THYROGLOSSAL CYST
Definition: It is regarded as Tubulodermoid arising from the persistent patent portion of the thyroglossal duct. It is the commonest midline swelling of neck during childhood and adolescence.
Aetiology:
Thyroglossal cyst is connected to the foramen caecum by remains of thyroglossal duct. Although the thyroglossal duct obliterates by the 8th to 10th week of gestation, occasionally it may remain patent. Thyroglossal cyst develops from persistent patent portion of the thyroglossal duct. Thyroglossal cyst can occur anywhere in the course of thyroglossal duct.
Pathology:
The cyst wall is lined by columnar epithelium sometimes squamous or cuboidal epithelium.
Contents:
Transparent jelly like material with cholesterol crystals.
Sites:
Anywhere between base of tongue and thyroid isthmus.
- Subhyoid (most common).
- Suprahyoid.
- Region of thyroid cartilage.
- At level of cricoid cartilage.
- Floor of mouth.
- In substance of tongue.
Clinical features:
1)Age:
a) Majority occurs in children younger than 10 years age, but it can occur at any age.
b) Patient may present with a painless lump in the midline of neck.
2) Inspection:
a) A swelling at the lower border of hyoid in midline or usually a little to the left.
b) Along long axis of neck.
c) Overlying skin is free and normal is color.
3) Palpation:
a) Fluctuant.
b) Transillumination: Rarely positive.
c) Swelling moves with deglutition and protrusion of tongue.
Diagnosis:
Diagnosis of a thyroglossal duct cyst is usually done by a physical examination. It is important to identify whether or not the thyroglossal cyst contains any thyroid tissue producing thyroid hormones.
Diagnostic procedures for a thyroglossal cyst include:
Type | Definition |
Blood testing of thyroid function. | |
Ultrasonography | Image capture of the degree of mass and its surrounding tissues including the thyroid gland. |
Thyroid Scan | Radioactive iodine or technetium (a radioactive metallic element) is used in this procedure to show any abnormalities of the thyroid. |
Fine Needle Aspiration | The removal of cells for biopsy, using a needle. |
CT scan | CT is often utilized only as a complementary technique for confirmation of diagnosis or for assessing complications. |
Treatment:
Sistrunk’s operation: Total excision of cyst or fistula with removal of central portion of the hyoid bone and core of tongue tissue around the tract in the suprahyoid tongue base to the foramen caecum.
Steps of Sistrunk’s operation:
- Patient positioning- The patient is placed in the supine position with a pillow under the shoulders and the head resting on a rubber headrest. The endotracheal tube can be inserted via the nose. Surgical drapes expose the midline part of the neck from the mandibular symphysis to the manubrium sterni. Access to the oral cavity can be left free when guidance with a finger is necessary during the operation.
- Incision- The horizontal incision, measuring a maximum of 5 cm, is situated at the midpoint between the superior edge of the thyroid cartilage and the hyoid bone. Dissection is performed with fine scissors, while staying clear of the lesion to avoid rupturing the cyst. By slightly ascending the cyst, the scissors expose the infrahyoid strap muscles. Dissection is continued by opening the linea alba and inferiorly as far as the isthmus of the thyroid and identification of a pyramidal lobe, when present.
- Resection of cyst and hyoid bone- Dissection is performed from below upwards, from the pyramidal lobe, when present, to the hyoid bone, with resection of prelaryngeal adipose connective tissue. The cyst is generally adherent to the inferior part of the hyoid bone. The body of the hyoid bone is resected en bloc with the cyst, after having released its superior and inferior muscle attachments. The thyroglossal duct is very rarely visible and is therefore dissected according to its theoretical course by resecting a cone of muscle, in which the inferior base corresponds to the body of the hyoid bone and the apex corresponds to the foramen caecum. The thyroglossal duct is then ligated before being sectioned.
- Drainage and closure- Hemostasis is ensured with bipolar coagulating forceps after having washed the cavity with physiological saline. The greater cornu of the hyoid bone and strap muscles are sutured with resorbable suture material. The incision is closed in subcutaneous and cutaneous planes after having inserted a suction drain. Skin closure can be performed by subcuticular running sutures (resorbable or non-resorbable monofilament suture material).
There are several versions of the Sistrunk procedure, these includes:
- Classic sistrunk operation: It includes excision of the center of the hyoid bone along with a thyroglossal duct cyst with removal of one-eighth inch diameter core of tongue muscle superior to the hyoid at a 45 degree angle up to the foramen caecum to include mucosa and removal of one-quarter inch of the center of the hyoid bone.
- Modified sistrunk operation: The dissection is done through the tongue base but not through the mucosa. The modified Sistrunk procedure is the procedure of choice in both primary and revision cases.
- Hyoid cartilage division: In cases where ossification of the hyoid bone is not mature, the non-fused cartilage portion can be divided by monopolar electro-cauterization or scissors.
Simple excision of cyst without removal of its tract leads to recurrence.
Complications:
- Recurrent infections when swelling increases in size and becomes painful.
- Fistula.
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