Blood supply to the intracavernous cranial nerves: comparison of the endoscopic and microsurgical perspectives

[Clinical anatomy of the Bernasconi-Cassinari artery]

The article provides a comprehensive overview of the Bernasconi-Cassinari's artery (marginal tentorial branch of internal carotid artery, r. marginalis tentorii a. carotis internae). It includes information on the history of its discovery, anatomical features, and topography. The interrelation between the anatomical features of this artery and the presence of neurological pathology in patients is discussed, along with neurosurgical treatment methodologies.

Blood Supply of Cranial Nerves Passing Through the Cavernous Sinus: An Anatomical Study and Its Implications for Microsurgical and Endoscopic Cavernous Sinus Surgery

Background

Despite improvements in surgical techniques, cranial nerve (CN) deficits remain the most frequent cause of disability following cavernous sinus (CS) surgery. The most common tumor affecting the CS is meningioma. They originate from lateral wall and have their blood supply from meningohypophyseal trunk (MHT) and inferolateral trunk (ILT). Pituitary adenomas commonly invade the CS through its medial wall and receive blood supply form medial branches of the internal carotid artery (ICA) (superior and inferior hypophyseal arteries). Some tumors may grow within the CS (e.g. trigeminal schwannomas, hemangiomas). These tumors are fed by all the intracavernous ICA branches. Tumors involving the CS may also displace the neurovascular structures, therefore, a better understanding of intracavernous neurovascular anatomy may reduce the postoperative morbidity associated with approaching CS tumors. In this anatomical study, the anatomic variations and their clinical implications of the intracavernous CNs' blood supply were evaluated through transcranial and endonasal routes.

Methods

Twenty sides of ten adult cadaveric formalin-fixed, latex-injected specimens were dissected in stepwise fashion under microscopic and endoscopic magnification. The origin and course of the intracavernous ICA branches supplying the intracavernous CNs are studied.

Results

The proximal segment of the oculomotor nerve receives blood supply from the ILT in 85%, and the tentorial artery of the MHT in 15% of specimens. The distal segment is exclusively supplied by the ILT. The proximal trochlear nerve receives blood supply from the ILT (75%) and the tentorial artery (25%); the distal segment is exclusively supplied by the superior orbital branch. The proximal third of the abducens nerve receives its vascularity exclusively from the dorsal meningeal artery, and its middle and distal thirds from the ILT. The ophthalmic and proximal maxillary segments of the trigeminal nerve also receive blood supply from the ILT. The distal maxillary segment is supplied by the artery of the foramen rotundum. All ILT branches terminate on the inferomedial aspects of the intra-cavernous CNs. Extensive anastomoses are found between ILT branches and the branches arising from external carotid artery.

Conclusion

Understanding the anatomy of the intracavernous ICA's branches is important to improving surgical outcomes with tumors involving the CS.

Endoscopic endonasal approach to the middle cranial fossa through the cavernous sinus triangles: anatomical considerations

The lateral limit of endoscopic endonasal surgery has yet to be defined. The aim of this study was to investigate the lateral limit of endoscopic endonasal surgery at the level of the sphenoid sinus. Access from the sphenoid sinus to the middle cranial fossa through the cavernous sinus triangles was evaluated by cadaver dissection. Anatomical analysis demonstrated that the medial temporal dura mater was exposed through the anterior area of the clinoidal triangle, anteromedial triangle, and superior area of the anterolateral triangle, indicating potential corridors to the middle cranial fossa. This study suggests that the cavernous sinus triangles are applicable in selected cases to manage middle cranial fossa lesions by endoscopic endonasal surgery.

