Periauricular Cystic Lesions

Diagnosis

Summary

First branchial cleft cysts have a characteristic periauricular location associated with the parotid gland and seventh cranial nerve that directly relates to their embryologic origin. It is this typical location that suggests the diagnosis and helps differentiate first branchial anomalies from other head and neck cystic masses, including other branchial apparatus lesions.

First branchial apparatus anomalies are congenital anomalies that occur during the development and differentiation of the mesodermal arches, ectodermal cleft, and endodermal pouch. Externally, the first and second branchial arches are separated by an ectodermally lined cleft, which is the only branchial cleft to give rise to an anatomic structure, the EAC. Internally, the first and second arches are separated by an endodermally lined pouch that gives rise to the eustachian tube and middle ear cavity. Either failure of the cleft/pouch to be completely obliterated or the presence of cell rests or remnants of the branchial apparatus can result in an external or internal sinus, a fistula, and/or an isolated cyst.

Consistent with the embryologic origin, first branchial apparatus lesions are most commonly located near the EAC in a preauricular or postauricular location. Because the posterior migration of the parotid gland and the anterior migration of the facial nerve (which arises from the second branchial arch) occur after the development of the first branchial cleft structures, first branchial cleft anomalies have a variable association with the parotid gland and facial nerve ( Figure 41-1 ).

Clinically, these anomalies typically present acutely in children following an upper respiratory tract infection, most commonly as a cystic inflammatory neck mass or abscess in the parotid gland. They also may present as a nontender neck mass. Recurrent, chronic otorrhea in the absence of chronic otitis should raise the suspicion for first branchial apparatus anomalies.

Infected lesions appear as an inflammatory mass or abscess on cross-sectional imaging, typically within the parotid gland adjacent to the EAC. Noninfected first branchial cleft cysts appear as a simple anechoic mass on ultrasound or as a unilocular cystic lesion on contrast-enhanced CT, respecting the adjacent structures and fascial planes, with minimal or no rim enhancement. They often are located within the parotid gland, with a variable association with the facial nerve. Sinus tracts and fistulae may be small and difficult to visualize on cross-sectional imaging but may be characterized with CT or fluoroscopic fistulograms to further aid in surgical planning. Treatment involves complete surgical excision with a parotidectomy and dissection to preserve the facial nerve; otherwise, recurrence is common. The variable location of first branchial apparatus lesions that are lying superficial, deep, or even in between branches of the facial nerve may complicate surgical resection.

Important lesions to consider in the differential diagnosis of a branchial cleft cyst include diseases arising in the lymph nodes, such as suppurative infection or metastases, as well as other causes of parotiditis, abscess, or cystic parotid neoplasms. In adults or elderly patients, it is extremely important to consider and exclude cystic, necrotic lymph node metastases as a primary differential diagnosis. Metastatic lesions most commonly arise from cutaneous squamous cell carcinomas or cutaneous malignant melanoma of the upper face or scalp. Parotid lymph nodes have afferent lymphatic drainage from the frontotemporal scalp, upper face, eyelid, conjunctiva, lacrimal gland, and anterior ear, including the EAC. Metastases and lymphatic malformations will appear more heterogeneous and may extend across neck compartments. Infected branchial cleft cysts may be difficult to differentiate from metastases or granulomatous infections, but clinical clues often help. MRI may help differentiate lesions, including lymphatic malformations and dermoids. When considering metastases as a differential diagnosis, look for a primary lesion typically arising from the skin of the face or scalp.

Spectrum of Disease

Branchial apparatus anomalies may present as cysts, sinuses, or fistulae, reflecting their embryologic origin. They may be contiguous with or have a sinus tract opening to the EAC (in approximately 44% of cases) or, rarely, to the tympanic membrane or middle ear.

Branchial cleft cysts almost always are present as a single entity. Multiple cysts or lesions within a similar location should raise the suspicion for other pathology, including parotid neoplasms, lymphoepithelial cysts in persons with HIV, Sjögren syndrome, or other causes of parotiditis. In older patients presenting with a cystic lesion, primary lesions, cutaneous metastatic squamous cell carcinoma, or melanoma should be suspected.

The Work classification divided first branchial cleft cysts into two types, which may affect the surgical approach ( Figure 41-2 ). Type 1 lesions are thought to be of ectodermal origin and are considered to be duplications of the membranous EAC. Type 1 lesions lie superior, lateral to the facial nerve, extending medial to the conchal cartilage, and are parallel to the EAC. These lesions may be removed with a retroauricular incision, keeping the skin of the external auditory meatus intact.

Type 2 lesions, which may have both mesodermal and ectodermal components, may present as cysts, sinuses, or fistulae. They may lie more inferior than type 1 lesions, lying below the angle of the mandible and deeper within the parotid gland, anterior to the sternocleidomastoid muscle. A tract from these lesions may course superficially and/or deep to the facial nerve, with a possible external opening in the upper neck over the angle of the mandible superior to the hyoid bone or internally, extending either inferior to the EAC or as a sinus tract to the EAC at the osseocartilaginous junction. To safely remove Work type 2 lesions at surgery, it is important to first identify the facial nerve in relation to the lesion at the stylomastoid foramen and trace it distally. These lesions also may involve the tympanic membrane or middle ear structures, which will affect the surgical procedure.

Rarely, first branchial apparatus lesions may lie anywhere along the nasopharynx or middle ear cavity and may lie as inferior as the angle of the mandible. Occasionally, a tract from the lesion may extend inferior to or open into the EAC at the osseocartilaginous junction. The first branchial pouch anomaly most commonly manifests as a short eustachian tube, clinically presenting in children with recurrent otitis media. A rare lateral nasopharyngeal cyst also may represent a first, or possibly a second, branchial pouch remnant, lying between the posterior pillar and the pharyngeal opening of the pharyngeal eustachian tube.