Congenital pharyngeal fistula: causes, symptoms, diagnosis, treatment

Congenital pharyngeal fistulas may be complete or incomplete. The former are of a through nature: an external opening in the skin of the anterior or lateral surface of the neck, the latter are of a blind nature: either an opening only in the skin with a fistula tract ending in the tissues of the neck, or vice versa, only an opening from the pharynx, also with a blind fistula tract in the tissues of the neck. Fistula tracts may be of different lengths and shapes. The localization of their external openings is extremely diverse. They may be located starting from the area anterior to the outer edge of the sternocleidomastoid muscle, to the area of the hyoid bone or downwards to the sternum. In the latter case, such an opening is most often located 1-2 cm above the sternoclavicular joint. Less often, such fistula tracts occur at the level of the larynx and very rarely - in the medial part of the neck, more often on the right. True median fistulas are located strictly along the midline, as is their fistula tract. These are blind fistulas that end in a sac (cyst) associated with the hyoid bone. Almost all pharyngeal fistulas are secondary, corresponding to branchial cysts of the thyroid gland. Complete medial fistulas are also observed, the internal opening of which is located in the region of the blind opening of the tongue; these fistulas represent a rudimentary formation of the embryonic thyroglossal canal. Fistulas located above the hyoid bone have also been described (there are also blind fistulas of the auricle, the openings of which open on the main curl - coloboma auris).

Congenital primary complete fistulas are true branchial (bronchiogenic) fistulas located below and lateral to the hyoid bone. As a rule, these skin openings of external fistulas are single and very narrow. They are covered with a crust, under which a small point of granulation tissue is sometimes noted.

The location of the internal opening of the complete fistula is more constant and is almost always located in the area of the palatine tonsils, behind the posterior palatine arch or less often at the level of the pharyngeal recess. It is very narrow and practically not visually determined. The communication between the two openings of the through (complete) fistula is tortuous and contains cavities, which prevents its probing. A thin probe can penetrate to the hyoid bone or to the angle of the mandible. When probing the external opening located above the hyoid bone, the probe encounters an obstacle at the bend of the fistula tract, which is almost always at the level of this bone. The trajectory of the tract, starting on the skin above the hyoid bone, passes the thickness of the dermis and superficial aponeurosis of the neck, deepens under the sternocleidomastoid muscle, reaches the hyoid bone, then enters under the posterior belly of the digastric muscle and ends in the area of the palatine tonsils. The styloglossus and styloglossus muscles cross the fistula superficially. It passes between the external and internal carotid arteries, is fused with the bed of these vessels, then crosses the hypoglossal and glossopharyngeal nerves, from which it receives nerve fibers.

As for the structure of the fistula tract itself, it has an outer fibrous membrane, which in some cases contains muscle fibers or cartilaginous tissue. In the walls of medial fistulas, which originate from the embryonic thyroglossal canal, one can often find parenchymatous tissue of the thyroid gland. The inner surface of the fistula tract, covering the outer fibrous layer, consists of stratified squamous keratinizing epithelium or stratified nonkeratinizing epithelium of the type of oral mucosa, or even of columnar epithelium with or without cilia of the type of embryonic pharyngeal-esophageal mucosa.

Diagnosis of congenital pharyngeal fistulas. The only symptom of congenital pharyngeal fistulas with an external opening that causes concern to the patient is the release of a drop of transparent watery or slightly viscous liquid, similar to saliva, from the fistula tract. However, during meals, this discharge becomes abundant and leads to irritation of the skin around the fistula opening. In rare cases, with complete fistulas, liquid food products can be released through them. During menstruation, this discharge can become bloody. Sometimes it is possible to palpate the fistula tract as a dense cord extending from the external opening to the hyoid bone. When probing the fistula tract with a thin flexible probe, it usually reaches the hyoid bone, causing coughing or shortness of breath. Sometimes a fistula can be detected between the tonsil and the posterior arch, manifested by a drop of mucopurulent discharge.

The introduction of methylene blue, milk or liquids with certain taste qualities (solutions of table salt, sugar, quinine) into the fistula can, in the case of a complete fistula, reach the pharynx and be detected visually or by the emergence of a certain taste sensation in the subject.

With the help of radiography using contrast materials, it is possible to identify the fistula tract in complete fistulas, however, incomplete deep fistula tracts are practically not detected with this method.

Treatment of congenital pharyngeal fistulas. The previously used non-surgical method, consisting of introducing sclerosing fluids (iodine solutions, silver nitrate, etc.) into the fistula, electrocautery, electrophoresis, etc., did not bring the desired results. The only effective treatment method is total extirpation of the fistula. However, such surgical intervention is very difficult, requiring appropriate skills and a good knowledge of the anatomy of the neck, since the surgeon encounters large vessels and nerves on his way. In case of fistulas of the thyroglossal canal, around which the hyoid bone develops during embryogenesis (transhyoid fistula), resection of the body of this bone is performed. However, often the consequences of such an operation in the form of cicatricial deformations of the pharynx and neck cause more discomfort to the patient than the fistula itself.

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