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Abstract
This report describes a patient who presented with subarachnoid hemorrhage and extensive right posterior inferior cerebellar artery territory infarct secondary to a dissecting aneurysm of the right intracranial vertebral artery. Urgent endovascular treatment was undertaken with plans for trapping of the diseased segment with coils. However, significant intralesional stenosis limited distal microcatheter access. Therefore, using proximal flow arrest and adjunctive coiling, the liquid embolic agent Onyx was injected within the pseudoaneurysm and was able to traverse the stenosis, resulting in proximal and distal parent vessel closure. There were no embolic complications. During the 3 month hospital stay, there was no rebleeding. The patient was discharged to skilled nursing facility and was lost to follow-up.
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Introduction
Onyx (ev3 Neurovascular, Irvine, California, USA) is a non-adhesive liquid embolic agent that is comprised of ethylene vinyl alcohol copolymer dissolved in dimethyl sulfoxide. It is approved for presurgical embolization of brain arteriovenous malformations (Onyx 18 and 34) and for the treatment of wide necked sidewall aneurysms (Onyx HD-500) but has been utilized for numerous off-label applications. Like n-butyl cyanoacrylate glue, Onyx has been used for parent vessel sacrifice to treat peripheral cerebral mycotic and dissecting aneurysms.1 These treatments may be complicated by small infarcts which are generally asymptomatic or minimally symptomatic.2 On the other hand, therapeutic occlusion of a proximal vessel such as the internal carotid or vertebral artery (VA) is typically performed with coils because liquid agents pose the risk of a significant embolic stroke. We describe the novel use of Onyx for endovascular closure of a dissecting pseudoaneurysm of the intracranial VA.
Case report
A middle aged patient presented with obtundation (high grade Hunt and Hess score) and was found to have diffuse posterior fossa subarachnoid and intraventricular hemorrhage associated with a large right cerebellar and hemi-medullary infarct (figure 1A–C). CT angiography demonstrated a dissecting aneurysm of the right intradural VA involving the origin of the posterior inferior cerebellar artery (PICA) (figure 1D). The patient was taken for urgent endovascular treatment.
(A) Non-contrast CT scan demonstrates diffuse subarachnoid hemorrhage with associated intraventricular hemorrhage and hydrocephalus. (B) CT angiography (CTA) source imaging reveals hypoattenuation involving the right posterior inferior cerebellar artery (PICA) territory including the right hemi-medulla (arrow), consistent with acute infarction. (C) This is confirmed on subsequent MRI diffusion imaging. (D) CTA reveals the ‘pearl and string’ sign of right intracranial vertebral artery dissection. Note the areas of luminal narrowing (arrows).
The procedure was performed under general anesthesia. No intravenous heparin was given due to the elevated risk of bleeding within the infarct. Diagnostic angiography was performed to assess collateral circulation and revealed robust posterior communicating arteries and a dominant left VA. There was antegrade flow within the right PICA which arose from the midportion of the pseudoaneurysm, proximal to an intra-aneurysmal focus of severe narrowing (figure 2). The anterior spinal artery was not visualized from the right VA. Given the infarct involvement of the entire PICA territory, including the medulla, it was deemed unnecessary to preserve the right PICA, and the therapeutic goal was endovascular trapping using coils. However, attempts to advance the 0.010 inch X-Pedion microwire (ev3 Neurovascular) past the region of intra-aneurysmal stenosis were unsuccessful and were abandoned due to the risk of perforation.
(A) Digital subtraction angiography (DSA) (anteroposterior oblique view) from a right vertebral artery injection demonstrates that the right posterior inferior cerebellar artery (PICA) (white arrow) arises from the dissecting aneurysm. Note the area of significant luminal narrowing (black arrow) just distal to the PICA origin. (B) Lateral view reveals narrowing at the PICA origin (white arrow). There are changes suggestive of fibromuscular dysplasia within the distal cervical right vertebral artery (black arrow).
