posterior nasal arterial circulation, an injection in the area of the sphenopalatine artery can be placed either (1) transorally via the greater palatine foramen or (2) transnasally via the sphenopalatine foramen, accessed at the basal lamella of the middle turbinate using 1% lidocaine with 1:100,000 epinephrine.
inspection of the orbits as needed during the case. The mucosa of the nasal cavity is decongested with a topical decongestant. To reduce bleeding from the posterior nasal arterial circulation, an injection in the area of the sphenopalatine artery can be placed either (1) transorally via the greater palatine foramen or (2) transnasally via the sphenopalatine foramen, accessed at the basal lamella of the middle turbinate using 1% lidocaine with 1:100,000 epinephrine.
 FIGURE 15.1 The ostia of the sphenoid sinuses are readily demonstrated on axial CT scan (arrows). Noting their position relative to the nasal septum on CT can be helpful when localizing the ostia within the sphenoethmoidal recesses in situ. |
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
