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Neck: Cysts, Sinuses, and Fistulas 235
Second Branchial Arch
Embryology
The first two branchial (or hyoid) arches and clefts, and second pharyn-
geal pouches appear in the 22-day old embryo. The second arch extends
down the neck (as the platysma) to overlap the second, third, and fourth
branchial clefts, forming a potential space—the cervical sinus of His.
The core of the hyoid arches forms a U-shaped cartilage, which forms
the upper part of the hyoid bone. The dorsal end forms the stapes and
the styloid process of the temporal bone.
Differentiation of the second branchial arch is shown below:
• Skin: lateral and anterior part of neck
• Bones: stapes, styloid process, upper part of body and lesser cornu
of hyoid
• Muscles: posterior belly of digastric, muscles of facial expression,
stapedius, stylohyoid, platysma
• Nerve: facial nerve
• Artery: stapedial (remnant of dorsal part of second aortic arch)
Source: Welch KJ, Randolph JG, Ravitch MM, O’Neill JA Jr, Rowe MI. Pediatric Surgery. Year
Book Medical Publishers, 1986. Used by permission. • Membrane: membrane of oropharynx
Figure 36.2: Coronal view of 5-week embryo showing branchial arches. The muscular element of the hyoid arch spreads like a fan to form
the muscles of facial expression, innervated by the facial nerve (Figure
36.4). Lymphocytes invade the lateral end of the second pharyngeal
pouch to form the palatine tonsils
Remnants
Complete fistulas, external sinuses, and cysts may occur as remnants
of the second branchial arch. Although congenital, the tiny openings
may not be obvious at birth. Attention is usually drawn to the problem
by persistent mucoid drainage and/or recurrent infection. Sinuses pres-
ent in the first decade of life, and cysts usually in the second decade.
The cysts and external openings of the second branchial cleft lie along
the anterior border of the sternomastoid muscle at the junction of the
upper two-thirds and the lower one-third (Figures 36.4 and 36.5). The
tract ascends along the carotid sheath to the level of the hyoid bone,
then turns medially between the branches of the carotid artery, behind
the posterior belly of the digastric and stylohyoid muscles, and in front
of the hypoglossal nerve to end in the tonsilla fossa (see Figure 36.1).
Source: Welch KJ, Randolph JG, Ravitch MM, O’Neill JA Jr, Rowe MI. Pediatric Surgery. Year Sinuses with external openings at the same site pursue the same course
Book Medical Publishers, 1986. Used by permission. before terminating blindly after variable distances. Secretions in bran-
Figure 36.3: Surgical management of first branchial arch fistula. chial cysts may take a while to accumulate because they are clinically
visible or palpable. The cysts may not, therefore, be clinically evident
Clinical presentation until late in childhood or early adolescence. Bacteria from the oral cav- 7
5
True anomalies of the first branchial cleft are uncommon. Skin tabs, pre- ity may contaminate the cysts, leading to an abscess in 25% of cases.
The cysts may be bilateral in 10% of the cases.
auricular cysts, and sinus tracts around the ear are not of branchial cleft
The cysts contain turbid fluid and therefore do not transilluminate
origin but occur from abnormal infolding and entrapment of epithelium
during the merger of the six hillocks of His that form the external pinna. 4,6 like cystic hygromas. Lymph node enlargement from tuberculosis,
tonsillitis, and lymphomas may present with neck masses to form
When they occur, first branchial cleft cysts present as a swelling
differential diagnosis.
in front of or behind the pinna. External openings of the fistula lie
below the mandible and above the hyoid bone. The tract may pass Investigation
superficial or deep to the main branches of the facial nerve and through A sinogram may be done to outline the course of the fistula, but it is not
the substance of the parotid gland with the internal opening into the a substitute for careful dissection at operation. Fine needle aspiration
external auditory canal, which forms the source of recurrent infection (FNA) cytology or excision may be needed to confirm the diagnosis,
(Figure 36.3). and this must be done aseptically to prevent introducing infection.
Management Management
If operation is deemed necessary, a curved incision is made to elevate Sclerotherapy has not been developed as a method of management;
the pinna and expose the parotid gland. The facial nerve and its trunks therefore, operative excision is the treatment of choice. Unless the
are identified and preserved. The tract is then dissected superiorly and whole tract is dissected, recurrences may occur, with the possibility of
then medially to the external auditory canal (see Figure 36.3). neoplastic degeneration in adult life.
8,9
Histologically, the tracts are lined by stratified squamous epithelium Operations to remove the cyst, sinus, and fistula are all approached
with skin appendages. Muscle fibres and cartilages may be seen in the the same way, with the patient under general anaesthesia with
deeper layers. endotracheal intubation.