Anatomical And Clinical Studies On Medial Wall Of Cavernous Sinus By Transsphenoidal Approach

Hypophyseal region is situated in the midline of skull base and is also the center of the cranial cavity. Many important anatomic structures, such as hypophysis, a pair of CS, ICA andⅢ～Ⅵcranial nerves are contained in this region. For several decades, many neurosurgeons and neuroanatomic scholars are dedicated to treat the lesions in the pituitary region. However, pituitary adenoma is the most common disease in this region, which also has been paid the most attention to. And the parasellar expansion of adenomas always provided tremendous disturbs for the fully dissection of tumor, if which has invaded into CS and enveloped the CS segment of ICA. Traditionally, the craniotomy was used to dissect the tumor, but the numerous neurovascular structures always occupied the surgical operation field that it was very difficult to dissect the tumor. And the dysfunction of cranial nerves always reduced the postoperative life condition of patients. Recently, with the progress of transsphenoidal surgical techniques and the improvement of operative instruments, the transsphenoidal approach has been applied widely to surgically dissect pituitary adenoma. Because of several advantages of this approach, such as the nearest distance, lowest injury and shortest operative time, it has been accepted by more and more neurosurgeons, and been paid more attention to by more and more neuroanatomic scholars. And the extension transsphenoidal approach has been mentioned more and more frequently to treat the parasellar or suprasellar lesions, especially the macroadenomas which has extended into CS. As we known, most of cranial nerves in CS are located in the lateral wall of CS. And because the operative manipulation was conducted from medial wall of CS in transsphenoidal approach, these nerves won't hinder the operative visual line. But how to use this approach better? After reviewing lots of previous literatures, the anatomical and morphological characteristics of sellar region were studied mostly in the transcranial approach. However, with the view angle of transsphenoidal approach, the morphological characteristics of pituitary gland, CS and the neurovascular structures in it has not bee reported detailedly. And there still lots of controversies and misunderstanding about this region. In order to make clear these problems, histological and anatomical methods were taken to investigate the morphological characteristics of fetal and adult specimens. And the related clinical issues were also considered to discuss the course, distribution and relationship of membranate and neurovascular structures of sellar region. Consequently, the histological and anatomical bases were provided for diagnosis and treatment of the correlated clinical diseases.【Objectives】1. Through the observation of all neurovascular Structures of sellar region in transsphenoidal approach by mean of histological and anatomical methods, and the comparing between morphological charactcristics of thcse structures with those in transcranial approach, the anatomy of sellar region will be more systematic and detailed.2. Becausc of the different surgical view angle and operative filed, there will be tremendous differences bctween the anatomical characteristics of sellar region of the two approaches. After the detailedly dcscription of the morphological results of this region, our study will also provide a good instruction for transsphenoidal operation to treat the lesions which invading the medial wall of CS.【Methods】1. Anatomical Study of Meningeal Architecture in Transsphenoidal Cavernous Sinus Surgical Approach.Histological and micro-dissection techniques were used to study 8 fetus and 10 adult cadavers respectively. The course and distribution of the membranate structures were observed. The thicknesses of membranes in the important anatomic regions were measured and analyzed histologically and anatomically.2. Anatomic study of arteries in transsphenoidal cavernous sinus surgical approach.Ten fixed cadavers' heads (six male, four female), the arteries of which were injected with red latex, Were used to perform transsphenoidal approach. The anterior wall of sphenoidal sinus and the floor of sellar turcica were opened as possible to expose floor dura mater of sella and inferior wall of CS. Then all branches of parasellar internal carotid artery (PSICA) were dissected carefully. And the anatomical data and morphological characteristic of these branches were measured and demonstrated, the result of which were compared with those in transcranial approach.3. Anatomical Study of Venous spaces in Transsphenoidal Cavernous Sinus Approach.The 4 of 10 sections rclatcd to thc intercavernous sinuses and basilar sinus were taken out to observed by optical microscopic. On the other hand, ten fixed cadavers' heads (six male, four female), the arteries and veins of which were injected with red and blue latex respectively, were used to perform transsphenoidal approach. The anterior wall of sphenoidal sinus and the floor of sellar turcica were open as possible to expose floor dura mater of sella and inferior wall of CS. After open them, the location of anterior and inferior intercavernous sinus were observed carefully. Then all spaces of CS were observed and measured. According to these results, the available venous spaces intraoperative were analysis and demonstrated.【Results】1. In all specimens, the pituitary glands were found encoated by intact proper tunics and pituitary capsules with no histological defects. The inferolateral part of pituitary capsule was thicker than the other pans, even including the sellae diaphragma and the roof of cavernous sinus (CS). Many connective tissue fibers arising from the lateral part of pituitary capsule "grow" into CS to join with the fibrous layer covering tunica vaginalis of neurovascular structures in CS. And this fibrous layer was also the inner layer of all walls of CS. At the ventral aspect of optic chiasm, the arachnoid and the pia mater fused together and extended downwards to be continuous with the proper tunic of hypophysis. At the border of diaphragmatic foramen, the diaphragm was found to stick closely to the proper tunic of the gland, with difficulty in distinguishing them.2. According to morphological charateristic, ICA in CS could be divided to two parts: PSICA and paraclival ICA (PCICA) in transsphenoidal approach. And the PSICA could be subdivided to three parts: upper, lower horizontal part and vertical part. In 9 of 20 sides CS (45%), Meningohypophyseal trunk originated from medial wall of inferior horizontal part of PSICA, 4 sides (20%) from the roof wall, 5 sides (25%) from lateral wall, 2 sides (10%) from medial wall of superior horizontal part. 16 of 20 sides (80%), The inferolateral trunk (artery of the inferior cavernous sinus) arouse from the lateral wall of vertical part, 1 sides (5%) from inferior horizontal part, 3 sides (15%) from meningohypohyseal trunk. McConnell's capsular arteries were only found in 5 sides (25%) of all species, which arise from the medial side of vertical part. And the diameter of this artery was 0.85±0.21mm, which was smaller than another branch of ICA.3. Through observation of all sections of fetal specimens, the separation of capsule and sellar floor dura cause the construction of the intercavernous sinus and basilar sinus. And in all corpse heads, 4 anterior (40%) and 5 inferior intercavernous sinuses (50%) were found. Anterior intercavernous sinus located below the optic protuberance. However, inferior intercavernous sinus located in the break-over from the sellar protuberance to the clival indentation. CSwas subdivided to three venous spaces: medial space, inferolateral space, dorsolateral space.【Conclusions】1. All walls of CS can be divided into two layers: the dural layer and the fibrous layer. And CS is a combination structure of venous caverns and veins. The physiological or pathological defects of membranate structures around diaphragmatic foramen region might be the key mechanism to cause the Empty sella.2. In transsphenoidal approach, because of the changing of optic view and field, the morphological characteristic of ICA in CS and branches intracavernous in transsphenoidal approach were different from those in transcranial approach. And the branches, which coursed medially, were a troublesome problem for treatment of those lesions involving this region. And it also was the major reason of artery blooding in transsphenoidal cavernous sinus approach. In order to reduce the blooding interoperation or post operation, understanding these anatomical and morphological of arteries in this region was the most important to surgically treat the lesion involving CS safely.3. In transsphenoidal approach, it is easy to open anterior and inferior intrecavernous sinus. As result, venous blooding would happen, and make distrouble to surgical treatment. In order to reduce the blooding interoperation or post operation, it is important to understand the location of intercavernous sinus. Reasonable utilization of these CS venous spaces could ensure that clinical neurosurgeons avoided injury of vescular and nerves intraoperative.