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  1. 1. Case Report #0640 Submitted by: Malisa Lester, M.D. Faculty reviewer: Emilio Supsupin Jr., M.D Date accepted: 3 January, 2010 Radiological Category: Principal Modality (1): Principal Modality (2): Neuro (Head and Neck) None CT
  2. 2. Case History 10 year old female presented to the emergency center for possible closed head injury following trauma.
  3. 3. Radiological Presentations
  4. 4. Radiological Presentations
  5. 5. Radiological Presentations
  6. 6. Radiological Presentations
  7. 7. Radiological Presentations
  8. 8. •Hematoma •Lingual thyroid •Suprahyoid thyroglossal duct cyst •Hemangioma Which one of the following is your choice for the appropriate diagnosis? After your selection, go to the next page. Test Your Diagnosis
  9. 9. The lower axial slices from a non-contrast brain CT demonstrates a focal midline hyperdensity in the posterior tongue base, measuring 1 cm and showing a lobular contour. The intracranial examination was negative. •Dermoid •Hemangioma •Lingual thyroid •Suprahyoid thyroglossal duct cyst Findings: Differentials: Findings and Differentials
  10. 10. Differential considerations for a midline mass in the oral cavity include: A thyroglossal duct cyst is a cystic mass along the course of the thyroglossal duct. They are most frequently seen either in the midline of the anterior neck at the level of the hyoid bone or within the strap muscles just off the midline. Classically, they have a thin wall and homogeneous attenuation with attenuation values corresponding to fluid (10-18 HU). Elevated attenuation values of cyst fluid reflect increased protein content and generally correlate with history of prior infections. A dermoid cyst classically appears as moderately thin-walled, unilocular mass. On CT, the central cavity is usually filled with a homogeneous, hypoattenuating (0-18 HU) fluid material. It may appear to be filled with “marbles”, due to the coalescence of fat into small nodules within the fluid matrix. The most common cervical location of a dermoid cyst is the floor of the mouth. The combination of the “sack of marbles” appearance and location in the submandibular or submental space is virtually pathognomonic of a dermoid cyst. A hemangioma is an infiltrative hypervascular mass, which may demonstrate calcifications (phleboliths) and may or may not be midline in location. Imaging findings characteristic of lingual thyroid are a round or oval, well-circumscribed midline or paramedian tongue mass, with density/intensity similar to normal thyroid tissue. The characteristic hyperdense appearance of the lesion on non-contrast CT is due to its iodine content. Discussion
  11. 11. Lingual thyroid. Given the midline location at the tongue base, the well circumscribed and characteristic hyperdense appearance of the mass without associated calcifications, fatty or cystic components, the most likely diagnosis is lingual thyroid. Diagnosis
  12. 12. A lingual thyroid is defined as thyroid tissue in an abnormal location in the tongue base or the floor of the mouth. Imaging characteristics of lingual thyroid include a well-circumscribed midline or paramedian tongue mass, with density/intensity similar to normal thyroid tissue. The most common location of a lingual thyroid is in the midline dorsum of the tongue, however, they may be less commonly found in the sublingual space or tongue root along the course of the thyroglossal duct. Lingual thyroid typically measures 1–3 cm and is usually round or ovoid in shape. On non-contrast CT, a lingual thyroid shows high density from iodine accumulation. Following contrast administration, avid homogeneous enhancement is seen. Lingual Thyroid
  13. 13. Picture of the mouth showing a raised, well circumscribed tissue at the base of tongue representing lingual thyroid (blue arrows) at the midline base of tongue (arrows) Courtesy of Dr. Soham Roy, Department of Otolaryngology Head and Neck Surgery UT Houston
  14. 14. Endoscopic view of the back of the oral cavity showing lingual thyroid (blue circle) Courtesy of Dr. Soham Roy, Department of Otolaryngology Head and Neck Surgery UT Houston Tonsillar pillar Tonsillar pillar
  15. 15. Lingual thyroid results from an arrest of the migration of the thyroid anlagen between the 3rd and 7th weeks of gestation. The arrest may be complete, resulting in no cervical thyroid (up to 75% of cases) or partial, with a cervical thyroid component in approximately 25% of cases. Patients who present with symptoms related to a lingual thyroid usually complain of dysphonia, throat fullness, or dysphagia. Rarely, infants can present with stridor or patients can present with hyperthyroidism. Additionally, a lingual thyroid can expand rapidly during puberty. Management of a lingual thyroid depends on the patient’s symptoms and may consist of follow-up with regular thyroid function tests for asymptomatic patients. Medical suppression therapy, radioiodine ablation, or surgical treatment may be employed for symptomatic patients. Lingual Thyroid
  16. 16. Courtesy of Dr. Edmund Kim, Department of Nuclear Medicine MD Anderson Cancer Center Ectopic thyroid may be multiple & may be found anywhere along the course of the thyroglossal duct. Nuclear medicine Tc-99m SPECT CT demonstrating multiple foci of ectopic thyroid tissues along the course of the thyroglossal duct [ ]
  17. 17. MR imaging of a lingual thyroid will demonstrate the following signal characteristics: T1: isointense to hyperintense compared to tongue musculature T2: isointense to hyperintense midline mass T1 post contrast: avid homogeneous enhancement Technetium 99m pertechnetate scan (preferred in children) or iodine 123 scan may be performed to confirm ectopic thyroid tissue. Lingual Thyroid
  18. 18. Teaching Points The characteristic increased density of a lingual thyroid [ ] on unenhanced CT is due to its iodine content. However, if CT is performed with contrast, the value of a radionuclide study is limited for several weeks following administration of iodinated contrast.
  19. 19. Teaching Points Scintigraphic study with iodine 123 or technetium 99m pertechnetate is an excellent modality in diagnosing lingual thyroid. Radionuclide scan shows a focal area of rounded increased activity at the level of the base of tongue. Most commonly, there is absence of uptake at the expected location of the thyroid gland as shown in this case. Courtesy of Dr. Soham Roy, Department of Otolaryngology Head and Neck Surgery UT Houston
  20. 20. Teaching Points
  21. 21. Teaching Points In more than 70% of cases, the lingual thyroid maybe the patient’s only functioning thyroid tissue. Sagittal & axial enhanced CT images of the neck [A & B] demonstrate a lingual thyroid (*). Axial and coronal CT images of the lower neck on the same patient [C & D] shows the absence of normal thyroid gland in its expected location at the lower neck. This case highlights the importance of evaluating for the presence of thyroid gland in its normal location. Removal of the lingual thyroid will render this patient permanently hypothyroid.
  22. 22. Grossman, R and Yousem, D. Neuroradiology: The Requisites, 2nd Edition. Elsevier Inc, Philadelphia, PA. 2003. Liess BD, et al. Arch Otolaryngol Head Neck Surg. 2007 Aug;133(8):835, 837-8. Pope, TL (ed). Aunt Minnie’s Atlas and Imaging Specific Diagnosis, 3rd Edition. Wolters-Kluwer Lippincott Williams and Wilkins, Philadelphia, PA. 2009. Som PM and Curtin HD (eds). Head and Neck Imaging vol. 2, 4th Edition. Mosby, St. Louis, Mo. 2003. Vazquez E et al. US, CT, and MR imaging of neck lesions in children. Radiographics 1995 January; 15:105 – 122. References