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The critical period of cervicofacial growth and differentiation occurs between weeks 4 through 8 of embryologic development.1 The beginning of this stage is characterized by the appearance of the frontonasal process—the precursor of the forebrain and upper face—with development soon thereafter of the optic and otic vesicles; the nasal placodes; the primitive mouth, or stomodeum; and five ridges on the ventrolateral surface of the embryonic head, which is known as the branchial system. Many of the symmetrically paired skeletal and neuromuscular structures of the head and neck arise from the first (mandibular), second (hyoid), third (pharyngeal), and fourth (laryngeal) arches of this fetal branchial system (Table 372-1). The skull, facial, and neck bones have begun to ossify by the end of the eighth fetal week, which coincides with a recognizable human embryonic face with easily discernible ears, eyelids, cheeks, nose, and upper and lower lips.

Table 372-1. Derivatives of the Pharyngeal Arches and Their Innervation

Most of the congenital anomalies of the face and neck are believed to arise from altered or arrested growth during this critical developmental stage. Such anomalies may initially manifest at birth as an asymptomatic palpable mass or a sinus or fistula opening; they alternatively may remain unnoticed until secondary infection causes acute presentation later in childhood.2 The anatomic location of such lesions often suggests their embryologic origin3 (Table 372-2).

Table 372-2. Congenital Malformations of the Neck

Branchial Anomalies

Lesions of the anterolateral neck are often of branchial system ...

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