Introduction: The sellar wall of the sphenoid sinus and its recesses have been previously studied,
but their intracranial relationships to the clinoid segment of the internal carotid
artery, chiasmatic sulcus, tuberculum, diaphragma sellae, and middle clinoid process
need further definition.
Objective: The objective of this study is to describe the intra- and extracranial relationships
of the recesses in the anterior sellar wall.
Methods: The middle clinoid was studied in 132 parasellar areas of dry skulls. Thirty-eight
parasellar areas of formalin-fixed/silicone-colored specimens were dissected. After
transsphenoidal endoscopic exposure, the optic, carotid, and sellar prominences; lateral
opticocarotid and tuberculum recesses; caroticosellar and medial opticocarotid points
were identified. High-speed drills opened 1-mm perforations at the reference points
to allow study of intracranial relationships.
Results: Two recesses and two junction points can be recognized in the sellar wall of the
sphenoid sinus in most cases: the lateral opticocarotid, and tuberculum recesses;
the medial opticocarotid, and caroticosellar points. The lateral opticocarotid recess
corresponds and often extends into the optic strut, and its medial projection is related
to the clinoid segment of the internal carotid artery. The level of the lateral aspect
of the distal dural ring, formed by the dura extending medially from the upper surface
of the anterior clinoid process around the carotid artery, is 1.15 mm superior to
the tuberculum recess. The deepest part of the tuberculum recess corresponds in 50%
of sphenoid sinuses to the tuberculum sellae, with the remainder being located within
a 2.5-mm range above or below the tuberculum recess. The diaphragma sellae attachment
is located at the level of the tuberculum recess or slightly inferior. When a carotid
cave is present, it can be referenced medial to the carotid artery between the medial
opticocarotid and caroticosellar points. No sinus prominence or recess corresponds
to the chiasmatic sulcus as the surface of the planum blends into the tuberculum recess.
The chiasmatic sulcus can be referenced in the sphenoid sinus in the area above the
tuberculum recess between both optic prominences. A clinically relevant middle clinoid
process (greater than 1.5 mm) is present in 21.1% of parasellar areas and joins the
anterior clinoid forming a caroticoclinoid ring in 2.94%. The superomedial point of
the middle clinoid process base is most frequently located approximately 1 mm inferior
and lateral to the caroticosellar point, with its highest part further inferior and
lateral. The middle clinoid is inferior to the medial opticocarotid point in all cases,
4.75 mm on average. The middle clinoid process protrudes inside the cavernous sinus;
in case of a caroticoclinoid ring, this structure forms part of the roof of the cavernous
sinus.
Conclusion: An understanding of the intra- and extracranial relationships of the recesses of
the sphenoid sinus will aid in accurately directing transsphenoidal approaches.
