Ultrasonography of the fetal neck in the second and third trimesters. Part 3. Anomalies of the anterior and anterolateral nuchal region.

Current ultrasound instrumentation yields high-resolution scans that allow accurate assessment of the fetal neck. Most neck structures are normally small and barely visible, so anomalous development can be easily identified, for example, when the nuchal fold is measured in the second trimester. The author examined the anterior and anterolateral nuchal region in a total of 15,200 second- and third-trimester scans obtained over a 10-year period. The abnormalities identified were differentiated with respect to their position (at the central midline or anterolateral or lateral to the midline) and ultrasonographic characteristics (solid, cystic or mixed; calcified or vascular). This pictorial essay depicts the ultrasonographic appearance of masses that can be detected antenatally, including thyroid masses, teratoma, thyroglossal duct cyst, cystic hygroma, hemangioma, branchial cleft cyst and other developmental cystic lesions. In addition, the methods of elucidating these lesions is described.