Atlanto-axial dislocation associated with anomalous single vertebral artery and agenesis of unilateral internal carotid artery
We report a case of 34-year-old male who presented with history of progressively increasing difficulty in walking and progressively increasing spastic quadriparesis for 7 years. He had pain and paresthesia in his right upper limb for the past 2 years. On examination, the tone was increased in all four limbs with power 4+/5 and hand grips of 60%. Bilateral planters were extensor. Posterior columns were impaired bilaterally. He had a short neck with low hair line with restricted rotational neck movement. Computed tomography (CT) showed atlanto-axial dislocation (AAD) with atlanto-dental interval (ADI) of 8 mm in both flexion and extension with partially occipitalized atlas and basilar invagination (BI) with basal angle of approximately 148° and tip of odontoid crossing the Wackenheim clival canal line. Magnetic resonance imaging of the CVJ showed significant compression of the cord at the CVJ []. Transoral decompression and posterior fusion was planned in view of fixed AAD (in view of no change of ADI in flexion and extension) and BI. C1 anterior arch was drilled and tip of the dens was drilled and excised and dura was partially visualized but was not opened. So as to have an adequate decompression, bony drilling was further carried out laterally and downward. While drilling on the left side there was brisk bleeding which was controlled with muscle, glue, gelfoam and floseal. In view of suspected injury to the VA, posterior fusion was deferred and traction was continued. Intra-arterial digital subtraction angiography was planned for diagnosis of suspected VA injury and necessary therapeutic intervention. However, before shifting for digital subtraction angiography (DSA) there was rebleeding from oral wound to require re exploration and hemostasis. Patient was shifted to DSA room. DSA showed absent left ICA and the right VA. The left middle cerebral artery (MCA) was filling through the left VA and the left anterior cerebral artery (ACA) was filling from the right ICA. The left VA was taking an anomalous course with the V3 segment curving medially and reaching up to the midline just behind the odontoid process. The VA was injured in its extradural part as it was injured behind the odontoid (and there was no sub-arachnoid blood on CT). The site of injury was visualized and the stent was placed across the rent []. Next day the pack was removed and no bleeding was noticed. The sensorium of the patient did not improve. CT showed diffuse brain edema and anti-edema measures were initiated, but on the 5th post-operative day the patient expired.