The inferior intercavernous sinus: An anatomical study with application to trans-sphenoidal approaches to the pituitary gland.

OBJECTIVES: The inferior intercavernous sinus is located below the pituitary gland in the sella turcica. Its presence has been controversial among anatomists because it is not always found on radiological imaging or during cadaveric dissections; however, it is becoming a better-known structure in the neurosurgical and radiological fields, specifically with respect to transsphenoidal surgery. Therefore, the present study was performed to better elucidate this structure at the skull base. PATIENTS AND METHODS: Fifty adult, latex injected cadavers underwent dissection. The presence or absence of the inferior cavernous sinus was evaluated and when present, measurements of its width and length were made. Its connections with other intradural venous sinuses were also documented. RESULTS: An inferior intercavernous sinus was identified in 26 % of specimens. In all specimens, it communicated with the left and right cavernous sinus. The average width and length were 3 mm and 9.5 mm, respectively. In the sagittal plane, the inferior intercavernous sinus was positioned anteriorly in 31 %, at the nadir of the sella turcica in 38 %, and slightly posterior to the nadir of the sella turcica in 31 %. In two specimens (15.4 %), the sinus was plexiform in its shape. In one specimen a diploic vein connected the basilar venous plexus to the inferior intercavernous sinus on its deep surface. CONCLUSION: An improved understanding of the variable anatomy of the inferior intercavernous sinus is important in pathological, surgical, and radiological cases.

Cavernous sinus and abducens nerve in human fetuses near term.

A long tortuous course of the abducens nerve (ABN) crossing a highly curved siphon of the internal carotid artery is of interest to neurosurgeons for cavernous sinus surgery. Although a "straight" intracavernous carotid artery in fetuses can change into an adult-like siphon in infants, there is no information on when or how the unique course of ABN is established. Histological observations of 18 near-term fetuses (12 specimens of frontal sections and 6 specimens of sagittal sections) demonstrated the following: (I) the ABN consistently took a straight course crossing the lateral side of an almost straight intracavernous carotid artery; (II) the straight course was maintained when sympathetic nerves joined; (III) few parasellar veins of the developing cavernous sinus separated the ABN from the ophthalmic nerve; and (IV) immediately before the developing tendinous annulus for a common origin of extraocular recti, the ABN bent laterally to avoid a passage of the thick oculomotor nerve. Since the present observations strongly suggested morphologies at birth and in infants, major angulations of the ABN as well as the well-known course independent of the other nerves in the cavernous sinus seemed to be established during childhood. In the human body, the ABN might be a limited example showing a drastic postnatal change in course. Consequently, it might be important to know the unique course of ABN before performing endovascular interventions and skull base surgery for petroclival and cavernous sinus lesions without causing inadvertent neurovascular injuries to neonates or infants.

Vena capitis prima and the cavernous sinus in human embryos and fetuses.

After the intracranial venous-drainage route is switched from the vena capitis prima (VCP) to the transverse sinus, the cavernous sinus is considered to develop from a connecting part of the VCP with the ophthalmic vein (OPV). Observations of histological sections from 12 embryos and 47 fetuses (6-35 weeks) demonstrated that (1) at six weeks, a major tributary of the VCP ran inferiorly in the plica ventralis at the mesencephalic flexure (future tentrium cerebelli) and merged with the OPV in the medial side of the trigeminal ganglion; (2) at seven weeks, being independent of the laterally located primary veins, the superior petrosal sinus (SPS) developed medially in the plica, ran superiorly, and appeared to make an initial confluence with the transverse sinus; (3) until 15-16 weeks, parasellar veins were limited to a few branches of the OPV without communication with the SPS on the lateral surface of the trigeminal ganglion; (4) after 15-16 weeks, parasellar veins increased in number and volume but did not yet drain into the SPS but rather into the newly built inferior petrosal sinus; and (5) near term, parasellar veins started venous drainage to the SPS, whereas few veins were evident around the intracavernous abducens nerve. Consequently, the inferior petrosal sinus might originate from a remnant of the VCP (the so-called pro-otic sinus), but after midterm, most parasellar veins appeared to develop from the OPV without any contribution of the SPS. These findings suggest that parasellar sinus-network might be established after birth.

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.

Dural Venous System in the Cavernous Sinus: A Literature Review and Embryological, Functional, and Endovascular Clinical Considerations.

