Unaltered,Endoscopic View of the Sphenoethmoid Recess Through the Second Pass

A wide view of the left sphenoethmoid recess (SER; Figure 1A and B) was encountered through the second pass without decongestion during routine diagnostic nasoendoscopy (4-mm 0° rigid endoscope; Karl Storz SE & Co. KG; Tuttlingen, Germany) in a middle-aged gentleman who presented with a history of recurrent epistaxis for the last 3 months.

Figure 1.

A and B, Details of the left sphenoethmoid recess could be seen by freely navigating a 0° 4-mm rigid endoscope in the undecongested second pass with a healthy, unatrophied nasal mucosa. The anatomic details could be visualized in a virgin, “unaltered” environment without mucosal and structural alteration. Asterisk, choana; MT, middle turbinate; PNA, posterior nasal artery (aka posterior septal artery); S, septum; SM, superior meatus; ST, superior turbinate.

Sphenoethmoid recess is a narrow cleft bounded medially by nasal septum (perpendicular plate of ethmoid, sphenoid rostrum), laterally by the superior turbinate (ST) and superior meatus, and posterosuperiorly by the anterior face of the sphenoid body. Sphenoethmoid recess opens anteroinferior into the nasal cavity and into the nasopharynx inferiorly. It receives drainage from the posterior ethmoid cells, and the sphenoid sinus through its ostium situated ∼1.5 cm above the choana. ¹ It can be approached through the second pass by rotating the endoscope underneath and medial to the middle turbinate (MT) where it forms the posterior—most limit of the pass. ² Its inferior aspect can be reached by directing the endoscope superior once the anterograde movement during the first pass is completed at the choana.

Sphenoethmoid recess is an important landmark for various endoscope-assisted surgeries. This area is reached at functional endoscopic sinus surgery through the lateral (transethmoid) approach when the posterior ethmoids and sphenoid are affected with chronic rhinosinusitis. Sphenoethmoid recess is also the conduit through the second pass for addressing isolated sphenoid diseases (sinusitis, fungal debris, mucocele, etc), for transsphenoid middle cranial fossa surgeries for pituitary lesions, and repair of skull-base defects (eg, in the planum sphenoidale). The posterior septal artery (PSA), aka the posterior nasal artery—one of the terminal branches of sphenopalatine artery (SPA)—runs horizontally across the sphenoid’s anterior face below its ostium. Posterior septal artery provides the nasoseptal branch that supplies the septum and forms the vascular pedicle for the Hadad-Bassagasteguy (nasoseptal) flap, the ubiquitous workhorse for anterior skull-base reconstruction. Posterior septal artery is also an important source of refractory posterior epistaxis; it may need to be cauterized separately if epistaxis continues following SPA ligation. This is because the SPA often provides its terminal branches prior to its exit through the sphenopalatine foramen. In such situations, the PSA might enter the nasal cavity through a separate bony canal in ∼16% patients. ³ Also, enlargement of the sphenoid ostium too inferiorly might lead to troublesome bleed due to inadvertent injury to the PSA or its branches.

Other than the transethmoid route, SER and the adjacent olfactory cleft are difficult-to-navigate areas in a virgin, undecongested nose with 4-mm endoscope. ² For adequate view, these areas need decongestion under endoscopic guidance by placing lignocaine–adrenaline cotton pledgets between the septum and the MT. Posteriorly, the recess may still be difficult to access without mobilizing the ST laterally. ^1,4 Also, the lower third of ST may need to be resected to visualize the natural sphenoid ostium, which lies lateral to ST in 17% patients. ^4,5 Manipulating the ST might injure the cribriform plate resulting in cerebrospinal fluid rhinorrhea; so, locating the natural ostium for sphenoidotomy is not mandatory. ¹ Visualization however might improve on the roomier side when there is gross septal deviation, or if a narrower (≤3 mm), angled (30°) endoscope is used. ²

In this patient, as a prerequisite to diagnostic nasoendoscopy, lignocaine–adrenaline cotton pledgets were being placed under endoscopic guidance along the nasal cavity floor, inferior turbinates, and anterior and lateral to the MTs. However, prior to placing the pledgets medial to the MT, the SER on the left side could be visualized in full anatomic details (Figure 1A and B). Nasoendoscopy revealed an otherwise healthy nasal mucosa. The SER on the right side could not be entered adequately, although there was no gross septal deviation. However, in the left-sided SER, the 0° 4-mm endoscope could be effortlessly negotiated without the need for mobilizing the ST. The left SER could therefore be viewed undecongested, “unaltered.” The SER was free of disease, and the natural sphenoid ostium could be located medial to the ST. The PSA was seen running across the anterior face of sphenoid, ∼0.8 cm from the lower edge of the natural ostium. Diagnostic nasoendoscopy seldom provides an adequate view of SER without decongestion, mobilization of ST, or using a small-caliber endoscope. ^1,2,4 Thus, the unaltered, endoscopic vision of SER in this patient was complete and wide, providing the scope to study the full regional anatomy with its applied surgical importance without mucosal and structural alteration. The present documentation thereby forms a brief visual resource of the endoscopic anatomy of SER for resident training and archiving purpose.