FLEX February 2024

Imaging of Pediatric Head and Neck Masses

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Fig. 6. Branchial cleft cyst. Recurrent branchial cleft cyst 2 years after resection demon strating mural thickening ( arrow ), an atypical feature likely related to prior infection.

Dermoid and epidermoid/cholesteatoma Subcutaneous and calvarial epidermoids typically appear as well-defined nonenhanc ing cystic lesions with high T2 signal and variable degrees of restricted diffusion ( Fig. 7 ). 18,19 Although dermoids can also have a cystic appearance similar to epider moids, dermoids tend to occur in the midline and may contain fat components and/or calcification. When multiple globules of fat are present, a sac of marbles appearance can result, with corresponding high T1 signal, and hypoattenuation on CT. Multiplanar high-resolution MRI enables detection of intracranial extension of a sinus tract asso ciated with nasal dermoids ( Fig. 8 ), which is useful for surgical planning. 20,21 Teratoma Teratomas of the head and neck can cause respiratory compromise due to mass effect, necessitating urgent surgical intervention. Imaging plays an important role in the assessment of these lesions, especially in preparation for surgery. 22 The presence of hypodense fat on CT ( Fig. 9 ) with corresponding T1 hyperintensity on MRI can be a helpful feature, but is not always present. 22 Teratomas may also contain calcification, which is well visualized by CT. Teratomas demonstrate variable degrees of cystic and solid enhancing components ( Fig. 10 ) and thus can be difficult to distinguish from other complex partially enhancing lesions, such as venolymphatic malformations. Thyroglossal duct cyst Thyroglossal duct cysts appear as thin-walled hypodense cystic lesions that may occur anywhere along the course of the thyroglossal duct, with thin enhancement of the cyst wall. Superimposed infection in a thyroglossal duct cyst may result in a thickened enhancing wall and inflammatory change in the adjacent tissues ( Figs. 11 and 12 ).

Vascular Lesions Venolymphatic malformations

Venolymphatic malformations typically appear as multicystic transpatial masses, most commonly occurring in the posterior cervical triangle. They often contain

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