9 Radiologic Evaluation of Vascular Malformations



10.1055/b-0034-101165

9 Radiologic Evaluation of Vascular Malformations

Daniel R. Lefton and Deborah R. Shatzkes

9.1 Introduction


Vascular malformations of the head and neck included in the International Society for the Study of Vascular Anomalies (ISSVA) classification are categorized into four major types: capillary malformation (CM), venous malformation (VM), lymphatic malformation (LM), and arteriovenous malformation (AVM). This system is based on the work published by Mulliken and Glowacki in 1982 and adopted by the ISSVA during its 1996 workshop. 1 The CMs, VMs, and LMs are considered slow-flow malformations, whereas AVMs are high-flow malformations. Combined malformations such as mixed venous LMs also occur and can be identified by the presence of multiple malformation elements.


Magnetic resonance imaging (MRI) is the mainstay for the imaging of VMs of the head and neck. The vast array of imaging sequences available with MRI, along with the multiplanar capability of MRI and the ability to assess contrast enhancement with gadolinium contrast agents, are ideal for differentiating the tissue characteristics unique to each of the vascular malformations. Computed tomography (CT) is a useful adjunct imaging technique for assessment of the adjacent osseous structures and for the identification of phleboliths.


The first goal of imaging is to determine whether the lesion is a VM as opposed to a hemangioma, congenital cyst, or other vascular tumor and to categorize the lesion into one of the four major types. This is accomplished by assessing the anatomical location and extent of the lesion, the presence or absence of prominent internal blood vessels, the presence or absence of phleboliths, the presence or absence of bone involvement with abnormal lysis or sclerosis, the enhancement characteristics, and the solid versus cystic nature of the lesion. Also important is defining the extent of the lesion, with particular emphasis on proximity to the airway, orbital contents, and major nerves such as the facial nerve. Involvement of the mandible or maxilla can also be crucial with respect to dental disease and potentially life-threatening hemorrhage, complicating dental extraction.


Additional roles for radiologic imaging include identifying other occult lesions, assessing for potential complications such as lesional hemorrhage or thrombosis, establishing a baseline examination, and assessing responses to therapy.



9.2 Capillary Malformations


The CMs include port-wine stains and telangiectasias; CMs typically affect the skin and subcutaneous tissues. The port-wine stain or nevus flammeus, is a slow-flow lesion characterized by a clinically apparent, well-circumscribed region of purplish skin discoloration and thickening. On radiologic imaging, these CMs may be occult or appear as an asymmetric region of enhancing cutaneous and subcutaneous soft tissue thickening ( Fig. 9.1 ).

Fig. 9.1 Axial T2-weighted image of a patient with a left premaxillary capillary malformation. There is asymmetric thickening of the skin and subcutaneous soft tissues at the level of the malformation.

A small percentage of patients with port-wine stains have Sturge-Weber syndrome (encephalotrigeminal angiomatosis). This syndrome is characterized by the presence of a CM in the distribution of one or more dermatomes of the trigeminal nerve in association with a pial angioma. The cerebral cortical tissue affected by the pial angioma will often develop typical tram-track calcification over time. Aberrant deep cortical venous drainage toward the ipsilateral lateral ventricle may also be present, with associated engorgement of the lateral ventricular choroids plexus. In addition, patients with Sturge-Weber syndrome who have an upper eyelid nevus flammeus typically have retinal choroidal angiomas ( Fig. 9.2 ). 2

Fig. 9.2 Sagittal T1-weighted image of a 12-year-old girl with Sturge-Weber syndrome. There is an enhancing retinal choroidal angioma in the posterior globe.


9.3 Venous Malformations


The VMs are slow-flow vascular malformations that are present from birth but may enlarge over time, often becoming clinically apparent in later years. 3 These malformations consist of endothelial-lined venous lakes lacking a smooth muscle layer. On MRI, VMs are well-defined lesions that are usually of intermediate signal on T1-weighted imaging and increased signal on T2-weighted imaging. These lesions enhance after intravenous gadolinium administration with a variable pattern, which can fill in over time ( Fig. 9.3 ). The enhancement is the imaging feature that most distinguishes VMs from LMs, as well as from other congenital cystic masses of the head and neck.

Fig. 9.3 (a,b) Axial T1-weighted gadolinium enhanced and axial T2-weighted images of a 2-year-old girl with a left masseteric venous malformation. Note the heterogeneous enhancement pattern, the lack of abnormally dilated vascular structures, and the diffusely increased T2 signal.

Although VMs can occur anywhere in the head and neck, there is a propensity for facial involvement, and these lesions may be found in the lips, masticator space, parapharyngeal space, buccal space, tongue, or intramuscularly. 4 There is a propensity for involvement of the masseter muscle. VMs can also be multispatial, tracking along normal vascular pathways ( Fig. 9.4 ). Intraosseous involvement, although not a typical feature, can occur. 5

Fig. 9.4 (a,b) Axial T1-weighted gadolinium enhanced and axial T2-weighted fat-suppressed images of a 26-year-old man with a multispacial venous malformation. Note the extension of the lesion from the level of the left pterygoid muscles anteriorly along the masseter to the subcutaneous tissues of the left upper lip.

Phleboliths are present in almost 50% of VM’s and when present are pathognomonic. 6 Although these can be seen with MRI as focal signal voids, they are best visualized with CT, where they appear as lamellated calcifications ( Fig. 9.5 ). 7 It is important to distinguish between focal signal voids on MRI representing phleboliths in a VM and prominent vascular flow voids, which are typically absent in VMs. The presence of prominent vascular flow voids would be indicative of a high-flow lesion, such as an AVM or hemangioma ( Table 9.1 ).

Fig. 9.5 (a,b) Coronal bone window computed tomography and coronal T1-weighted gadolinium-enhanced magnetic resonance images of two patients with phleboliths in the right facial venous malformations.






































































Table 9.1 Imaging characteristics of vascular lesions of the head and neck

Vascular lesion:


CM


VM


LM


AVM


Hemangioma


Prominent vessels:


No


No


No


Yes


Yes


Enhancement pattern:


Cutaneous and subcutaneous


Enhances, may fill in over time


Only periphery or septations enhance


Patchy ill-defined enhancement


Enhances


Tissue involved:


Skin and subcutaneous


Well-defined lesion


Well-defined lesion, cystic, may have fluid levels


No well-defined lesion, soft tissue swelling


Well-defined lesion, solid


Phleboliths:


No


Yes


No


No


No


Bone involvement:


Adjacent bone may be hypertrophic


Rarely occurs


May occur with hypertrophy of bone


May be involved with lytic lesions


May occur


T2 signal:


Intermediate


High


High unless there is internal hemorrhage


Mildly increased


Intermediate


T1 signal:


Intermediate


Low


Usually low but may be high from blood or lipids


Low


Intermediate


Abbreviations: CM, capillary malformation; VM, venous malformation; LM, lymphatic malformation; AVM, arteriovenous malformation.

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Jun 15, 2020 | Posted by in HEAD AND NECK SURGERY | Comments Off on 9 Radiologic Evaluation of Vascular Malformations
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