Medial portion of the cavernous sinus: quantitative analysis of the medial wall

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.

Relationship between optic nerve length and interoptic angle in the prediction of optic chiasm location

INTRODUCTION AND OBJECTIVES

The sellar region is an area in the base of the skull that is among the most common sites for tumors of the central nervous system. Surgical interventions are currently performed via different routes. While the optic chiasm occupies its expected position in 70% of the population, it can deviate from this position. In such cases, surgery involving this region becomes more difficult as the known surgical routes are narrowed. Advance awareness of these variations can help surgeons to identify the optimal route for safe surgical intervention in the sellar region. By performing simple measurements of both the lengths of the optic nerves and the angle between them, a surgeon can predict the location of the chiasm.

MATERIALS AND METHODS

Twenty specimens collected from autopsies performed at Bursa Forensic Medicine İnstitute were examined to determine the optic chiasm types and the relationships between the surrounding subchiasmal structures.

RESULTS

Among the 20 specimens, we found two prefixed (10%), 10 normo-fixed (50%), and eight postfixed chiasms (40%). The mean interoptic angle was 81.03 (±17.41)⁰. Prefixed chiasms had angles in the range 115.36°-124.76 ° (mean 120.06 [±6.65]⁰), normo-fixed chiasm angles were between 83.11° and 97.53 ° (mean 86.07 [±6.73]⁰), and postfixed chiasms ranged between 53.01 ° and 78.71 ° (mean 69.20 [±9.13]⁰). The length of the right optic nerve ranged between 6.95 and 13.83 mm (mean 10.25 [±1.81] mm), and the length of the left between 7.25 and 12.51 mm (mean 10.40 [±1.47] mm). Obtuse angles indicated that the chiasm was prefixed, and acute angles were indicative of a postfixed chiasm. There was a strong negative correlation between optic nerve lengths and the interoptic angle; thus, as the length of the nerves increases, the interoptic angle becomes more acute.

CONCLUSIONS

We have proposed a simple measurement of the optic nerve lengths and the angle between them to predict the relative location of the OC, which can be done easily on MRI.

Clinical and therapeutic implications of cavernous sinus invasion in pituitary adenomas

Invasion of the cavernous sinus by pituitary adenomas impedes complete surgical resection, compromises biochemical remission, and increases the risk of further tumor recurrence. Accurate preoperative MRI-based diagnosis or intraoperative direct inspection of cavernous sinus invasion are essential for optimal surgical planning and for tailoring postoperative therapeutic strategies, depending on whether a total resection has been achieved, or tumoral tissue has been left in surgically inaccessible locations. The molecular mechanisms underlying the invasive behavior of pituitary adenomas remain poorly understood, hindering the development of targeted therapies. Some studies have identified genes overexpressed in pituitary adenomas invading the cavernous sinus, offering insights into the acquisition of invasive behavior. Their main limitation however lies in comparing purely intrasellar specimens obtained from invasive and non-invasive adenomas. Further, precise anatomical knowledge of the medial wall of the cavernous sinus is crucial for grasping the mechanisms of invasion. Recently, alongside the standard intrasellar surgery, extended endoscopic intracavernous surgical procedures with systematic selective resection of the medial wall of the cavernous sinus have shown promising results for invasive secreting pituitary adenomas. The first- and second-generation somatostatin agonist ligands and cabergoline are used with variable efficacy to control secretory activity and/or growth of intracavernous remnants. Tumor regrowth usually requires surgical reintervention, sometimes combined with radiotherapy or radiosurgery which is applied despite their benign nature. Unraveling the molecular pathways driving invasive behavior of pituitary adenomas and their tropism to the cavernous sinuses is the key for developing efficient innovative treatment modalities that could reduce the need for repeated surgery or radiotherapy.

MRI 3D SPACE T2WI for Pituitary Adenoma Cavernous Sinus Invasion Diagnosis

OBJECTIVE

This study aims to assess the utility of magnetic resonance imaging (MRI) 3D SPACE T2-weighted imaging (T2WI) sequences in evaluating cavernous sinus invasion by pituitary adenomas.

