Recurrent posterior circulation infarcts secondary to vertebral artery external compression treated with endovascular deconstruction

Abstract

When multiple, recurrent infarcts occur in spite of maximal medical management, the level of suspicion for atypical vascular injury should be heightened. We present a case of a patient who presented with recurrent posterior circulation infarcts despite optimized medical management. On imaging, he was found to have external anatomical vertebral artery muscular and/or osseous compression leading to repetitive vascular injury and strokes. Recurrent intimal injury and vertebral artery to intracranial emboli despite anticoagulation and subsequent dual antiplatelet therapy necessitated definitive operative management. Surgical bypass, external surgical decompression, reconstructive endovascular, and deconstructive endovascular techniques were carefully considered. A deconstructive endovascular approach was chosen as the least morbid option. The use of endovascular plugs such as a microvascular plug provides a quick and effective means of achieving a therapeutic parent artery occlusion in lieu of traditional coil occlusion. Although reserved as a last resort, parent artery occlusion can be a viable option to treat recurrent strokes, particularly in a nondominant vertebral artery.

Introduction

Vertebral artery (VA) dissections leading to posterior circulation infarcts are common and generally respond well to conservative management with anticoagulation or antiplatelet therapy. Bow Hunter’s syndrome (vertebrobasilar insufficiency) is one well-described mechanism of injury; however, there are many other extravasal etiologies.^1,2 When posterior circulation infarcts occur in spite of maximal medical management, the level of suspicion for atypical vascular injury should be heightened.^3,4 Herein, we report a case of a patient who presented over the course of three years with recurrent posterior circulation infarcts unresponsive to maximal medical management who likely had an external anatomical VA compression leading to repetitive vascular injury and infarcts.

Case report

A 56-year-old right-handed male with a past medical history of hypertension, hyperlipidemia, asthma as well as a history of neck “popping” movements and frequent chiropractic manipulations was evaluated numerous times over three years for recurrent posterior circulation strokes of unknown etiology.

The patient presented with vertiginous symptoms before each stroke consisting of a “hot flash” sensation with nausea, emesis, diplopia, and dysarthria. The first year he suffered infarcts on two separate occasions (in the right posterior inferior cerebellar artery and bilateral posterior cerebral artery territories). A computed tomography angiogram (CTA) of the neck showed a short-segment intraluminal filling defect of the right VA proximal to its entrance into the transverse foramen at C4. The patient was diagnosed with a VA dissection and treated initially with aspirin monotherapy, bridging to warfarin. Four months later, he suffered his third posterior cerebral artery territory infarct. He was transitioned to warfarin and clopidogrel. The family sought a second opinion and had a catheter cerebral angiogram, suffering an intraprocedural embolic stroke without detection of luminal abnormality. Aspirin monotherapy was again utilized. Two years later, the patient was diagnosed with another ischemic event in the right thalamus with an unremarkable workup, but the right VA was seen abutting the transverse process of C5 on CTA of the neck (Figure 1(a) and (b)). Since this event occurred while on aspirin, he was again switched to clopidogrel.

Figure 1.

(a) Axial computed tomography angiography (CTA) with contrast showing compression of the right vertebral artery (VA) between the C5 transverse process (thin arrow) and the longus colli muscle (thick arrow) with external compression and a luminal filling defect (arrowhead) (b) Coronal CTA showing compression of the right VA by the longus colli muscle (thin white arrow) against the C5 transverse process (deep and laterally).

After four months, he presented to our hospital with a right superior quadrantanopia, anomia, and episodic memory impairment. Magnetic resonance imaging (MRI) showed scattered posterior circulation infarcts including a left posterior cerebral artery territory infarct involving the entire left medial temporal lobe. MR angiogram (MRA) revealed tapering of the left P1 segment and frank occlusion of the P2 segment. A CTA also showed a small linear filling defect in the right VA at the location of an acute bend. A cerebral angiogram showed focal kinking at the level of external compression of the right VA. The mild corresponding luminal irregularity was visible (Figure 2(a) and (b)). Angiography showed filling of the right posterior inferior cerebellar artery and intracranial circulation via a dominant left VA. No supply to the anterior spinal artery (artery of the cervical enlargement) from the VA was identified. After considering reconstructive options such as stenting or bypass, the decision was made to perform endovascular deconstruction rather than open surgical ligation. Two microvascular plugs were deployed (spanning from the C4–5 disc space to the mid-C6 vertebral body, Figure 2(d)) with full therapeutic anticoagulation (activated clotting time >250) via an ipsilateral transradial approach to successfully occlude the nondominant VA (Figure 2(c)) within 30 s to prevent distal emboli. The procedure was tolerated well and the patient was started on apixaban on post-procedure day two. He has remained stable with no vertiginous symptoms reported at six-month follow-up. Follow-up CTA reveals opacification of all intracranial vessels via the dominant, patent left VA (Figure 3).

Figure 2.

(a) Digital subtraction angiography (DSA) and (b) unsubtracted angiogram from right vertebral artery injection showing deviation and luminal irregularity (curved arrow). Complete occlusion (black arrow) of the vessel on DSA (c) after placement of two microvascular plugs; radio-opaque markers (white arrows) seen on magnified unsubtracted (d) microcatheter angiogram.

Figure 3.

