Branchial Cysts, Sinuses and Remnants

Embryology: Branchial arches are structures that appear in the fourth week of development on either side of the head and neck. Paired outpouchings from the inner lining of the early part of the mouth and throat along with clefts (inward indentations) appear along with muscular, nervous structures, and connective tissue in the neck area. Continued development in this area, from the outpouchings and from the clefts results in the ear canal, tonsil, throat structures, parathyroid glands and thymus. There are four distinct clefts, each giving rise to abnormalities if incomplete development occurs or there is a failure of these primitive structures to go away.

Of the branchial cleft anomalies, 75 percent arise from the second cleft, 20 percent from the first, and a few remaining from the third and fourth clefts (Figure 1).

Cysts (fluid-filled structures) developing from these structures usually present later in childhood than do sinuses (small openings that end blindly or attach to a cyst), while left over pieces of cartilage are usually found in infancy or at birth. A complete communication between the inside of the throat and outside of the skin is called a fistula. Fistulas from the second and third pouches exit the skin just in front of the large muscle in the neck, the sternocleidomastoid muscle. Mucus may be noted to come from a small opening and a fistula from here may go up through the neck until it ends in the region of the tonsil. These fistulas may be on both sides in 10-15 percent of the cases.

Any combination of sinus tract with cyst (small connection which connects with the skin on one end and the cyst on the other) or without cyst (blind ending connection) can occur between any location from the throat to the skin.

Abnormalities of the first branchial cleft present as a cyst or sinus lying behind the parotid gland, which is located at the back of the jaw in the neck and may not cause symptoms until adulthood. Left over cartilage from the second branchial arch are more common than those of the first and are usually found in the mid or lower neck. They may be attached to the skin, just under the skin, or in the muscle, and usually do not have a sinus with them. Appropriate treatment is surgical removal.

Cysts and sinuses from the third branchial cleft are uncommon. They occur in the same area as the second, but may enter the throat through a different course. Those of the fourth branchial cleft are rare and may present as abscesses in the lower part of the neck, on the left side usually more than the right, and may be associated with infection of the thyroid gland. Surgical removal may involve removal of the upper pole of the thyroid gland along with the connection that goes into the throat just to the side of the larynx, or voicebox, in what is called the pyriform sinus.

Diagnosis
The diagnosis of sinuses is based on visually seeing it and recognizing it. Clear mucus material may drain intermittently and can be expressed by pressing on the area. Blind-ending sinus tracts may appear as mere dimples in the skin and may be associated with a small piece of extra cartilage material. Cysts may not have an external opening. Such cysts often present in older infants and children as a mass, which may feel very much like a solid tumor and are distinguished by ultrasound showing a fluid-filled cystic mass, rather than a solid mass.

Treatment
Almost all branchial sinuses should be excised early in life (age 6 months), as repeated infection is common resulting in scarring that makes resection later more difficult. When infection does occur, antibiotic administration and, if necessary, incision with drainage of the cyst should occur before definitive surgery.

Articles and graphics adapted from O'Neill: Principles of Pediatric Surgery. © 2003, Elsevier.

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