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

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).

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.

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.

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).