A third branchial pouch sinus is similar to a fourth branchial pouch sinus in its course and presentation.
A fourth branchial pouch sinus, like most congenital conditions, is generally believed to manifest as symptoms during the first or second decade of life.
(20) Secondary infections of branchial pouch cysts have also been described in humans, (6,8,15) and there is 1 report of Actinomyces species as the organism cultured.
The vestigial remnant theory, which is most widely accepted, states that failure of a branchial cleft, branchial pouch, or the cervical sinus to obliterate during embryogenesis can result in a cyst.
The superior parathyroid gland and the ultimobranchial body develop from the fourth branchial pouch, also in the vicinity of the piriform sinus.
Like other branchial pouch remnants, third pouch anomalies most frequently present as soft, nontender, well-circumscribed masses on the anterior margin of the sternocleidomastoid muscle.
Fourth branchial pouch anomalies most frequently manifest as recurring episodes of deep neck infections and/or abscesses or acute suppurative thyroiditis.
Failure to demonstrate a sinus argues strongly against the diagnosis of a fourth branchial pouch anomaly.
The initial phase of craniofacial morphogenesis is characterized by the formation of the BAs, which arise during pharyngeal development when the lateral wall of the pharynx becomes invaginated, forming the structures known as the branchial pouches; in the outer embryo, the pharyngeal endoderm becomes depressed, forming the fissures known as the branchial clefts (2).
Using in situ hybridization analysis, it was found that between the HH14 and HH18 stages, Hey1 expression was primarily localized to the endoderm of the branchial pouches. Previous studies highlight the importance of the endoderm in BA organization not only through the formation of the branchial pouches as the first signal of pharyngeal segmentation but also as a source of signaling to the neighboring ectoderm and mesenchyme (19).
Unlike the predominantly longitudinal orientation of the scales on most of the body, at least some of the scales covering the pharyngobranchial region have an oblique long axis, being aligned anterodorsally to posteroventrally (Figs 5A, B, 6D) in a manner that suggests that the branchial pouches or row of branchial openings was also oblique, as it is in anaspids (Blom et al.
First, we must continue to try to find evidence for the number and arrangement of the external branchial openings and the internal branchial pouches or slits, the most significant remaining lack in our understanding.