Anatomic Variations of the Sphenoid Sinus and Their Impact on Trans-sphenoid Pituitary Surgery

Abstract

Introduction: The trans-sphenoid access to the pituitary gland is becoming the most common approach for pituitary adenomas. Preoperative evaluation of the anatomy of the sphenoid sinus by computed tomography (CT) scan and magnetic resonance imaging (MRI) is a routine procedure and can direct the surgical decision.

Purpose: This work determines the incidence of the different anatomical variations of the sphenoid sinus as detected by MRI and CT scan and their impact on the approach.

Methods: The CT scan and MRI of 296 patients operated for pituitary adenomas via a trans-sphenoid approach were retrospectively reviewed regarding the different anatomical variations of the sphenoid sinus: degree of pneumatization, sellar configuration, septation pattern, and the intercarotid distance.

Results: There were 6 cases with conchal pneumatization, 62 patients with presellar, 162 patients with sellar, and 66 patients with postsellar pneumatization. There was sellar bulge in 232 patients, whereas this bulge was absent in 64 patients. There was no intersphenoid sinus septum in 32 patients, a single intersphenoid septum in 212 patients, and an accessory septum in 32 patients. Intraoperatively, the sellar bulge was marked in 189 cases and was mild in 43 cases.

Discussion: The pattern of pneumatization of the sphenoid sinus significantly affects the safe access to the sella. A highly pneumatized sphenoid sinus may distort the anatomic configuration, so in these cases it is extremely important to be aware of the midline when opening the sella to avoid accidental injury to the carotid and optic nerves. The sellar bulge is considered one of the most important surgical landmarks, facilitating the access to the sella. The surgical position of the patient is also a crucial point to avoid superior or posterior misdirection with resultant complications. It is wise to use extreme caution while removing the terminal septum.

Conclusion: Different anatomical configurations of the sphenoid sinus can seriously affect the access to the sella via the nose. The surgeon should be aware of these findings preoperatively to reach the sella safely and effectively.

Keywords: Sphenoid sinus; pituitary adenoma; pneumatization; trans-sphenoid approach.

Figure 1

Computed tomography scan of the sella, coronal cuts, bone window, showing conchal or absence of pneumatization of the sphenoid sinus.

Figure 2

T1-weighted magnetic resonance imaging of the sella, sagittal cuts, showing presellar pneumatization of the sphenoid sinus with absent sellar bulge.

Figure 3

T1-weighted magnetic resonance imaging of the sella, showing postsellar pneumatization of the sphenoid sinus, with prominent sellar bulge (arrow) and a pneumatized Dorsum sella (arrowhead).

Figure 4

Computed tomography scan of the sella, coronal cuts, bone window, showing lateral pneumatization of the greater wings of the sphenoid sinus and multiple sphenoid sinus septa.

Figure 5

T1-weighted magnetic resonance imaging of the sella, showing a postsellar pneumatization of the sphenoid sinus and a pneumatization of the planum sphenoidale (arrowhead).

Figure 6

T1-weighted magnetic resonance imaging of the sella, showing an intersphenoid septum pointing toward the left internal carotid artery.