What is Branchial Cleft Cysts?
Branchial cleft cysts are harmless growths that form before birth and make up about one-third of all growths found in the neck at birth. These cysts can appear at any age and are usually located along the front edge of the sternocleidomastoid muscle, which is a muscle on the side of your neck. Most of these cysts are classified as ‘second branchial cleft cysts’. They typically become noticeable after an infection in the upper part of the respiratory system (like a cold or flu). The size of the cyst often changes, getting larger and smaller in line with the progression and treatment of the infection.
What Causes Branchial Cleft Cysts?
Branchial cleft cysts are a type of growth that forms when cells from a structure in your neck, called the cervical sinus, get trapped and form a pocket or cyst. This cyst is lined with tissue known as epithelial tissue. Branchial cleft cysts can also form from leftover tissue from a group of tonsils in the throat known as Waldeyer’s ring. It’s not always pure branchial cleft cysts that form; sometimes they can be mixed or combined with other types.
To understand how these cysts form, we need to look at the early stages of pregnancy. During the fourth week of a baby’s development in the womb, certain structures form in the neck region. These are known as branchial (pharyngeal) clefts and they are important because they contribute to the formation of the head, neck, and upper chest. They form six arches that create outside grooves and inside pouches in the body. These pouches are linked to wings on either side and are lined with endoderm, which is a type of tissue. The arches are lined with mesoderm, another tissue type, and the outsides are lined with ectoderm.
Each of these arches have certain structures and nerves associated with them. The nerves generally run in front of the artery associated with each arch. The only exception is the sixth arch where the nerve runs behind the artery. Let’s break it down:
The first arch, also known as the mandibular arch, is connected to the trigeminal (V) nerve and a part of the artery that degenerates. The second arch is connected to the facial (VII) nerve and a part that degenerates of the second aortic arch. If this part doesn’t go away, a stapedial artery persists. The third arch is connected to the glossopharyngeal nerve (cranial nerve IX), and the common and internal carotid arteries. The fourth arch is connected to the superior laryngeal nerve (a branch of the vagus (X) nerve), the aorta on the left, and the proximal subclavian artery on the right. The fifth arch doesn’t develop fully and tends to degenerate. The sixth arch gives rise to the pulmonary artery and the ductus arteriosus on the left. It also gives way to a branch of the vagus (X) nerve, the recurrent laryngeal nerve. Lastly, the 12th cranial nerve lies beneath all the arches.
Risk Factors and Frequency for Branchial Cleft Cysts
Branchial cleft cysts are the main reason for birth-related neck lumps, making up about one-third of all such lumps. They are the most common type of lump found on the side of the neck, with 2% to 3% appearing on both sides. Although these cysts occur more often in people with a family history of them, they do not favor any particular gender or racial group. They are usually discovered during childhood, but adults can also have them.
Signs and Symptoms of Branchial Cleft Cysts
A branchial cleft cyst is usually a soft, painless lump on the side of the neck. However, it can become inflamed, painful, and potentially filled with pus during an upper respiratory infection.
There are four different types of branchial cleft cysts, each with their unique features:
- First branchial cleft cysts: This category takes up 5% to 25% of all branchial cleft cysts and has two subtypes – Work’s Type I and Type II. A Type I cyst shows up as a cyst near the ear (preauricular). This type of cyst runs parallel to the external ear canal and ends in the middle ear. The Type II cyst can be found along the lower jaw (mandible), near the ear or under the jaw. These are more common and contain both outer and middle layers of embryonic tissue. These cysts end within or near the ear canal.
- Second branchial cleft cysts: This is the most typical type, accounting for up to 95% of all branchial cleft cysts. These run between the internal and external carotid arteries and end in the tonsillar fossa (if there’s an associated sinus). They are found deep to the second arch derivatives and superficial to the third arch derivatives.
- Third branchial cleft cysts: These cysts are more commonly found on the left side, in the lower part of the front of the neck. They may appear as an abscess, neck mass, or thyroid inflammation. These cysts run superficially to the tenth cranial nerve and the common carotid artery, and deep to the ninth cranial nerve. If a tract is present, it passes through the thyrohyoid membrane above the superior laryngeal nerve and opens into the upper piriform sinus.
- Fourth branchial cleft cysts: These are rare and usually present as a low neck mass, beneath the platysma muscle, in front of the sternocleidomastoid muscle. The tract of a fourth branchial cleft cyst loops around the twelfth cranial nerve, runs behind the common carotid artery and thyroid, and then runs through the cricothyroid membrane below the superior laryngeal nerve. It then drains into the apex of the piriform sinus.
Knowing the specific features of each cyst can help medical professionals in diagnosing and treating these conditions.
Testing for Branchial Cleft Cysts
There are a few different medical imaging methods used to identify a branchial cleft cyst, a type of benign (non-cancerous) growth that develops in the neck or throat. Ultrasound, computed tomography (CT) scanning, and magnetic resonance imaging (MRI) are three common techniques.
Ultrasound imaging can be useful for detecting larger cysts. Similarly, a CT scan with a special dye (contrast) can reveal a cyst, which typically appears as a well-defined, radiating area. Additionally, CT scans can help doctors identify structures both below and above the cyst, which can provide more insight into the specific type of branchial cleft cyst.
An MRI with a contrast agent called gadolinium can help highlight a branchial cleft cyst, making it stand out more clearly in the images. MRI is typically more effective for assessing a particular type of branchial cleft cyst known as type II first branchial cleft cyst. This is because the MRI provides a better view of the parotid gland (a major salivary gland located in front of your ears) and any neighbouring nerve structures, which could be involved with the cyst.
Treatment Options for Branchial Cleft Cysts
The treatment for a branchial cleft cyst, which is a type of noncancerous lump, typically involves a complete surgical removal. If a cyst is discovered when an infection is present, it’s advisable to wait until the infection clears up before scheduling the operation. Doctors tend to avoid opening and draining the cyst if possible, as this can make complete removal harder later on.
For certain types of branchial cleft cysts, known as third and fourth branchial cleft cysts, a partial removal of the thyroid gland might be required. In such cases, the doctor may use a tool to directly view any openings in the pyriform sinus, a part of the throat, as this can help locate the cyst. Some experts believe that simply using heat (a procedure called cautery) to treat the portion of the pyriform sinus connected to the cyst can effectively manage third and fourth branchial cleft cysts.
What else can Branchial Cleft Cysts be?
Certain conditions might look alike, so it’s important to correctly identify them. These conditions include:
- Hemangioma (a benign tumor of blood vessels)
- Ectopic thyroid or salivary gland tissue (where the tissue is located in an unusual place)
- Lymphadenopathy (enlargement of lymph nodes).
Possible Complications When Diagnosed with Branchial Cleft Cysts
Possible Side Effects:
- Infection
- Formation of pus-filled areas
- Damages to nearby nerves during removal