The cavernous sinus (CS) is one of the cranial dural venous sinuses. It differs from other dural sinuses due to its many afferent and efferent venous connections with adjacent structures. It is important to know well about its complex venous anatomy to conduct safe and effective endovascular interventions for the CS. Thus, we reviewed previous literatures concerning the morphological and functional venous anatomy and the embryology of the CS. The CS is a complex of venous channels from embryologically different origins. These venous channels have more or less retained their distinct original roles of venous drainage, even after alterations through the embryological developmental process, and can be categorized into three longitudinal venous axes based on their topological and functional features. Venous channels medial to the internal carotid artery "medial venous axis" carry venous drainage from the skull base, chondrocranium and the hypophysis, with no direct participation in cerebral drainage. Venous channels lateral to the cranial nerves "lateral venous axis" are exclusively for cerebral venous drainage. Venous channels between the internal carotid artery and cranial nerves "intermediate venous axis" contribute to all the venous drainage from adjacent structures, directly from the orbit and membranous skull, indirectly through medial and lateral venous axes from the chondrocranium, the hypophysis, and the brain. This concept of longitudinal venous axes in the CS may be useful during endovascular interventions for the CS considering our better understandings of its functions in venous drainage.

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.

Embryology of the internal carotid artery dural crossing: apropos of a continuous series of 48 specimens.

The aim of this study was to describe the embryologic and foetal development of the anterior paraclinoid region and more precisely the relationship of the internal carotid artery to the dura mater. This has been done by examining a collection of histological sections, representing a continuous series of 48 embryologic and foetal specimens, covering the period of the first 6 months of intra-uterine life. Neurological and vascular elements develop during the embryologic period; the internal carotid artery is recognizable in the various sections of its course and acquires a histological adult parietal constitution. The foetal period corresponds to the development of the meningeal structures. The superior, medial and lateral walls appear on the fifteenth week of amenorrhoea and do not change after that. The internal carotid artery enters subarachnoid space accompanied by a sleeve of mesenchymatous cells, which fixes it to the anterior clinoid process. The constitution of this sleeve, arising from the superior wall of the lateral sellar compartment, remained independent of the principle vascular part, which allows the formation of a plan of cleavage. The foetal relations of the dura mater and the internal carotid artery were seen to be different from those of adult subjects described in the literature, suggesting an existence of period of maturation postnatally.

[Complete imaging study of internal carotid artery agenesis with intercavernous anastomosis]. / Imagerie complète de l'agénésie de l'artère carotide interne avec anastomose inter-caverneuse.

We report a complete imaging study of an exceptional developmental anomaly of the internal carotid artery in a 42-year-old man presenting with a few days history of left visual blurring. MRI and conventional angiography demonstrated unilateral cervical and petrous agenesis of the left internal carotid artery, with an intercavernous anastomosis. CT-scan revealed total absence of the bony carotid canal. We briefly review the embryological hypotheses and discuss clues to correct diagnosis.

Anatomy of the cavernous sinus region.

The cavernous region was examined in 20 fetuses, injected with Micropaque, and in 5 adults. The lateral wall of the cavernous region in fetuses was noticed to have four layers. The superficial membrane represents the dural sheath. The second membrane of dense connective tissue involves the trochlear nerve. The third layer, formed by loose connective tissue, involves the oculomotor nerve, and the ophthalmic and maxillary division. The fourth layer, which represents the lateral wall of the cavernous sinus, involves the abducent nerve. The meningohypophyseal trunk can be complete or incomplete. The inferolateral trunk and its branches were found to supply the cavernous portions of the mentioned cranial nerves. The obtained data make the anatomic basis for neurosurgical operations in the cavernous region.

Development of the cavernous sinus in the fetal period: a morphological study.

The development and morphological structure of the lateral sellar compartment (LSC), an interdural space containing the cavernous sinus (CS), cranial nerves, and internal carotid artery (ICA), was investigated by histological examination of sections of the LSC and cerebral venograms from human fetal specimens. Twenty-eight LSC coronal sections were obtained from 14 fetuses of 13-32 weeks' gestation. Venograms of 11 other fetuses of 13-32 weeks' gestation were studied to observe changes in venous drainage. The CS appeared as a collection of small venous canals with an endothelial layer. These venous canals gradually became much larger through expansion and unification. The CS and basilar venous plexus were demonstrated as a faint cluster of small vessels on venograms obtained after 13 weeks' gestation. The dura mater increased in thickness and collagen fiber networks developed around all the components in the LSC after 23 weeks' gestation. The LSC lateral wall could not be histologically differentiated as separate multiple layers. Branching and joining of the cranial nerve fascicles were completed with the envelopment of collagen fibers after 23 weeks' gestation. The ICA at 13-15 weeks' gestation ran straight within the LSC, becoming tortuous before birth. CS formation occurs through the development of venous canals without smooth muscle layers, followed by web-formation by collagen fibers in the mesenchymal interstices. LSC formation, including the dense dura mater and an internal structure like that seen in the adult, is largely completed before birth.

