Atypical case of arteriovenous malformation invading into a pedicled medial arm flap

Abstract

A 54-year-old woman who had previously undergone total excision of an arteriovenous malformation (AVM) of lower lip and chin along with pedicled medial arm flap reconstruction, presented with recurrence of swelling in the same region. The patient reported progressive difficulty in feeding, talking and constant aching pain besides aesthetic concerns. On evaluation, recurrence of AVM with invasion into the flap substance was identified. We performed debulking surgery, which resulted in a considerable reduction in pain and improved lower lip functioning and aesthetic appeal of the face. This case is unique due to the rare presentation of an AVM invading the normal flap tissue. Such a finding has never been reported before for a pedicled flap, along with details of the histopathology and imaging description. There are lacunae in the understanding of the progression of vascular malformations and this additional information will add to the existing literature on AVM.

Background

Vascular malformations are lesions which have anomalous vascular channels and are grouped into different types based on their pathological characteristics.¹ Arteriovenous malformation (AVM) is one such subtype that can occur at any place in the body, with the head and neck region being the most prevalent, possibly due to their embryological representation of high surface area to volume ratio.²

AVMs have a higher predilection for females compared with males.³ Although it is present at birth, it is not evident in most people. The AVM is initially housed in the tissues in a nascent form, and gradually, with an increase in the blood flow, it expands and grows in size.⁴ As it progresses to involve the normal vasculature, the blood is shunted across healthy blood vessels by the arteriovenous (AV) connections leading to progressive left-to-right shunting. This in turn results in increased venous and right-sided heart pressures. Shunting of flow can lead to vascular steal syndromes, presenting as ischaemia of the structures distal to the lesion. High-output heart failure is rare, but can be seen in large, widespread untreated lesions.^{5 6}

Early diagnosis and management with a combination of conservative, endovascular and surgical treatments provide the best chance for improved outcomes in individuals with AVMs. Surgical excision is recommended for big, symptomatic lesions to enhance the patient’s quality of life. Even after surgical resection, there is a substantial risk of recurrence.⁷

This report describes an atypical case of extremely delayed recurrence of AVM invading into the pedicled medial arm flap reconstruction, 35 years after the initial surgery. The peculiar presentation of an AVM invading normal flap tissue makes this case unique. It clearly illustrates that gaps remain in our knowledge of how vascular malformations evolve overtime.

Case presentation

A 54-year-old woman presented with swelling of her lower lip and chin to our outpatient clinic. Her main problems were pain, difficulty in speaking, discomfort while eating and abnormal appearance of the lower part of the face. The swelling began insidiously 5 years ago, involving only the lip and proceeded slowly over time but over the last 2 years, it had rapidly progressed to involve the entire lower lip and chin. The vermilion had widened; its margins appeared irregular and hyperpigmented in comparison to the upper lip. The swelling appeared more prominent along the oral commissures. The chin was also widened, though the underlying bone seemed to be uninvolved. A scar line of previous surgery was present on the chin running from one corner of the mouth to the other, extending posteriorly and inferiorly. A hyperpigmented area of size 7×3 cm was present just behind the scar line in the submental region (figure 1).

Figure 1.

Preoperative clinical photographs showing the anatomical location and extent of lesion.

The patient stated that a similar swelling was present since birth which had increased in size over time. It was excised 35 years ago, and the defect was reconstructed using a pedicled medial arm flap from the left arm (online supplemental figure 1). She had no comorbidities nor any significant family history.

AVMs are present at birth and grow proportionally with the individual, generally manifesting in the second or third decade, as it did initially with this patient. The duration, anatomic location and size of AVMs all influence the clinical characteristics, which typically point to the diagnosis. At this presentation, based on the clinical scenario, we suspected recurrence of AVM and proceeded to confirm with imaging.

Investigations

Vascular imaging is required as the initial step in confirming the clinical diagnosis and determining the lesion’s extent. We performed an MRI which revealed a 6×2 cm hyperintense lesion in the subcutaneous area, encompassing the lower lip, with multiple flow voids (high-flow vessels) reaching up to the alveolar processes on a deeper level. Because the flap is normally not very vascular, the presence of numerous high-flow vessels suggested the creation of new vascular channels within the flap (figure 2). Punch biopsies were taken from two sites: the surface of the flap tissue and the submental hyperpigmented area, which revealed a slow-flow AVM on histology.

Figure 2.

Contrast-enhanced MRI of face showing AVM in the chin and lower lip region.

Differential diagnosis

The differential diagnosis of AVM predominantly includes other types of vascular malformation and vascular tumours. This patient already had a past surgical history so the first suspicion was recurrence of AVM. Other soft tissue swellings, though less likely can present in a similar manner including neurofibroma and lipoma.

Treatment

While planning the surgery, we decided to approach the lip lesion along the full length of the vermilion margin and through the previous scar. The anterior surface of the flap was raised, and debulking of the subcutaneous fat along with the residual lesion was carried out. The AVM was observed to be infiltrating into the orbicularis oris muscle, and so a section of the muscle was resected and repaired to maintain oral competence (figure 3). The wound was closed in layers over rubber drains, which healed uneventfully (figure 4). The operative specimen histopathology report showed fibro adipose tissue and skeletal muscle bundles along with variably sized thick and thin walled small blood vessels, consistent with the findings of a vascular malformation.

