On MRI of the neck, a cystic lesion is found anterior to the sternocleidomastoid muscle, posterior to the submandibular gland, lateral to the carotid space. It has a thin rim, homogeneous T2 bright contents, and no enhancement. In which embryological structure does this lesion most likely originate?

• A Thyroglossal duct — midline or paramidline lesion
• B Second branchial cleft cyst — anterior to SCM, posterior to SMG, lateral to carotid sheath ✓
• C Dermoid cyst — midline floor of mouth
• D Cystic hygroma (lymphatic malformation) — posterior triangle, multiseptated

Explanation

The second branchial cleft cyst is the most common branchial apparatus anomaly (90%). Its characteristic location is anterolateral to the carotid sheath, posterior to the submandibular gland, and anteromedial to the SCM at the junction of the middle and lower thirds of the neck. On MRI it is homogeneously T2 bright (simple cystic contents), thin-walled, and non-enhancing unless infected. Thyroglossal duct cysts are midline at or below the hyoid bone, embedded in/near the strap muscles. Cystic hygromas are posterior triangle multiloculated T2 bright lesions. Dermoid cysts are midline submental, often with fat signal.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.