METHODS

Data were collected from patients who underwent continuous pituitary MRIexaminations at the Medical Imaging Center of our hospital from October 2019 to February 2021. Eligible cases were evaluated for sagittal and axial T1WI sequences, coronal 3D SPACE T2WI sequences, and sagittal and coronal enhanced T1-weighted imaging (T1WI) sequences using the INFINITT PACS workstation. The Wilcoxon signed-rank test for paired samples and the Mann-Whitney U test for 2 independent samples were used to statistically analyze differences in image quality scores among various groups. In addition, the sensitivity, specificity, positive predictive value, and negative predictive value of each observation index were compared with intraoperative results.

RESULTS

3D SPACE T2WI showed superior cavernous sinus imaging quality compared with contrast enhanced T1WI and T2WI plain scans (P < 0.05). The sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 90.0%, 55.60%, and 100.0%, respectively. The accuracy for pituitary adenoma invasiveness diagnosis based on cavernous sinus medial wall integrity was 94.40%.

CONCLUSIONS

The imaging quality of the medial wall of the cavernous sinus on the 3D SPACE T2WI plain scan sequence surpassed that of contrast enhanced T1WI TSE-enhanced scans and T2WI TSE plain scans. The continuous observation of the medial wall of the cavernous sinus using this sequence holds great diagnostic value for assessing cavernous sinus invasion by pituitary adenomas. This strategy is more reliable than traditional MRI observation indicators.

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 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.

Histology of the Porous Oculomotorius: Relevance to Anterior Skull Base Approaches

Objective: Mobilization of cranial nerve III (CNIII) at its dural entry site is commonly described to avoid damage from stretching during approaches to the parasellar, infrachiasmatic, posterior clinoid, and cavernous sinus regions. The histologic relationships of CNIII as it traverses the dura, and the associated surgical implications are nonetheless poorly described. We herein assess the histology of the CNIII-dura interface as it relates to surgical mobilization of the nerve. Methods: A fronto-orbitozygomatic temporopolar approach was performed on six adult cadaveric specimens. The CNIII-dural entry site was resected and histologically processed. The nerve-tissue planes were assessed by a neuropathologist. Results: Histologic analysis demonstrated that CNIII remained separate from the dura within the oculomotor cistern (porous oculomotorius up to the oculomotor foramen). Fusion of the epineurium of CNIII and the connective tissue of the dura was seen at the level of the foramen, with no clear histologic plane identified between these structures. Conclusion: CNIII may be directly mobilized within the oculomotor cistern, while dissections of CNIII distal to the oculomotor foramen should maintain a thin layer of connective tissue on the nerve.

Arachnoid and dural reflections

The dura mater is the major gateway for accessing most extra-axial lesions and all intra-axial lesions of the central nervous system. It provides a protective barrier against external trauma, infections, and the spread of malignant cells. Knowledge of the anatomical details of dural reflections around various corners of the skull bases provides the neurosurgeon with confidence during transdural approaches. Such knowledge is indispensable for protection of neurovascular structures in the vicinity of these dural reflections. The same concept is applicable to arachnoid folds and reflections during intradural excursions to expose intra- and extra-axial lesions of the brain. Without a detailed understanding of arachnoid membranes and cisterns, the neurosurgeon cannot confidently navigate the deep corridors of the skull base while safely protecting neurovascular structures. This chapter covers the surgical anatomy of dural and arachnoid reflections applicable to microneurosurgical approaches to various regions of the skull base.

