In order to understanding these anomalies it should be first known the development of thyroid gland
Development of thyroid gland
the thyroid gland develops from the thyroglossal duct (median bud of the pharynx) during the fourth embryonic week and passes ventrally from the foramen caecum at the back of the tongue to the pharynx just below the position of the developing hyoid cartilage . this line of descend is called the thyroglossal duct thus formed usually degenerates but it is incomplete regression results in the following
which are rarely evident at birth as
which 1- may occur with patent or closed thyroglossal duct 2- may occur at any age but 40%present in the age group 0-10 years 3- incidence :male = female 4- midline usually but may deviate slightly 5- commonest midline cervical tumour in infants 6- does not usually transilluminate 7- usually situated above or below the hyoid bone 8- moves up on protrusion of tongue it is lined by squamous or ciliated pseudostratified epithelium and may contain thyroid or lymphoid tissue which may be dysplastic in the wall .
the diagnosis is made on clinical grounds but many surgeons request an ultrasound or radioisotope scan preoperatively to exclude ectopic thyroid tissue
this is not congenital but results from infection in or inadequate excision of a thyroglossal cyst it is 1- midline orifice with tract leading cranially 2- cresentic fold of skin (concavity faces down) at skin orifice 3- mucopurulent discharge 4- recrrent infection 5- lined by columnar epithlium
Treatment by Sistrunk,s operation this is the operation of choice for thyroglossal cyst and sinus a transverse incision is made over the cyst (transverse elliptical incision around the mouth of a sinus)and the tract followed up between the strap muscles to the hyoid bone . the tract , duct cyst or sinus is then excised with the central portion of the hyoid bone to prevent the recurrence . for suprahyoid cysts or sinuses . the tract should be followed to the base of the tongue
lingual and aberrant thyroid
A lingual thyroid gland
Represents failure of descend of part or all of the embryonic thyroid gland from the foramen caecum . in most cases it represents the only thyroid tissue present . it may remain symptomless or develop any of the recognized thyroid abnormalities . clinical problem occur most commonly in young women when physiological hypertrophy at time of pregnancy or development of an adenoma occur .
Symptoms and sign
Include 1- dysphagia 2- speech impairment 3- respiratory obstruction 4- haemorrhage 5- smooth vascular dark red projection at the base of the tongue
Excision is required if malignant change occurs
a papillary thyroid carcinoma