The suboccipital cavernous sinus

Abstract

The authors studied the microsurgical anatomy of the suboccipital region, concentrating on the third segment (V3) of the vertebral artery (VA), which extends from the transverse foramen of the axis to the dural penetration of the VA, paying particular attention to its loops, branches, supporting fibrous rings, adjacent nerves, and surrounding venous structures. Ten cadaver heads (20 sides) were fixed in formalin, their blood vessels were perfused with colored silicone rubber, and they were dissected under magnification. The authors subdivided the V3 into two parts, the horizontal (V3h) and the vertical (V3v), and studied the anatomical structures topographically, from the superficial to the deep tissues. In two additional specimens, serial histological sections were acquired through the V3 and its encircling elements to elucidate their cross-sectional anatomy. Measurements of surgically and clinically important features were obtained with the aid of an operating microscope. This study reveals an astonishing anatomical resemblance between the suboccipital complex and the cavernous sinus, as follows: venous cushioning; anatomical properties of the V3 and those of the petrous-cavernous internal carotid artery (ICA), namely their loops, branches, supporting fibrous rings, and periarterial autonomic neural plexus; adjacent nerves; and skull base locations. Likewise, a review of the literature showed a related embryological development and functional and pathological features, as well as similar transitional patterns in the arterial walls of the V3 and the petrous-cavernous ICA. Hence, due to its similarity to the cavernous sinus, this suboccipital complex is here named the "suboccipital cavernous sinus." Its role in physiological and pathological conditions as they pertain to various clinical and surgical implications is also discussed.

Anatomical Features and Clinical Significance of Radiculomuscular Artery Variants Involving the Suboccipital Segment of Vertebral Artery

“…In an aberrant V3 demonstrated by DSA and another aberrant V3 observed in the cadaver specimen, the muscular branch of the radiculomuscular artery accompanying the posterior ramus of the C-2 nerve [1] was found to arise from the aberrant V3. It is reasonable to assume that the aberrant V3 corresponded to a hyperplastic radiculomuscular artery, together with its radiculomedullary branch.…”

“…The microsurgical anatomy of the suboccipital segment (V3) of the vertebral artery (VA) has been previously studied [1][2][3] because of its clinical significance. The V3 is further subdivided into two parts: a horizontal (V3 h) and a vertical (V3 v) segment ( [1]; Fig.…”

“…The V3 is further subdivided into two parts: a horizontal (V3 h) and a vertical (V3 v) segment ( [1]; Fig. 1).…”

“…The radiculomuscular artery, the largest branch of the V3 ( [1]; Fig. 1), arises below the transverse foramen of the atlas and gives rise to two branches: 1) the radiculomedullary branch, which accompanies the C-2 nerve laterally and vascularizes the C-2 ganglion, the C-2 nerve and the spinal cord and 2) the muscular branch, which accompanies the posterior ramus of the C-2 nerve ( [1]; Fig. 1).…”

“…lateral, far lateral, suboccipital midline and upper cervical) the radiculomuscular artery and its branches can be dissected [2,4] and iatrogenic injury to an important variant related to this artery or its branches poses a greater risk to PICA or even to the VA ( [1]; Fig. 1); therefore, in this study we focused on the aforementioned variations in the distal VA related to radiculomuscular artery from the viewpoint of microsurgical anatomy.…”