- Department of Neurosurgery, PGIMER, Chandigarh, India
- Department of Radiodiagnosis, PGIMER, Chandigarh, India
Department of Radiodiagnosis, PGIMER, Chandigarh, India
DOI:10.4103/2152-7806.133642Copyright: © 2014 Salunke P. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Salunke P, Sahoo SK, Ghuman MS. Bilateral inverted vertebral arteries (V3 segment) in a case of congenital atlantoaxial dislocation: Distinct entity or a lateral variant of persistent first intersegmental artery?. Surg Neurol Int 31-May-2014;5:82
How to cite this URL: Salunke P, Sahoo SK, Ghuman MS. Bilateral inverted vertebral arteries (V3 segment) in a case of congenital atlantoaxial dislocation: Distinct entity or a lateral variant of persistent first intersegmental artery?. Surg Neurol Int 31-May-2014;5:82. Available from: http://sni.wpengine.com/surgicalint_articles/bilateral-inverted-vertebral-arteries-v3-segment-in-a-case-of-congenital-atlantoaxial-dislocation-distinct-entity-or-a-lateral-variant-of-persistent-first-intersegmental-artery/
Background:Anomalous vertebral arteries (VAs), commonly involving the persistent first intersegmental artery (FIA), are often seen with congenital atlantoaxial dislocations (AAD). Here we describe an unusual variant consisting of bilateral VAs with normal loops but passing below the C1 (inverted VA) arch, distinctly different from the FIA.
Case Description:A 9-year-old boy presented with a spastic quadriparesis. Preoperative radiographic studies showed an irreducible AAD with an occipitalized CO-C1 and C2-3 fusion. Although both VAs exhibited proximal and distal loops like normal VA, the distal loops did not pass through the C1 transverse foramina and coursed inferior to the C1 arch instead. With this critical preoperative information, both VAs could be better safeguarded during dissection of the C1-2 facets.
Conclusion:In the case presented, although the course of the inverted VAs is similar, the norm, they coursed inferior to both C1 arches. Careful evaluation of the preoperative radiological studies allowed for careful dissection of the inverted VA (horizontal loop) while opening the C1-2 joint for subsequent alignment (e.g. reduction) and bony fusion. This information also facilitates safer insertion of lateral mass screws (e.g. choosing the appropriate C1 screw length to gain adequate bony purchase without compromising anomalous VA).
Keywords: Bilateral, injury prevention, operative steps, persistent first intersegmental artery, vertebral artery anomaly
A major anomaly of the vertebral artery (VA), involving the persistent first intersegmental artery (FIA), is often encountered with congenital atlantoaxial dislocations (AAD).[
A 9-year-old boy presented with a progressive spastic quadriparesis following trivial trauma. X-ray studies showed an occipitalized CO-C1 and congential C2-3 fusion; both contributed to an irreducible AAD resulting in cervico-medullary junction compression. Of interest, the C1 sagittal inferior facet angles measured 138°.[
Preoperative images – Top row: X-ray and MRI of CVJ showing AAD. Adjacent to it is axial CT angio image showing C1 transverse foramina without vertebral artery (yellow arrows). VAs are seen medially (red arrows). Middle row: 2D CT angio images in parasagittal and coronal plane passing through C1-C2 joint showing acute C1 inferior sagittal facetal angle (yellow arrow) and bilateral inverted VA (red arrows). Bottom row: 3D CT angio showing bilateral inverted VA (red arrows) in relation to C1-C2 facet joint. The course of VA is akin to normal except that it passes inferior to transverse foramina and C1 facet
As the patient was incompletely reduced with traction, surgical intervention was warranted. The C1-2 joints were approached posteriorly, and both C2 nerve root ganglia were cut to expose the anomalous VAs just anterior to it. In order to avoid inadvertent injury to the VAs, the loops crossing the C1 facets were carefully exposed; the posterior wedge of the C2 and anterior wedge of the C1 facets were drilled making the inferior facet angle flat in order to reduce the AAD. Spacers and bone grafts were placed in the C1-2 joint spaces. Next, the VAs were gently retracted inferiorly to insert the C1 lateral mass screws, which were sufficiently tightened to leave enough space between the screw head and the facet surface for the VA; the postoperative CT also showed adequate reduction [Figure
Intraoperative images showing Bilateral anomalous VA's (*) and its horizontal course posterior to inferior C1 facet. The course can be traced from C2 transverse foramen and then ventral to the C2 root ganglion (# cut C2 root), forming a horizontal redundant loop posterior to the inferior C1 facets. Images show sequential exposure of bilateral C1-2 joints and placement of spacers with bone graft (BG). Note the gentle inferior retraction of the anomalous horizontal VA loop to expose the inferior C1 facet and placement of C1 screws leaving enough space to avoid its compression by the screw head
(a and b) Midsagittal and coronal CT images showing complete reduction of Atlanto-axial dislocation. (c and d) parasagittal CT images passing through right and left C1 and C2 facets with screws and spacers. Note the flat drilled surface of C1 facets (white arrows) as compared with preoperative. Also note the adequate space between the posterior surface of inferior C1 facet and the screw head, enough to house the anomalous VA loop without compressing it
The VAs usually course postero-laterally after exiting the C2 transverse foramen, forming a short proximal loop that then enters the transverse foramen of the atlas. It then courses obliquely on the dorsum of the posterior arch of atlas forming the distal loop before penetrating the dura [
Comparison of normal VA, upside down VA and persistent first intersegmental artery (FIA). Note the presence of short proximal and a horizontal distal loop both in normal and upside down VA. These loops are absent in FIA, which, directly crosses medially after exiting C2 transverse foramina. The upside down VA reaches just short of the C1 transverse foramina and the horizontal loop lies below the C1 unlike the normal VA
The anatomical variations involving the VA between C1 and C2 have been well described.[
Embryology of the VA
Embyrologically, the VA is formed by vertical channels interconnecting the cervical intersegmental arteries. During the course of time, these intersegmental arteries disappear and vertical connections persist.[
The anomalies of VA are commonly seen distal to the C2 transverse foramen and are comprised of persistent channels.[
Anomalous VA pose a surgical challenge
VA anomalies pose a surgical challenge as these anomalous vessels may be injured during drilling of facet surfaces, placement of spacers, and the insertion of lateral mass screws.[
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