Vertebral arterial injury (VAI) remains a fatal complication of C1-C2 posterior screw fixation. Herein, we report asymptomatic bilateral VAI that was caused by screws following C1-C2 posterior fixation. A 34-year-old woman with cerebral palsy experienced quadriplegia after a fall. Cervical computed tomography (CT) showed increased ADI, with os odontoideum, for which C1 pedicle screw and C2 pedicle-lamina screw fixation were performed. Cervical magnetic resonance imaging (MRI) conducted for postoperative weakness in shoulder elevation demonstrated a well-decompressed spinal cord. However, neck CT angiography revealed bilateral vertebral artery (VA) violations by the C1 pedicle screw that induced occlusion of the V2 and V3 segments of both VA, with intact V4 segments. Diffusionweighted imaging showed no evidence of infarction. Cerebral angiography showed reconstitution of posterior circulation via the left fetal posterior communicating artery. Steroid treatment-induced improvement in shoulder elevation to the preoperative level, and no neurological deterioration has been detected for 3 years postoperatively. Prevention of VAI is one of the most important objectives when performing posterior cervical screw fixation. The screw should be inserted considering the rotation of C1 and C2. Notably, variations in cerebral circulation, which enable collateral blood flow to the posterior circulation, can lead to different sequelae in patients with iatrogenic VAI.
Keywords: Atlanto-axial fusion; collateral circulation; iatrogenic; os odontoideum; vertebral artery.