Third pharyngeal pouch sinuses: Report of a bilateral case with a review of the embryology and literature

Abstract Bilateral pharyngeal sinuses were found in a 71‐year‐old male Caucasian anatomic cadaver. As their ostia opened through the piriform recesses cranio‐ventral to the plicae of the internal branches of the superior laryngeal nerves, they were determined to be of third pharyngeal (branchial) pouch origin. A publication review revealed that this instance was the tenth case of third pharyngeal pouch sinuses reported in the English literature, and the third case describing a bilateral occurrence. Histologic sections showed the sinuses were lined with a stratified squamous epithelium that was complexly evaginated on the lateral sinus wall. Despite the tendency to accumulate ingested matter, the sinus epithelium showed no chronic pathology. A review of branchial embryology suggested that the relative rarity of third (and fourth) pharyngeal pouch vestiges may be partly explained by the “ascensus” of the hypoglossal nerve and the aortic arch migrations lateral to the pharyngeal regions derived from these more caudal branchial pouches. However, as the literature of the last two decades has surprisingly revealed reports of 28 cases of fourth pharyngeal pouch sinuses, the third pouch sinuses are now the rarest of the reported endobrachial vestiges.