Transoral Robotic Excision of Ectopic Lingual Thyroid: Case series and literature review Prisman, E; Patsias, A; Genden EM** Corresponding Author: Eitan Prisman MD FRCSC [email protected] Clinical Assistant Professor, Division of Otolaryngology Head and Neck Surgery Vancouver General Hospital, University of British Columbia. Gordon & Leslie Diamond Health Care Centre 4th Floor‐2775 Laurel Street, Vancouver, British Columbia Canada V5Z 1M9 Phone Number: 604‐875‐4126 Fax Number: 604‐875‐4221 Alexis Patsias MD [email protected] Senior Clinical Research Coordinator The Icahn School of Medicine at Mount Sinai The Mount Sinai Medical Center Department of Otolaryngology Mount Sinai School of Medicine One Gustave Levy Place ‐ Box 1189 New York, NY 10029‐6574 Eric M. Genden MD, FACS [email protected] Professor and Chairman Otolaryngology‐ Head and Neck Surgery Professor of Neurosurgery and Immunology The Icahn School of Medicine at Mount Sinai Director of the Head Neck and Thyroid Center The Mount Sinai Medical Center Department of Otolaryngology Mount Sinai School of Medicine One Gustave Levy Place ‐ Box 1189 New York, NY 10029‐6574 P ‐ (212) 241‐2258 F‐ (212) 831‐3700
Key Words: Transoral Robotic Surgery, Lingual thyroid, minimally invasive, minimal morbidity.
This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as an ‘Accepted Article’, doi: 10.1002/hed.23757
Abstract Background: Surgical excision of an ectopic lingual thyroid has traditionally been associated with significant morbidity and has therefore been reserved for patients with severe obstructive symptoms or suspected malignancy. Transoral Robotic Surgery (TORS) has provided a minimally invasive approach to completely and safely excise ectopic lingual thyroid. Methods: Three index cases were identified from the detailed clinical database of TORS patients. A systematic review of the management of ectopic lingual thyroid in the English literature was performed. Results: TORS assisted excision of a lingual thyroid gland was successfully performed in 3 patients with excellent functional outcomes. Conclusions: TORS assisted excision of an ectopic lingual thyroid is a safe and feasible treatment modality with minimal morbidity, and in experienced hands, should be offered as a valid treatment for this pathology.
Introduction The presence of ectopic thyroid at the tongue base, termed a lingual thyroid, is a rare congenital anomaly resulting from the incomplete descent of the thyroid gland from the foramen cecum to the neck during week 4‐7 of embryogenesis.(1) The reported rate of lingual thyroids is approximately 1 in 200,000 and increases to 1 in 6,000 in patients with thyroid disease.(2) The majority of ectopic thyroids are asymptomatic and do not require treatment. However, a minority of patients develop obstructive symptoms including dysphagia, dysphonia, bleeding, dyspnea or obstructive sleep apnea.(1, 3) Traditionally, surgical intervention has been reserved for symptomatic patients failing conservative therapy.(4) The thyroid gland forms in week 4 of embryogenesis from a median endodermal thickening at the base of the pharynx forming a thyroid diverticulum and then descends via the thyroglossal duct to its final position anterior to the trachea by week 7.(5, 6) Therefore, ectopic thyroid tissue can be found anywhere along this tract of decent from the foramen cecum to the isthmus. Classically, the lingual thyroid is present at the base of tongue in the midline between the circumvallate papillae and the epiglottis.(4) Transoral surgical access to the tongue base, and intraoperative visualization of the ectopic thyroid tissue is challenging and therefore a multitude of open surgical approaches have been described including a midline labiotomy, madibulotomy, tongue‐split or cervical pharyngotomy approach.(7‐9) Transoral robotic assisted surgery (TORS) is an emerging minimally invasive approach to the oropharynx and hypopharynx with decreased morbidity that provides