Color Doppler study of the venous circulation in the fetal brain and hemodynamic study of the cerebral transverse sinus.

OBJECTIVES: To describe the venous circulation in the fetal brain; to describe the normal blood flow velocity waveform in the transverse sinus and to establish normal reference ranges for the second half of gestation. POPULATION: A total of 126 pregnant women with uncomplicated pregnancies at 20-42 weeks of gestation. METHODS: A combination of color-coded Doppler and two-dimensional real-time ultrasound was used to identify the main venous systems in the fetal brain. Blood flow velocity waveforms of the transverse sinus were obtained from a transverse plane of the head at the level of the cerebellum. RESULTS: A waveform could be obtained in the cerebral transverse sinus in 98% of the cases. The waveform obtained was triphasic with a forward systolic component, a forward early diastolic component and a lower forward component in late diastole. Reverse flow during atrial contraction was seen before 28 weeks and the diastolic flow increased with gestation thereafter. Pulsatility and resistance indices decreased and flow velocities increased in the transverse sinus throughout gestation. CONCLUSION: The venous circulation of the fetal brain can be identified by color Doppler. The gestational age-related decrease in resistance and increase in flow velocities suggest that hemodynamic studies of the cerebral transverse sinus might have clinical implications in studying compromised fetuses.

Is there a dural wall between the cavernous sinus and the pituitary fossa? Anatomical and MRI findings.

We compared MRI studies of the sellar area and embryological and adult histological studies of the cavernous sinuses and pituitary fossa. MRI studies were performed in 50 normal subjects with coronal sections using a fast inversion-recovery sequence to demonstrate the dural walls of the cavernous sinus and pituitary fossa. With this sequence, dura mater appears as a high-signal linear structure. The lateral and superior walls of the cavernous sinus was easily identified on all studies, but demonstration of a dural wall separating the cavernous sinus from the pituitary fossa was not possible. These results correlated well with embryological and adult histological studies obtained from 14 specimens. The absence of a strong separation between the pituitary fossa and the cavernous sinus explains the high incidence of extension of pituitary tumours to the cavernous sinuses and vice versa.

Anatomy and embryology of the lateral sellar compartment (cavernous sinus) medial wall.

In order to study the microanatomy of the lateral sellar compartment (cavernous sinus) medial wall, serial histological sections of human fetuses and adults, as well as dissections under operative microscope, were performed. The results were compared to high resolution Magnetic Resonance Images in human, to microdissections and to serial histological sections in adult nonhuman primates (Papio Cynocephalus anubis). We were able to show that the sellar compartment and both lateral sellar osteodural compartments are not separated from each other by a dural wall, but by a more or less dense, interrupted, fibrous tissue which derived from the mesenchyme surrounding the hypophysis, carotid artery, cranial nerves and venous channels. In the human fetus, the previous mentioned structures are located in a unique interperiosteodural space. Histoarchitecture of the superior and lateral wall dura-mater was different from the underlying mesenchyme derived connective tissue and was easily distinguished through histological examination. These findings correspond to MRI data. We conclude that there is no medial dural wall limiting the lateral sellar compartment (cavernous sinus), both parasellar and the hypophyseal compartment should be considered as a unique extradural space. The only dense connective tissue surrounding the pituitary gland is its own glandular capsule and the periosteum.

Anatomic relationships of the orbital muscle of Müller in human fetuses.

A study was carried out in twenty human fetuses on the relationships of the orbital muscle of Müller. This muscle forms a lamina of smooth muscle fibres that cover the inferior orbital fissure. The latter is very wide during the fetal period because ossification of the bones that delimit this region is still incomplete. Some fibres of the orbital muscle extend along the superior orbital fissure under the inferior ophthalmic vein and the lower wall or floor of the cavernous sinus. This association suggests a possible influence on autonomically mediated vascular dynamics.

The venous system of the lateral sellar compartment (cavernous sinus): an histological and embryological study.

