ANOMALIES OF THE ANTERIOR NUCHAL REGION

• Most normal structures of the anterior neck, especially the thyroid gland, carotid sheath, upper airway and trachea are small and barely visible. Abnormalities arising anteriorly therefore usually evident although rarely encountered.
• Fetal neck is usually held in a neutral position; marked hyperextention (in the absence of iniencephaly or torticollis) warrants a careful search for an anterior or laterally situated mass.
• Detection of anteriorly situated lesions are important as even small lesions can compress the airways necessitating urgent post natal intubation.
• Antenatal differentiation, although not always possible, is based on:
1. Position of the lesion.
2. Sonographic characteristics: solid, cystic, mixed, calcified or vascular.
3. Relationship to the major vessels of the neck.
4. Associated abnormalities - polyhydramnios, fetal tumor elsewhere eg adrenal gland, or bony abnormalities.

CENTRAL MIDLINE ANTERIOR NUCHAL LESIONS

S – SOLID; C – CYSTIC; M - MIXED

Lesion	Ultrasound Appearance		Relationship to jugular v. and carotid artery	Other comments
	S/C/M	Other features
Goiter	S	Fetal tachycardia IUGR, advanced bone age.	Anteromedial	Associated with maternal thyrotoxicosis or congenital cretinism.
Thyroid Cyst Text -Fetal Goiter	C		Anterior	Associated with maternal thyrotoxicosis. May arise laterally and be confused with a branchial cleft cyst.
Teratoma	S C M	± calcium. Marked neck hyperextention Polyhydramnios (30%)	Anteromedial	Enlarges rapidly. Vascular but no venous lakes helps distinguish from hemangioma. 80% die without post- natal resection.
Thyroglossal duct cyst (34-37)	C	Located below mandible but is otherwise similar to lymphangioma	Anterior or anteromedial	75% midline 25% lateral to midline DDX branchial cleft cyst.
Laryngocele	C		Medial	Indistinguishable from thyroglossal duct cyst
Hygroma	C	Usually non septated No hydrops	Anterior	Usually isolated Resolves spontaneously No relationship to Aneuploidy or XO.
Tracheal stenosis atresia.	S C	Polyhydramnios Echogenic lungs	Medial	Trachea usually visualized, as it is fluid filled.
Hemangioma (33,34)	S C M	Color flow on pulsed doppler	Usually anterior	MRI helful in planning treatment
Lingual lymphangioma (35,36)	C M	Appearance dependent on ehich subtype predominates (capillary;cavernous;cystic hygroma).	Anaterior	Thin walled multiseptated hypoechogenic mass. Size varies from small collections of fluid to large cysts.
Cervical meningocele / anterior encephalocele (34-36)	C	Spinal defect may be difficult to demonstrate antenatally.
Congenital epulis (38-39)	S	Single or multiple Found on maxillary alveolar ridge or mandible		Congenital gingival granular cell tumor Benign intraoral tumor Cases have only been detected in late second or third trimester.
Congenital ranula (38-40)	C	Indistinuishapble fro other cystic lesion by Sonography alone		Dilatation of the sublingual and submandibular ducts in the floor of the mouth. Classified according to location: Simple ranulas – floor of the mouth. Cervical ranulas – paracervical region Plunging ranulas – near the superior airways
Intra-oral duplication cysts (41-43)	C	Tend to occur in the floor of the mouth.		1.8% of alimentary tract duplications were noted in the cervical region in one study. May not be diagnosed for years if they are small and symptomatic.

FETAL GOITER (9-15)

Antenatal diagnosis is essential as timely recognition and treatment is essential to achieve normal growth and neurological development. Untreated fetal hypothyroidism may result in mental retardation, language, motor and spatial problems, growth retardation, congenital heart block and delayed skeletal maturation.

A large fetal thyroid gland may also result in fetal malposition due to hyperextension of the neck, tracheal obstruction, esophageal compression and polyhydramnios, neonatal asphyxia and death.

Risk factors for fetal goiter (goiter in the fetus may be due to either hypothyroidism or hyperthyroidism):

1. Previous medical therapy for hyperthyroidism.

2. Previous high dose irradiation of the neck.

3. Thyroid autoimmune disease (thyroiditis).

4. Family history of thyroid disease.

5. Treatment with amiodarone.

6. Type I maternal diabetes mellitus.

7. Hypopituitarism.

Fetal Hypothyroidism:

Transient fetal hypothyroidism is most frequently associated with maternal ingestion of anti-thyroid drugs (propylthiouracil –PTU; carbimazol; I-131 in pregnant women).

Fetal Hyperthyroidism is usually secondary to maternal autoimmune disease. In Graves disease the mother produces several IgG thyroid stimulating immunoglobulins which can cross the placenta and cause fetal hyperthyroidism.

CERVICAL TERATOMA

Fetal teratomas consist of ectodermal, endodermal and mesodermal germ-cell tissue including central nervous tissue. Mature and immature teratomas are distinguished by the degree of differentiation of the tissue.

Cervical teratomas in the fetus are rare. They have an incidence of 1 in 20 000–40 000 live births and account for about 6% of all fetal teratomas (16-18). Airway obstruction in the newborn because of tracheal compression or occlusion has been reported as the cause of an 80–100% mortality rate in untreated cervical teratomas in the neonatal period(19-21). Other researchers in the last decade have reported mortality rates of approximately 20–30% (22-24).

