Intracranial Connections of the Vertebral Venous Plexus: Anatomical Study with Application to Neurosurgical and Endovascular Procedures at the Craniocervical Junction.

BACKGROUND: Descriptions of intracranial extensions of vertebral venous plexuses are lacking. OBJECTIVE: To identify vertebral venous plexuses at the craniocervical junction in cadavers and describe them. METHODS: The authors dissected 15 ink-injected, formalin-fixed, adult cadaveric heads and measured cranial extensions of the spinal venous plexuses. RESULTS: All specimens had vertebral venous plexuses at the craniocervical junction composed of multiple interwoven vessels concentrated anteriorly (anterior vertebral plexuses), posteriorly (posterior vertebral venous plexuses), and laterally (lateral vertebral venous plexuses). Veins making up the plexus tended to be largest for the anterior internal vertebral venous plexus. On 33%, a previously unnamed lateral internal vertebral venous plexus was identified that connected to the lateral marginal sinus. The anterior external vertebral venous plexus connected to the basilar venous plexus via transclival emissary veins in 13%; remaining veins connected either intracranially via small perforating branches through the anterior atlanto-occipital membrane (33%) or had no direct gross connections inside the cranium (53%). The anterior internal vertebral plexus, which traveled between layers of the posterior longitudinal ligament, connected to the anterior half of the marginal sinus in 33% and anterolateral parts of the marginal sinus in 20%. The posterior internal venous plexus connected to the posterior aspect of the marginal sinus on 80% and into the occipital sinus in 13.3%. The posterior external venous plexus connected to veins of the hypoglossal canal in 20% and into the posterior aspect of the marginal sinus in 13.3%. CONCLUSION: Knowledge of these connections is useful to neurosurgeons and interventional radiologists.

Venous structures at the craniocervical junction: anatomical variations evaluated by multidetector row CT.

The aim of this study was to evaluate the anatomy of and normal variations in the craniocervical junction veins. We retrospectively reviewed 50 patients who underwent contrast-enhanced CT with a multidetector scanner. Axial and reconstructed images were evaluated by two neuroradiologists with special attention being paid to the existence and size of veins and their relationships with other venous branches around the craniocervical junction. The venous structures contributing to craniocervical junction venous drainage, including the inferior petrosal sinus (IPS), transverse-sigmoid sinus, jugular vein, condylar vein, marginal sinus and suboccipital cavernous sinus were well depicted in all cases. The occipital sinus (OS) was identified in 18 cases, including 4 cases of prominent-type OS. The IPS showed variations in drainage to the jugular vein through the jugular foramen or intraosseous course of occipital bone via the petroclival fissure. In all cases, the anterior condylar veins connected the anterior condylar confluence to the marginal sinus; however, a number of cases with asymmetry and agenesis in the posterior and lateral condylar veins were seen. The posterior condylar vein connected the suboccipital cavernous sinus to the sigmoid sinus or anterior condylar confluence. The posterior condylar canal in the occipital bone showed some differences, which were accompanied by variations in the posterior condylar veins. In conclusion, there are some anatomical variations in the venous structures of the craniocervical junction; knowledge of these differences is important for the diagnosis and treatment of skull base diseases. Contrast-enhanced CT using a multidetector scanner is useful for evaluating venous structures in the craniocervical junction.

Bilateral type 1 proatlantal arteries with absence of vertebral arteries.

The persistent proatlantal artery is a well-described communication between the carotid and vertebrobasilar system. However, persistence of bilateral proatlantal arteries is exceptionally rare. Although usually noted as an incidental finding, the presence of a proatlantal artery, particularly when bilateral, may result in unusual symptoms or may have implications for therapy. We report a case of bilateral proatlantal arteries, describe their embryology, and consider potential clinical implications of this finding.

Bow hunter's stroke associated with atlantooccipital assimilation--case report.

A 39-year-old male presented with bow hunter's stroke manifesting as repeated vertebrobasilar ischemic attacks induced by head rotation 45 degrees to the left. Three-dimensional computed tomography angiography clearly showed the occluded right vertebral artery (VA) between the axis and atlas. Single photon emission computed tomography study showed diffuse hypoperfusion of the brain stem and bilateral cerebellar hemispheres, suggesting hemodynamic compromise of these regions. He refused surgery and was treated conservatively. The most likely mechanism is that the affected VA was fixed by the ossification of the atlantooccipital membrane, vascular groove, and transverse foramen of the atlas, and therefore became elongated and compressed by head-turning.

Critical neck position as an independent risk factor for posterior circulation stroke. A magnetic resonance angiographic analysis.

The purpose of this study was to compare the effects of critical neck angulation (rotation and hyperextension) on vertebral artery perfusion in symptomatic and control populations and to determine whether this represents a risk factor for ischemic stroke. In a cross-sectional study, 64 symptomatic individuals with well-documented brainstem ischemic events (average age, 70.9 yr) and 37 control subjects (average age, 66.3 yr) were evaluated using a dynamic magnetic resonance angiography technique designed to mimic activities of daily living. Abnormalities of perfusion at the atlantoaxial and atlantooccipital junction and distal vertebral artery were recorded and scored independently by two neuroradiologists. Volume flow analysis was also recorded at the basilar artery, and distal and proximal vertebral arteries. Symptomatic subjects displayed a consistent pattern (56.4%) of contralateral hypoperfusion at the atlantoaxial and atlantooccipital junction and distal segments (grades 3 and 4) (p < 0.001). Unsuspected hypoplasia was noted in 13% of the symptomatic subjects with a right-sided preponderance (88%), suggesting developmental susceptibility. Occlusion was noted in all subjects with contralateral neck rotation. Postpositional ischemia was present (68%) and correlated with female gender (p < 0.001), severity of stenosis (p < 0.001), vascular risk factors (p < 0.001), and microinfarction on magnetic resonance images (p < 0.05). Flow analysis showed low basilar artery perfusion (< 25 ml/min) in 63.6%, and unsuspected steal with neck motion in 4 subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Rotational occlusion of the vertebral artery at the atlantoaxial joint: is it truly physiological?

We present a patient with vertebrobasilar insufficiency, with vertigo and horizontal nystagmus, induced by turning the head to the right. Angiography demonstrated transient occlusion of the left vertebral artery at the atlantoaxial joint during rotation of the head. The pathogenesis and angiographic findings are discussed.

Persistent proatlantal artery.

A case of persistent proatlantal artery is described and the developmental anatomy reviewed. This vessel, arising from the internal carotid artery in the neck, is liable to be confused with the hypoglossal artery, but unlike the latter it forms the vertebral artery outside the skull and enters through the foramen magnum.