exceptional three dimensional visualization and instrument navigation.(10) Three cases of TORS excision of lingual thyroid gland are presented and the surgical technique described. Case1: A 27‐year old female with a prior history of hypothyroidism and celiac disease presented with a two months history of progressive dysphagia, intermittent shortness of breath and gastroesophageal reflux. On examination, a 4 cm midline symmetric mass at the base of the tongue with an unremarkable overlying mucosa was visualized. Partial oropharyngeal closure was noted during deglutition. Computed tomography demonstrated an enhancing 4 x 4 cm midline mass consistent with a lingual thyroid, with an absent cervical thyroid gland. Initial conservative management with thyroid hormone replacement did not relieve her symptoms. Case 2: A 24‐year‐old female presented with a two‐year history of progressive dysphonia, dysphagia, odynophagia and gastroesophageal reflux. Family history was significant for a sibling with thyroid agenesis. Oral cavity examination revealed a tongue base mass obstructing the oropharynx with no palpable cervical thyroid tissue. Fiberoptic examination demonstrated a large smooth base of tongue mass with a compromised oropharyngeal airway. An MRI revealed a small thyroid gland in the normal position with a large base of tongue mass consistent with a lingual thyroid. A radioactive iodine scan confirmed uptake at the tongue base and anterior trachea. Conservative medical management failed to relieve her obstructive symptoms. Case 3:
A 54‐year‐old female with a longstanding history of hypothyroidism, progressive voice changes, snoring and obstructive sleep apnea presented with a two month history of shortness of breath and dysphagia. In addition she was unable to tolerate intubation for an elective surgical procedure due to a large base of tongue mass. Fiberoptic examination demonstrated an extensively large midline tongue mass consistent with a lingual thyroid. Computer tomography of the neck revealed a 6cm x 4cm base of tongue mass with no cervical thyroid tissue (Figure 1). Suppressive doses of thyroid hormone produced no significant improvement. Operative Technique Nasotracheal intubation allows for an unobstructed view of the tongue base. An appropriate dose of muscle relaxant and induction dexamethasone are essential to optimize access and limit postoperative edema, respectively. The operating room and da Vinci robot are set up in the usual fashion and has been previously described. (11) A 30° endoscope is calibrated and balanced. We prefer using the CO2 laser over the monopolar cautery to decrease thermal damage and associated edema to adjacent structures. (11) A 2‐0 silk suture is placed in the anterior tongue and anterior traction is applied while the tongue blade of the FK retractor is inserted to optimize view of the lingual thyroid. The 30° endoscope is inserted face up, followed by a 5‐ mm either spatula monopolar cautery or LISA laser and a 5‐mm Maryland forceps. An incision is carried through the mucosa and submucosa at the anterior border of the lingual thyroid (Figure 2). Posterior traction on the lingual thyroid helps delineate the plane between the lingual thyroid and lingual musculature. There is a relatively avascular plane between the
lingual thyroid and surrounding musculature and tongue base. Multiple small vessels traverse this plane that can easily be addressed with the monopolar spatula or suction bovie. The plane is carefully dissected anteriorly and is carried through posteriorly along a broad plane until the lingual thyroid is circumferentially free from the underlying musculature. A suction bovie is applied as necessary to maintain hemostasis. The ectopic gland was removed in its entirety. No additional margins were obtained. Care was taken not to violate the thyroid tissue in order to maintain both operative and postoperative hemostasis. There were no attempts to debulk the thyroid gland in order to maintain viable thyroid tissue in the tongue base.
