A congenital preauricular fistula is one of the most common congenital ear malformations. It results from abnormal development of the first and second branchial arches or incomplete closure of the first branchial groove during embryonic development, and is an autosomal dominant genetic disorder.
Clinical manifestations
The fistula is often unilateral but can also be bilateral. It typically presents with a small blind-ending tract opening onto the skin of the external ear, mostly anterior to the helix, but also at the upper posterior edge of the helix, tragus, or lobule. The fistula is usually narrow, with varying depths and lengths, and may have branches. It is often located around the facial nerve and parotid gland, and almost all fistulas connect to the perichondrium of the ear cartilage. The tract is lined with stratified squamous epithelium and contains hair follicles, sweat glands, and sebaceous glands. When pressed, a small amount of white, viscous, or caseous secretion may exude from the opening. Typically, there are no symptoms, but secondary infections can cause local redness, swelling, and pain, and often lead to abscess formation. After an abscess ruptures, it may form a pus-draining fistula, and scars often develop once the infection is controlled.
Figure 1 Congenital preauricular fistula
Treatment
If there is no history of infection, no treatment is necessary.
If infection is present, acute inflammation should be controlled before surgery. If there is a local abscess, it should be incised and drained, with surgery following once the inflammation is controlled. For recurrent infections not controlled by conservative treatment, surgery can be performed during the infection period.
During fistula excision surgery, a small amount of methylene blue can be injected into the fistula preoperatively to aid identification during the procedure. A probe can also be used to guide the complete removal of the fistula and its branches. The fistula is often closely related to the lateral perichondrium of the tragus. If the fistula passes through the auricular cartilage, part of the cartilage may be removed. Postoperatively, pressure dressing is recommended to prevent hematoma or seroma formation, which could lead to infection.