The first branchial fissure fistula is caused by the abnormal development of the first branchial fissure, which is closely related to the external auditory canal, and is also known as congenital external auditorial canal fistula. In the fourth week of the embryo, the first branchial cleft groove gradually deepens, and its dorsal part becomes the original external auditory canal, which forms the ear nail cavity in the middle and disappears at the ventral end. If the ventral side of the first branchial sulcus disappears incompletely during the 2nd ~ 4th month of the embryo, ectodermal tissue residues closely related to the external auditory canal can be formed.
Gestational age variants with developmental impairment can manifest in a variety of forms, such as cysts, fistulas, or sinus tracts, and may be present alone or accompanied by auricular and external auditory canal malformations, which have the same pathological features as congenital ear canal fistulas.
Recent studies retrospectively analyzed the clinical and otological features of 109 patients with abnormalities of the first branchial slit. Pearson's chi-square test and Fisher's exact test were used to compare the differences between the Work classification and the influencing factors of postoperative facial paralysis in 86 patients who were followed up and explored.
Patients with abnormalities of the first branchial fissure present with otological symptoms, including cysts or fistulas in the external auditory canal (EAC) and periauricular (43.2%), microtia (3.7%), EAC webbing (1.8%), otitis media (1.8%), and otorrhea (4.6%). Eighty-five cases (78.0%) had type I first branchial slit anomalies and 24 cases (22.0%) had type II. Type II (58.3%) was more likely to be located deep in the facial nerve (FN) and undergo superficial parotid resection (79.2%) than type I first branchial cleft anomaly. This difference was statistically significant (P < .001). The incidence of facial paralysis after the abnormality of the first branchial cleft in the deep part of the facial nerve was higher (P < .05).
The majority of patients (55.0%) had otological symptoms. The abnormality of the first branchial cleft in Type II of Work is usually located deep to the facial nerve and is often superficially parotid resected. Postoperative facial palsy is associated with an abnormality of the first branchial cleft located deep in the facial nerve, but not with the type of Work.
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