Diagnostic ultrasound ( PDFDrive )

1640 PART V Pediatric Sonography
Differential Diagnosis of Suprahyoid
Cystic Lesions
PAROTID SPACE
Branchial apparatus cyst type I
Parotid mucus retention cyst
Tumors with cystic components
Parotid abscess
Lymph node necrosis
Lymphatic malformation
SUBMANDIBULAR SPACE
Branchial apparatus cyst type II
Ranulae
Dermoid or epidermoid
Thyroglossal duct cyst
Vallecular cyst
Lymph node necrosis
Lymphatic malformation
below the level of the mylohyoid muscle, termed “plunging
ranulae.” 20 Rarely, the lesions are bilateral, and some large lesions
extend into the parapharyngeal space. Imaging of a simple ranula
on ultrasound demonstrates a unilocular cyst. If infected, the
lesion may show internal debris, poorly deined borders, and
adjacent inlammation (Fig. 48.20). hese lesions are managed
with intraoral marsupialization or surgical resection.
Midline lesions in the suprahyoid area include dermoid or
epidermoid tumors and thyroglossal duct cysts. A cyst of the
vallecula results from retained secretions in the mucous glands
of the pharyngeal wall. 78 hese cysts can be congenital or acquired
and can cause upper airway obstruction resulting in death. 79,80
he lesions are midline and on sonography appear as a hypoechoic
or an anechoic cystic mass, behind and below the tongue 81
(Fig. 48.21).
Masticator Space
Ultrasound is helpful in evaluating pathology in the masticator
space as well as excluding parotid gland involvement. he two
most common sot tissue masses to consider in the masticator
space are sarcomas and vascular malformations. It is important
to remember that the masseter and pterygoid muscles are oten
involved in venous malformations. 82 An uncommon homogeneous
mass to consider is benign hypertrophy of the masseter muscle. 74
However, tumor iniltration of the muscle from leukemia or
lymphoma can mimic hypertrophy; thus, clinical correlation is
essential (Fig. 48.22). In the presence of trauma, a hematoma
appearing as a hypoechoic area may be demonstrated. Inlammatory
lesions also may develop, including secondary or primary
myositis or osteomyelitis of the mandible, oten in the presence
of an infected tooth. Cellulitis and sot tissue abscesses may
accompany these infections. 15
INFRAHYOID SPACE
he infrahyoid deep cervical fascia is split into supericial, middle,
and deep compartments 7 (Fig. 48.23). he supericial layer at
this level is the suprasternal space, lying above the sternum and
anterior to the sternothyroid and sternohyoid muscles. he
visceral space is delineated by the middle layer of deep cervical
fascia. he visceral space contains the thyroid, parathyroid,
trachea, esophagus, paraesophageal lymph nodes, and recurrent
laryngeal nerve.
Thyroid Gland
Normal Anatomy
he thyroid gland originates as an outpouching in the foramen
cecum at the base of the tongue. he tissue descends by the
seventh week of gestation to lie anterior to the larynx and upper
A
B
FIG. 48.20 Ranula. Ten-year-old child with neck pain. (A) Well-deined lobular hypoechoic lesion containing debris but with acoustic enhancement
and lack of internal low centered between the right sublingual gland and loor of the mouth. (B) Coronal fat-saturated T1-weighted magnetic resonance
image after contrast showing the wall-enhancing cyst in continuity with the sublingual gland (arrow), plunging below the tongue.