Radionuclide Thyroid Scintigraphy and Computed Tomography in the Evaluation of the Thyroglossal Duct Cyst

Abstract

甲狀腺舌導管囊腫在臨床上之診斷並無多大困難，在孩童期間常因舌骨與甲狀軟骨間 之頸中線出現囊腫而被發現。因易發生感染，故應及早切除，同時作組織學診斷。治 療前的評估檢查包括：側面頸 部X光片或乾式X光像，甲狀腺功能檢查，超音波掃描 、甲狀腺放射性 同位素掃描及電腦斷層掃描（C.T.）。本篇報告1986年元月至1987 年 5月間由本院耳鼻喉科門診經臨床診斷為甲狀腺舌導管囊腫的17位患 者至本科接 受甲狀腺同位素掃描及電腦斷層攝影。其電腦斷層檢查結 果顯示正確診斷率達93%（ 13/14），只有一例偽陽性的個案。甲狀腺 同位素掃描對於診斷率無法與電腦斷層攝 影相比，唯對異位性甲狀腺 組織的偵測及功能之測定是電腦斷層攝影所無法取代的 。因此，這兩 種檢查應為相輔相成，並無重覆或相抵觸。在電腦斷層攝影方面本研 究發現，過去有關文獻所未提及之電腦斷層攝影之特異性徵象---即 一管狀組織由舌 底延著前頸部中線伸展到甲狀腺 ，並伴隨著一個周邊 顯影之囊腫，此正是一個典型 之甲狀腺舌導管 囊腫的特異性病理變化 。The thyroglossal duct cyst originates from the epithelial remnants of the thyroglossal tract which invaginates at the dorsum of the tongue, that represents the primary analog of the thyroid gland. Conventional radiographic findings are usually negative since it is a cyst. Seventeen cases with clinical impression of thyroglossal duct cyst were referred for preoperative evaluation by radionuclide thyroid scintigaphy and computed tomography (CT ). As a final result, 14 cases were surgically and pathologically proved to be thyroglossal duct cyst ( including 2 cases of recurrence). The rest 3 cases were found to be nodular goiter 1 case; papillary carcinoma 1 and normal thyroid tissue 1. We found that radionuclide thyroid scintigraphy is not accurate in the diagnosis of thyroglossal duct cyst as compared with CT which showed an accuracy rate of 93% (14/15) with only one false- positive as in the case with mere normal thyroid tissue. The computed tomographic appearence of thyroglossal duct cyst is rather characteristic with cystic appearence ( pure cystic 7 /15; multiseptated cyst with lobulations 1/15; septated cyst 8/15 ; and one with tubular 1/15), and peripherial enhancement after intravenous contrast medium administration. Most of the lesions are at midline (11/15), and only 6 at slight lateral positon. We found that it is a pathogonomic CT finding for thyroglossal duct cyst whenever a tubular cystic structure extending from tongue base along the midline of the anterior neck to the thyroid is demonstrated.