Post‐Operative Care All patients tolerated the procedure with no intra operative or immediate postoperative complications. Two patients were extubated at the end of the procedure, admitted overnight for observation and resumed a soft diet and discharged home on the first postoperative day. To prevent any airway complications, one patient was kept intubated overnight due to the size of the resected gland. Two patients without cervical orthotopic thyroid tissue were prescribed thyroid replacement on their first postoperative day. There were no complications of bleeding or aspiration and all patients had their obstructive symptomatology resolve. Follow up at one month revealed a well healed longitudinal midline scar at the tongue base. Discussion
Ectopic thyroid tissue develops due to the failure or incomplete decent of thyroid tissue during embryogenesis. This rare embryological aberration can occur at any moment during the migration of the thyroid along its normal path of descent from the foramen cecum of the tongue to the isthmus of the thyroid between the third week and seventh week of fetal life.(8, 12) As the primitive thyroid descends along the midline, it remains connected to the pharyngeal pouch by its stalk, the thyroglossal duct, which normally involutes and atrophies by the sixth to eight fetal week(13). Ectopic thyroid tissue may mimic a thyroglossal duct cyst, and can be differentiated based on a radioactive iodine thyroid scan(3). Thyroid ectopia is most commonly found in the tongue base (lingual), although sublingual, prelaryngeal, substernal/mediastinal and other rare sites such as the precardial sac, heart, breast, pharynx, esophagus, trachea, lung, duodenum, pancreas, gallbladder, mesentery of the small intestine, adrenal gland and skin has been reported(1, 2, 5, 14‐19). In addition, dual ectopic thyroid has been described(20, 21), and cannot be ruled out by the presence of a normally located thyroid gland(22). Ectopic thyroid tissue is estimated to occur approximately in 1 in 200,000 individuals and 1 in 6000 patients with thyroid disease(2). The clinical incidence ranges between 1 in 4000 to 1 in 10 000 people.(1) However this is likely to be an underestimate due to the frequent incidental discovery of ectopic thyroid during surgery and postmortem studies(23), with a reported 10% incidence in 200 consecutive necropsies(24). There is a marked female sex predominance ranging from 4:1 to 7:1(4) and most commonly presents during times of increased dependence on thyroid hormone such as during childhood, adolescence, pregnancy and menopause. An
increase of circulating TSH levels during this time contributes to the growth of the ectopic thyroid tissue and consequently, it’s clinical surfacing(15). Family members of lingual thyroid patients have a higher incidence of thyroid disease compared to the population at large(25). Most ectopic lingual thyroids are asymptomatic and are discovered on routine oral examination. Clinical evidence of hypothyroidism is found in 33 – 62% of cases(4, 26); while 65‐ 75% of patients with symptomatic lingual thyroids have no other functional thyroid tissues(27). Symptoms are related to the enlargement of the thyroid tissue and include dysphagia, dysphonia bleeding, dyspnea(1) and OSA(3). Difficult intubation due to hemorrhage and airway compromise has been reported(28). Most lingual thyroid glands contain histologically normal tissue, but there are reports of carcinoma arising within a lingual thyroid gland.(4, 23)Carcinoma arising in the lingual thyroid is extremely rare, with an estimated incidence of 1%._ENREF_13(23) On examination, a raised smooth midline tongue mass posterior to the circumvallate papillae, with a light pink or blue coloration and little or no palpable cervical thyroid tissue is highly suspicious for a lingual thyroid. Hemorrhagic changes may be present, with frank ulceration and bleeding(4). Further endoscopic evaluation is necessary to determine airway patency, gland size and differentiate other possible anomalies such as hemangioma, vallecular cyst or hypertrophied lingual tonsil(4). Associated symptoms of hypothyroidism should increase suspicion. Diagnosis is confirmed by either technetium‐99m pertechnetate radionuclide scintigraphy or by radioactive iodine uptake scan, which effectively detect ectopic thyroid tissue(6) and simultaneously assist in determining the presence or absence of an eutopic thyroid gland. This
method avoids entirely the need for diagnostic biopsy(16) which carries the risk of bleeding and hemorrhage(29). US, CT and MRI may aid in defining the extension and location of the ectopic thyroid gland. Recent use of single photon emission computed tomography in combination with standard computed tomography allows a more precise spatial visualization of the ectopic gland in three dimensions(6). Thyroid function tests should be obtained, which often demonstrate normal to marginal gland function, with normal to decreased levels of T3 and T4 and elevated levels of TSH and thyroglobulin(4). Treatment of this pathology is based upon clinical presentation, but remains somewhat controversial with a lack of clear consensus. The presence or absence of symptoms provides the best initial guide to treatment. Asymptomatic, euthyroid patients are best left untreated, but must be followed to monitor the development of possible complications. Thyroid suppressive therapy with exogenous thyroid hormone, in an attempt to remove the stimulus for gland enlargement, is the pillar of medical management and has been the first line of treatment for mildly symptomatic patients. However suppressive therapy is not always successful and may take a prolonged period of time to achieve an appreciable decrease in the size of the gland.(8, 9)
Other interventions have been applied including radiofrequency ablation and radioactive
iodine. (30, 31) Transoral resections have been previously reported, (32) however they have been limited by surgical access and visibility. Therefore more invasive open approaches including lateral transcervical approaches and midline labiotomy or mandibulotomy have been described.(8, 9) The emergence of TORS has provided a safe and effective option to access and dissect the oropharynx, and this technique has been recently successfully applied in a single case in the treatment of a lingual thyroid(33). These cases illustrate the safety and
implementation of this technique and add credence to TORS as a valid option in the treatment of this pathology. Conclusions Ectopic lingual thyroid is a rare congenital anomaly that most commonly is asymptomatic, however when significantly large it can cause obstructive symptoms affecting deglutition, airway or gastroesophageal reflux. Transoral robotic surgery is a safe and minimally invasive approach to successfully remove ectopic lingual thyroid tissue with minimal morbidity.
