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