What is Thyroglossal Duct Cyst?
Thyroglossal duct cysts are a common type of birth defect in the neck, with about 7% of the population having them. These cysts can develop in any part of the thyroid gland’s path, starting from the base of the tongue to the lower part of the neck. They often appear as small fluid-filled sacs in the middle of the neck, generally near the small U-shaped bone we call the hyoid bone.
What Causes Thyroglossal Duct Cyst?
A thyroglossal duct cyst is a lump that can form in the neck due to issues that happen when a baby is still developing in the womb. It starts from a part called the thyroglossal duct, which connects the tonge to the thyroid, a gland in your neck. This thyroid gland starts to develop in the third week of pregnancy, initially appearing near a part of the tongue known as the foramen cecum.
As the baby grows, the thyroid moves further down, going past the developing hyoid bone, another structure in the neck. By the time the baby is about seven weeks old, the thyroid is situated in its final position, lower down in the neck, in front of the trachea (the tube that carries air from your nose and mouth to your lungs).
The thyroglossal duct is a narrow tube that’s left behind following the thyroid’s journey. Its function was connecting the thyroid gland to the foramen cecum during development. In around half the population, a part of it becomes a portion of the thyroid gland called the pyramidal lobe. This duct usually disappears by the tenth week of pregnancy. However, if it doesn’t disappear completely, it can start to secrete fluid which can cause inflammation and potentially form a thyroglossal duct cyst.
Risk Factors and Frequency for Thyroglossal Duct Cyst
Thyroglossal duct cysts, which occur in approximately 7% of the global population, appear in both males and females equally. Most common in children, these cysts also appear in adults at different rates. They’re commonly associated with the hyoid bone, which is found in the neck. Their location can vary:
- About 20% to 25% occur above the hyoid bone (suprahyoid level).
- Between 15% to 20% are found at the level of the hyoid bone.
- And 25% to 65% are situated below the hyoid bone (infrahyoid level).
Signs and Symptoms of Thyroglossal Duct Cyst
Thyroglossal duct cysts are usually found as movable lumps in the middle of the neck, near a bone called the hyoid. Most of the time, they don’t cause any symptoms. Nonetheless, sometimes they can become infected, turning into an abscess, or start to drain fluid periodically. When the person sticks out their tongue or swallows, the lump moves up. These cysts are usually found at the same level as the hyoid bone or below it.
Testing for Thyroglossal Duct Cyst
If you or your child may have a thyroglossal duct cyst, imaging tests can help confirm this and check the health of the thyroid tissue. In some cases, if healthy thyroid tissue isn’t found in the lower part of the neck, this could mean lifelong thyroid medication is needed after surgery.
For this process, an ultrasound is usually the first step. Ultrasounds are great because they are widely available, affordable, and noninvasive. This means they don’t expose patients to radiation or require sedation, making them particularly safe for children. While CT scans and MRI scans can also be used to examine thyroglossal duct cysts and healthy thyroid tissue, usually an ultrasound is all that’s needed.
Some doctors may suggest a thyroid function test before surgery. This can be useful if thyroid tissue is expected to be in unusual places, but generally, research doesn’t recommend routine blood tests for simple thyroglossal duct cysts.
Treatment Options for Thyroglossal Duct Cyst
If you have thyroglossal duct cysts, which are abnormal growths in the neck, the best course of action is usually to remove them surgically. This is done mainly to prevent recurring infections and because there is a very small chance they could become cancerous. However, just removing the cysts often leads to them coming back in about half of all cases.
As a result, doctors usually prefer to use a procedure called the Sistrunk operation. By removing not just the cyst, but also the central part of a small bone in your neck called the hyoid bone, and a piece of the base of your tongue, the Sistrunk operation has shown to be much better at preventing the cysts from returning.
It’s important to note, however, that doctors will not perform the Sistrunk procedure if you have an ongoing infection. In this case, you would first be given antibiotics to clear up the infection, and the operation would be scheduled after you’ve recovered. Also, before surgery, doctors would check to see if you have any other functional thyroid tissue (a gland in your neck that produces hormones). Even if you don’t, the operation can still be done, but you might have to take hormone replacement therapy afterwards.
What else can Thyroglossal Duct Cyst be?
