Pictoral Essay: Congenital Anomalies of the Branchial Apparatus Authors Institutions

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.

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.

Branchial Apparatus By the end of 4th week of gestation, four well-defined pairs of branchial arches are visible externally; the fifth and sixth arches are small and cannot be seen on the embryonic surface.

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.

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.

Branchial Derivatives

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.

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. Examples of a second branchial apparatus internal and external sinus tract. Second image is a complete third branchial apparatus fistula tract.

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.

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. From 6-8 weeks, the parotid gland forms from endoderm within the mouth and branches posteriorly toward the ear. At the same time, the facial nerve and muscle migrate anteriorly. Because the parotid gland and facial nerve have a somewhat later embryonic development, a vestigial first branchial anomaly can insinuate itself in a variable relation to the parotid gland or facial nerve.

10 year old female presenting with fistula.

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.

Four types of 2nd BCC Bailey type I: Bailey type II: Bailey type III: 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.

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.

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

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.

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

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.

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. Origin at pyriform sinus, descends below aortic arch, coarses in front of aorta in neck to cervical sinus of His.

Case 1: Child with right facial mass. Submandibular Gland Carotid Sheath Sternocleidomastoid

Case 2: Child with purulent drainage from EAC.

Case 3: Child presenting with neck mass.

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

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.

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