Approach to sphenoid sinus according to standard ent textbook

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Approach to the Sphenoid Sinus

(Sources: Cummings Otolaryngology, KJ Lee's Essential Otolaryngology, Scott-Brown's Otorhinolaryngology)

Anatomy and Ostium Landmarks

The sphenoid sinus is the most posterior paranasal sinus. Its natural ostium drains into the sphenoethmoidal recess (SER) - the space medial and posterior to the superior turbinate, anterior to the anterior sphenoid wall, and lateral to the nasal septum.

Key landmarks (Cummings):

The ostium is consistently medial to the superior turbinate
Located approximately halfway to two-thirds up the anterior sphenoid wall
Situated at 6.2-8.0 cm (average 7.1 cm) from the nasal spine at an angle of 30-34 degrees to the nasal floor
Always lower than the level of the maxillary sinus roof - following this landmark prevents inadvertent skull base penetration
Approximately 1.5 cm above the choana

Sphenoid ostium landmarks - 7cm at 30 degrees from nasal spine; note ICA relation to intersinus septum

Critical danger: Intersinus septae frequently attach to the bony canal of the ICA. These must be removed without any torsion if resection is needed. The ICA and optic nerve are dehiscent in 20% and 5% of cases respectively.

Surgical Approaches

1. Transnasal (Direct) Approach

Indications: Isolated sphenoid sinus disease, or approaching tumours within the sphenoid skull base. Performed through one nostril.

Steps:

Middle turbinate is carefully medialized with a Freer elevator (avoid destabilizing the basal lamella)
The superior turbinate is identified and its inferior half cut sharply at the transition of the vertical to horizontal segment
The sphenoid ostium is visualized in the SER, medial to the superior turbinate attachment
A stapes curette is used to bluntly palpate and curette the ostium edges
Ostium enlarged with a 2-mm Kerrison rongeur or sphenoid mushroom punch
If using a microdebrider - blades directed medially and inferiorly only (never lateral - risks ICA/optic nerve)
Lowering the anterior sphenoid face: beware the posterior septal branch of the sphenopalatine artery coursing in the mucosa overlying the inferior sphenoid face

If access is narrow: the posterior middle turbinate can be partially removed with microscissors. Initial sphenoidotomy is made with a micro-Kerrison punch at the ostium, enlarged inferiorly avoiding the septal artery.

2. Transethmoidal Approach

Indications: When a sphenoethmoidectomy is to be performed; often done prior to ethmoid skull base dissection.

Steps (KJ Lee):

Complete posterior ethmoidectomy first
The superior turbinate is cut sharply at the vertical-horizontal junction to directly visualize the sphenoid ostium (medial to superior turbinate attachment)
The safest entry is via the natural ostium (not by punching through the posterior wall of the most posterior ethmoid cell)
A stapes curette bluntly palpates and curettes the ostium edges
Further enlargement with Kerrison rongeurs and sphenoid mushroom punches

From within the ethmoid, there are two methods (Cummings):

Enter through the inferomedial part of the most posterior ethmoidal cell (less preferred)
Formally identify the sphenoid ostium in the SER via the superior turbinate landmark (preferred)

The inferior third of the superior turbinate may be resected for full visualization. Resection of the inferior half does not appear to disrupt olfactory function, but overresection must be avoided as the superior turbinate bears olfactory fibers.

Endoscopic steps of left sphenoid sinusotomy: (A) Identifying SER, (B) Ostium in SER medial to ST, (C) Inferior ST resection, (D-E) Punch enlarging ostium, (F) Completed sinusotomy with skull base identified

3. Transseptal Approach

Indications: Pituitary adenomas, lesions of the sella/parasellar region, clivus, and parasellar tumours. Provides midline access while protecting lateral structures (ICA, optic nerve).

Steps (Cummings):

Submucoperiosteal infiltration with ropivacaine 0.75% + epinephrine 1:100,000 (hydraulic dissection)
Vertical hemitransfixion incision at the caudal edge of the septal cartilage
Elevation of septal flaps (as in septoplasty)
Disarticulation of the osseocartilaginous junction - preserve the uppermost part to avoid postoperative dorsal nasal saddling
Fracture the posterior septal attachment to the perpendicular lamina of the ethmoid
Resect the posterior septal bone (Jansen-Middleton forceps) to expose the sphenoid rostrum
Elevate mucoperiosteum of the anterior sphenoid wall until both ostia are visualized
Open anterior wall with Kerrison micropunch, enlarge with 5-mm diamond bur
Sphenoidotomy made large enough to introduce a 4-mm endoscope and instrument simultaneously

4. Transseptal-Transnasal (Binostril, Four-Hand) Approach

Described by Stamm et al. (2008). Enables work by two surgeons with four hands without nasal septal perforation.

Key steps:

Hemitransfixion incision unilaterally with bilateral subperichondrial/periosteal dissection
Cartilage incised 1 cm posterior to anterior limit, preserving the L-shaped strut of cartilage
Bony septum removed, inferior portion left as midline landmark
A pedicled mucoperichondrial flap (based on sphenopalatine artery - the Hadad-Bassagasteguy flap) is elevated on the contralateral side for skull base reconstruction

Ostium Enlargement - Principles

Once the ostium is identified (Cummings):

Insert a small curette, opening directed first inferiorly and medially - avoid trauma to the nasal septum
Use a small sphenoid punch or microdebrider to widen
Avoid circumferential opening - prevents postoperative stenosis; preserve ostium mucosa medially
Beware of small arterial branches from the sphenopalatine artery inferiorly, medially, or laterally
A 30-degree angled endoscope helps visualize disease in superior and lateral recesses
Instrumentation posteriorly, posterolaterally, or superiorly must be done carefully (ICA, optic nerve, skull base)

Classification of Sphenoid Surgery (KJ Lee)

Type	Description
Type I	Identification of ostium without further intervention
Type II	Enlargement of ostium to the level of the cranial base and inferiorly to one-half of sinus height
Type III	Widening the ostium to its most lateral extent

Extended Sphenoid Procedures / "Sphenoid Rescue"

Indications: Extensive disease, previous surgical failure, large mucocele, fungus balls, extensive nasal polyposis.

Includes:

Bilateral extended sphenoidotomies
Posterior nasal septectomy
Sphenoid rostrum resection
Intersinus septectomy
Goal: create a common sphenoid cavity with broad drainage

Pneumatization Patterns (Scott-Brown)

Relevant for surgical planning - especially for transphenoidal approaches to pituitary tumours:

Type	Frequency	Description
Sellar	90%	Pneumatization posterior to sella turcica
Pre-sellar	9%	Pneumatization up to the anterior sella
Conchal	1%	Shallow, minimal pneumatization with trabecular bone between sinus and sella

Lateral pneumatization into the pterygoid root creates a lateral sphenoid recess, which runs between the second division of the trigeminal nerve (V2) and the vidian nerve.

Danger Points Summary

ICA - dehiscent in ~20%; intersinus septae often attach to it
Optic nerve - dehiscent in ~5%; at risk with lateral microdebrider use
Sphenopalatine artery (posterior septal branch) - runs over the inferior sphenoid face
Skull base - stay below the maxillary sinus roof level; use the calibrated probe (7 cm from nasal sill at 30 degrees)
Olfactory fibers on superior turbinate - avoid overresection

- Cummings Otolaryngology Head and Neck Surgery, Ch. 44 & 177 - KJ Lee's Essential Otolaryngology, Ch. on ESS - Scott-Brown's Otorhinolaryngology Head & Neck Surgery Vol. 1, Ch. 87

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