Microanatomic study on extension to the medial compartment of cavernous sinus by extended transsphenoidal approach

Objective To provide the anatomical evidence for extended transsphenoidal approach into the medial compartment of cavernous sinus.Methods Fifty adult cadaveric head specimens were dissected in detail under an operating microscope for observing and measuring the lateral wall of sphenoid sinus,sella turcica,cavernous sinus and related structures.The transsphenoidal approach was extended by stripping the ventral bone of cavemous sinus,cutting the median wall of cavernous sinus to exposure the median compartment.Results In 58% cases,the internal carotid artery(ICA)was prominent beyond the median wall of sphenoid sinus,and in 3%,the prominence was of canal form.The medial wall of cavernous sinus had two separate components.In its upper part,the medial wall of the cavernous sinus was formed by the dural layer of the pituitary gland without bony support;in its lower part,the medial wall of cavernous sinus was formed by the periosteal dura of the sella turcica and supported by the bone of the lateral wall of the sphenoid sinus.The mean distance between the two medial walls of the cavernous sinus was(14.8±2.7)mm.The medial compartment of cavernous sinus was located between the ICA(C4 segment)and pituitary gland,and was filled with venous plexus,with the largest width of 7 mm.The veins were often twisted and occluded because of ICA prominence.No cranial nerves traversed the medial compartment.The ICA was the first major structure encountered in the exploration of the cavernous sinus through a transsphenoidal approach.Conclusion The data prove the safe and feasibility of the clinical application of the extended transsphenoidal approach into the medial compartment of cavernous sinus.