A neurosurgical assessment of the blood supply in the optochiasmatic system: a cadaveric-anatomic study

The chiasmal and subchiasmal surfaces are of critical importance in connection with the performance of surgical procedures owing to the critical blood supply to these areas. Recently, the perforating arteries providing the blood to the optic nerves and chiasm have gained attention as they significantly affect the morbidity from surgical approaches. Intraoperative preservation of these perforating arteries is considered critical to prevent further visual loss. Thirty autopsy specimens, including the optic apparatus, were examined for their perforating arteries feeding the optic chiasm and optic nerves. The optic nerves and chiasmal surfaces were divided into four zones based on the presence and numbers of perforating arteries as anterior superior-posterior superior surfaces and anterior inferior-posterior inferior surfaces. The superior surface of the optic chiasm was supplied by the A1 segments of the bilateral anterior cerebral arteries and by the perforating arteries originating from the anterior communicating artery. On the other hand, the inferior surface of the optic chiasm was fed by the bilateral posterior communicating arteries and by the supraclinoidal segments of the bilateral carotid arteries. We demonstrated the anatomical involvement of a large number of nourishing arteries in feeding the optic apparatus related to the perforating arteries by classifying them into zones based on the surgical approaches, which has been rarely reported in the literature.

Diagnosis of Pituitary Adenoma Biopsies by Ultrahigh Resolution Optical Coherence Tomography Using Neuronal Networks

OBJECTIVE

Despite advancements of intraoperative visualization, the difficulty to visually distinguish adenoma from adjacent pituitary gland due to textural similarities may lead to incomplete adenoma resection or impairment of pituitary function. The aim of this study was to investigate optical coherence tomography (OCT) imaging in combination with a convolutional neural network (CNN) for objectively identify pituitary adenoma tissue in an ex vivo setting.

METHODS

A prospective study was conducted to train and test a CNN algorithm to identify pituitary adenoma tissue in OCT images of adenoma and adjacent pituitary gland samples. From each sample, 500 slices of adjacent cross-sectional OCT images were used for CNN classification.

RESULTS

OCT data acquisition was feasible in 19/20 (95%) patients. The 16.000 OCT slices of 16/19 of cases were employed for creating a trained CNN algorithm (70% for training, 15% for validating the classifier). Thereafter, the classifier was tested on the paired samples of three patients (3.000 slices). The CNN correctly predicted adenoma in the 3 adenoma samples (98%, 100% and 84% respectively), and correctly predicted gland and transition zone in the 3 samples from the adjacent pituitary gland.

CONCLUSION

Trained convolutional neural network computing has the potential for fast and objective identification of pituitary adenoma tissue in OCT images with high sensitivity ex vivo. However, further investigation with larger number of samples is required.

Anatomy of the dura mater venous sinus of Alouatta belzebul

The anatomy of the dura mater's venous sinuses is important in the veterinary clinical and surgical area, for cranial procedures and interventions of wild animals, in addition to assisting in the management of neurological diseases, which can prevent serious complications. The macroscopic anatomy of the venous sinuses of the dura mater of Alouatta belzebul was studied. Five adult specimens, males and females, were dissected and fixed in 10% formaldehyde solution. In the dura mater of the Alouatta belzebul, nine venous sinuses were observed, being them dorsal sagittal sinus, ventral sagittal sinus, transverse sinus, straight sinus, sigmoid sinus, temporal sinus, parietal sinus, basilar sinus and cavernous sinus, with morphological similarities in origin, path and destination of blood flow to the internal jugular vein, assisting in the venous drainage function of the brain in this species. These data are similar to those found in other species of non-human and human primates such as Saimiri sciureus, Sapajus libidinosus and Homo sapiens. Of the venous sinuses observed, the cavernous sinus was of considerable clinical and surgical importance in Alouatta belzebul due to its topographic arrangement next to the internal carotid artery and pituitary gland, data that corroborate Sapajus libidinosus, Macaca fascicularis, Macaca mulatta, Papio ursinus, Cercopithecus pygerithrus and Galago senegalensis. In this context, the knowledge of the macroscopic anatomy of the venous sinuses of the dura mater may contribute to the role of veterinarians in less invasive surgical procedures in non-human primates such as Alouatta belzebul and other mammals.

