O.F THE NECK Pathological the same manner that facial clefts and fistulae may result from bronchial clefts and sulci, so the embryonal development of the neck may give rise to incomplete closures, to scat tering of nuclear particles, and to persistence of primordial. sulci and ducts.
At the sides or in the median line of the neck small fistula may be observed which secrete a milky fluid either spontaneously or upon pres sure. According to their location these fistula are divided into median and lateral. The lateral ones are always situated at the anterior margin of the sternoeleidomastoid muscle above or below the hyoid bone (Karew ski). These have an internal communication in the vicinity of the tonsil while the median ones open under the tongue at the foramen excum.
These fistula may extend from the skin throne' the cervical tissues into the buccal cavity, and then they are called complete fistula.
According to whether the fistula terminates in a eul-dc-sac or has only an interior or exterior aperture, they are called incomplete exterior or incomplete interior fistube.
The intrusion of amniotic bands into the embryonal furrows, etc., is said to explain these malformations as in the deformities of other parts. Heredity, which has frequently been observed in these cases, brings up the biological factor for consideration.
Up to a short time ago there was not much uniformity of opinion as to the history of development of these structures. Ashersohn was the first to assume a connection with the branchial clefts. According to Rabb they are remnants of the branchial duet which runs outward from the second inner bronchial furrow to the sinus eerviealis, which latter corresponds to the second exterior bronchial furrow in which the third and fourth bronchial ridges will be situated later through processes of growth and involution (Karewski).
All these explanations, however, do not answer the question as to the etiology of the median cervical fistula. At first it was assumed that it was a communication with the glottis, but this has never been proved. Investigations by IIis, however, have demonstrated that the median cervical fistula can be explained without difficulty by the development of the median lobe of the thyroid gland.
In a two-weeks-old embryo the anterior wall of the primitive buccal cavity develops a recess lined with cylindrical epithelium and growing downward in the form of a duct. Cells begin to form at the wall which later show the character of thyroid gland. The lower end of the duct develops into the thyroid, while the upper end is obliterated. But in about 30 per cent. of adults particles of thyroid consistency, mucous
glands which were swept along, epithelial debris and lymph follicles, are, according to Weglowsky, found scattered along the entire route from the foramen cfectim to the thyroid cartilage.
Occasionally the entire duct, or its anterior or posterior end, may persist in the shape of a fistula, and parts of the duct may later appear as cysts. Development on this principle also explains the histological difference in structure and lining of these fistulae, and cysts.
According to further investigations of Weglowsky the lateral cer vical fistuhe originate in a similar manner. In the third week of em bryonal life two cavities are formed at the sides of the pharynx in the fourth and third fissures which are changed into canals by growing downward. The canal originating in the fourth fissure is changed at its lower end to thyroid tissue, while that of the third fissure is intended for thymus formation. It runs transversely over the entire neck and ends at the sternum. The canals are lined with cylindrical epithelium, but in places stratified pavement epithelium may be found. Mucous glands and lymphatic structures are embedded in their tissue. According to this explanation the lateral fistulm will have to be regarded as remnants of these canals. Their course coincides with that of the thymus duct which commences below the tonsils, passes downward and outward over the hypoglossus nerve, and gradually disappears in its course toward the sternum the carotids to the inner border of the sterno MeidomastMd muscle.
The thyroid ducts are shorter and terminate in the vicinity of the glottis.
This explanation brings uniformity into the etiology of all cervical fistulte and the cystic structures resulting from them, whether they have developed from canal remnants or follicles or as dermoid cysts front epithelial masses that have been swept along.
The fistula., when freely exuding, are not only uncomfortable to the patient, but also frequently lead to eczema of the skin at the site of the discharge.
The treatment of fistula as well as their corresponding cysts can only consist in radical extirpation, care being taken that their removal be as complete as possible (resection of the hyoid bone), since any vestiges may lead to relapses and cyst formation. The extirpation will be considerably facilitated by the previous passage of a hair sound, but the wall of the ducts is usually so tender that a false passage may easily he made (Broca, v. Hacker).
Any other method of treatment, cauterization, etc., has practically no beneficial effect.