Figure 3.

Intraoperative photograph showing the AVM invasion into orbicularis oris muscle. AVM, arteriovenous malformation.

Figure 4.

Immediate postoperative outcome.

Outcome and follow-up

The patient experienced a significant cosmetic improvement. By the end of the first week, her pain had diminished and her swelling had decreased. Early in the postoperative period, she complained of slight oral incompetence, which improved after 4 weeks. By the conclusion of 6 weeks, her speech improved considerably. The patient regained strong oral competency and a satisfactory chin contour by the eighth month follow-up. (figure 5).

Figure 5.

Clinical photograph of patient at 8-month follow-up showing good aesthetic outcome.

Discussion

It is thought that the AVM has an embryological origin from a single endothelial cell line. During embryogenesis, an aberrant signal in the apoptosis results in residual vascular plexus cells having limited differentiation leading to the manifestation of a vascular malformation.⁸

The diagnosis of AVM needs clinical examination, and a combination of imaging consisting of ultrasound, colour Doppler and MRI to provide further information in cases of doubtful clinical features. These imaging modalities can assist in confirming a particular attribute of the lesion, defining anatomic boundaries and planning the extent of surgical excision. Lesions over the head and neck regions need attention due to functional as well as aesthetic problems.⁹

AVMs can have a congenital or post-traumatic aetiology. Traumatic AVM can result after penetrating trauma or blunt trauma, where the artery and vein are traumatised in the vicinity of each other which leads to the development of a single AV fistula at the site of injury.¹⁰ The treatment of post-traumatic cases requires surgical excision of the anomalous connection. On the other hand, congenital AVM, mostly presents with diffuse and multiple swellings and may spread to adjacent sites with time.^{9 10} Owing to these factors, the recurrence rate is significant such that even after surgical excision, a high rate of AVM relapse is possible.⁷

In our patient, post removal of the lesion first time, the defect was covered with a pedicled medial arm flap which was gradually invaded by an AVM leading to the current presentation. This phenomenon is very rare, and so far, only a single case has been reported in the literature for a pedicled flap.¹¹ The development of AVM in a flap postsurgery may occur due to trauma or invasion of the subclinical AVM into the flap. In free flaps, there is some evidence of the development of AVM following microvascular anastomosis.^{12 13} In such circumstances, cross-clamping or trauma may have caused the AVM to grow, resulting from the formation of an AV fistula and a localised anomalous connection.¹³

In pedicled flaps however, the flap survival depends on the revascularisation of the flap from the recipient bed and margins through neovascularisation or angiogenesis. After the division of the flap’s attachment from the donor site, the recipient site becomes its sole supply. The development of anomalous AV connections is controlled by neural, humoral and other local factors which can be influenced by growth factors such as vascular endothelial growth factor, and hypoxia inducing factor.¹⁴ In the postoperative period, due to ongoing flap revascularisation, changes in the local milieu may have enabled the spread of AVM into the flap vasculature. Warwick described a case of cross finger flap invasion by AVM in the hand. The authors hypothesised a similar pathway of connection between neovascularisation of the flap and progression of the AVM.¹¹

After a free flap reconstruction, the peripheral residual AVM may remain quiescent.¹⁵ Even the post-traumatic fistula tend to remain confined to a single site. Whereas in our case the pedicled flap was fully invaded by AVM unlike free flap or post-traumatic instances. The plausible cause may be due to the differences in the pattern of vascular organisation in free and pedicled flaps. Intraoperatively, we found the vascular channels continued into the orbicularis oris muscle showing the pattern of invasion of AVM into the normal tissue. (figure 3). A new hyperpigmented area (AVM) developed some years back over the skin over the submental area adjacent to the flap. There are two possible mechanisms to explain this pathology, it was either due to the presence of congenital AV communication and the imbalance in local factors that lead to the development of AVM in the flap tissue or, it was due to neovascularisation occurring in the flap due to a high level of local growth factors. There seems to be a complex molecular and genetic pathway involved in the development of abnormal AV channels which requires further research, however, the rarity of such a case scenario makes this somewhat of a challenge.

Patient’s perspective.

I am very happy and satisfied with the outcome of the surgery. Now, I feel less self-conscious about appearance of my face. Previously, whenever I used to go out in public, I would cover my face with my dupatta (Indian women’s clothing accessory), but now I don’t. Though I am still bothered by the reddish hyperpigmentation under my chin, but I have accepted that considering the nature of my disease, this is the best possible result that can be achieved. At least my lips don’t look bulky, like before. I was extremely afraid after it recurred, I thought previous surgery had failed and I would require another flap surgery and this time from my other arm, which I didn’t want. That’s why I waited 5 years to seek treatment. But I am glad that I came to this hospital which has given me wonderful treatment with minimum discomfort. I thank the doctors for my treatment.

Learning points.

• The pathogenesis of arteriovenous malformation (AVM) is still abstruse.

• The invasion of an AVM into a pedicled flap is a rare occurrence with no well-defined mechanism.

• A combination of factors like the presence of microscopic fragments of subclinical AVM and high growth factors milieu leads to abnormal neovascularisation and invasion of the flap.

• The aim of the treatment of large AVMs should be to provide a better quality of life to the patient using a combination of conservative, endovascular and surgical treatments.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).