Challenging Knosp high-grade pituitary adenomas

OBJECTIVE

Parasellar growth is one of the most important prognostic variables of pituitary adenoma surgery, with adenomas regarded as not completely resectable if they invade the cavernous sinus (CS) but potentially curable if they displace CS structures. This study was conducted to correlate surgical treatment options and outcomes to the different biological behaviors (invasion vs displacement) of adenomas with parasellar extension into the superior or inferior CS compartments or completely encasing the carotid artery (Knosp high grades 3A, 3B, and 4).

METHODS

This was a retrospective cohort analysis of 106 consecutive patients with Knosp high-grade pituitary adenomas with parasellar extension who underwent surgery via a primary endoscopic transsphenoidal approach between 2003 and 2017. Biological tumor characteristics (surgical status of invasiveness and tumor texture, 2017 WHO classification, proliferation rate), extent of resection, and complication rate were correlated with parasellar extension grades 3A, 3B, and 4 on preoperative MRI studies.

RESULTS

Invasiveness was significantly less common in grade 3A (44%) than in grade 3B (72%, p = 0.037) and grade 4 (100%, p < 0.001) adenomas. Fibrous tumor texture was significantly more common in grade 4 (52%) compared to grade 3A (20%, p = 0.002), but not compared to grade 3B (28%) adenomas. Functioning macroadenomas had a significantly higher rate of invasiveness than nonfunctioning adenomas (91% vs 55%, p = 0.002). Mean proliferation rate assessed by MIB-1 was > 3% in all groups but without significant difference between the groups (grade 3A, 3.2%; 3B, 3.9%; 4, 3.7%). Rates of endocrine remission/gross-total resection were significantly higher in grade 3A (64%) than in grade 3B (33%, p = 0.021) and grade 4 (0%, p < 0.001) adenomas. In terms of complication rates, no significant difference was observed between grades.

CONCLUSIONS

According to the authors' data, the biological behavior of pituitary adenomas varies significantly between parasellar extension patterns. Adenomas with extension into the superior CS compartment have a lower rate of invasive growth than adenomas extending into the inferior CS compartment or encasing the carotid artery. Consequently, a significantly higher rate of remission can be achieved in grade 3A than in grade 3B and grade 4 adenomas. Therefore, the distinction into grades 3A, 3B, and 4 is of importance for prediction of adenoma invasion and surgical treatment considerations.

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.

The medial wall of the cavernous sinus. Part 1: Surgical anatomy, ligaments, and surgical technique for its mobilization and/or resection

OBJECTIVE

The medial wall of the cavernous sinus (CS) is often invaded by pituitary adenomas. Surgical mobilization and/or removal of the medial wall remains a challenge.

METHODS

Endoscopic endonasal dissection was performed in 20 human cadaver heads. The configuration of the medial wall, its relationship to the internal carotid artery (ICA), and the ligamentous connections in between them were investigated in 40 CSs.

RESULTS

The medial wall of the CS was confirmed to be an intact single layer of dura that is distinct from the capsule of the pituitary gland and the periosteal layer that forms the anterior wall of the CS. In 32.5% of hemispheres, the medial wall was indented by and/or well adhered to the cavernous ICA. The authors identified multiple ligamentous fibers that anchored the medial wall to other walls of the CS and/or to specific ICA segments. These parasellar ligaments were classified into 4 groups: 1) caroticoclinoid ligament, spanning from the medial wall and the middle clinoid toward the clinoid ICA segment and anterior clinoid process; 2) superior parasellar ligament, connecting the medial wall to the horizontal cavernous ICA and/or lateral wall of the CS; 3) inferior parasellar ligament, bridging the medial wall to the anterior wall of the CS or anterior surface of the short vertical segment of the cavernous ICA; and 4) posterior parasellar ligament, which anchors the medial wall to the short vertical segment of the cavernous ICA and/or the posterior carotid sulcus. The caroticoclinoid ligament and inferior parasellar ligament were present in most CSs (97.7% and 95%, respectively), while the superior and posterior parasellar ligaments were identified in approximately half of the CSs (57.5% and 45%, respectively). The caroticoclinoid ligament was the strongest and largest ligament, and it was typically assembled as a group of ligaments with a fan-like arrangement. The inferior parasellar ligament was the first to be encountered after opening the anterior wall of the CS during an interdural transcavernous approach.

