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Posterior circulation infarct without apparent vertebral artery injury following realignment of atlantoaxial dislocation
Mandeep S Kataria, Pravin Salunke, Madhivanan Karthigeyan, Shivanna Puneeth
Department of Neurosurgery, Postgraduate Institute of Medical Education & Research (PGIMER), Chandigarh, India
|Date of Submission||01-May-2021|
|Date of Decision||27-Oct-2021|
|Date of Acceptance||07-Feb-2022|
|Date of Web Publication||30-Jan-2023|
Department of Neurosurgery, PGIMER, Sector 12, Chandigarh 160012
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Risk of injury to normal vertebral artery (VA) unlike that associated with an anomalous VA is infrequent during posterior C1–C2 reduction for congenital atlantoaxial dislocation (AAD). An ischemic event resulting from such indirect injury is a rare occurrence. A 14-year-old boy with severe AAD/basilar invagination underwent C1–C2 joint manipulation and fixation with an uneventful intraoperative course. Although his immediate postsurgical period was unremarkable, he sustained sudden and rapid neurological worsening on day 3. He developed multiple posterior fossa infarcts and finally succumbed. VA can be indirectly injured possibly due to excessive distraction/manipulation of C1–C2 joints. The lesson learnt is that anticipation of such injuries along with proactive anticoagulation treatment can potentially alter patient outcome.
Keywords: Atlantoaxial, basilar invagination, C1–C2, distraction, infarct, ischemia, posterior fixation, posterior fossa
| Introduction|| |
For congenital craniovertebral junction (CVJ) instability, posterior C1–C2 joint reduction and fixation is currently the desired treatment method. This condition can be associated with a normal course of vertebral artery (VA) or an anomalous arterial anatomy in approximately 25% of cases., Although the VA in its aberrant path carries risk of injury during steps such as soft tissue dissection, C1–C2 joint drilling, and screw placement, a normal course usually does not greatly interfere with these operative steps. A normal VA that is endangered during extremes of C1–C2 manipulation is less often described. We present a case of delayed onset postoperative posterior circulation stroke following complete reduction of severe atlantoaxial dislocation (AAD) without an apparent injury to the VA.
| Case Report|| |
A 14-year-old boy presented to us with progressive spastic quadriparesis over 1 year duration. Computed tomography (CT) of CVJ with reconstruction revealed severe vertical AAD/basilar invagination (BI) [Figure 1]. It also showed bony anomalies such as assimilated C1 arch and highly incurved occiput. CT angiography (CTA) showed dominant left VA with a normal course. The arterial segment between C2 and C1 was almost transversely oriented because of severe AAD. A magnetic resonance (MR) imaging of the cervical spine showed syrinx involving the cervical and upper thoracic spinal cord.
|Figure 1: A–C: Preoperative CT images. Mid-sagittal section (A) shows atlantoaxial dislocation with BI; parasagittal (B) and coronal (C) sections show extreme obliquity of C1–C2 joints. D and F: Three-dimensional CTA images. Lateral (D and E) and posterior (F) views show absent VA on the right side (D) and dominant left VA (asterisk) (E and F)|
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The patient underwent posterior C1–C2 joint reduction and fixation. With the child prone on skeletal traction and following standard subperiosteal dissection and exposure, the articular facets were comprehensively drilled and metallic spacers (5 mm on the left joint and 7 mm on the right joint) were placed. The joints were fixed in the reduced position with the C1 lateral mass and C2 pedicle screws under neuronavigation guidance; the vertical AAD was significantly reduced. There was no VA injury, and the entire procedure remained uneventful. In the immediate postoperative period, CT scan confirmed excellent C1–C2 reduction and alignment with satisfactorily placed screws and spacers [Figure 2].
