1. Dept. of Radiology, UNC Chapel Hill
Branchial Cleft Cysts
David M. Chaky, MD
Dept. of Radiology, UNC Chapel Hill

2. Introduction
The embryologic model is used to explain the origins of all branchial apparatus anomalies.
The most accepted theory proposes that vestigial remnants result from incomplete obliteration of the branchial apparatus or buried cell rests, and, thus, if cells are trapped  in the branchial apparatus during  the embryologic stage, they can  form branchial cysts later in life.

3. The branchial apparatus consists of a series of  6 mesodermal arches separated from each other externally by ectodermal-lined branchial clefts (grooves) and internally by endodermal- lined pharyngeal pouches.
By the end of the 4th week of gestation, 4 well-defined pairs of branchial arches are visible externally; the 5th and 6th arches are small and cannot be seen on the embryonic surface.

4. Embryology and Anatomy
Branchial System: 6 pairs of pharyngeal arches separated by endodermally lined pouches and ectodermally lined clefts.
Each arch consists of a nerve, artery, and cartilaginous structures.
The remaining neck musculature gains contributions from cervical somites.

5. Common Lateral Neck Masses in Infancy
Branchial cleft anomalies
Laryngoceles
Dermoid and Teratoid Cysts
Sternocleidomastoid Pseudotumor of Infancy (fibromatosis colli)
Plunging ranulas
Adenopathy

6. First Branchial Cleft Cysts
Imaging Findings
Best diagnostic clue: Cystic mass around pinna and EAC (type I) or extending from EAC to angle of mandible (type II)
Well-circumscribed, non enhancing or rim-enhancing, low-density mass
If infected, may have thick enhancing rim or be dense internally
Top Differential Diagnoses
*Benign Lymphoepithelial Cysts
*Venolymphatic Malformation (VLM)
*Suppurative Adenopathy/Abscess
*Nontuberculous Mycobacterial Adenitis

7. First Branchial Cleft Cysts
Type I
Ectodermal Duplication anomaly of the EAC with squamous epithelium only.
Parallel to the EAC
Pretragal, post auricular
Connection with TM or Malleus>Incus
Surgical Excision

8. First Branchial Cleft Cysts
Type II
Squamous epithelium and other ectodermal components
Anterior neck, superior to hyoid bone.
Courses over the mandible and through the parotid in variable position to the Facial Nerve.
Terminates near the EAC bony-cartilaginous junction.
Surgical excision- superficial parotidectomy

9. First Branchial Cleft Cyst, Type 2

10. First Branchial Cleft Cysts
Accounts for 8% of all branchial apparatus remnants
Most common location for 1st BCC to terminate is in EAC between its cartilaginous & bony portions

11. Second Branchial Cleft Cysts
Most Common (90%) branchial anomaly
Painless, fluctuant mass in anterior triangle
Inferior-middle 2/3 junction of SCM, deep to platysma, lateral to IX, X, XII, between the internal and external carotid and terminate in the tonsillar fossa
Surgical treatment may include tonsillectomy

12. Second Branchial Cleft Cysts
Imaging Findings
Low density cyst with non enhancing wall & surrounding soft tissues, unless infected
If infected, wall is thicker & enhances with surrounding soft tissues appearing "dirty" (cellulitis) or internally dense
Top Differential Diagnoses
Lymphangioma
Thymic cyst
Suppurative jugulodigastic node
Cystic vagal schwannoma
Cystic malignant adenopathy (ALWAYS CONSIDER THIS POSSIBILITY IN ADULTS!)

13. Second Branchial Cleft Cysts

14. Second Branchial Cleft Cysts
* Epidemiology: 2nd BCC account for > 90% of all branchial cleft anomalies in teens and adults, 66-75% in children
* Most common signs/symptoms: Painless, compressible lateral neck mass in child or young adult
* Neck mass often chronic, recurrent, increasing in size with upper respiratory tract infection
* Beware an adult with first presentation of "2nd BCC”
* Mass may be metastatic node from head & neck SCCa primary tumor

15. Third Branchial Cleft Cysts
Rare (<2%)
Similar external presentation to 2nd BCC
Internal opening is at the pyriform sinus, then courses cephalad to the superior laryngeal nerve through the thyrohyoid membrane, medial to IX, lateral to X, XII, posterior to internal carotid
Surgical approach must visualize recurrent layngeal nerves- Thyroidectomy incision

16. Third Branchial Cleft Cysts

17. Third Branchial Cleft Cysts
Imaging Findings
*Best diagnostic clue: Unilocular thin-walled cyst in posterior cervical space (posterior triangle)
*May occur anywhere along course of 3rd branchial cleft or pouch
Top Differential Diagnoses
* 2nd branchial cleft cyst
* 4th branchial cyst
* Lymphangioma
* Infrahyoid thyroglossal duct cyst
* Suppurative adenopathy
* External laryngocele
* Cystic-necrotic lymph node

18. Fourth Branchial Cleft Cysts
Courses from pyriform sinus apex caudal to superior laryngeal nerve, to emerge near the cricothryoid joint, and descend superficial to the recurrent laryngeal nerve.

19. Fourth Branchial Cleft Cysts

20. Fourth Branchial Cleft Cysts
Imaging Findings
* Best diagnostic clue: Unilocular thin-walled cyst in superior lateral aspect of LEFT thyroid lobe with associated thyroiditis
* May occur anywhere from LEFT pyriform sinus apex to thyroid lobe
* Morphology: Unilocular & thin-walled unless infected
Top Differential Diagnoses
* Thyroglossal duct cyst
* Thymic cyst
* 3rd branchial cleft cyst
* Lymphangioma
* Thyroid colloid cyst
* Parathyroid cyst
* Thyroid abscess

21. Fourth Branchial Cleft Cysts
Clinical Issues, may present as:
* Recurrent neck abscesses
* Recurrent suppurative thyroiditis
* Imaging diagnosis of left thyroid lobe abscess in pediatric patient should strongly suggest diagnosis of infected 4th BCC