Microarchitecture of the cavernous sinus walls: Clinical implications for pituitary adenomas

The cavernous sinus (CS) is often invaded by pituitary adenomas, crossing the medial wall (MW), while the lateral wall (LW) is rarely breached. The structural differences between these walls remain poorly understood. This study investigated collagen subtypes distribution in human fetal and adult CS specimen to explore the basis for MW-specific invasion.

Twenty-two CS from eleven adult cadaveric human heads and two fetal specimens were dissected via transcranial and endoscopic approaches. Samples from the MW, LW, anterior wall, and diaphragm sellae were analyzed for collagen types I-IV staining by immunohistochemistry.

All CS walls were identifiable in adult and fetal specimen. The MW and LW were composed of loose collagenous tissue; cranial nerves were present in the LW. In adults, type I collagen was weakly expressed in the MW and absent in the LW and fetal CS. Type II collagen appeared only in fetal cartilage. Type III collagen was present in the MW and partially in the LW of adults, and across both dural layers in fetuses. Type IV collagen was absent in adult dura but weakly present in fetal dura and strongly expressed in pituitary, perineurium, and carotid walls.

Collagen composition within the cavernous sinus undergoes marked changes with age, characterized by an increase in type I and III and a decline in type IV collagen. The structural differences, particularly between the MW and LW, may underlie the MW's increased vulnerability to invasion by pituitary adenomas, potentially driven by MMP-dependent degradation pathways.