References 1. Toso A, Colombani F, Averono G, Aluffi P, Pia F. Lingual thyroid causing dysphagia and dyspnoea. Case reports and review of the literature. Acta otorhinolaryngologica Italica : organo ufficiale della Societa italiana di otorinolaringologia e chirurgia cervico‐facciale 2009;29(4):213‐7. 2. Di Benedetto V. Ectopic thyroid gland in the submandibular region simulating a thyroglossal duct cyst: a case report. Journal of pediatric surgery 1997;32(12):1745‐6. 3. Barnes TW, Olsen KD, Morgenthaler TI. Obstructive lingual thyroid causing sleep apnea: a case report and review of the literature. Sleep medicine 2004;5(6):605‐7. 4. Williams JD, Sclafani AP, Slupchinskij O, Douge C. Evaluation and management of the lingual thyroid gland. The Annals of otology, rhinology, and laryngology 1996;105(4):312‐6. 5. Porqueddu M, Antona C, Polvani G, et al. Ectopic thyroid tissue in the ventricular outflow tract: embryologic implications. Cardiology 1995;86(6):524‐6. 6. Dolezal J, Vizda J, Horacek J, Spitalnikova S. Lingual thyroid: diagnosis using a hybrid of single photon emission computed tomography and standard computed tomography. J Laryngol Otol 2013:1‐3. 7. Terris DJ, Seybt MW, Vaughters RB, 3rd. A new minimally invasive lingual thyroidectomy technique. Thyroid : official journal of the American Thyroid Association 2010;20(12):1367‐9. 8. Vairaktaris E, Semergidis T, Christopoulou P, Papadogeorgakis N, Martis C. Lingual thyroid: a new surgical approach‐‐a case report. Journal of cranio‐maxillo‐facial surgery : official publication of the European Association for Cranio‐Maxillo‐Facial Surgery 1994;22(5):307‐10. 9. Atiyeh BS, Abdelnour A, Haddad FF, Ahmad H. Lingual thyroid: tongue‐splitting incision for transoral excision. The Journal of Laryngology and Otology 1995;109:520‐524. 10. Genden EM, Kotz T, Tong CC, et al. Transoral robotic resection and reconstruction for head and neck cancer. The Laryngoscope 2011;121(8):1668‐74. 11. Genden EM, Desai S, Sung CK. Transoral robotic surgery for the management of head and neck cancer: a preliminary experience. Head Neck 2009;31(3):283‐9. 12. Haffly GN. The spectacular lingual thyroid and midline anterior cervical ectopic thyroid. Transactions of the Pacific Coast Oto‐Ophthalmological Society annual meeting 1976;57:137‐43. 13. Chanin LR, Greenberg LM. Pediatric upper airway obstruction due to ectopic thyroid: classification and case reports. The Laryngoscope 1988;98(4):422‐7. 14. Ferlito A, Giarelli L, Silvestri F. Intratracheal thyroid. J Laryngol Otol 1988;102(1):95‐6. 15. Kumar R, Sharma S, Marwah A, Moorthy D, Dhanwal D, Malhotra A. Ectopic goiter masquerading as submandibular gland swelling: a case report and review of the literature. Clinical nuclear medicine 2001;26(4):306‐9. 16. Pollice L, Caruso G. Struma cordis. Ectopic thyroid goiter in the right ventricle. Archives of pathology & laboratory medicine 1986;110(5):452‐3. 17. Eyuboglu E, Kapan M, Ipek T, Ersan Y, Oz F. Ectopic thyroid in the abdomen: report of a case. Surgery today 1999;29(5):472‐4. 18. Liang K, Liu JF, Wang YH, Tang GC, Teng LH, Li F. Ectopic thyroid presenting as a gallbladder mass. Annals of the Royal College of Surgeons of England 2010;92(4):W4‐6. 19. Maino K, Skelton H, Yeager J, Smith KJ. Benign ectopic thyroid tissue in a cutaneous location: a case report and review. Journal of cutaneous pathology 2004;31(2):195‐8. 20. Hazarika P, Siddiqui SA, Pujary K, Shah P, Nayak DR, Balakrishnan R. Dual ectopic thyroid: a report of two cases. J Laryngol Otol 1998;112(4):393‐5.
