1

Introduction

Vascular malformations are a group of congenital abnormally-formed channels, comprising arterial, venous, lymphatic, and capillary malformations, which grow proportionally with an individual without regression. These anomalies are commonly further categorized into either high or low-flow lesions. We present a unique case of a venous vascular malformation (VVM) involving the floor of the mouth. VVM is invariably classified as a low-flow lesion due to its positioning as a post-capillary entity without arteriovenous shunting . These irregular conduits are often characterized by a soft, compressible, nonpulsatile tissue mass that may exhibit a blue tinge due to the collection of ectatic venous channels underneath the dermis. Further findings upon physical examination may include expansion of the malformation with the Valsalva maneuver, and flattening of the protrusion with applied pressure.

In general these abnormal connections are asymptomatic. However, they may also come to attention as a result of thrombosis, swelling, and pain, as well as symptoms secondary to mass effect such as dysphagia and difficulty with phonation . Only symptomatic cases or those which cause significant cosmetic concern are usually managed. Venous malformations can potentially be misdiagnosed as dermoid cysts, or benign teratomas, due to their common features on various imaging modalities. In our case, this VVM involving the floor of the mouth was initially misdiagnosed by a panel of experienced neuroradiologists as a dermoid tumor due to its unusual presentation on history and physical, and uncharacteristic features on computed tomography (CT) and magnetic resonance imaging (MRI). The diagnosis was later amended to VVM of the submandibular space upon additional findings on catheter angiography. This report seeks to outline the commonalities upon imaging that may result in an ambiguous case, and outline specific features that can help clinicians more confidently consolidate a diagnosis.

2

Case report

A 45-year-old woman with a five year history of a soft tissue mass in the submandibular region was referred for otolaryngology consultation at our institution when her primary care provider noted an anterior neck midline mass which was palpable in the submandibular space together with concerning historical details. The patient described occasional dysphagia, and in June of 2011 experienced an episode of self-resolving pain and swelling of the lesion. She had non-contributory history, including no prior aneurysms, AVMs or hereditary vascular syndromes. She was a non-smoker taking no medications. Physical examination also revealed a slight bulge in the right floor of the mouth, without discoloration. The mass was firm on palpation, did not change size based on head positioning, and no bruits could be auscultated. The patient noted that the lesion had exhibited progressive growth over the past five years, with a period of regression during her pregnancy several years ago. At this point the differential diagnosis for the lesion included a dermoid or epidermoid cyst. In order to elucidate a differential diagnosis, imaging was performed.

On Feb 1 2012, gadolinium-enhanced MRI of the mass in T1 and T2 weighted imaging ( Fig. 1 ) revealed a lesion with T1 hypersensitivity and variable T2 signal. These results were followed-up with CT angiography on Feb 22, 2012, which showed internal enhancement ( Fig. 2 ) possibly attributable to saponification, calcification, or rupture of the presumed dermoid cyst. However this pattern of enhancement was felt to be unusual, and digital subtraction angiography was performed to exclude a primarily vascular lesion. Contrast injection into the external carotid artery ( Fig. 3 ) revealed a slow-flowing lesion consisting of serpiginous, venous pouches without arteriovenous shunting, confirming the diagnosis of a low flow VVM within the submandibular space.

Coronal (A) T1 weighted and (B) T2 weighted MR images of the submandibular space revealed a complex lesion with predominantly T1 hypointense signal and mixed T2 signal owing to partially-thrombosed venous lakes.

Axial (A) and sagittal contrast-enhanced CT (B) of the head and neck revealed marked internal enhancement and additional pockets of enhancement common in varicose veins.

Digital subtraction angiography acquired following left external carotid artery injection illustrating multiple low-flow serpiginous venous enclosures without arterial involvement or shunting.

As the patient did not present with any symptoms aside from occasional dysphagia, the patient felt that this VVM had minimal impact on their quality of life, and she elected to avoid the risks of surgical excision. Moreover, in discussion with the care team, it was felt that as the patient was past the age of events which could induce rapid growth of the lesion, namely puberty and pregnancy, there was minimal likelihood of significant change in the lesion. The patient continues to be periodically monitored on an outpatient basis by our service and has continued to be asymptomatic to-date.