Case series: variations in the embryology of congenital midline cervical clefts.

Congenital midline cervical clefts (CMCC) is a clinical diagnosis and represents a spectrum of rare developmental anomalies. Fewer than 100 cases have been reported overall, the first being described by Bailey in 1924 (1). It is not a true cleft because it does not include a gap between adjacent skin flaps. It is thought to represent a failure of midline fusion of the branchial arches although this is controversial. It is a clinical diagnosis and presents at birth with a ventral midline defect of the skin of the neck. This consists of a skin tag (nipple-like projection), an atrophic mucosal surface and a caudal sinus. It may be associated with a subcutaneous fibrous cord, which can cause a vertical midline tethering restricting cervical extension. Associated defects may be a median cleft of the mandible, tongue and lower lip. There may be an associated delay in mandibular development and hypoplasia or absence of neck structures such as the hyoid bone. Associated thyroglossal and bronchogenic cysts may occur as well as defects in other parts of the body such as a sternal cleft (2). CMCC has been previously reported in the literature as being of a branchial origin, however a review of the histology of previous cases suggests a combined branchial and bronchogenic component (2-6). We report on two cases that presented with the clinical picture of a classical CMCC. Our first case appears to have a bronchogenic origin with possible branchial components and the second case appears to be solely branchial in origin. There is much debate as to the embryology of this clinical entity; we shall endeavour to address the main theories.