21. Ulug T, Ulubil SA, Alagol F. Dual ectopic thyroid: report of a case. J Laryngol Otol 2003;117(7):574‐6. 22. Huang TS, Chen HY. Dual thyroid ectopia with a normally located pretracheal thyroid gland: case report and literature review. Head & neck 2007;29(9):885‐8. 23. Klubo‐Gwiezdzinska J, Manes RP, Chia SH, et al. Clinical review: Ectopic cervical thyroid carcinoma‐‐review of the literature with illustrative case series. The Journal of clinical endocrinology and metabolism 2011;96(9):2684‐91. 24. Sauk JJ, Jr. Ectopic lingual thyroid. The Journal of pathology 1970;102(4):239‐43. 25. Farrell ML, Forer M. Lingual thyroid. The Australian and New Zealand journal of surgery 1994;64(2):135‐8. 26. Yoon JS, Won KC, Cho IH, Lee JT, Lee HW. Clinical characteristics of ectopic thyroid in Korea. Thyroid : official journal of the American Thyroid Association 2007;17(11):1117‐21. 27. Batsakis JG, El‐Naggar AK, Luna MA. Thyroid gland ectopias. The Annals of otology, rhinology, and laryngology 1996;105(12):996‐1000. 28. Ghabash MB, Stephan JC, Matta MS, Helou MR. Lingual thyroid: a rare cause of difficult intubation. Middle East journal of anesthesiology 2011;21(3):441‐3. 29. Prasad KC, Bhat V. Surgical management of lingual thyroid: a report of four cases. J Oral Maxillofac Surg 2000;58(2):223‐7. 30. Dasari SD, Bashetty NK, Prayaga NS. Radiofrequency ablation of lingual thyroid. Otolaryngol Head Neck Surg 2007;136(3):498‐9. 31. Danner C, Bodenner D, Breau R. Lingual thyroid: iodine 131: a viable treatment modality revisited. Am J Otolaryngol 2001;22(4):276‐81. 32. Richardson JR, Lineback M. Radioactive iodine in the diagnosis and treatment of lingual thyroid adenoma. Laryngoscope 1952;62(9):934‐43. 33. James T. May IV JGN, Tapan A. Padhya. Transoral robot‐assisted excision of a lingual thyroid gland. Transoral robot‐assisted excision of a lingual thyroid gland 2011;Volume 5(Issue 3):217‐22
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Head & Neck
Figure 1: Computed tomography of the head and neck at the time of diagnosis revealing a large and well defined base of tongue mass consistent with a lingual thyroid and an absent cervical thyroid gland. 400x156mm (96 x 96 DPI)
John Wiley & Sons, Inc.
Head & Neck
Figure 2: A transoral robotic assisted incision is carried through the mucosa and submucosa at the anterior border of the lingual thyroid. Posterior traction on the lingual thyroid helps delineate the plane between the lingual thyroid and lingual musculature. The plane is carefully dissected anteriorly and is carried through posteriorly along a broad plane until the lingual thyroid is circumferentially free from the underlying musculature. 179x197mm (150 x 150 DPI)
John Wiley & Sons, Inc.
