Medial wall of the cavernous sinus: microanatomical diaphanoscopic and episcopic investigation

To elucidate the question whether expansion of pituitary adenomas into the cavernous sinus (CS) has to be regarded as focal penetration rather than invasion, a microanatomical study of the medial wall (MW) of the CS was performed. Fourteen sellar hemiblocks underwent microsurgical dissection from lateral and medial approach. The thickness of the MW of the CS was examined by diaphanoscopy. The internal carotid artery (ICA) was adherent to the MW in five cases. In five specimens the lateral wall of the sella turcica consisted of a single layer without perforations. In nine cases this wall had two layers. There was no perforation of both layers in any case. Diaphanoscopy revealed thin MW in the lateral border of the sella (n = 13), below the horizontal segment of the ICA (n = 10), and antero-inferiorly to the carotid syphon (n = 9). Expansion into the CS may be facilitated by low anatomical resistance against chronic tumor growth.