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

Anatomy of the medial wall of the cavernous sinus: A systematic review of the literature

The existence, composition, and continuity of the medial wall of the cavernous sinus (MWCS) have been extensively studied and debated. However, the precise nature of this membrane remains unknown. Understanding the anatomical characteristics of the MWCS is crucial, notably in relation to pituitary adenomas, which often invade the cavernous sinus. Indeed, surgical treatment of those tumors is frequently incomplete because of such invasion. The anatomical and molecular basis of the peculiar and often lateralized tropism of adenomatous cells to the cavernous sinus is not yet understood and it has been suggested repeatedly that the MWCS is physiologically frail. During the past three decades, there have been several conflicting accounts of the existence, composition, and continuity of this medial wall, but methodological differences and varying definitions could have contributed to the current lack of consensus regarding it. The aim of this systematic review was to summarize previously published data concerning the existence, anatomy, composition, and continuity of the MWCS.

The "candy wrapper" of the pituitary gland: a road map to the parasellar ligaments and the medial wall of the cavernous sinus

PURPOSE

The anatomy of the medial wall of the cavernous sinus (MWCS) and parasellar ligaments (PLs) has acquired increasing importance in endoscopic endonasal (EE) surgery of the cavernous sinus (CS), including resection of the MWCS in functioning pituitary adenomas (FPAs). Although anatomical studies have been published, it represents a debated topic due to their complex morphology. The aim is to offer a description of the PLs that originate from the MWCS and reach the lateral wall of the cavernous sinus (LWCS), proposing the "candy wrapper" model. The relationships between the neurovascular structures and histomorphological aspects were investigated.

METHODS

Forty-two CSs from twenty-one human heads were studied. Eleven specimens were used for EE dissection; five underwent a microscopic dissection. Five specimens were used for histomorphological analysis.

RESULTS

Two groups of PLs with a fan-shaped appearance were encountered. The anterior group included the periosteal ligament (55% sides) and the carotico-clinoid complex (100% sides), formed by the anterior horizontal and the carotico-clinoid ligaments. The posterior group was formed by the posterior horizontal (78% sides), and the inferior hypophyseal ligament (34% sides). The periosteal ligament originated inferiorly from the MWCS, reaching the periosteal dura. The anterior horizontal ligament was divided in a superior and inferior branch. The superior one continued as the carotid-oculomotor membrane, and the inferior branch reached the CN VI. The carotico-clinoid ligament between the middle and anterior clinoid was ossified in 3 sides. The posterior horizontal ligament was related to the posterior genu and ended at the LWCS. The inferior hypophyseal ligament followed the homonym artery. The ligaments related to the ICA form part of the adventitia.

CONCLUSION

The "candy wrapper" model adds further details to the previous descriptions of the PLs. Understanding this complex anatomy is essential for safe CS surgery, including MWCS resection for FPAs.

The Party Wall: Redefining the Indications of Transcranial Approaches for Giant Pituitary Adenomas in Endoscopic Era

The evolution of endoscopic trans-sphenoidal surgery raises the question of the role of transcranial surgery for pituitary tumors, particularly with the effectiveness of adjunct irradiation. This narrative review aims to redefine the current indications for the transcranial approaches for giant pituitary adenomas in the endoscopic era. A critical appraisal of the personal series of the senior author (O.A.-M.) was performed to characterize the patient factors and the tumor's pathological anatomy features that endorse a cranial approach. Traditional indications for transcranial approaches include the absent pneumatization of the sphenoid sinus; kissing/ectatic internal carotid arteries; reduced dimensions of the sella; lateral invasion of the cavernous sinus lateral to the carotid artery; dumbbell-shaped tumors caused by severe diaphragm constriction; fibrous/calcified tumor consistency; wide supra-, para-, and retrosellar extension; arterial encasement; brain invasion; coexisting cerebral aneurysms; and separate coexisting pathologies of the sphenoid sinus, especially infections. Residual/recurrent tumors and postoperative pituitary apoplexy after trans-sphenoidal surgery require individualized considerations. Transcranial approaches still have a critical role in giant and complex pituitary adenomas with wide intracranial extension, brain parenchymal involvement, and the encasement of neurovascular structures.