Page 14 of 14
Key Words: Transoral Robotic Surgery, Lingual thyroid, minimally invasive, minimal morbidity.
This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as an ‘Accepted Article’, doi: 10.1002/hed.23757
Abstract Background: Surgical excision of an ectopic lingual thyroid has traditionally been associated with significant morbidity and has therefore been reserved for patients with severe obstructive symptoms or suspected malignancy. Transoral Robotic Surgery (TORS) has provided a minimally invasive approach to completely and safely excise ectopic lingual thyroid. Methods: Three index cases were identified from the detailed clinical database of TORS patients. A systematic review of the management of ectopic lingual thyroid in the English literature was performed. Results: TORS assisted excision of a lingual thyroid gland was successfully performed in 3 patients with excellent functional outcomes. Conclusions: TORS assisted excision of an ectopic lingual thyroid is a safe and feasible treatment modality with minimal morbidity, and in experienced hands, should be offered as a valid treatment for this pathology.
Introduction The presence of ectopic thyroid at the tongue base, termed a lingual thyroid, is a rare congenital anomaly resulting from the incomplete descent of the thyroid gland from the foramen cecum to the neck during week 4‐7 of embryogenesis.(1) The reported rate of lingual thyroids is approximately 1 in 200,000 and increases to 1 in 6,000 in patients with thyroid disease.(2) The majority of ectopic thyroids are asymptomatic and do not require treatment. However, a minority of patients develop obstructive symptoms including dysphagia, dysphonia, bleeding, dyspnea or obstructive sleep apnea.(1, 3) Traditionally, surgical intervention has been reserved for symptomatic patients failing conservative therapy.(4) The thyroid gland forms in week 4 of embryogenesis from a median endodermal thickening at the base of the pharynx forming a thyroid diverticulum and then descends via the thyroglossal duct to its final position anterior to the trachea by week 7.(5, 6) Therefore, ectopic thyroid tissue can be found anywhere along this tract of decent from the foramen cecum to the isthmus. Classically, the lingual thyroid is present at the base of tongue in the midline between the circumvallate papillae and the epiglottis.(4) Transoral surgical access to the tongue base, and intraoperative visualization of the ectopic thyroid tissue is challenging and therefore a multitude of open surgical approaches have been described including a midline labiotomy, madibulotomy, tongue‐split or cervical pharyngotomy approach.(7‐9) Transoral robotic assisted surgery (TORS) is an emerging minimally invasive approach to the oropharynx and hypopharynx with decreased morbidity that provides
exceptional three dimensional visualization and instrument navigation.(10) Three cases of TORS excision of lingual thyroid gland are presented and the surgical technique described. Case1: A 27‐year old female with a prior history of hypothyroidism and celiac disease presented with a two months history of progressive dysphagia, intermittent shortness of breath and gastroesophageal reflux. On examination, a 4 cm midline symmetric mass at the base of the tongue with an unremarkable overlying mucosa was visualized. Partial oropharyngeal closure was noted during deglutition. Computed tomography demonstrated an enhancing 4 x 4 cm midline mass consistent with a lingual thyroid, with an absent cervical thyroid gland. Initial conservative management with thyroid hormone replacement did not relieve her symptoms. Case 2: A 24‐year‐old female presented with a two‐year history of progressive dysphonia, dysphagia, odynophagia and gastroesophageal reflux. Family history was significant for a sibling with thyroid agenesis. Oral cavity examination revealed a tongue base mass obstructing the oropharynx with no palpable cervical thyroid tissue. Fiberoptic examination demonstrated a large smooth base of tongue mass with a compromised oropharyngeal airway. An MRI revealed a small thyroid gland in the normal position with a large base of tongue mass consistent with a lingual thyroid. A radioactive iodine scan confirmed uptake at the tongue base and anterior trachea. Conservative medical management failed to relieve her obstructive symptoms. Case 3:
