Absence of skin discoloration after transarterial embolization of a subcutaneous auricular arteriovenous malformation with PHIL

Abstract

Background and objective

One of the treatment options for arteriovenous malformations consists of embolization, with a choice of various embolic agents, with or without subsequent surgical excision. If embolization is offered without subsequent surgery, the embolic material will stay in situ, in which case the consistency and color become important in superficial lesions. The purpose of this case report is to describe if the use of a novel liquid embolic agent (PHIL) is well suited for treatment of superficial AVMs without subsequent surgery.

Case description

A 30-year-old male presented with a painful reddish, pulsatile swelling of the left ear that had been present for more than 10 years. Angiography confirmed an arteriovenous malformation supplied by the superficial temporal artery and the posterior auricular artery. The lesion was successfully treated by embolization with PHIL, through the superficial temporal artery. A minute residual shunt, from the posterior auricular artery, was accepted. Immediate disappearance of pulsatile tinnitus was reported. Moreover, return of normal skin color was observed without discomfort from the embolic deposits. This result has been stable throughout one year of clinical follow-up.

Conclusion

To our knowledge, this is the first case report describing PHIL embolization as a treatment option for superficial arteriovenous malformations without the necessity for subsequent surgery. The white color and rubbery consistency are beneficial characteristics of PHIL in treatment of subcutaneous lesions, especially in cosmetically relevant locations.

Introduction

Arteriovenous malformations (AVMs) are vascular lesions that present as a direct communication between an artery and a vein without capillary connections but with a tangle of intervening vessels, known as the nidus.^1,2 They are usually located intracranially, but can be present extracranially. Extracranial AVMs are most commonly found in the head and neck region and more specifically the cheek, ear and nose.^1,3

Auricular AVMs may be asymptomatic or present with a variety of symptoms including bleeding, erythema, pain, tissue ulceration, pruritus, headache, edema, tinnitus and conductive hearing loss.⁴ During puberty and adolescence the AVM lesion typically expands, which may result in functional disturbance and cosmetic deformities.^1,4,5 If treatment is considered, this may consist of intranidal embolization (either transarterially or through direct puncture), surgical excision or both.^1,6,7 Many factors, such as the symptoms, the extent, the complexity and the location of the lesion, play a role in determining the appropriate treatment strategy. If the lesion is small enough to consider only embolization, without subsequent surgery, the characteristics of the embolic agent need to be considered, as this material will remain in situ. n-Butyl-2-cyanoacrylate (nBCA), for instance, becomes very hard and may lead to discomfort if deposited very superficially and in sufficient quantities.^8–10 ONYX (ev3 Endovascular, USA) and Squid (Emboflu, Switzerland), on the other hand, contain an ethylene vinyl alcohol copolymer (EVOH) dissolved in dimethyl sulfoxide (DMSO), which has a softer consistency after precipitation, but is black from the suspended micronized tantalum powder. This may lead to dark skin discoloration.¹¹

Precipitating hydrophobic injectable liquid (PHIL, MicroVention, USA) is a novel liquid embolic agent used in fistulas and AVMs.^12–14 This agent has the same consistency as ONYX, but has a white color. Therefore, PHIL is a better candidate in the treatment of superficial lesions that do not necessarily need subsequent surgery.

Case report

Clinical presentation

In 2013, a 30-year-old male patient with an unremarkable medical history was referred to our clinic with a pulsatile swelling of the superior helix of the left auricle. Symptoms included slowly progressive local pain, pulsatile tinnitus, and cosmetic disturbance for more than 10 years. These symptoms interfered with his sleeping pattern. Previously, an ENT specialist had punctured the lesion, which yielded only blood. Upon physical examination, the superior helix of the left auricle was slightly enlarged and showed a red-purple discoloration (Figure 1). It contained a soft, compressible, pulsatile mass. No other peri-auricular abnormalities were palpable or visible. There was no bruit.

Figure 1.

A preoperative image of the left ear shows enlargement of the superior helix and discoloration of the auricle in a 30-year-old man.

Non-contrast-enhanced magnetic resonance imaging (MRI) performed in the referring center demonstrated the swollen aspect of the auricle with a number of prominent flow voids in the anterior aspect, in keeping with a small AVM fed by branches of the external carotid artery (Figure 2).

Figure 2.

Pre-embolization non-contrast-enhanced transverse MRI of the brain, showing a number of prominent flow voids (some of these are depicted by the arrows) in the anterior aspect of the left auricle.

MRI: magnetic resonance imaging.

We performed catheter angiography demonstrating the AVM nidus, which spanned approximately 4 cm of the helix. An enlarged branch of the superficial temporal artery was clearly the dominant feeder, with some minor secondary feeding from the posterior auricular artery (Figure 3).

Figure 3.

Pre-embolization angiogram of the AVM. (a) AP and (b) lateral view demonstrating the AVM nidus (asterisk), a branch of the superficial temporal artery as dominant feeder (arrow), and the vein (arrowhead). Minor secondary feeding from the posterior auricular artery is shown ((b), thin arrow).