In order to avoid manipulation of the dominant left VA, it was decided to use Onyx 34 to traverse the stenosis and occlude the parent vessel distal to the dissection. A Hyperglide 4 mm×10 mm balloon microcatheter (ev3 Neurovascular) was advanced into the distal cervical right VA (to C3) to provide proximal flow arrest during treatment (figure 3A). The balloon was inflated and microcatheter injection confirmed absence of antegrade flow—there was no collateral inflow at C1 or C2. Subsequently, two 4 mm×8 mm Micrus Ultipaq coils (Micrus Endovascular, San Jose, California, USA) were deposited within the pseudoaneurysm to serve as a nidus for Onyx cast formation (figure 3A). The Echelon 14 microcatheter (ev3 Neurovascular) was positioned within the coil mass during Onyx injection. Onyx 34 was injected intermittently into the pseudoaneurysm (figure 3B) with the aid of blank roadmap imaging. The initial Onyx cast was contained within the coil loops. Further injections resulted in a controlled propagation of the Onyx into the proximal and distal segments of the parent vessel (figure 3C). There was no Onyx fragmentation or distal embolization noted during the treatment. Post-treatment angiography demonstrated no antegrade or retrograde filling of the aneurysm and no evidence of embolic complications (figure 4). MRI performed the next day revealed no new cerebral or posterior fossa infarcts. Unfortunately, the post-procedure clinical examination remained poor and consistent with a locked-in state. The patient was awake and able to follow axial commands (raising eyebrows, etc). There was minimal activity in the extremities and no verbalization. The patient subsequently underwent suboccipital craniectomy for infarct swelling and later required a ventriculoperitoneal shunt. After 3 months, the patient was discharged to a skilled nursing facility. There was no rebleeding during the hospital stay. The patient was subsequently lost to follow-up.
(A) Lateral roadmap angiography demonstrates coil placement within the pseudoaneurysm with a loop in the proximal posterior inferior cerebellar artery (white arrow). The treatment was performed under proximal flow arrest using a Hyperglide balloon (black arrow). (B) Magnified blank mask imaging reveals the initial Onyx cast (arrow) which is contained within the coil mass. (C) Unsubtracted anteroposterior oblique image demonstrates the final coil mass and Onyx cast. Note Onyx within the parent vessel proximal and distal to the dissection (arrows).
Post-treatment digital subtraction angiography (DSA) from a right vertebral artery (VA) injection (A; lateral view) demonstrates no antegrade flow into the dissecting aneurysm. There is collateral filling to the distal posterior inferior cerebellar artery (PICA) (white arrow) via a tiny PICA branch arising from the V3 segment. DSA from a left VA injection (B; anteroposterior view) reveals no retrograde filling of the dissection and no embolic complications.
Discussion
Intracranial VA dissecting aneurysms are devastating lesions that result in subarachnoid hemorrhage, ischemic stroke or, as in this patient, both.3 4 Early rebleeding occurs in approximately 70% of untreated cases, often within 24 h, and with a mortality rate approaching 50%.5 Hence they require urgent treatment.
Treatment may be performed either surgically or endovascularly.4 Definitive therapy requires trapping of the diseased segment to prevent re-rupture either via antegrade or retrograde flow. Rebleeding has been reported to occur in 14% of patients treated with proximal occlusion only.4 However, trapping is a viable option only if there are no branch vessels arising from the dissection, and if there is adequate collateral flow distally.6 Otherwise, proximal occlusion alone or surgical bypass followed by trapping may be preferable to preserve flow within the PICA or anterior spinal artery. In the absence of good collaterals, reconstructive strategies such as stenting or stent assisted coiling may be used.7
Endovascular trapping is typically performed with coils, which are deposited in a distal to proximal fashion.6 However, as in the case presented here, severe luminal narrowing within the diseased segment may preclude distal access for coiling.4 In this situation, a liquid embolic agent such as Onyx may be helpful for traversing the stenosis and achieving vessel closure at both ends of the lesion. We have shown that this may be safely and effectively performed using proximal flow arrest and adjunctive coiling. The addition of coils serves as a scaffold for the initial Onyx kernel and may help to prevent excessive Onyx migration and fragmentation.
Importantly, we do not advocate this approach as firstline therapy. When antegrade access to the distal segment is difficult, the standard approach is via the contralateral VA. However, it does carry some risk to the contralateral vessel. Our technique may be useful in situations where access from the other side may be difficult due to excessive tortuosity or high risk due to the presence of atherosclerotic disease or fibromuscular dysplasia.
Footnotes
Competing interests None.
Patient consent Obtained.
Ethics approval The study was conducted with the approval of the Massachusetts General Hospital institutional review board.
Provenance and peer review Not commissioned; externally peer reviewed.