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Neurol India. 2015 May-Jun;63(3):382-91. doi: 10.4103/0028-3886.158218.

Risk stratification of vertebral artery vulnerability during surgery for congenital atlanto-axial dislocation with or without an occipitalized atlas.

Author information

1
Department of Neurosurgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India.

Abstract

CONTEXT:

Variability in dimensions and course of vertebral artery (VA) makes it vulnerable to injury during surgery for congenital atlanto-axial dislocation (AAD) with or without an occipitalized atlas.

AIMS:

This prospective study attempts to define anatomical variations that render VA at the craniovertebral junction (CVJ) vulnerable to injury during transoral decompression and posterior stabilization procedures; and, to propose a classification that helps in preoperative risk stratification.

SETTINGS AND DESIGN:

A prospective study.

MATERIALS AND METHODS:

104 patients (65 with AAD; 39 controls) underwent a three-dimensional multiplanar computed tomographic angiogram to study anatomical variations in VA size, course, and anomalous medial deviation as well as in the type of axial isthmus and rotational deformity/tilt at the CVJ. The VA/foramen transversarium diameter; "stretched loop" sign of VA; and C1-2 facet joint angle were also assessed.

STATISTICAL ANALYSIS USED:

A medial VA deviation that brought it in close proximity to the trajectory of the surgical approach was evaluated (P ≤ 0.05 significant).

RESULTS:

An increased predisposition to VA injury was present in 23 (35.4%) patients (persistent first intersegmental artery [n = 20; 30%]; fenestrated VA [n = 1; 1.53%], and low-lying posterior inferior cerebellar artery [n = 2; 3.0%]) where VA crossed the C1-2 facet joint; 8 (12%) with an anomalous medial deviation; 12 (18%) with a high-riding VA at C2 and a narrow axial isthmus; and 13 (20%) with rotation/tilt at the CVJ. A normal score of 5 was obtained in 21 patients; and a score of 6-9 (that progressively indicated an increased vulnerability of VA to iatrogenic injury) in 44 patients. The "AAD with an occipitalized atlas" group was associated with a significant medial deviation of VA (right: P = 0.00 and left: P = 0.001).

CONCLUSIONS:

A preoperative detailed risk assessment of anatomical variations in the size and course of VA at the CVJ significantly reduces chances of its iatrogenic injury.

PMID:
26053811
DOI:
10.4103/0028-3886.158218
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