The trochlear nerve: microanatomic and endoscopic study

The purpose of the present study was to analyze the relationships of the trochlear nerve with the surrounding structures through both endoscopic and microscopic perspectives. The aim was to assess the anatomy of the nerve and to carry out a thorough description of its entire course. A comprehensive anatomically and clinically oriented classification of its different segments is proposed. Forty human cadaveric fixed heads (20 specimens) were used for the dissection. The arterial and venous systems were injected with red and blue colored latex, respectively, in the transcranial dissection. For illustrative purposes, the arterial vessels were injected alone in endoscopic endonasal procedures. A CT scan was carried out on every head. Median supracerebellar infratentorial, subtemporal, fronto-temporo-orbito-zygomatic, and endoscopic endonasal transsphenoidal approaches were performed to expose the entire pathway of the nerve. A navigation system was used during the dissection process to perform the measurements and postoperatively to reconstruct, using dedicated software, a three-dimensional model of the different segments of the nerve. The trochlear nerve was divided into five segments: cisternal, tentorial, cavernous, fissural, and orbital. Detailed and comprehensive examination of the basic anatomical relationships through the view of transcranial, endoscope-assisted, and pure endoscopic endonasal approaches was achieved. As a result of a thorough study of its intra- and extradural pathways, an anatomic-, surgically, and clinically based classification of the trochlear nerve is proposed. Precise knowledge of the involved surgical anatomy is essential to safely access the supracerebellar region, middle fossa, parasellar area, and orbit.

The medial tentorial artery of Bernasconi-Cassinari: a comprehensive review of its anatomy and neurosurgical importance

PURPOSE

The medial tentorial artery (MTA) of Bernasconi-Cassinari has been associated with many neurosurgical pathologies, including tentorial and petroclival meningiomas, dural arteriovenous fistulae, hemangioblastomas, moyamoya disease, arteriovenous malformations, trigeminal neuromas, and malignant gliomas. This vessel may function as a source of collateral blood supply for the posterior circulation. Our goal was to elucidate the MTA by compiling information about it in one concise article for clinicians and neurosurgeons who need to know about the anatomy and clinical significance of this artery.

METHODS

We reviewed the medical literature for information dealing with the anatomy, pathology, and surgery of the MTA and its clinical implications.

RESULTS

Based on the literature, the MTA commonly arises from the cavernous segment of the internal carotid artery and at times, may provide important collateral blood flow to the posterior circulation. This vessel is roughly 2 cm long and has a wavy appearance on angiography. It is usually a single trunk and often supplies the oculomotor, trochlear, and abducens nerves. The MTA may be seen on normal angiography and may be involved in the blood supply of petroclival and tentorial meningiomas.

CONCLUSIONS

A thorough knowledge of its anatomy and variations is important to clinicians interpreting imaging and neurosurgeons operating in this region. Detailed knowledge of this vessel may shed light on therapeutic options regarding its associated pathologies.

Endoscopic orientation of the parasellar region in sphenoid sinus with ill-defined bony landmarks: an anatomic study

The sphenoid bony landmarks are important for endoscopic orientation in skull base surgery but show a wide range of variations. We aimed to describe an instructional model for the endoscopic parasellar anatomy in sphenoid sinuses with ill-defined bony landmarks. Five preserved injected cadaveric heads and four sides of dry skulls were studied endoscopically via transethmoid, transsphenoidal approach. The parasellar region was exposed by drilling along the maxillary nerve (V2) canal [the length of the foramen rotundum (FR) between the middle cranial fossa and the pterygopalatine fossa]. This was achieved by drilling in the inferior part of the lateral wall of posterior ethmoids immediately above the sphenopalatine foramen. Cavernous V2 was traced to the paraclival internal carotid artery (ICA). Cavernous sinus (CS) apex was exposed by drilling a triangle bounded by V2 and its canal inferiorly, bone between FR and superior orbital fissure (SOF) anteriorly, and ophthalmic nerve (V1) superiorly. Drilling was continued toward the annulus of Zinn (AZ) and optic nerve superiorly and over the intracavernous ICA posteriorly. Endoscopic measurements between V2, SOF, AZ, and opticocarotid recess were obtained. Endoscopic systematic orientation of parasellar anatomy is presented that can be helpful for approaching sphenoid sinus with ill-defined bony landmarks.