The Circular Sinus: An Anatomic Study with Neurosurgical and Neurointerventional Applications

Abstract

Skull base surgery requires knowledge of the intracranial venous sinuses, which overall have been well studied. However, the intercavernous sinuses and their contribution to the so-called circular sinus have received scant attention. Dissection was performed on 35 latex-injected cadaveric heads with attention to the morphology of the anterior and posterior intercavernous sinuses. A scale was created to describe the presence and morphology of the intercavernous sinuses, and morphometrics were performed. Both anterior and posterior intercavernous sinuses were identified in 28 specimens (80%; type I). Of the 80% with both sinuses, a circular connection between these was found in 25% (type II). Only the anterior intercavernous sinus was observed in six specimens (17%; type III), and only the posterior sinus was seen in one specimen (2.9%; type IV). No specimen lacked both the anterior and the posterior intercavernous sinuses. The anterior intercavernous sinus was larger than the posterior intercavernous sinus in most specimens (n=28). The anterior intercavernous sinus occupied the entire anterior wall of the sella turcica in five specimens. An inferior intercavernous sinus was present in only six specimens (17%) and was usually smaller than the anterior or posterior intercavernous sinuses. A true "circular sinus" (type II) is present in only a few cases; both intercavernous sinuses disconnected are found in most specimens. No intercavernous sinus was found within the free edge of the diaphragma sella, which is typically depicted. These data are useful for invasive and minimally invasive procedures of the parasellar region.