CONCLUSIONS

The authors introduce a classification of the parasellar ligaments and their role in anchoring the medial wall of the CS. These ligaments should be identified and transected to safely mobilize the medial wall away from the cavernous ICA during a transcavernous approach and for safe and complete resection of adenomas that selectively invade the medial wall.

Review of Surgical Anatomy of the Tumors Involving Cavernous Sinus

The lesions involving cavernous sinus (CS) and lateral sellar region includes tumors, vascular lesions, infection, inflammation, and trauma. Tumors associated with CS cause significant distortion of the microanatomy posing an additional surgical challenge to the neurosurgeons. The surgical approach and microsurgical anatomy with respect to the origin and growth of the tumor within the CS region have not been comprehensively described in recent years. We conducted a review of literature concerning CS and associated tumors, complied through MEDLINE/OVID and using cross-references of articles on PubMed with the keywords cavernous sinus, CS tumors, pituitary adenoma, meningioma, schwannoma, chordoma, CS hemangiomas, extradural, interdural, intradural, skull base, gamma knife radiosurgery, endoscopic endonasal approach. Based on the tumor origin and growth pattern, the tumors associated with CS can be classified into three categories: Type-I: tumor originating from CS, Type-II: originating from lateral wall of CS, and Type-III: extraneous origin and occupying CS. The review focuses on approach to a tumor within each type of tumor in the CS region. The emphasis is that the tumor growth pattern and significant distortion of the CS anatomy caused by the tumor growth should be considered while planning the optimal surgical approach for tumors in this region to ensure complete tumor resection with minimal neurovascular morbidity.

Revisit the Cavernous Sinus from Fetus to Adult-New and Old Data

This article highlighted three advances in the study of the cavernous sinus: (1) the initial formation of the sinus reticulum in early development of the sphenoid bone before ossification (2) extension of reticulum of the sinus and connection with other venules, and (3) the cavernous sinus and the nerves evolved inside this sinus during gestation, for example, the trigeminal nerve already formed bundles of motor and parasympathetic components during fetal development. This ontogenetic study further confirmed the cavernous sinus is not a single or a dual set of sinuses, but a group of extensions of venous sinuses or sinusoids. These new insights were integrated with previous understandings of the cavernous sinus to form this review article. Anat Rec, 301:819-824, 2018. © 2017 Wiley Periodicals, Inc.

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.

Anatomical restrictions in the transsphenoidal, transclival approach to the upper clival region: a cadaveric, anatomic study

OBJECTIVE

Tumours in the clival region are difficult to remove surgically. Before the 1970s, clival tumours had very high mortality and morbidity rates.

METHODS

An anatomic dissection was performed on 24 spheno-occipital bone blocks obtained from 28 adult cadavers. The internal carotid artery, paraclival carotid tubercle, sixth cranial nerve and dorsum sellae in the upper clival region were analyzed qualitatively and quantitatively. For the histological evaluation, 4 samples were decalcified and sagittal sections were cut. From the eight blocks obtained, 32 incisions were made in the axial plane, and the tissue was analyzed.

RESULTS

Using microscopy, a clival recess was clearly identified in 15 of the 24 (62.5%) samples. Paraclival carotid tubercles were observed in 19 (79.16%) of the samples. In the upper clival and petroclival region, the sixth cranial nerve had directional changes at the dural porus, the petrous apex and the lateral wall of the cavernous segment of the internal carotid artery. At the dorsum sellae level, the distance between the medial surfaces of both internal carotid arteries was a mean of 15.33 ± 2.12 mm. This distance at the pharyngeal tubercle was a mean of 38.95 ± 4.67 mm. On all the histological sections, the distance of the sixth cranial nerve from the dural porus to the cavernous sinus was within the basilar plexus, along with the subarachnoid membranes around it. On the petrous apex level, the sixth cranial nerve was fixed to the petrous apex and the internal carotid artery with connective tissue formed by dense collagen fibres. The sixth cranial nerve and the internal carotid artery are tightly surrounded by dense collagen connective tissue, and the relative proximity between the carotids on the dorsum sellae level can be easily damaged during the transsphenoidal-transclival approach. Similarly, due to the ligamentous fixation on the dural porus and the petrous apex surfaces, there is a high risk of injury to the carotid artery and sixth cranial nerve.

