The cavernous sinus (CS) is a parasellar dural envelope containing an important venous pathway. The venous channels, which have an endothelial layer and no smooth muscle layer, are located in connective tissue. In the early embryonic stages, the neural tube is surrounded by the primitive capillary plexus and undifferentiated mesenchymal tissue, the primary meninx, and initially drains into the primary head sinus (PHS) through the anterior, middle, and posterior dural plexus (ADP, MDP, and PDP). Subsequently, following enlargement of the brain and differentiation of the mesenchyme, two major primary sinuses, the pro-otic sinus and the primitive tentorial sinus, become prominent. The pro-otic sinus is the remnant of the short segment of the PHS cranial to the MDP and the stem of the MDP. The CS originates from the plexiform channels medial to the trigeminal ganglion, namely the medial tributaries of the pro-otic sinus. The stem of the pia-arachnoidal vein draining into the ADP represents the primitive tentorial sinus. It is considerably elongated due to expansion of the cerebral hemisphere, and migrates medially toward the CS. The morphological changes in the CS and primitive tentorial sinus exhibit considerable variation in cerebral venous drainage patterns. Embryological knowledge facilitates interpretation of the anatomy of the CS, and it is useful to perform safe and beneficial endovascular treatment for the CS.

The cavernous sinus (CS) is a dural sinus located on each side of the pituitary fossa. Neoplastic and vascular lesions, such as arteriovenous fistulas, frequently involve the CS. This sinus plays a role as a crossroad receiving venous blood flow from the facial, orbital, meningeal, and neural venous tributaries. The relationship between these surrounding relevant veins and the CS, as well as the CS itself, varies anatomically. For safe and effective surgical and endovascular treatment of lesions involving the CS, knowledge of the anatomy and variations of the CS and the relevant surrounding veins is highly important. In this section, the anatomy and variations of the CS and the relevant surrounding veins are outlined.

The arterial anatomy of the parasellar area is complex in that it deals with extracranial–intracranial anastomosis and supply to various cranial nerves in a small area. Pathologies such as hypervascular tumors and shunts are not uncommon and require good knowledge of anatomy in planning the treatment. In this article, the basic anatomy of the arterial supply in this region is discussed, covering the origins, territories, relation to the cranial nerves, and the connections among different systems.

Cavernous sinus (CS) dural arteriovenous fistulas (AVF), which are most common in middle-aged females, present with benign symptoms such as exophthalmos, chemosis, and orbital bruit. Benign CS dural AVF without cortical venous drainage (CVD) have the rare potential for development of CVD with neurological symptoms, even without treatment. On the other hand, aggressive type AVF with CVD can cause more aggressive symptoms such as cerebral hemorrhage. As symptoms are highly related to the drainage pattern, it is important to understand the anatomy of the CS itself, shunt point, and draining vein when treating the lesion. In general, the drainage route is gradually diminished by thrombosis and compartmentalization within the CS according to progression of the angiographical stage. At the restrictive stage, the disease is usually treated by endovascular treatment, particularly transvenous embolization.

Cavernous sinus dural arteriovenous fistulae (CSdAVFs) are characterized by the shunts between dural arteries and dural veins surrounding the cavernous sinus (CS), causing ocular symptoms in addition to intracranial hemorrhage and infarction. As surgical access is difficult, endovascular treatment (EVT) has been considered and performed as the first-line therapy for decades. Although there have been recent advances in techniques and devices, transvenous embolization (TVE) with platinum coils remains the most common procedure. There are multiple access routes to the CS, such as the inferior petrosal sinus, superior ophthalmic vein (SOV), and intercavernous sinus from the contralateral CS. To extirpate the shunt, packing the entire sinus with coils is adopted, occasionally resulting in persistent cranial nerve palsy (CNP) due to compression of the coil mass. To avoid this complication, selective shunt occlusion (SSO), in which the coils are placed in the shunted pouch (SP) defined by the small restricted space where the arterial flow converges, is an effective and safe method. Transarterial embolization (TAE) is another option and use of liquid embolic materials, such as Onyx may be promising; however, the potential risk of ischemic nerve injury due to undesirable ante/retrograde influx of the liquid materials is of concern. In conclusion, EVT, especially TVE, is a safe and effective method for managing CSdAVFs. Understanding the angioanatomy consisting of the feeding artery, shunt point, and the drainage route, including the latent vessels, is essential for a good outcome.

A direct carotid cavernous fistula (CCF) is an abnormal shunt between the internal carotid artery (ICA) and the cavernous sinus (CS). Traumatic CCF is the most common type, accounting for up to 75% of all CCFs. For the management of direct CCF, endovascular therapy has become the standard.

For successful endovascular therapy, evaluation of the size and location of orifice of the CCF, venous drainage, and tolerance for ICA occlusion on cerebral angiography is necessary. Multi-planner reformatted images of 3D rotation angiography are useful to visualize the fistula and compartments of the CS precisely.

Due to the limited commercial availability of detachable balloons, detachable coils have become a widely employed endovascular tool for the treatment of direct CCFs. The advantageous aspects of coil application are their easy retrievability and better control. In the case of large/multiple fistulas, adjunctive techniques, including balloon- and stent-assisted techniques, are often needed to occlude the CCF while preserving the ICA. To avoid cranial nerve palsy related to over-packing of the CS with detachable coils or a detachable balloon, selective embolization of the fistula portion is required. Use of liquid embolic materials and covered stents was recently reported as another adjunctive technique. In cases in which it is impossible to occlude the CCF while preserving the ICA, parent artery occlusion (PAO) is considered. The selection of additional/alternative techniques and devices depends on the anatomy and hemodynamics of each CCF, and the skill and experience of individual operators.

Besides cavernous sinus (CS) dural arteriovenous fistulas (AVFs), AVF may develop around the parasellar region. They can cause various symptoms, and some of them may show similar symptoms to those of CS dural AVF. Therefore, these AVFs may be misdiagnosed as CS dural AVFs. In this review, we divided parasellar AVFs into four groups based on their locations related to the CS: anterior group (orbit), anterolateral group (sphenoid wing), posteroinferior group (inferior petrosal sinus and clivus), and posterior group (superior petrosal sinus and petrosal vein). Although parasellar AVFs share common points, there are many differences between the four groups. We herein discuss commonalities and differences in parasellar AVFs based on a review of the literature and our experience.

Embolization of hypervascular tumors has been widely performed for over four decades, particularly for preoperative meningioma. Several benefits of preoperative embolization have been reported, including reduced blood loss, surgical time and surgical complications, and improved outcomes. However, the technical details of both embolization and surgical procedures, and lesions widely vary. Thus, the actual benefits of preoperative embolization have not been clarified by prospective randomized studies. Procedure-related complications due to embolization developed in 3%–12% in previous studies. For parasellar lesions, both surgical resection and embolization have a higher risk of complication than for lesions at other locations because of the complicated neurovascular anatomy in the parasellar area. Therefore, close attention should be paid to the detailed vascular anatomy, embolic material, and related information for embolization and resection in individual cases to improve patient outcomes.