| Modifications of the transsphenoidal approach have been proposed in an attempt to enhance the surgical removal of lesions extending beyond the limit of the sella turcica, particularly for lesions involving the supradiaphragmatic intradural space, the medial compartment of cavernous sinus (CS) and the clival region as well. These extensions of the transsphenoidal approach expose anatomic structures not frequently visualized during standard transsphenoidal surgery. It is very important to study and assess the novel approach as the clinical application is very limited. The objective of this report is to provide pertinent anatomic data and details for the clinical application of the extended transsphenoidal approach; to probe the anatomic characteristic and method under microscope and endoscope; and to provide imaging anatomy basis for the extended approach.Adult cadaver heads fixed in formalin were used to dessect, observe, measure and photograph the relationship between the neural and vascular structure and the important anatomic landmarks related to the extended transsphenoidal approach under microscope and endoscope. The sellar regions of four specimens were examined histologically to observe themedical wall of the CS. Twenty adult cadaver head specimens were studied through thinner CT scanning with coronal, sagittal, axial position, to provide the imaging anatomy basis related to the extended transsphenoidal approach.The results are as follows:1. The extension to the supradiaphragmatic intradural space by the transsphenoidal approach was limited by the optical canals, the posterior ethmoidal neurovascular bundle and the cribriform plate. The surgical access may be enlarged by forming posterior ethmoid cells and sphenoidal sinus into a single foramen. The distance between the optic nerves at their entrance into the optic canals and orbits was 15.8 2.69mm and 24.6 2.38mm respectively. Among the posterior ethmoidal neuro vascular bundle 15 branches ( 37.5% ) were located in sphenoethmoidal lamina, 16 (40%) in posterior ethmoidal cell, and 9 (22.5%) at the anterior wall of the posterior ethmoidal cell. The distance between the sellar turcica anterior wall and the posterior ethmoidal neurovascular bundle was 16.8 2.36mm, and the distance between the sellar turcica anterior wall and cribriform palate was 20.54 4.37mm.The extension to the clivus by the transsphenoidal approach was limited by the tubal torus and the hard plate. The distance between the lowest point and the midpoint of sella turcica was 43.6 4.5mm. Thesurgical operation was limited in this area because of the covert clivus behind the sella, which was blocked by hypophysis, the inferior hypophyseal artery supplying posterior lobe of hypophysis and dural of sellar floor, the communication of posterior circular sinus, the basilar sinus and the circular sinus.The extension to the CS by the transsphenoidal approach was limited by nasal piriform orifice and bony posterior nasal aperture, and also affected by the pneumatization of the sphnoidal sinus itself. Thus it was obviously more difficult than the extension to the supradiaphragmatic intradural space and the clivus. In this report the width of the bottom of the nasal piriform bony orifice was 25.4 1.23mm. The inferior and lateral boundary of the bony posterior nasal aperture were the palatine horizontal plate and the medial pterygoid plate respectively. The distance between the medial pterygoid plates was 25.9 1.76mm. The width of view field was 2.5cm. The mean distance between the ICAs at the tuberculum sellae was 13.8 0.67mm, which could ensure the exposure of the medial compartment of CS. The exposure of the contralateral CS could be enlarged by the removal of frontal process of the maxilla and removal of the medial pterygoid plate was helpful to surgery. The mobilization of ICA could expose the cranial nerves of the lateral wall of CS. There existed hazards in the removal ofthe cavernous sinus carotid artery due to the dissection of the distal...
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