Diagnostic ultrasound ( PDFDrive )

CHAPTER 48 The Pediatric Head and Neck 1651
A
B
FIG. 48.39 Type I Branchial Cyst. (A) Four-year-old child with swelling and pain inferior to the left ear. Longitudinal sonogram demonstrates
an elliptical heterogeneous hypoechoic lesion lacking color low, supericial and inseparable from the parotid gland. (B) Axial computed tomography
scan obtained 2 months later after treatment with antibiotics conirms well-deined cystic lesion (arrow) embedded in the supericial lobe of the
left parotid.
Congenital Lesions
Branchial Anomalies
he branchial (pharyngeal) apparatus develops between the
fourth and sixth week of gestation. he structure consists of
six pairs of mesodermal branchial arches separated by ive
paired internal endodermal pharyngeal pouches and ive paired
external ectodermal branchial clets, or grooves. Abnormalities
in development of this apparatus may result in the formation
of a cyst, sinus tract, or istula, although most branchial lesions
present as cysts. 140,141 Sinus tracts communicate with either
skin or mucosa of the upper airway when a pouch or groove
fails to obliterate; if both pouch and groove fail, then a istula
between skin and mucosa develops. A cyst occurs when a groove
remnant forms an epithelial line space without communication.
142 Branchial anomalies, ater thyroglossal duct cysts, are
the second most common congenital head and neck lesions in
children, with the majority arising from the type II apparatus. 141,142
Branchial anomalies, particularly when bilateral, may be part
of branchio-oto-renal syndrome, a disorder that also manifests
with bilateral preauricular pits and renal abnormalities. 143 On
sonography, branchial malformations typically appear as a simple
or complex cyst with through transmission. hese lesions are
susceptible to hemorrhage or superimposed infection, but
predisposition to cancer remains controversial. 93 Treatment of
choice is surgical resection or istulectomy, with a 4% rate of
recurrence. 143,144
First branchial anomalies represent 8% to 10% of all anomalies
and appear as a cyst or sinus adjacent to the external auditory
canal, the pinnae, or the parotid gland, extending to the level of
the mandible angle 143 (Fig. 48.39). hese lesions can be supericial
or deep, even embedded into the parotid gland with variable
relationship to the facial nerve. 144,145 Some demonstrate a tract
to the external auditory canal.
Second branchial anomalies represent 90% of all branchial
apparatus malformations. 143 Cysts of the type II branchial anomaly
result from persistence of the cervical sinus. 144-146 During development
of the branchial apparatus, the second arch expands
downward to meet and merge with the ith arch, thus covering
the second, third, and fourth arches and forming a cervical sinus
of His. 130,146 Because of this embryology, many anatomic type II
cysts are possible. hese cysts are diferentiated (Bailey) into
four types. 144 Type I is deep to the platysma muscle. Type II, the
most common, is anterior to the sternocleidomastoid, posterior
to the submandibular gland, and lateral to the carotid sheath.
Type III cysts are anatomically between the internal and external
carotid arteries, posteromedial to the sternocleidomastoid and
lateral to the pharynx (Fig. 48.40). Type IV cysts are adjacent
to the pharyngeal wall.
hird and fourth branchial anomalies are rare, with incidence
of type III 2% to 8% and type IV 1% to 2%. 143 hird branchial
apparatus anomalies originate at the base of the pyriform sinus
and pass above the superior laryngeal nerve (Fig. 48.41), whereas
fourth branchial anomalies originate at the apex of the pyriform
sinus and extend through the cricothyroid membrane and beneath
the superior laryngeal nerve. 143,147 hird and fourth anomalies
may manifest as a cyst in the lower anterior neck but more
commonly appear as a pyriform sinus or istula (Fig. 48.42). he
anatomy of the lesion is typically a let-sided tract (89%) extending
from the pyriform sinus to the anterior lower neck adjacent to
the thyroid. 148 Patients may have recurrent neck infection, abscess
(39%), or suppurative thyroiditis (33%). 101,148 On sonography,
the thyroid oten appears heterogeneous because of adjacent
inlammation. In some cases, an air-containing intrathyroid or
perithyroid cystic mass may be present, representing a complicating
abscess. 49 A barium swallow study or CT with oral barium
may be beneicial to deine the tract, usually inconspicuous on
sonography. 149