Computed tomography angiography oblique coronal curved reformation three months after treatment, showing filling of the vertebrobasilar circulation from the dominant left vertebral artery with retrograde filling of the proximally occluded right vertebral artery (arrowhead), supplying the posterior inferior cerebellar artery (not shown).

Discussion

VA loops and kinks are thought to be congenital, though various life factors related to aging or aberrant anatomy can lead to acquired kinking.^5,6 Acquired kinks can be due to extravasal compression by muscle tendons, the crossing sympathetic trunk or its branches, sympathetic nerves, fascial bands, osteophytes, vertebral column deformation, and other rare etiologies.^5,6 The V1 and V2 segments are at greatest risk. ⁵

In our case, imaging yielded the possible source of extravascular compression by identification of an acute band at the level of C5 prior to the vessel’s entrance into the transverse foramen. Our main hypothesis for the mechanism of intimal injury was that the patient was repeatedly injuring his VA from direct trauma with the adjacent transverse process of C5 given his habit of neck cracking. In a review of 1059 operations performed on VA kinks, Pauliukas notes with confidence that “when the vertebral artery enters the canalis transversarium at the fifth transverse process or higher, it is always entrapped at the entrance into the transverse process between the longus colli muscle tendon and the underlying transverse process.” ⁵ The patient may have been transiently injuring his VA upon head turning or cracking with the ensuing vascular vertigo being a warning for the strokes that followed. The mechanical muscular and osseous external compression caused at the V1–V2 junction over time may have led directly to intraluminal damage and the creation of a prothrombotic state with a downstream shower of emboli.

Kinks related to extravascular compression of various etiologies have been corrected by straightening and fixation, segmental resections and end-to-end anastomoses, stent-assisted angioplasty, endovascular coil embolization, and open surgical approach with correction of aberrant anatomy.^1,3,7–9 Endovascular plugs (MVP (Medtronic; Minneapolis, MN) and the Amplatzer Vascular Plug (AVP) (St. Jude Medical Inc; St. Paul, MN)) have been used for vessel occlusion, specifically in VA pathology such as vertebral-VA fistulas, VA-internal carotid artery (ICA) fistulas, fusiform VA aneurysms, dissecting VA aneurysms, VA dissections presenting with subarachnoid hemorrhage, and iatrogenic VA-penetrating injury as well as in preoperative embolization of cervical vertebral sarcoma and other encasing neck tumors.^9–16 The use of endovascular plugs for parent artery occlusion (PAO) to treat an extravasal VA compression has not been reported. To our knowledge, this is the first time that endovascular plugs have been used for therapeutic PAO of a VA in the setting of dissection due to extravasal compression causing infarcts.

The only direct complications reported related to the use of MVP or AVP in PAO of ICAs were in trauma cases with reports of two post-procedure border zone infarcts. In the literature review of VA PAO using endovascular plugs, there was one report of a post-procedure lateral medullary stroke presumably from small perforator sacrifice. ¹⁶ The proximal VA typically does not supply important vessels other than the anterior spinal artery (artery of cervical enlargement), which can be easily visualized angiographically. The use of MVP occlusion, in this case, was uneventful and technically simple thanks to careful review of cross-sectional and angiographic anatomy.

Traditionally, PAO has been performed with detachable coils. Coil shape, size, density, appearance, and quantity affects the outcome of mechanical embolization. ¹⁷ MVP is a relatively newer technology also used to treat various cervical artery pathologies and occlusion is rapid, limiting the potential for distal embolic complications during the intervention. The device consists of an expandable cage with a Nitinol exoskeleton covered by a polytetrafluoroethylene (PTFE) membrane on its proximal and peripheral surfaces.^16,18 There are four currently available models with diameters of 3 mm, 5 mm, 7 mm, and 9 mm indicated for placement in vessels with diameters of 1.5–3 mm, 3–5 mm, 5–7 mm, and 7–9 mm, respectively. ¹⁸ Advantages of MVP use over coils use include compatibility with several different microcatheter sizes, the ability to easily resheathe and redeploy the device in cases in which repositioning is needed, decreased number of devices needed to treat, decreased radiation dose, the speed of vessel occlusion, and decreased cost.^16,18 Rapid VA occlusion with endovascular plugs to minimize the risk of the embolic phenomenon is particularly valuable because of the technical inability to perform PAO under flow reversal or balloon occlusion as is typical in the setting of carotid artery sacrifice. ¹⁹

Conclusion

In the setting of recurrent posterior circulation strokes despite optimized medical management, the absence of pathology indicative of dissection on MRA or CTA does not always exclude the existence of injury. Cross-sectional and luminal imaging may not be sensitive enough to depict luminal integrity and there is a lack of familiarity with the appearance of external vascular compression. The mechanism of VA injury can be dynamic, especially in the case of extravasal compression, further compromising the ability to characterize these lesions on static imaging. Once extravasal compression has been detected or postulated, the goal of therapy is to modulate or eliminate the source of compression by operative intervention or prevent artery-to-artery embolus by endovascular means. Both endovascular reconstructive and deconstructive techniques have been employed. PAO is safe and technically simple, particularly in a nondominant VA injury. The use of deconstruction, particularly with the advent of single-device occlusion methods, provides a quick and effective means of achieving a therapeutic vessel PAO when intimal pathology is directly responsible for recurrent strokes and should be considered in these patients.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.