Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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July 9, 2020
Vertebral Artery Transection Secondary to Penetrating Trauma
- Background:
- The vertebral artery typically originates from the subclavian artery and has 4 segments V1–V4 as it ascends from the transverse process of C6 (V1), ascends all the way to C2 (V2), exits C2 into the dura (V3), and joins the basilar system (V4).
- Traumatic cerebrovascular injury is rare and associated with significant morbidity unless identified and treated promptly.
- CTA is the best modality of imaging in penetrating trauma or when the patient’s injury or presenting symptoms are consistent with Denver criteria. While MR angiography is non-inferior, it is time-consuming and should not be the initial modality of imaging, especially because the penetrating object can be ferromagnetic.
- Clinical Presentation:
- Patients can either be asymptomatic (like in this case) or present with posterior circulation stroke symptoms like imbalance, dysphagia, dysphonia, Horner syndrome, or difficulty with visual focus (Wallenberg syndrome).
- Key Diagnostic Features:
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Lack of contrast flow beyond the segment of the transected artery containing the penetrating foreign body on cerebral angiogram
- Narrowing or luminal irregularity of the affected vertebral artery compared with the contralateral side is often seen.
- The “flame sign” is a tapering seen on CTA or plain angiograms that is telltale for dissection. This is demonstrated in image B.
- It is important to assess the patency of the remaining vertebrobasilar system (ie, if there is retrograde reflux of contrast from the contralateral vertebral artery down the basilar into the affected artery), as a lack of such patency would favor open surgical intervention instead of endovascular therapy, as access around the vertebrobasilar system would be compromised.
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- Important Imaging Features Worth Mentioning:
- It is important to assess the patency of the carotid, internal jugular vein, and presence of active extravasation, as this may change the mode of treatment from endovascular to open (surgical).
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It is not uncommon to have injury of surrounding structures like the trachea and esophagus, which classically manifests as a lucency (air leak) around the prevertebral soft tissues.
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It is crucial to identify any aberrant origins of blood vessels in these circumstances, as it can help the interventionalist guide their catheter appropriately (image D).
- Differential Diagnoses:
- Vertebral artery thrombosis: Depending on the extent of thrombosis, it can manifest as a small intimal irregularity all the way to a completely flow-limiting lesion. Thrombosis is often comorbid with dissection and transection.
- Vertebral artery dissection: Typically appears as an intimal flap separated from the media and adventitia; if a pocket of blood pools between the media and adventitia, it can create a segmental widening called a pseudoaneurysm.
- Procedural vertebral artery vasospasm: This typically is a transiently flow-limiting lesion during an angio-interventional procedure and demonstrates normal flow at the beginning of the procedure. This occurs as a temporary reaction of placing a foreign body (especially a guiding catheter) inside the artery.
- Rotational vertebral artery occlusion: Also known as bow hunter syndrome, this is a phenomenon of transient vertebrobasilar insufficiency manifesting as vertigo, blurry vision, and ipsilateral tingling as a consequence of compression of the dominant vertebral artery by a neighboring transverse process or osteophyte while rotating the head to the side. Flow returns to normal when the patient brings their head back to midline, which can be seen on a dynamic cerebral angiogram.
- Treatment:
- The Denver scale is typically used in blunt cerebrovascular injury, but can help to describe the extent of vascular injury. The scale grades injuries from I–V, I being minor intimal irregularity that responds well to antiplatelet therapy and V requiring either definitive emergent endovascular therapy or temporizing endovascular therapy followed by definitive vascular surgery. Grade II (intimal tear with narrowing), grade III (pseudoaneurysm), and grade IV (complete thrombosis/occlusion) are progressively less responsive to antiplatelet therapy and require stenting or revascularization.
- Patency of the vertebrobasilar system is important for definitive endovascular therapy to be successful, otherwise surgical ligation followed by revascularization is needed.
- A follow-up MRI is needed to rule out acute stroke after embolization.
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Recent case studies have shown successful neurologic outcomes with endovascular treatment of grade V injuries.