CONCLUSION

This study determines the relationship between the sixth cranial nerve and the internal carotid artery at the upper clivus and to provide morphologic details that is essential for the risks of transclival surgery.

Microsurgical anatomy of membranous layers of the pituitary gland and the expression of extracellular matrix collagenous proteins

BACKGROUND

There are several reports about the microanatomical and histological features of sellar and parasellar membranous structures and clinical studies about MMP proteinase as a predictive factor. However, studies on collagen contents of sellar and parasellar membranous structures are limited. We demonstrated the membranous structures surrounding the pituitary gland and defined extracellular matrix (ECM) collagenous proteins, collagen I-IV expression patterns of sellar and parasellar connective tissues.

METHODS

The study was carried out on ten fresh postmortem human bodies at the Forensic Medicine Institution. Cavernous sinuses were resected with sellar structures and were stored at -80°C liquid nitrogen tanks. Medial wall of the cavernous sinus, pituitary capsule and pituitary tissue samples were obtained for RT-PCR. Opposite side specimens were used for histological and immune staining studies. Collagens I-IV were studied by immunohistochemical and reverse transcription polymerase chain reaction (RT-PCR) methods.

FINDINGS

The pituitary capsule and medial wall were identified as two different structures. The fibrous membrane, as the third membrane, was identified as staying whole in eight of ten specimens. Increased type IV collagen was determined in the pituitary gland, medial wall and pituitary capsule, respectively, in both RT-PCR and immunhistochemical studies. Immunhistochemical studies revealed that collagen I was strongly expressed in both the medial wall and pituitary gland.

CONCLUSION

Increased type IV collagen was detected especially in pituitary tissue, the medial wall and the pituitary capsule by immune staining and RT-PCR. Type IV collagen was considered to be an important factor in the progression of adenoma and invasion.

Anatomical aspects in the transsphenoidal-transethmoidal approach to the optic canal: an anatomic-cadaveric study

BACKGROUND

Determining anatomic landmarks during a transsphenoidal-transethmoidal approach to the optic canal region is of critical importance.

METHODS

Sella-parasella sphenoid bone blocks were extracted from adult cadavers. Anatomic dissections were performed in the optic canal region using a surgical microscope in 30 samples. Quantitative measurements were done using photographic techniques. For histological evaluation, coronal and longitudinal cross-sections were taken from the bilateral optic canal in seven decalcified samples.

RESULTS

Optic protuberance (OP), carotid protuberance (CP), medial opticocarotid recess (MOCR) and lateral opticocarotid recess (LOCR) were defined as lateral landmarks determining the width of the opening in the extended transsphenoidal-transethmoidal approach. Among all anatomic markers, LOCR was the most determinant lateral marker with tubercular recess the most prominent central marker. OPs showing the optic canal direction and inter-recessal sulci had similar distinguishing rates in the sphenoid sinus base. Inter-recessal sulci formed by OPs and CPs were observed between MOCR and LOCR in most samples. In histologic sections, the dural sheath was thicker inferolaterally to the optic nerve compared to superiorly and medially; collagen arrangement was dense and irregular.

CONCLUSION

Although LOCRs and tubercular recesses are safe and prominent markers in extended transsphenoidal-transethmoidal approaches, other anatomic markers should also be taken into consideration to perform an efficient optic canal approach and optic canal decompression. Other factors for safe dissection are the length of the optic canal, bone thickness, adherence of dural structures and the course of the intradural ophthalmic artery.

