RESUMO
The brain is supplied with arterial blood via 4 major arteries of two arterial systems. It is well known that the intracranial arteries have a different structure than the extracranial [loosing their elastic, collagenous, and muscular elements, thus becoming thinner]. There is a circumscribed transitional pattern portion in both arterial systems. This transitional pattern portion of the carotid artery [petrous cavernous portion] is the intracavernous portion of the artery. Is there any functional relevance of the complex cavernous venous structure to surround this transitional arterial segment? Does the vertebral artery also have a similar complex venous structure surrounding the transitional pattern portion? If so, is there any functional importance or relation to health and disease of such a complex structure? We studied in depth and detail both the gross and the microsurgical anatomy of the suboccipital region where the vertebral artery transgress the base of the skull before penetrating the dun. This area contains the complex of the vertebral artery [VA], its periarterial autonomic neural plexus, its branches, and the adjacent spinal nerves, all of which are cushioned in a rich venous compartment. This region can be the site of vascular, neoplastic, degenerative, congenital, or traumatic diseases, the surgical management of which demands an in depth understanding of the anatomy. We concentrated upon the third segment [V3] of the VA, which extends from the transverse foramen of the axis to the dural penetration of the VA. We also studied the surrounding venous structures of V3 Our study revealed an astonishing anatomical and structural resemblance between the atlanto-occipital venous compartment and the cavernous sinus. A review of the literature showed their related embryological development as well as their functional and pathological features, in addition to a similar transitional structural pattern of the related V3 and the petrous-cavernous portion of the internal carotid artery [ICA]. Hence we called this anatomical complex the [atlanto-occipital cavernous sinus]. We also discussed its various functional roles and its relationship to the adjacent structures and the clinical and surgical implications of these factors