A 54‐year‐old female with a longstanding history of hypothyroidism, progressive voice changes, snoring and obstructive sleep apnea presented with a two month history of shortness of breath and dysphagia. In addition she was unable to tolerate intubation for an elective surgical procedure due to a large base of tongue mass. Fiberoptic examination demonstrated an extensively large midline tongue mass consistent with a lingual thyroid. Computer tomography of the neck revealed a 6cm x 4cm base of tongue mass with no cervical thyroid tissue (Figure 1). Suppressive doses of thyroid hormone produced no significant improvement. Operative Technique Nasotracheal intubation allows for an unobstructed view of the tongue base. An appropriate dose of muscle relaxant and induction dexamethasone are essential to optimize access and limit postoperative edema, respectively. The operating room and da Vinci robot are set up in the usual fashion and has been previously described. (11) A 30° endoscope is calibrated and balanced. We prefer using the CO2 laser over the monopolar cautery to decrease thermal damage and associated edema to adjacent structures. (11) A 2‐0 silk suture is placed in the anterior tongue and anterior traction is applied while the tongue blade of the FK retractor is inserted to optimize view of the lingual thyroid. The 30° endoscope is inserted face up, followed by a 5‐ mm either spatula monopolar cautery or LISA laser and a 5‐mm Maryland forceps. An incision is carried through the mucosa and submucosa at the anterior border of the lingual thyroid (Figure 2). Posterior traction on the lingual thyroid helps delineate the plane between the lingual thyroid and lingual musculature. There is a relatively avascular plane between the
lingual thyroid and surrounding musculature and tongue base. Multiple small vessels traverse this plane that can easily be addressed with the monopolar spatula or suction bovie. The plane is carefully dissected anteriorly and is carried through posteriorly along a broad plane until the lingual thyroid is circumferentially free from the underlying musculature. A suction bovie is applied as necessary to maintain hemostasis. The ectopic gland was removed in its entirety. No additional margins were obtained. Care was taken not to violate the thyroid tissue in order to maintain both operative and postoperative hemostasis. There were no attempts to debulk the thyroid gland in order to maintain viable thyroid tissue in the tongue base.
Post‐Operative Care All patients tolerated the procedure with no intra operative or immediate postoperative complications. Two patients were extubated at the end of the procedure, admitted overnight for observation and resumed a soft diet and discharged home on the first postoperative day. To prevent any airway complications, one patient was kept intubated overnight due to the size of the resected gland. Two patients without cervical orthotopic thyroid tissue were prescribed thyroid replacement on their first postoperative day. There were no complications of bleeding or aspiration and all patients had their obstructive symptomatology resolve. Follow up at one month revealed a well healed longitudinal midline scar at the tongue base. Discussion
Ectopic thyroid tissue develops due to the failure or incomplete decent of thyroid tissue during embryogenesis. This rare embryological aberration can occur at any moment during the migration of the thyroid along its normal path of descent from the foramen cecum of the tongue to the isthmus of the thyroid between the third week and seventh week of fetal life.(8, 12) As the primitive thyroid descends along the midline, it remains connected to the pharyngeal pouch by its stalk, the thyroglossal duct, which normally involutes and atrophies by the sixth to eight fetal week(13). Ectopic thyroid tissue may mimic a thyroglossal duct cyst, and can be differentiated based on a radioactive iodine thyroid scan(3). Thyroid ectopia is most commonly found in the tongue base (lingual), although sublingual, prelaryngeal, substernal/mediastinal and other rare sites such as the precardial sac, heart, breast, pharynx, esophagus, trachea, lung, duodenum, pancreas, gallbladder, mesentery of the small intestine, adrenal gland and skin has been reported(1, 2, 5, 14‐19). In addition, dual ectopic thyroid has been described(20, 21), and cannot be ruled out by the presence of a normally located thyroid gland(22). Ectopic thyroid tissue is estimated to occur approximately in 1 in 200,000 individuals and 1 in 6000 patients with thyroid disease(2). The clinical incidence ranges between 1 in 4000 to 1 in 10 000 people.(1) However this is likely to be an underestimate due to the frequent incidental discovery of ectopic thyroid during surgery and postmortem studies(23), with a reported 10% incidence in 200 consecutive necropsies(24). There is a marked female sex predominance ranging from 4:1 to 7:1(4) and most commonly presents during times of increased dependence on thyroid hormone such as during childhood, adolescence, pregnancy and menopause. An