The medial wall and medial compartment of the cavernous sinus: an anatomic study using plastinated histological sections

The medial wall of the cavernous sinus (CS) has a significant role in evaluation and treatment of pituitary adenomas. This study was conducted to clarify the fine architecture of the medial wall and medial compartment of the CS at both macro- and micro-levels in twenty-one human cadaveric heads by using the epoxy sheet plastination technique. The sellar part medial wall is an intact dural layer that separates the CS from the pituitary gland. This dural wall adhered to the diaphragma sellae and the periosteum of the sella turcica to form fibrous triangles. Eight micro-protrusions of the pituitary gland were found at both sides of that wall. The thickness of the sellar part medial wall at its central portion was significantly thinner than that at the other surrounding portions. From the superior view, tortuous intracavernous carotid arteries can be divided into outward bending type and inward bending type. The inward bending intracavernous carotid was apt to bent towards the central part of the sellar part medial wall, where there were usually wide and short fibrous bands with more densely stained connective tissues between them. The micro-protrusion of the pituitary gland in the medial wall of the CS could provide an anatomical basis for the occult tumor invasion and the recurrence of residual tumor. Different bending facing states of tortuous intracavernous carotid arteries in the lateral direction may be a factor of the determination of the direction of growth of pituitary tumors.

Pituitary Adenomas and Invasiveness from Anatomo-Surgical, Radiological, and Histological Perspectives: A Systematic Literature Review

Invasiveness in pituitary adenomas has been defined and investigated from multiple perspectives, with varying results when its predictive value is considered. A systematic literature review, following PRISMA guidelines, was performed, searching PubMed and Scopus databases with terms that included molecular markers, histological, radiological, anatomical and surgical data on invasiveness of pituitary adenomas. The results showed that differing views are still present for anatomical aspects of the sellar region that are relevant to the concept of invasiveness; radiological and histological diagnoses are still limited, but might improve in the future, especially if they are related to surgical findings, which have become more accurate thanks to the introduction of the endoscope. The aim is to achieve a correct distinction between truly invasive pituitary adenomas from those that, in contrast, present with extension in the parasellar area through natural pathways. At present, diagnosis of invasiveness should be based on a comprehensive analysis of radiological, intra-operative and histological findings.

Ectopic Adrenocorticotropic Hormone–Secreting Pituitary Adenomas: An Underestimated Entity

BACKGROUND: The diagnosis of Cushing disease is based on endocrinological pa-rameters, with no single test being specific. In some patients, dynamic thin-slice sellar magnetic resonance imaging fails to detect a pituitary tumor.

OBJECTIVE: The purpose of this study is to investigate the role of ectopic pituitary adenoma in this situation.

METHODS: In a retrospective chart review, 5 patients (6%) with ectopic adenomas were identified in 83 consecutive patients undergoing transsphenoidal surgery for adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas by 1 surgeon.

RESULTS: In all 5 patients (all female, 32-41 years of age), an exclusively extrasellar ACTH-secreting adenoma was excised. Three adenomas were located in the cavernous sinus, 1 in the sphenoid sinus, and 1 in the ethmoidal cells. Histologically, none of the tumors showed signs of aggressiveness. Three of the 5 adenomas specifically expressed somatostatin receptor 5. In 4 patients with Cushing disease, postoperative remission was obtained, with 1 recurrence after 14 months. In the patient with Nelson syndrome, ACTH decreased from >800 to <80 pg/mL. Three patients underwent previous surgery elsewhere, including 1 hypophysectomy. In this case, the ectopic adenoma (positive for somatostatin receptor 5) in the ethmoidal cells turned out to be positive on gallium 68 DOTATATE positron emission tomography/computed tomography.

CONCLUSION: The incidence of primarily ectopic ACTH-secreting adenomas in this series was 6%. In cases of negative MRI findings, an ectopic ACTH-secreting adenoma should be taken into account. 68Ga DOTATATE positron emission tomography/computed tomography may identify ectopic pituitary adenomas. Hypophysectomy should always be avoided in primary surgery for CD.

