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Year : 2015  |  Volume : 63  |  Issue : 6  |  Page : 1009--1012

Anomalous vertebral artery is not a deterrent to C1-2 joint dissection and manipulation for congenital atlantoaxial dislocation

Pravin Salunke, Sushant Sahoo, Arsikere N Deepak 
 Department of Neurosurgery, Postgraduate Institute of Medical Education and Research, Chandigarh, Punjab and Haryana, India

Correspondence Address:
Pravin Salunke
Department of Neurosurgery, Postgraduate Institute of Medical Education and Research, Chandigarh, Punjab and Haryana

How to cite this article:
Salunke P, Sahoo S, Deepak AN. Anomalous vertebral artery is not a deterrent to C1-2 joint dissection and manipulation for congenital atlantoaxial dislocation.Neurol India 2015;63:1009-1012

How to cite this URL:
Salunke P, Sahoo S, Deepak AN. Anomalous vertebral artery is not a deterrent to C1-2 joint dissection and manipulation for congenital atlantoaxial dislocation. Neurol India [serial online] 2015 [cited 2020 Jan 17 ];63:1009-1012
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We have read the recently published manuscript written by Sardhara et al.[1] The authors have attempted to stratify the risk of vertebral artery (VA) injury during surgery and have given a scoring system based on dominance, the course, its relationship to the C2 transverse foramen, and the C1–2 rotational deformity or tilt. The scoring system, though tedious, comprehensively covers most of the situations where the artery is likely to get injured.

The most important factor is the choice of approach. If sublaminar wiring is planned for posterior fusion, the risk is negligible whatever be the score. Second, a surgeon is usually comfortable with one approach and is unlikely to switch to a lesser-practiced approach even though the artery is at risk. Third, dealing with the C1–2 facets is the most important step in achieving reduction and a good long-term outcome. Finally, occasional presence of supernumerary joints increases the risk of injuring the associated anomalous VA many folds.[2] We have described various anomalies of the VA and the operative steps to safeguard it without compromising the C1–2 joint dissection [Figure 1] and [Figure 2].[3] These anomalous situations in the presence of congenital atlantoaxial dislocation (CAAD) would yield a poorer outcome.{Figure 1}{Figure 2}

In cases of CAAD, we dissect and drill the oblique C1–2 facets comprehensively till they are flat akin to those in normal individuals.[4],[5] Metallic spacers are placed within the joint space to prevent settling. The final realignment in all planes is achieved by manipulation of the facets after insertion of the C1 lateral mass and C2 pedicle screws using the rod holder as a lever and the C2 screw tulip as a fulcrum.[6] This is irrespective of the status of the C1 arch, occipitalized or free. There is a risk of injuring the VA in each of the aforementioned steps depending on its exit from the C2 foramen and its course up to the foramen magnum.

In our experience, we noticed some sort of VA anomaly in approximately 40% of our 100 cases with CAAD operated in the past 3 years. Most of them were seen with an occipitalized atlas. In all cases, the VA was traced from the C2 transverse foramen. Placing a thin dissector medial to the VA protects it while inserting the C2 pedicle screw irrespective of the location of the transverse foramen. In case of the persistentfirst intersegmental artery (FIA), the artery is dissected from the C2 nerve root, which is usually dorsal to the VA.[3] Cutting the C2 ganglion not only provides a panoramic view of the C1–2 joint but also gives an opportunity to dissect the anomalous VA. Once the artery is dissected along its crossing length, it can be safeguarded.[3] It can be gently retracted superiorly while dissecting the joint and inserting the spacer.[3] In the case of an inverted VA (VA passes beneath the C1 arch hugging the C1 inferior facet), the artery is not at risk while dissecting and drilling the joint but is likely to get injured during insertion of the C1 facet screws.[7] In these cases, the VA is dissected and gently retracted inferiorly while inserting the C1 facet screws.[7] Similarly, the posterior inferior cerebellar artery (PICA) may originate from the proximal V3 segment and cross the C1–2 joint. The artery can be dissected and safeguarded.[8] In cases of fenestration, the danger is in yanking the branch from the major vessel, leading to a catastrophe.[3] The fenestrated branch itself can be coagulated if necessary. Finally, while fastening the rods and screws, the anomalous VA should not be compromised [Figure 1] and [Figure 2]. The anomalous VA is redundant as compared with the stretched normal VA in CAAD and can easily be manipulated without the risk of thrombosis.[9]

By following the aforementioned steps, we have been able to safeguard the VA in all 37 cases. Only in one case, the anomalous VA could not be retracted inferiorly and required occipital squama to C2 fusion. The VA anomaly per se should not be a deterrent to dissection of C1–2 joints and insertion of screws, and the change of surgical strategy is more of an intraoperative decision. Nevertheless, the score given by Sardhara et al., gives the surgeon a fair bit of idea regarding the steps that require attention to avoid injury to the anomalous VA.

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1Sardhara J, Behari S, Mohan BM, Jaiswal AK, Sahu RN, Srivastava A, et al. Risk stratification of vertebral artery vulnerability during surgery for congenital atlanto-axial dislocation with or without an occipitalized atlas. Neurol India 2015;63:382-91.
2Salunke P, Futane S, Sharma M, Sahoo S, Kovilapu U, Khandelwal NK. 'Pseudofacets' or 'supernumerary facets' in congenital atlanto-axial dislocation: Boon or bane? Eur Spine J 2015;24:80-7.
3Salunke P, Futane S, Sahoo SK, Ghuman MS, Khandelwal N. Operative nuances to safeguard anomalous vertebral artery without compromising the surgery for congenital atlantoaxial dislocation: Untying a tough knot between vessel and bone. J Neurosurg Spine 2014;20:5-10.
4Salunke P, Sharma M, Sodhi HB, Mukherjee KK, Khandelwal NK. Congenital atlantoaxial dislocation: A dynamic process and role of facets in irreducibility. J Neurosurg Spine 2011;15:678-85.
5Salunke P, Sahoo SK, Deepak AN, Ghuman MS, Khandelwal NK. Comprehensive drilling of the C1-2 facets to achieve direct posterior reduction in irreducible atlantoaxial dislocation. J Neurosurg Spine 2015:1-9. [Epub ahead of print].
6Salunke P, Sahoo S, Khandelwal NK, Ghuman MS. Technique for direct posterior reduction in irreducible atlantoaxial dislocation: Multi-planar realignment of C1-2. Clin Neurol Neurosurg 2015;131:47-53.
7Salunke 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 persistentfirst intersegmental artery? Surg Neurol Int 2014;5:82.
8Salunke P, Futane S. Anomalous posterior inferior cerebellar artery crossing the C1-2 facet in a patient with atlanto-axial dislocation associated with Down's syndrome. Acta Neurochir (Wien) 2013;155:1953-4.
9Sawlani V, Behari S, Salunke P, Jain VK, Phadke RV. "Stretched loop sign" of the vertebral artery: A predictor of vertebrobasilar insufficiency in atlantoaxial dislocation. Surg Neurol 2006;66:298-304.