BRANCHIAL CLEFT CYSTS AND REMNANTS

Branchial cleft cysts are congenital epithelial cysts, which arise on the lateral neck from a failure of obliteration of the second branchial cleft in embryonic development.

EMBRYOLOGY

Brachial remnants (cysts, fistula, skin tags, chondrocuteneous vestige) are developmental anomalies of this system. Cervical chondrocutaneous branchial remnants are usually embedded in the anterior border of the sternocleidomastoid muscle and appear as skin tags.

At the fourth week of embryonic life, the development of 4 branchial (or pharyngeal) clefts results in 5 ridges known as the branchial (or pharyngeal) arches, which contribute to the formation of various structures of the head, neck, and thorax. The second arch grows caudally and ultimately covers the third and fourth arches. The buried clefts become ectoderm-lined cavities, which normally involute around week 7 of development. If a portion of the cleft fails to involute completely, the entrapped remnant forms an

These four arches are separated by four paired clefts and pouches.

1.   The first pharyngeal pouch gives rise to the eustachian tube, middle ear and mastoid cells.

2.    The second pouch forms the supratonsillar fossa.

3.    The third pouch develops into the thymus gland and upper parathyroid glands.

4.   The fourth pouch gives rise to the lower parathyroid gland and part of the thyroid gland.

 

LOCATION

There are four different types of cysts classified according to their location. Superficial cysts are found anterior to the sternocleidomastoid muscle. Cysts found anterior to the carotid artery and jugular vein are most frequently encountered. Another group of cysts are found extending to the pharynx and the final group are those cysts that extend between the vessels and the lateral wall of the pharynx.

The first branchial cleft cysts are generally located in the lower pole of the parotid gland and are often first noticed in middle age.

A branchial cleft cyst is the most common branchial abnormality with 80–90% arising from the second branchial cleft. Branchial cleft cysts can occur anywhere from the mandibular angle (tonsillar fossa) to the supraclavicular area

Anomalies arising from the third and fourth branchial cleft are uncommon but when present they present as fistulas of the pyriform sinus and abscesses.

 

ULTRASOUND

 

Uncomplicated cysts present as a recurrent, painless, fluctuant and non-tender neck mass often seen in later childhood and adulthood. Prentation in the fetus, although not common has been reported.

·        Well-defined anaechoic, thin wall cystic mass that displaces the carotid sheath medially or posterolaterally and the sternocleidomastoid muscle posteriorly or posterolaterally.

·        May uncommonly appear solid if the content is mucoid or contains cholesterol.

·        When infected, the cyst usually acquires a thick wall with echogenic debris within, in which case the cyst may then be surrounded by lymph nodes.

 

Case 1

Case 2

 

 

 

REFERENCES

 

1. Suchet I Ultrasonography of the fetal neck in the second and third trimesters. Part 3. Anomalies of the anterior and anterolateral nuchal region Can Assoc Radiol J 1995; 46:426-433