Emerging Histopathological and Genetic Parameters of Pituitary Adenomas: Clinical Impact and Recommendation for Future WHO Classification

The review assesses immunohistochemical findings of somatostatin receptors and of metalloproteinases in different pituitary adenoma types and the significance of molecular genetic data. Current evidence does not support routine immunohistochemical assessment of somatostatin or dopamine receptor subtype expression on hormone-secreting or nonfunctioning pituitary adenomas. Further prospective studies are needed to define its role for clinical decision making. Until then we suggest to restrict membrane receptor profiling to individual cases or for study purposes. The problems of adenoma expansion and invasion are discussed. Despite partially contradictory publications, proteases clearly play a major role in permission of infiltrative growth of pituitary adenomas. Therefore, detection of at least MMP-2, MMP-9, TIMP-2, and uPA seems to be justified. Molecular characterization is important for familial adenomas, adenomas in MEN, Carney complex, and McCune-Albright syndrome and can gain insight into pathogenesis of sporadic adenomas.

Histological structure of the medial and lateral walls of cavernous sinus in human fetuses

PURPOSE

The aim of this study is to elucidate the architecture of these fine structures in human fetuses.

METHODS

The histological examination of medial wall (MW) and lateral wall (LW) was performed in 15 normal human fetuses. Eleven fetuses were female and four were male. The gestational age ranged between 14 and 35 weeks. The weight ranged between 180 and 1750 g. The wall samples (two MW and two LW from each fetus) were obtained by microsurgical technique and underwent histological examination. Each wall was examined for the structure and composition of collagen and elastic fibers, ganglions, peripheral nerves, and vessels.

RESULTS

A total of 60 wall samples (30 MW and 30 LW) were examined in 15 fetuses. Loose connective tissue composed of type III collagen was observed in both of the walls. Elastic fibers were observed only in three wall samples (two MW and one LW). Ganglion was detected in 11 samples (nine in LW and two in MW), and peripheral nerve was found in 28 walls (18 LW and 10 MW). Vessels were observed in 51 samples (26 LW and 25 MW). None of the walls was stained with type I collagen.

CONCLUSIONS

The structure of LW and MW of the cavernous sinus (CS) in fetuses is mainly composed of collagen tissue while some elastic fibers are supported by this tissue. Type III collagen is the main component of fetal CS walls. Because of the weak histological structure, CS may be more prone to tumor invasion in infants.

Endoscopic, endonasal variability in the anatomy of the internal carotid artery

BACKGROUND

Classic three-dimensional schemas of the internal carotid artery (ICA) for transcranial approaches do not necessarily apply to two-dimensional endoscopic views. Modifying an existing ICA segment classification, we define endoscopic orientation for the lacerum (C3) to clinoid (C5) segments through an endonasal approach.

METHODS

In 20 cadaveric heads, we classified endoscopic appearance based on shape and angulation of C3 to C5 segments. Distances were measured between both arteries, and between the ICA and pituitary gland.

RESULTS

We identified 4 common ICA patterns: types I through III matched side-to-side, whereas type IV was asymmetric. In 80% of specimens, the pituitary gland had direct contact with the ICA. In 20% of specimens, a space existed between the pituitary gland and the cavernous segment. Access to the posterior aspect of the cavernous sinus medial to the cavernous segment was possible without retraction of the artery or pituitary gland. Spaces between the lacerum and cavernous segments were trapezoid (80%) and hourglass (20%).

CONCLUSIONS

Distinguishing which ICA type courses between the lacerum and clinoid segments can help clarify the relationships between the artery and its surrounding structures during endoscopic approaches. Adapting the classic terminology of ICA segments provided consistency of endoscopic relevance, defined potential endoscopic corridors, and highlighted the critical step of arterial contact.

Expression of extracellular matrix-proteins in perisellar connective tissue and dura mater

PURPOSE

To describe the pattern of expression of extracellular matrix (ECM) proteins in perisellar connective tissue.

METHODS

Dural and perisellar specimens from ten individuals were investigated immunohistochemically for collagens I to IV, tenascin, fibronectin, elastin, laminin, and vitronectin.

FINDINGS

Collagen I and III and fibronectin were strongly expressed and collagen IV, tenascin, and vitronectin were moderately expressed in the boundaries of the sella and around the CS. In six of nine specimens from the anterior boundary of the sella, and in 11 of 19 samples from the lateral boundary of the sella (medial wall of CS), two different layers could be detected by the expression of different ECM proteins. None of the antigens generally allowed differentiation between two layers of the pituitary envelope.

CONCLUSIONS

The pituitary boundary may consist of a single or a double layer, infrequently differentiated from each other by the expression of different ECM proteins.