Suprahyoid and Infrahyoid Neck Overview

Imaging Approaches & Indications

Neither CT nor MR is a perfect modality for imaging the extracranial H&N. MR is most useful in the suprahyoid neck (SHN) because it is less affected by oral cavity dental amalgam artifact. The SHN tissue is less affected by motion compared with the infrahyoid neck (IHN); therefore, the MR image quality is not degraded by movement seen in the IHN. Axial and coronal T1 fat-saturated enhanced MR is superior to CECT in defining soft tissue extent of tumor, perineural tumor spread, and dural/intracranial spread. When MR is combined with CT of the facial bones and skull base, a clinician can obtain precise mapping of SHN lesions.

CECT is the modality of choice when IHN and mediastinum are imaged. Swallowing, coughing, and breathing makes this area a "moving target" for the imager. MR image quality is often degraded as a result. Multislice CT with multiplanar reformations now permits exquisite images of the IHN unaffected by movement.

High-resolution ultrasound also has a role. Superficial lesions, thyroid disease, pediatric neck lesions, and nodal evaluation with biopsy are often best done by ultrasonography.

Many indications exist for imaging the extracranial H&N. Exploratory imaging, tumor staging, and abscess search comprise 3 common reasons imaging is ordered in this area. Exploratory imaging, an imaging search for any lesion that may be causing the patient's symptoms, is best completed with CECT from skull base to the clavicles.

Squamous cell carcinoma (SCCa) staging is best started with CECT, as both the primary tumor and nodes must be imaged, requiring imaging from the skull base to clavicles. MR imaging times and susceptibility to motion artifact make it a less desirable exam in this setting. Instead, MR is best used when specific delineation of exact tumor extent, perineural spread, or intracranial invasion is needed.

When the type and cause of H&N infection are sought, CECT is the best exam. CECT can readily differentiate inflammation from abscess. CT can also identify salivary gland ductal calculi, odontogenic infections, mandible osteomyelitis, and intratonsillar abscess as causes of infection.