|Figure 2: Upper panel: Postoperative CT images (A–D). Mid-sagittal CT section (A) demonstrates complete reduction of AAD/BI. Axial (B and C) and coronal (D) sections show satisfactorily placed screws and joint spacer. Lower panel: CT head after neurological worsening shows bilateral posterior fossa infarcts (E and F) and obstructive hydrocephalus (G and H)|
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The child was doing well until 48 hours after which he developed respiratory distress along with altered sensorium and worsening of quadriparesis. Because reintubation was not possible, an emergency bedside tracheostomy was performed to secure his airway. A repeat CT imaging showed no evidence of re-dislocation or an implant malfunction. However, patchy arterial infarcts were visible in the posterior fossa with obstructive hydrocephalus [Figure 2]. Before any further investigation, the child’s neurology rapidly worsened leading to death.
| Discussion|| |
Iatrogenic VA injuries have been reported in 1.35% of cases during posterior C1–C2 fixation, mostly during bone/joint drilling and instrumentation. Such injuries can occur in patients with both anomalous and normal VA, and are apparent during surgery. In the event of a significant or dominant sided injury, patients may present with posterior circulation stroke or with pseudo aneurysm, and their sequelae.
In its normal course, the third segment of the VA that traverses between the C2 transverse foramen and the dural entry may be stretched due to an excessive translational mobility between the C1 and C2 vertebra, and can manifest as posterior circulation stroke. However, a posterior fossa stroke resulting from an indirect VA injury during C1–C2 manipulation, similar to the one we describe, has seldom been described. In patients with severe AAD, the VA segment between the C2 and the C1 has already been stretched and a distraction while attempting to realign the atlantoaxial joints can further compromise it. This distraction possibly gives rise to an arterial kinking or its intimal dissection leading to a thromboembolic event with the resultant posterior-circulation stroke in a delayed fashion. This mechanism of VA injury is similar to a low-grade blunt VA injury, which has been known to present with ischemic symptoms in the posterior circulation. Such vascular events may present immediately or in a delayed fashion up to 3–6 months after injury., The other mechanisms that could predispose to postoperative infarcts in AAD patients could be a minor VA injury, especially on the dominant side and that goes unnoticed during the surgery. Certain VA anomalies such as fenestration or medial looping can also cause an indirect vascular injury during C1–C2 joint dissection.
Traditionally, blunt VA injury has been managed with anticoagulation or antiplatelet therapy with no consensus on one’s superiority over the other. Nevertheless, there is evidence that untreated patients face higher incidence of ischemic complications when compared with those intervened early with anticoagulation/antiplatelet therapy., Hence, it is preferable to initiate anticoagulant therapy immediately after surgery in patients requiring extreme C1–C2 joint manipulation. Of late, we have been practicing this protocol in elderly patients who require VA manipulation; intravenous heparin (80 U/kg bolus followed by infusion of 18 U/kg/h for 24–48 h) and aspirin (75 mg for 6 weeks) were administered. This index pediatric case hints that such prophylactic anticoagulation may be needed even in non-elderly candidates subjected to excessive C1–C2 distraction/manipulation. Although there may be some chance of anticoagulant related hematoma formation and bleeding in the immediate post period, one needs to weigh its benefits against this related risk. Besides, starting anticoagulation therapy in an evolved infarct may predispose to hemorrhagic transformation. Whenever feasible, an immediate postoperative digital subtraction angiogram (DSA) can be considered in AAD patients requiring extreme joint manipulation or VA handling. However, this investigation is limited by relatively invasive nature. A CTA or MR angiography as an alternative in such cases is difficult to interpret because of metallic artifacts. We acknowledge that in our patient, a DSA could not be performed; a rapid downhill course precluded such workup. To prevent VA-associated ischemic events, one may consider performing C1–C2 fixation in a partially reduced or in situ position. However, the neurological benefit is likely to be suboptimal with such procedures.
In conclusion, the case emphasizes the need for an extra clinical caution and pro-active management in patients managed for severe AAD in order to prevent such postoperative catastrophe.
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Conflicts of interest
There are no conflicts of interest.
Statement of ethics
The research was conducted ethically in accordance with the World Medical Association’s Declaration of Helsinki. The child’s parents have given their written informed consent for publication of data and images. Information revealing the subject’s identity is avoided.
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[Figure 1], [Figure 2]