Usually fetal cervical teratomas are considered benign; however, the malignant transformation of fetal cervical teratomas has been reported (20).

ULTRASOUND

- The sonographic findings of cervical teratomas typically include solid and cystic structures within a heterogeneous mass mass.

- In up to 50% of cases calcifications might be seen within the mass while cartilage or bone tissue is less common (25).

- Polyhydramnios due to impairment of fetal swallowing might be seen in up to one third of the cases.

- The extent of vascularization can be assessed by Doppler flow imaging.

- Magnetic resonance imaging has also been described as providing essential information about the diagnosis and the anatomy of giant fetal neck masses and the adjacent airway (26).

ASSOCIATED MALFORMATONS

Associated malformations are rare, although there have been reports of lung and upper airway hypoplasia (19, 23).

DIFFERENTIAL DIAGNOSIS

- cystic hygroma,

- lymphangioma,

- hemangioma

- cervical meningocele

- thyroglossal duct cyst

- esophageal diverticula

- dermoid cyst

- brachial cleft cyst

- epignathus

- congenital goiter.

OUTCOME

Jordan and Gauderer reviewed 194 cases of fetal teratoma without regard to the prenatal diagnosis (20). They reported an overall mortality of 37% with 15% of the cases being stillborn or moribund at delivery. Fifty-one percent of the fetuses were born with severe respiratory distress and 43% of those fetuses subsequently died. Furthermore, in 13% of cases that underwent surgery, the newborns died from surgical complications or metastasis. In 2% of the 194 cases the teratoma was malignant^.

According to more recent literature the reported mortality and morbidity of cases with fetal teratoma has decreased (22): the mortality rate has decreased to 18% and in only 33% of cases was severe respiratory distress present at delivery. Mortality due to operative treatment has reduced to 4%. Whether improved prenatal and perinatal management or bias due to selection of reported cases accounts for these data has to be established.

Axt-Fliedner and Hendrik (27) report the unfavorable outcome of a fetus with a giant teratoma which extended to the anterolateral right aspect of the neck and thorax. After Cesarean section a patent fetal airway could not be established.

LARYNGEAL CYSTS (48-54)

Laryngeal cysts in children:

• Aryepiglottic cysts represent the most common
• Vallecular cysts or pre-epiglottic cysts are lesscommon

Vallecular cysts (mucous retention cyst, epiglottic cyst, base-of-the-tongue cyst and more recently ductal cyst.

• Benign, but may cause airway obstruction and even death if not treated appropriately (a mortality rate of about 40% in children has been reported.
• They are unilocular, of variable size arising from the lingual surface of the epiglottis and containing clear, non-infected fluid.
• Probably result from obstruction of mucous glands at the base of the tongue.
• They are lined with mucous glands and therefore as mucous secretion continues the lesion gradually increases in size.
• Vallecular cysts with respiratory epithelium are rare.
• Embryology:

o The respiratory system appears as an endodermal outgrowth from the ventral wall of the foregut immediately caudal to the hypobranchial eminence (when the embryo is approximately 3 weeks old).

o The ventrally placed respiratory bud then becomes separated from the dorsal portion, the esophagus, except at the entrance to the larynx, where it maintains its communication with the foregut through the laryngeal orifice.

o The remaining part of the gut contributes to the development of the stomach and duodenum, just caudal to the liver.

o Because of the proximity of the primitive gut and the pharyngeal arches, which contain the developing tongue, embryonal remnants of the gut may appear in the tongue. These epithelial remnants may subsequently contribute to the development of cystic lesions of the tongue.

· Vallecular cysts are rarely associated with other fetal anomalies.

· Complications include polyhydramnios; pulmonary hypoplasia; trachea, cervical vessels and hypoglossal nerve compression.

· Differential Diagnosis – see table above.

CONGENITAL RANULA (29-30)

• Results from a dilatation of the sublingual or submaxillary gland ducts in the floor of the mouth.
• These pseudocysts are normally located in the sublingual space between the mylohyoid muscle and the lingual mucosa, and can be classified according to their localization:
• simple ranulas (in the floor of the mouth)
• cervical ranulas (in the paracervical area)
• plunging ranulas near the superior airway.
• ultrasonographically they are indistinguishable.

MUCOCELES (31)

• Mucoceles of the oral cavity refer to collections of mucus resulting from obstruction of, or leakage from a major or minor salivary gland.
• Mucoceles occur commonly in the oral cavity, typically on the lower tip but also in unusual locations, such as in young patients.

HETEROTOPIC GASTROINTESTINAL CYST (32)

· Intra-oral duplication cysts of the alimentary tract are rare. They tend to occur in the floor of the mouth or within the tongue.

· 1,8 % of alimentary tract duplications were noted to be in the cervical region. They are usually diagnosed in the newborn period but may be undetected for years if asymptomatic and small.

VALLECULAR CYSTS (44-48)

· Sporadic. 

· Most likely result from obstruction of mucous gland at the base of the tongue.

· Lined with mucous glands and with continued mucous secretion, the lesion gradually increases in size.

· Vallecular cyst is considered to be more common in adults than children.

• Because of the proximity of the primitive gut and the pharyngeal arches, which contain the developing tongue, embryonal rests of the gut may become misplaced in the developing tongue. It is believed that these epithelial remnants may subsequently contribute to the development of cystic lesions of the tongue.

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