Cervicofacial Congenital Cysts and Fistulas


The development of the pharynx in the embryo determines the appearance of the main endocrine glands of the head and neck, arising from evaginations that we call pouches. These coincide on the outside with the system of pharyngeal arches, whose skeletal, nervous and arterial derivatives are shown in Table 2. These arches separated by grooves give the embryo the appearance of the gills of the fish, but at no time do they coincide outside with the interior as it happens in them.

The 1st and 2nd pharyngeal bags will give rise to the tympanic tube recess, from which the middle ear and the eustachian tube will be formed, the ventral component of the 2nd will give rise to the intramygdalin fossa. The dorsal wing of the 3rd pouch will give rise to the lower parathyroid, the ventral wing from the 3rd pouch to the thymus. The 4th pouch originated, its dorsal component will form the upper parathyroid, its ventral wing is actually the 6th bag or last gill body that supposes constitutes the interfollicular cells of the thyroid. This bilateral system leaves in its middle zone the odd tubercle and the hypobranchial eminence, which originate the tongue and thyroid.

Once these structures are outlined, to understand the formation of branchial cysts, we need to know a structure called the cervical sinus. The growth of the arches is different, so that the 1st and 2nd develop a lot, leaving the 3rd and 4th arches submerged in a shallow ectodermal fossa that we call cervical sinus. Likewise, the epipericardial crest rises enclosing the cervical sinus more deeply, from this crest the mastoid sternocleid muscle, the trapezius and the infrahoid muscles and the floor of the mouth will be formed, likewise the spinal and hypoglossal nerves, that is, these structures are not cranial, but were incorporated into the skull in the evolution of mammals.

The approximate area of the cervical sinus with triangular shape, is determined by derivatives of the epipericardial crest, the sternocleidomastoid, the trapezius, the infrahoid musculature and the floor of the mouth, the elements derived from the hyodes, thyroid and cricoid cartilage arches are within the cervical sinus, the hypoglossal nerves and their descending loop are always posterior to the cervical sinus.

In fact the growth of the 2nd arch is so important that it protrudes covering the gill slits as it happens in ossified fish, also determines that in muscular derivative of this arch, the platysma covers these structures, over time the cervical sinus is detached from the surface by closing the external orifice, the sinus is obliterated and normally leaves no remains.

EmbriologíaEmbriologíasinus in the embryonic period and its position in the adult a) cervical sinus b) cervical sinus in the adult c) epipericardial crest.