Pictoral Essay: Congenital Anomalies of the Branchial Apparatus

1. Pictoral Essay: Congenital Anomalies of the Branchial Apparatus Authors Institutions

2. Objectives: • Understand Embryology of the branchial apparatus and embryogenesis of its anomalies. • Understand various classifications of branchial anomalies. • Recognize and interpret imaging findings associated with anomalies of the branchial apparatus. • Direct workup using various imaging modalities used in evaluation of branchial anomalies.

3. Embryology of Branchial Apparatus • 4th week of gestation. • Six mesodermal arches • Branchial clefts – ectodermally lined. • Pharygeal pouches – endodermally lined. • CN and Aortic arch accompany each branchial arch.

4. Branchial Apparatus

5. Development of Branchial Apparatus • 1st Arch, Cleft, and Pouch persist. • 2nd Arch increases in thickness and proliferates caudally • 2nd, 3rd, and 4th Cleft form cervical sinus of His. • Sinus of His lined by ectoderm.

6. Further Differentiation • 1st Branchial cleft becomes external auditory canal • Cervical Sinus of His obliterated • Pharyngeal pouches develop into thymus, parathyroid glands, and ultimobranchial body, then migrate to their final position.

8. Branchial Derivatives

10. Embryogenesis • Vestigial remnants – resulting from incomplete or failed obliteration of branchial apparatus. • Buried cell rests – cells are trapped in branchial apparatus and form branchial cleft cysts later in life.

11. Branchial Anomalies • Sinus – incomplete tract, opens externally • Fistula – communicated both externally and internally from persistence of both cleft and pouch. • Cyst – no internal or external comunication.

12. Radiographic Evaluation • Begins with Ultrasound • Non ionizing, non invasive. • Determines cystic vs. solid; size, and extent. • Color doppler – vascularity. • CT • Morphologic characterization and staging. • Bone structures, calcifications, deep soft tissue anatomy • Low dose neck CT to avoid excess radiation. • MRI • Multiplanar capability • Absence of ionizing radiation. • Superior contrast resolution and anatomic characterization of soft tissues. • Often requires sedation.

13. First Branchial Anomalies • 5-8 % of all defects. • Middle aged women. • 1st Branchial structures: maxilla, mandible, eustacian tube, external auditory canal, middle ear structures. • Completed by 6-7 wks. • Can insinuate within Parotid gland.

14. 10 year old female presenting with fistula.

15. Second Brancial Apparatus Anomalies • Vast majority (>95%) of branchial anomalies. • ¾ of anomalies are cysts. • Fistulas and sinuses present earlier. • Passes between internal and external carotid arteries and ends near tonsillar fossa. • External communication with cervical sinus of His.

16. Four types of 2nd BCC • Bailey type I: • most superficial • Anterior surface SCM • Bailey type II: • Classic location • Bailey type III: • Extends medially between ICA and ECA bifurcation • Bailey type IV: • Lies in pharyngeal mucosal space.

17. 41 year old male with neck mass. • Bailey type II: • most common. • Remnant of cervical sinus of His. • Classic location: • Anterior to SCM • Lateral to carotid space • Posterior to submandibular gland.

18. 10 mo. Child presented with neck mass. Suspected abscess.

19. Third Branchial Apparatus Anomalies. • Very rare. • Requires careful anatomic examination. • Pierces the thyrohyoid membrane and enters pyriform sinus • Posterior to carotid vessels • Anterior to Vegus nerve. • Posterior compartment behind SCM. • Joins Cervical Sinus of His.

20. Child with Neck Fullness. • Cystic mass in left posterior compartment • Beneath SCM. • Posterior to Carotid vessels.

21. Fourth Branchial Apparatus Anomalies. • Very rare: complete fistula not reported. • Origin at apex of pyriform sinus, penetrates thyrohyoid membrane. • Descends below aortic arch • Inferior to superior lanryngeal nerve. • Superior to recurrent laryngeal nerve. • Cervical sinus of His.

22. 3 yo with recurrent neck abscess. • Infected cyst anterior to carotid artery • May communicate with pyriform sinus or cervical sinus of His • Track descends below aortic arch.

23. Case 1: Child with right facial mass. SubmandibularGland Carotid Sheath Sternocleidomastoid

24. Case 2: Child with purulent drainage from EAC.

26. Case 3: Child presenting with neck mass.

27. Review • Defects in branchial apparatus include branchial, thymic, and parathyroid anomalies. • Manifest as cysts, sinuses, fistulas, and ectopic glands. • Embryogenesis: vestigial remnants from incomplete obliteration or buried cell rests. • Radiography, US, CT, MRI used for evaluation

28. Review • Branchial Cleft Anomalies: Fistulae, cysts, sinuses. • Four types: Type II Branchial Cleft Cysts most common. • Classic location BCC II: anterio-medial to SCM, displacing submandibular glands anteriorly, lateral to carotid vessels. • Types II – IV merge externally as Cervical sinus of His. • Types III and IV are rare and require careful anatomic examination for differentiation.

29. References 1. Benson MT, Dalen K, Mancuso AA, et al.: Congenital abnormalities of the branchial apparatus: embryology and pathologic anatomy. Radiographics 12:739-748, 1992. 2. Meuwly JY, Lepori D, Theumann N, et al.: Multimodality Imaging Evaluation of the Pediatric Neck: Techniques and Spectrum of Findings. Radiographics 25:931-948, 2005. 3. Koeller K, Alamo L, Adair C, Smirniotopoulos J.: Congenital Cystic Masses of the Neck: Radiologic-Pathologic Correlation. Radiographics 19:121-146, 1999. 4. Langman J. Medical Embryology 3rd Ed. Baltimore: Williams & Wilkins, 1975; 234-236. 5. Barry H. The aortic arch derivatives in the human adult. Anat Rec 1951; 111:221-238.