Third branchial cleft anomalies

Rare
In children and young adults
3rd and 4th cleft anomalies together are 2nd most common congenital lesion of posterior cervical space (posterior to SCM) (most common - cystic hygroma)

Location:
Posterior to CCA or ICA, between XI and XII N, above superior laryngeal N
If fistulous, it courses thru thyrohyoid membrane to pyriform sinus

Association:
Associated with ectopic or undescended parathyroid
Associated with parathyroid adenomas

Clinical features:
Painless fluctuant mass in posterior triangle
Increases during infection

Imaging:
Unilocular cystic mass in posterior cervical space

Differentials:
Distinguishing 3rd from 4th is difficult, since both have relationships with the pyriform sinus.

Management:
Surgical excision

References:
1. Koeller KK et al. Congenital Cystic Masses of the Neck: Radiologic-Pathologic Correlation. Radiographics. 1999;19:121-146