The microanatomy of the lateral sellar or parasellar venous system (so-called cavernous sinus) is poorly understood and is still passionately debated. The exact nature of this venous structure is not yet clear whether it is a plexus or a sinus. In order to understand the anatomy of this area better, an embryological and adult microanatomical study was performed. Serial histological sections of human embryos and fetuses of well determined ages (6, 7, 8, 10, 11, 12, 14, 30 weeks) were used. The adult study was performed with microdissections and serial histological sections of laterosellar compartments. The analysis of this material confirms that the parasellar venous system is a true sinus, on the embryological and histological point of view. They differ from true veins. As other dural sinuses, it may contain different types of channels: from simple venous canal to complex venous plexus. The opinions of different authors are reviewed in the introduction and discussed with the results.

Acquired carotid-cavernous fistula caused by traumatic intracavernous rupture of an embryonic anastomosis.

This case of traumatic carotid-cavernous fistula was caused by rupture of a peculiar ipsilateral intracavernous anastomosis between the accessory meningeal artery and the redundant deep recurrent ophthalmic artery. In the opposite cavernous sinus there was an obvious anastomosis between the accessory meningeal artery and the ophthalmic artery, probably located in the lateral part of the cavernous sinus. The patient was successfully treated with transarterial embolization followed by surgery of the cavernous sinus. In light of the vascular embryology, it is possible that unusual embryonic connections between the primitive dorsal ophthalmic artery and the accessory meningeal artery already existed in both cavernous sinus areas.

[Sheaths of cranial nerves in the lateral wall of the cavernous sinus. An embryological and anatomical study]. / Les gaines des nerfs crâniens dans la paroi latérale de la loge parasellaire. Etude embryologique et anatomique.

The present study has been carried out in order to better understand the so-called cavernous sinus lateral wall anatomy. Special attention has been drawn at the sheaths of the cranial nerves running through it. Serial sections of the parasellar region of four human embryos (7, 10, 11, 12 week-old), two fetuses (14 week-old and 7 month-old), one adult and cadaveric microdissections (14 cavernous sinus) have been used. We could observe that the oculomotor and the trochlear nerve possess meningeal sheaths, which accompany the nerves into the parasellar lodge up to the anterior clinoid process for the oculomotor nerve. However, the remaining distal portion of these nerves are embedded in a peripheral sheath. Conversely, the meninges of the Meckel's cave stop at the trigeminal ganglion, its branches have only peripheral sheaths and are located, as the venous system, in an "interperiosto-dural space". The presence of arachnoid granulations into the lateral and superior walls of the lodge, around the trigeminal ganglion, near the oculomotor, trochlear and ophthalmic nerves explains the location of meningiomas in these areas. These anatomical findings could provide the basis for a classification of meningiomas of the cavernous sinus and help the surgeon to preserve the uninvolved cranial nerves.

[Plea for a unifying concept of the cavernous sinus and the trigeminal cavity]. / Plaidoyer pour un concept uniciste du sinus caverneux et de la loge trigéminale.

The object of this study is a scientific research in human and compared anatomy of the cavernous sinus and Meckel's cave. The observations made in the foetus and human adult are compared to these made in non human primates and domestic mammals, the cavernous sinus and the Meckel's cave contribute to realize a entirety that we call "a morphological and functional anatomical system". The human cavernous sinus and Meckel's cave are described as an indissociable parasellar space representing a heavy traffic area for vascular and nervous structures. In the human and non human primates, the authors observe a parasellar space which agreed with the concept of "trigeminal-cavernous anatomical system". In the cat, the same observations are made and an osseous outline closing the roof of the parasellar space is observed; this is the evidence of a more ancient osseous or cartilaginous wall. The authors demonstrate in the last part of this study that the morphogenesis of this trigeminal-cavernous system is in relation with the phylogenic development of its morphological and functional environment, that we call the "externation". This study is of interest: to a best understanding of the tumors involving the cavernous sinus, to a semantic point of view: an attempt to a review of the terminology applied to the cavernous sinus and Meckel's cave.

[The cavernous sinus: development, anatomy, radio-anatomy and clinical implications]. / La loge caverneuse: développement, anatomie, radio-anatomie et implications cliniques.

Cavernous sinus is an important region rich in neurological structures. Its development and its anatomy are very complex and the purpose of our work is to correlate embryology, anatomy and semiology of this region and its content. Interest of medical imaging of cavernous sinus and referred structures is enhanced.