Surgical limits in transnasal approach to opticocarotid region and planum sphenoidale: an anatomic cadaveric study

BACKGROUND

The significance of medial and lateral opticocarotid recesses and the planum sphenoidale region in skull base pathologies for the transsphenoidal-transplanum approach were evaluated.

METHODS

The sphenoid bone block samples were extracted from adult cadavers. Dissections and measurements in the opticocarotid and planum sphenoidale regions were performed in 29 samples using a surgical microscope. For histologic evaluation, oblique sections through the bilateral opticocarotid regions were obtained and examined in eight samples.

RESULTS

Optic, carotid prominences, and medial and lateral opticocarotid recesses can be identified as lateral markers intraoperatively to the extent of the exposure. The lateral opticocarotid recess was observed to be prominent in all samples. In all samples, the groove formed by optic and carotid prominences between the medial and lateral opticocarotid recesses was seen. This groove was designated the inter-recess sulcus. In the transsphenoidal-transplanum approach, the area needed for a reliable bone resection was measured as a mean of 237.32 ± 30.96 mm(2). The mean angle between optic nerves was 115.41 ± 18.39 degrees. The mean anteroposterior length of the planum sphenoidale was 14.84 ± 1.52 mm. In histologic sections, collagenous ligaments between the anterior part of cavernous sinus and the adventitia layer of internal carotid artery were more frequent and regular than the inferior part of optic nerve.

CONCLUSIONS

The lateral opticocarotid recess is a reliable and persistent indicator for extended transsphenoidal surgery. To approach the opticocarotid region near the internal carotid artery and optic nerve, a careful dissection is needed to minimize surgical injuries to the optic nerve and carotid artery. Other factors determining a reliable bone resection are the anteroposterior length of the planum sphenoidale and the distance and width of the angle between optic nerves. Attention should be given to individual anatomic variations of the region when planning and performing transsphenoidal-transplanum surgery.

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.

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

PURPOSE

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.

METHOD

Fourteen sellar hemiblocks underwent microsurgical dissection from lateral and medial approach. The thickness of the MW of the CS was examined by diaphanoscopy.

FINDINGS

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).

CONCLUSIONS

Expansion into the CS may be facilitated by low anatomical resistance against chronic tumor growth.

The implications of microsurgical anatomy for surgical approaches to the sellar region

The knowledge of the normal anatomy and variations regarding the management of tumors of the sellar region is paramount to perform safe surgical procedures. The sellar region is located in the center of the middle cranial fossa; it contains complex anatomical structures, and is the site of various pathological processes: tumor, vascular, developmental, and neuroendocrine. We review the microsurgical anatomy (microscopic and endoscopic) of this region and discuss the surgical nuances regarding this topic, based on anatomical concepts.

Comparison of lateral and superior walls of the pituitary fossa with clinical emphasis on pituitary adenoma extension: cadaveric-anatomic study

Pituitary adenomas extend to the suprasellar region via diaphragmal passage and extend to the cavernous sinus via the medial wall (MW). Better understanding of the dynamics of suprasellar and parasellar extension of sellar region pathologies requires microanatomical comparison of diaphragma sellae (DS) and the MW of the cavernous sinus. This study provides the first detailed quantitative assessment between DS and MW of the cavernous sinus. Microanatomical details and histopathological examinations of the DS and MWs of the cavernous sinus were studied in sphenoid block samples obtained from adult cadavers, and the thicknesses of the DS and the MW of the cavernous sinus were measured. Mean thickness of the DS was 216.73 +/- 51.26 microm in the center and 367.33+/-133.66 microm in the periphery. Mean thickness of the lower third of the MW was 161.53+/-53.86 microm and that of the upper third was 278.46+/-162.79 microm. Difference between the thicknesses of the upper and lower thirds was significant (P<0.001). When the central thickness of the DS and lower third of the MW were compared, a significant difference was found (P<0.01). Our measurements suggest that when the DS is thick and the stalk opening is complete, the thickness of the lower third of the medial wall could be the major determinant of parasellar extension.