Vertebral Artery Injury

Key Images

Introduction

Incidence of vertebral artery injury (VAI)   0.5% of all trauma patients  70% of VAI in blunt trauma has associated cervical fracture 33%-39% of all cervical spine fractures  0.3% anterior cervical spine surgery 4.1-8.2% posterior cervical spine surgery (C1-2 transarticular screws) Pathophysiology blunt traumatic injury pathoanatomy highest injury risk at point of entry into C6 transverse foramen second highest risk at C1-2 articulation iatrogenic injury during elective surgery  safe zone C1: avoid dissection cephalad to the C1 posterior arch > 1.5 cm lateral to midline   C1 lateral mass screw should be placed in a 10 degrees medial and 22 degreees cephalad trajectory  Prognosis impact of VAI difficult to predict many patients initially asymptomatic some progress to cerebral ischemia or stroke with permanent neurologic deficit  variable symptomatology

Anatomy

4 arterial segments V1 extraosseous origin at subclavian artery, anterior to C7 transverse process, to the entry point of C6 transverse foramen V2 within the transverse foramina of C6-C1 most traumatic injuries occur here high risk during drilling, tapping, insertion of lateral mass or pedicle screws V3 superior aspect of the arch of atlas to foramen magnum VA is vulnerable during lateral exposure and laminectomy of C1 high risk of C1-2 transarticular screws are directed caudally and laterally V4 intradural extension from foramen magnum to unite with contralateral vertebral artery forms the basilar artery most injuries from cervical trauma in V2 (foraminal segment)  Anomalous anatomy reported prevalence of 2.7% in anterior cervical surgery transverse foramen may be medial to or within 1.5mm of the uncovertebral joint reported prevalence of 2.3-20% in the atlantoaxial region high-riding C2 foramen C2 pedicle erosion C2 lateral mass thinning

Classification

Biffl VAI Injury Grading Grade I  • arteriographic appearance of vessel dissection/intraumural hematoma; <25% luminal stenosis   Grade II  • intraluminal thrombosis or raised intimal flap; dissection/intramural hematoma with >25% luminal stenosis Grade III  • pseudoaneurysm Grade IV  • vessel occlusion Grade V  • vessel transections

Presentation

History  consists of recent: cervical spine trauma C1 or C2 fractures subaxial facet fractures and dislocations elective surgery of the cervical spine or craniocervical junction Symptoms variable in presentation and time of onset vertebrobasilar insufficiency manifests with dizziness vertigo nausea diplopia blindness ataxia bilateral weakness oropharyngeal dysfunction

Imaging

Radiographs xrays of certain fracture patterns raise suspicion for VAI CT angiography (CTA)  identification of local occlusion or extravasation sensitivity reported at 100% indications for the trauma patient (any single criteria is an indication) unexplained central or lateralizing neurologic deficit evidence of acute cerebral infarct on CT scan of head GCS <9 evidence of diffuse axonal injury facial fracture or Le Fort type-II or III fracture cervical spine fracture or subluxation C1, 2, 3 fracture Fracture extension into the transverse foramen VAI demonstrated in 20% cervical spinal cord injury hanging injuries major thoracic injury or first-rib fracture Magnetic resonance angiography (MRA) identification of local occlusions/stenosis sensitivity 93.9% indications cervical spine fractures with neurologic deficits attributable to damaged vertebral or basilar artery perfusion sensitivity and specificity

Treatment

Post-operative anticoagulation goal is to prevent thromboembolic sequelae of injury intravenous heparin acetylsalicylic acid (aspirin) indications first line of treatment modalities heparin, aspirin, clopidogrel, IV thrombolysis, glycoprotein IIb/IIIa antagonists (abciximab, eptifibatide, tirofiban) contraindications: major intracranial infarction intraspinal hematoma/arteriovenous fistula Operative reduction and stabilization as neccessitated by fracture pattern Surgical techniques to control hemorrhage (see Techniques) Immediate intra-operative angiography can assist intra-operative decision making Post-operative management following iatrogenic injury observation further intervention dictated by clinical course immediate post-operative angiography detects vascular complications confirms adequate collateral cerebral circulation allows embolization of fistulae or pseudoaneurysm

Techniques

Hemostatic tamponade utilization of topical hemostatic agents, bone wax if injured during C1-2 transarticular screw placement, can tamponade by screw insertion risks include: delayed hemorrhage fistula formation Microvascular repair allows restoration of normal blood flow minimizes risk of ischemic complications technically demanding Direction ligation consider intraoperative angiography first to evaluate collateral circulation risks certain morbities cerebellar infarction loss of flow via the posterior inferior cerebellar atery (PICA) isolated cranial nerve paresis hemiplegia IR-guided embolization

Complications

Complications may occur days to years following injury arteriovenous fistula late-onset hemorrhage pseudoaneurysm may be delayed presentation thrombosis with embolic incidents cerebral ischemia/Stroke persistent vertigo death