Medically, congenital preauricular fistula is divided into simple type, infectious type and secretory type. Congenital preauricular fistula accounted for 82.58%, secretory fistula accounted for 3.87%, and simple fistula accounted for 13. 15%. Among them, the simple type will not be infected for life and does not need surgery.

Disease pathology

Congenital preauricular fistula is a common autosomal dominant genetic disease, which is caused by poor fusion of the six knolls of the first 1 and the second branchial arch that form the auricle in embryonic stage or incomplete sealing of the first 1 branchial groove. According to domestic sampling survey, its incidence rate is 1.2%, which can occur on one side or both sides, and the ratio of unilateral to bilateral is about 4: 1. The ratio of male to female is about 17: 1.

The fistula opening is very small, mostly located in the front of the helix foot, followed by the base of the helix foot and the front of the ear. Most of them can be seen in these three parts, and a few can be seen in the triangular fossa of auricle or concha cavity. The other end is a blind tube. Fistula varies in depth and length, generally 1 ~ 1.5cm, with visible branches. There are three common branches: the upper branch extends to the inside of the spiral about 0.5cm, and the other branch can extend to the bottom of the spiral; The inferior branch expands into cyst, the infected cyst is completely destroyed, and the adhered cellulose or granulation tissue proliferates, and its epidermis is often dark red, some go deep into auricular cartilage, some can go deep into external auditory canal, or reach the surface of mastoid. The lumen wall is stratified squamous epithelium with hair follicles, sweat glands and sebaceous glands.

Pathologically, there is a fistula on the surface of the skin specimen, which is a branched or curved blind tubular structure. The wall of the tube is fibrous connective tissue, covered with stratified squamous epithelium or pseudo-stratified fibrous columnar epithelium, sometimes both, or accompanied by chronic inflammation. There are some elastic cartilage in the deep wall. The outer mouth is a small depression in the skin, and there may be a small amount of white sebum-like substance when it is squeezed, which has a slight smell. When infected, the local area is red, swollen, painful and purulent. In severe cases, the surrounding tissues are swollen and the skin can fester into multiple leakage holes. After the pus is discharged, the inflammation subsides and can temporarily heal, but it often recurs and forms scars, which are more common near the hairline in the front and upper part of the tragus. Fistula is deep and old, which can affect the cartilage and auricle of ear canal, but generally does not affect the posterior sulcus and ear canal bone.