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Neck: Cysts, Sinuses, and Fistulas 237

3,14
Contributions of the sixth branchial arch are shown below: the body of the hyoid bone. The duct usually spontaneously obliterates,
• Skin: none but remnants may be found anywhere from the base of the tongue to the
pyramidal lobe of the thyroid gland (Figure 36.9), although 80% are jux-
• Cartilage: cricoid, arytenoids, rings of trachea and bronchi taposed to the hyoid bone. 15
• Muscles: intrinsic muscles of larynx (except cricothyroid, stylopharyn- Clinical Presentation
geus, tensor palate) Most thyroglossal cysts are clinically evident before the child is 10 years old.
• Nerve: recurrent laryngeal branch of vagus Males and females are affected equally. The cysts present as round masses
in the midline of the neck that move up and down with swallowing and with
• Artery: pulmonary artery on right side, ductus arteriosus on left side
protrusion of the tongue because of their connection to the hyoid bone. They
• Membrane: hypopharynx are soft to firm in consistency, mobile, and nontender unless infected.
Remnants
Anomalies of the fourth branchial pouch very rarely may produce a cyst
or a fistula very low in the neck behind the sternomastoid muscle. On the
right side, the tract goes behind the subclavian artery; on the left side, it
goes under the arch of the aorta. It opens into the cervical oesophagus.
Midline Cervical Clefts
Midline cervical clefts (Figure 36.6) are due to imperfect midline fusion
of the paired branchial arch tissue about the fourth week of embryonic
development. These present as raw, weeping areas in the midline of
the lower neck. They may have irregular skin tabs or shallow sinuses.
Management is usually conservative. If excision is deemed necessary, a
Z-plasty may be done to prevent ugly scars or contractures. Figure 36.6: Midline cervical cleft.
Dermoid Cysts
Dermoid (inclusion) cysts (Figure 36.7) are caused by entrapment of
epithelium of branchial arch origin at the time of embryologic midline
fusion. Most of the cysts are in the midline, are firm in consistency, and
may be attached to overlying skin (Figure 36.7). They do not move with
swallowing or protrusion of the tongue. They usually do not have any
deep-seated tracts and are easily excised surgically through a transverse
collar-stud incision.
Teratomas
Teratomas are tumours composed of multiple tissues foreign to the ana-
tomical locus. 1,2,12 These tissues cannot have resulted from metaplasia.
They develop adjacent to normal anatomical structures or organs and Figure 36.7: Dermoid cyst.
are generally attached by limited vascular pedicles. The most com-
mon sites for teratomas are the gonads and the sacrococcygeal areas.
2
These sites embryologically allow deviation of early germinal issue to
disorganised complex teratomas. Teratomas are also common in the
neck region (Figure 36.8). Most teratomas are benign. They produce
secondary symptoms due to their pressure effects on adjacent organs.
Investigation
Teratomas may be soft to firm in consistency because they may contain
cystic areas. They may be confused with cystic hygromas. Neck ultra-
sound and/or aspiration, under aseptic conditions, may be necessary to
confirm the diagnosis.
Management
Complete excision of the teratoma should be the desired goal. Figure 36.8: Teratoma.
Incomplete excision may lead to recurrence of the mass, recurrent
infection, draining sinuses, or the possibility of malignant change. 1,13
Thyroglossal Cysts
Thyroglossal cysts are the most common midline masses in children,
14
accounting for 70% of all congenital cervical lesions. They can occur
at any age, and one-third become obvious in adult life.
Embryology
The thyroid gland develops as a diverticulum from the foramen caecum
of the tongue, descending in front of the trachea in company with the
thymus and the inferior parathyroid glands. It reaches its final position
by the 7th week of embryonic life. 14–16 The hyoid bone develops at about
the same time, from the second and third arches, and fuses anteriorly so
that the thyroglossal duct may pass anterior to, through, or posterior to Figure 36.9: Thyroglossal cyst.