AVM: arteriovenous malformation; AP: anteroposterior.

After angiography, we referred the patient to a plastic surgeon in our hospital to consider surgical treatment. Since the cosmetic disturbance was one of the main reasons to seek treatment, plastic surgery was not expected to yield a satisfactory result and the patient was referred back to us to consider endovascular treatment.

Treatment

As a first treatment option we offered transarterial embolization. Since the cosmetic disturbance was one of the major symptoms for the patient, we felt surgery would be a less favorable option. Furthermore, if embolization did not yield a desirable result, surgery would still be a possibility. We chose PHIL as the embolic agent for its white color and rubbery consistency, which we felt would contribute to a cosmetically desirable result. Superselective catheterization of the dominant feeder from the superficial temporal artery was performed with a Marathon catheter (MicroVention, USA). Stepwise embolization from a single catheter position was performed with PHIL, much like one would perform with ONYX (Figure 4). Post-embolization series from the external carotid artery demonstrated a minute residual nidus in the posterior aspect of the lesion, fed by small branches from the posterior auricular artery (Figure 5). This was left untreated to avoid endangering the facial nerve.¹⁵ The residual was too small for direct puncture and subsequent surgery was still not deemed advantageous. If growth of the lesion were to occur in the future, surgery could still be considered.

Figure 4.

(a) AP and (b) lateral fluoroscopic images during embolization demonstrating the PHIL cast located in the left ear. The arrowheads delineate the cast in the lateral projection.

AP: anteroposterior; PHIL: precipitating hydrophobic injectable liquid.

Figure 5.

Post-embolization angiogram demonstrating a small residual nidus (arrowhead) fed by small branches from the posterior auricular artery, which was not further treated.

Follow-up

After embolization, the patient reported immediate disappearance of the pulsatile tinnitus. Follow-up was performed at one, 15 and 48 weeks postoperatively. The auricle had not changed in size, was no longer pulsatile, had a more natural skin color and was less compressible in some locations of the helix (Figure 6). The slight increase in firmness of parts of the helix did not cause pain or discomfort.

Figure 6.

Postoperative image of the left ear, showing an auricle of similar size and a normal skin color.

Discussion

We report on the management of a small auricular AVM causing pulsatile swelling, pain and tinnitus using a novel intra-arterial embolic agent with distinct characteristics that render it applicable even in very superficial lesions and in cosmetically disturbing locations. Since the nidus was filled with embolic agent, the AVM did not decrease in size, which may be considered a cosmetic downside of this technique. However, since skin color reverted to normal, pulsations subsided and the embolic material remained soft enough not to cause discomfort, the result was quite satisfactory in this case. Moreover, this approach avoids surgical scars, while surgery still remains a future treatment option.

In general, several approaches in the treatment of AVMs have been described, including surgery, embolization, sclerotherapy and radiotherapy or any combination of these.^{1–4,6,16,17} The individualized treatment strategy will be guided by many factors, including size, location and angioarchitecture of the lesion itself, but also adjacent structures (including the skin) and vicinity of feeding pedicles to important collaterals. Furthermore, the goal of treatment is not always an angiographic cure, but may also include a cosmetically desirable result or resolution of symptoms such as pain, discomfort and tinnitus. In our opinion, care should be taken not to prioritize an angiographic cure over the safety of the procedure, especially when an AVM is not life-threatening.

A wide variety of embolic agents is available when transarterial embolization is considered.¹⁸ Since collateral vascularization to an AVM is abundant and any residual arteriovenous shunt after embolization may recruit new feeding vessels from these collaterals leading to lesion persistence, intranidal penetration of embolic material yields the most prolonged effect. Therefore, the dominant strategy in endovascular AVM treatment is intranidal deposition of liquid embolics.^{11,13,19–23} Some of these embolic agents, e.g. nBCA, harden, resulting in pain or discomfort.^8–10 Other agents, such as ONYX or Squid, contain suspended micronized tantalum powder for visualization under fluoroscopy. This results in a black vessel cast, which may lead to skin discoloration.¹¹ PHIL, like ONYX and Squid, consists of an EVOH copolymer dissolved in DMSO, but for fluoroscopy purposes it has an iodine component covalently bonded to the EVOH copolymer instead of suspended micronized tantalum powder. Therefore, PHIL is white instead of black, while preserving other properties of EVOH copolymers such as its softer consistency after precipitation. Furthermore, the absence of a metallic component leads to a more homogenic radiodensity during embolization, reduces artifacts at follow-up imaging and should reduce the risk of microcatheter blockage.

Conclusion

This is the first report on the use of PHIL for its cosmetically appealing characteristics in an extracranial and superficially located AVM. In subcutaneous lesions amenable to sole endovascular treatment, we believe it holds definite advantages over its current alternatives.

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.