When doctors are trying to diagnose a thyroglossal duct cyst, they have to rule out other conditions that may display similar symptoms. Often, they will consider conditions related to midline neck masses, cystic neck masses, and even other cysts that can occur in the neck region. Remember, the final diagnosis often cannot be confirmed until detailed pathology tests are done.
- Cystic metastatic lymph nodes, which could potentially be a sign of thyroid cancer or squamous cell carcinoma in the upper throat
- Dermoid or epidermoid cysts, which can also be midline cystic neck masses
- Second branchial cleft cysts, which are found in the front of the neck but not related to the hyoid bone
Identifying the relationship of the cyst with the hyoid bone (a horseshoe-shaped bone in the front of the neck) helps doctors distinguish thyroglossal duct cysts from other neck cystic masses.
Surgical Treatment of Thyroglossal Duct Cyst
Less than 1% of the time, a type of cyst in the neck, known as a thyroglossal duct cyst, turns into cancer. The most frequently occurring type of cancer from these cysts is papillary carcinoma (92.1%), closely followed by squamous cell carcinoma (4.3%).
Thyroglossal duct cyst carcinoma, or cancer, usually shows up as a painless lump in the middle of the neck. Most of the time (73.3%), it’s discovered by chance during lab analysis after the cyst’s removal.
Usually, adults get diagnosed with this type of cancer, typically at an older age compared to those who only have the non-cancerous cyst.
The treatment for thyroglossal duct cyst papillary carcinoma usually involves a surgery called the Sistrunk procedure. This is followed by the doctor checking your neck lymph nodes and thyroid for possible spread of the cancer. Depending on how far the disease has spread, complete removal of the thyroid, surgery to remove the lymph nodes in the neck, and/or radioactive iodine treatment may be needed.
The good news is, the likelihood of recovery from this type of cancer is exceptionally high, with a survival rate of 99.4%. The chance of the cancer coming back is also low, at 4.3%.
What to expect with Thyroglossal Duct Cyst
After undergoing a type of surgery known as the Sistrunk procedure, patients usually have an excellent outcome. About 10% of patients who have this surgery for a condition called thyroglossal duct cysts might experience a return of the cyst. However, the chance of the cyst coming back is much higher if the surgery doesn’t involve removing the middle third of a small bone in the neck called the hyoid bone. It’s also worth noting that around 1% of these cysts turn out to be cancerous, which is usually only discovered after the cyst has been surgically removed.
Possible Complications When Diagnosed with Thyroglossal Duct Cyst
The primary complication that may occur following the Sistrunk procedure is a return of the thyroglossal duct cyst, which can happen in approximately 10% of patients. Factors that may contribute to this recurrence include incomplete removal of the cyst, rupturing the cyst during surgery, the surgeon’s skill and experience, and if there’s an infection present. Surprisingly, even when the surgery is performed without technical precision recurrence can still occur.
Another possible but highly uncommon complication from the Sistrunk procedure is injury to the larynx or the windpipe. This could cause problems with the airway, swallowing and voice quality. This can happen if the thyroid cartilage is mistakenly removed instead of the hyoid bone. It’s crucial to correctly identify the hyoid bone, thyroid cartilage, and the membrane between the thyroid and hyoid bones to prevent this issue during surgery.
Damage to the hypoglossal nerve (the nerve that controls tongue movements) is also very rare but has been reported after the Sistrunk procedure. This can result in half the tongue becoming paralyzed. The hypoglossal nerve travels on the outer side of the Hyoglossus muscle and the inner side of the Stylohyoid muscle near the lateral part of the hyoid bone. It’s critical to maintain the removal of hyoid bone towards the medial side of the lesser cornu (a structure on the hyoid bone) to avoid injury to the hypoglossal nerve.
Potential Complications:
- Recurrence of the thyroglossal duct cyst
- Injury to the larynx or windpipe, affecting airway, swallowing or voice
- Damage to the hypoglossal nerve resulting in partial tongue paralysis
Recovery from Thyroglossal Duct Cyst
After having the Sistrunk procedure, which is a type of surgery, patients are advised not to do any strenuous lifting for 2 to 6 weeks. The presence of a surgical drain is dependent on the size of the thioglossal duct cyst, which is a kind of noncancerous lump that occurs in the neck. If there’s a drain, it will typically be removed a few days after the operation. Painkillers or antibiotics might be prescribed to help with recovery after the surgery. Most people are usually able to go back to work or school about 1 week after the surgery.
