Europearl Journal

of Radiology, 11 ( 1990) 207-211 201

Elsevier

EURRAD

00073

MR findings in thyroglossal duct cysts: report of two cases Alfred0 Blandino l, Laura Salvi ‘, Emanuele Scribano 2, Gaetano and Ignazio Pandolfo2 ‘Institute of Oncology. and ‘Institute of Radiological Sciences,

(Received

Key words: Magnetic resonance

1 March 1990; accepted

imaging, thyroglossal

Chirico ‘, Marcello

Longo 2

University of Messina, Messina, Ita&

after revision 19 April 1990)

duct; Magnetic resonance cyst

imaging, hyoid; Thyroglossal

duct, MR; Thyroglossal

duct,

Abstract

Two patients with thyroglossal duct cysts have been studied with CT and MR. The typical CT feature of these cystic upper-neck lesions are depicted in literature, conversely MR findings are not well known. The homogeneous high intensity on Tl-weighted images, higher than simple cyst or fluid, is the most typical feature of the thyroglossal cyst.

Introduction Thyroglossal cysts are congenital midline benign cervical masses that arise from what remains of the thyroglossal duct [l-7]. CT features of these cystic neck lesions are well depicted in literature [ 8,9] ; however, to our knowledge, there are no reports about MR findings. The MR appearance of two thyroglossal duct cysts are presented.

images and a high intensity in the first T2 echoes, with progressive loss of signal intensity in later echoes (Fig. 2). At surgery a cystic mass of 4 x 7 cm was removed. The lesion was characterized by a thin wall lined by stratified squamous epithelium, and brownish mucoid fluid with few cellular elements (macrophages and RBC) and a high protein content (14 mg/ml). The final histological diagnosis was thyroglossal duct cyst.

Case 1

Case 2

A 36-year-old man came to our observation for a progressively enlarging mass in the midline of the upper neck and tongue base. Physical examination showed a smooth expansive lesion that moved with swallowing and tongue protrusion. CT showed a well circumscribed cystic lesion in the midline of the upper neck anterior to the hyoid bone, extending into the tongue base in a partmedian location (Fig. 1). Sagittal and axial MR showed a homogeneous pearshaped lesion with a slightly higher signal intensity than that of muscle and cerebral tissue on Tl-weighted

A 39-year-old man noted a progressively enlarging painless mass in the cervical region. CT showed a well circumscribed, low-density lesion, with a thin enhanced wall in the thyrohyoid region, posterior to the hyoid bone (Fig. 3). On the Tl-weighted axial and sagittal images, a homogeneous lesion with high signal intensity, intermediate among fat and cellular tissue, was shown (Fig. 4) with high intensity in all echoes on T2 images (Fig. 5). At surgery, a thin-walled cystic mass containing a straw-coloured fluid with a high protein content was removed. The histological diagnosis was thyroglossal duct cyst.

Address for reprints: Dr. Alfred0 Blandino, 98100 Messina, Italy. 0720-048X/90/$03.50

0

1990 Elsevier

Via Ducezio

Science Publishers

No. 7,

B.V. (Biomedical

Division)

Fig. 1. Case 1: Axial (a and b) and coronal (c) CT scans showed a cystic lesion anterior to the hyoid base, extending cranially in the tongue base.

Fig. 2. Case 1: Axial (a) and sag&al (b) Tl-weighted images (TR 400/TE 30). The mass shows a homogeneous intensity signal higher than the surrounding muscles. The sagittal multiecho images (c and d) (TR1800/TE 30,60,90, 120, 180,210,240) show a high signal intensity in the first echoes (c) with progressive loss of signal in later echoes compared with CSF (d).

Fig. 3. Case 2: Axial CT scan (a and b) demonstrate a well circumscribed cystic lesion located in the thyrohyoid region, anterior to the thyroid cartilage and posterior to the hyoid bone.

Fig. 4. Case 2: Axial (a) and sagittal (b) Tl weighted images (TR 450/TE 30). The thyroglossal similar to the subcutaneous fat.

Discussion The thyroid gland originates from the foramen cecum, situated at the junction between the anterior two thirds and posterior one third of the tongue. During its normal embryologic development, the thyroid descends as a bilobed diverticulum in front of the pharynx. The gland remains connected to the foramen cecum by a tubular structure: the thyroglossal duct, which normally disappears by the eighth to tenth week of life. If a

cyst is characterized

by a high signal intensity

portion of the duct persists, a cyst will occur as a result of the secretion of colloid-like material from its epithelial lining [l-7]. The thyroglossal duct is closely associated with the hyoid bone, so that the thyroglossal cyst may be located either anteriorly, posteriorly or within the hyoid bone [ 9,101. According to their location, the cysts may be classified as either suprahyoid (20%), at the level of the hyoid bone (15 %) or infrahyoid (65 %) [ 8, lo]. The typical CT features of these cysts are a well

Fig. 5. Case 2: (a, b, c and d) T2 images (TR 2000/TE 60, 120, 180, 240) with circular homogeneously high in all echoes.

circumscribed midline low-density lesion in the upper neck, closely related to the hyoid bone [8,9]. Conversely, MR findings are not well known. There are few reports on MR of thyroglossal cysts [8,11]. In our two cases, the cysts were characterized by a high signal intensity on the Tl-weighted images. The signal was higher than that of a ‘simple cyst’ and intermediate when compared to cellular and fat tissue. High intensity was also noted in the T2 images. The high protein content of the fluid was probably responsible for these features. It is known that proteins in water

surface oil. The signal intensity

of the cyst is

solution enhance spin-lattice relaxation and therefore shorten Tl [ 121. The fluid protein has a shorter Tl relaxation time than simple fluid, such as in CSF or other simple cysts, and is characterized by a signal intensity similar or slightly higher than that of normal cellular tissue on Tl images. Also, on T2 images protein fluid has a high signal intensity. We believe that demonstration of a midline upper neck lesion in the typical site of thyroglossal duct, with homogeneous high intensity on Tl-weighted images,

can confidently cyst.

be diagnosed

as a thyroglossal

duct

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