increase of circulating TSH levels during this time contributes to the growth of the ectopic thyroid tissue and consequently, it’s clinical surfacing(15). Family members of lingual thyroid patients have a higher incidence of thyroid disease compared to the population at large(25). Most ectopic lingual thyroids are asymptomatic and are discovered on routine oral examination. Clinical evidence of hypothyroidism is found in 33 – 62% of cases(4, 26); while 65‐ 75% of patients with symptomatic lingual thyroids have no other functional thyroid tissues(27). Symptoms are related to the enlargement of the thyroid tissue and include dysphagia, dysphonia bleeding, dyspnea(1) and OSA(3). Difficult intubation due to hemorrhage and airway compromise has been reported(28). Most lingual thyroid glands contain histologically normal tissue, but there are reports of carcinoma arising within a lingual thyroid gland.(4, 23)Carcinoma arising in the lingual thyroid is extremely rare, with an estimated incidence of 1%._ENREF_13(23) On examination, a raised smooth midline tongue mass posterior to the circumvallate papillae, with a light pink or blue coloration and little or no palpable cervical thyroid tissue is highly suspicious for a lingual thyroid. Hemorrhagic changes may be present, with frank ulceration and bleeding(4). Further endoscopic evaluation is necessary to determine airway patency, gland size and differentiate other possible anomalies such as hemangioma, vallecular cyst or hypertrophied lingual tonsil(4). Associated symptoms of hypothyroidism should increase suspicion. Diagnosis is confirmed by either technetium‐99m pertechnetate radionuclide scintigraphy or by radioactive iodine uptake scan, which effectively detect ectopic thyroid tissue(6) and simultaneously assist in determining the presence or absence of an eutopic thyroid gland. This
method avoids entirely the need for diagnostic biopsy(16) which carries the risk of bleeding and hemorrhage(29). US, CT and MRI may aid in defining the extension and location of the ectopic thyroid gland. Recent use of single photon emission computed tomography in combination with standard computed tomography allows a more precise spatial visualization of the ectopic gland in three dimensions(6). Thyroid function tests should be obtained, which often demonstrate normal to marginal gland function, with normal to decreased levels of T3 and T4 and elevated levels of TSH and thyroglobulin(4). Treatment of this pathology is based upon clinical presentation, but remains somewhat controversial with a lack of clear consensus. The presence or absence of symptoms provides the best initial guide to treatment. Asymptomatic, euthyroid patients are best left untreated, but must be followed to monitor the development of possible complications. Thyroid suppressive therapy with exogenous thyroid hormone, in an attempt to remove the stimulus for gland enlargement, is the pillar of medical management and has been the first line of treatment for mildly symptomatic patients. However suppressive therapy is not always successful and may take a prolonged period of time to achieve an appreciable decrease in the size of the gland.(8, 9)
Other interventions have been applied including radiofrequency ablation and radioactive
iodine. (30, 31) Transoral resections have been previously reported, (32) however they have been limited by surgical access and visibility. Therefore more invasive open approaches including lateral transcervical approaches and midline labiotomy or mandibulotomy have been described.(8, 9) The emergence of TORS has provided a safe and effective option to access and dissect the oropharynx, and this technique has been recently successfully applied in a single case in the treatment of a lingual thyroid(33). These cases illustrate the safety and
implementation of this technique and add credence to TORS as a valid option in the treatment of this pathology. Conclusions Ectopic lingual thyroid is a rare congenital anomaly that most commonly is asymptomatic, however when significantly large it can cause obstructive symptoms affecting deglutition, airway or gastroesophageal reflux. Transoral robotic surgery is a safe and minimally invasive approach to successfully remove ectopic lingual thyroid tissue with minimal morbidity.
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Head & Neck
Figure 1: Computed tomography of the head and neck at the time of diagnosis revealing a large and well defined base of tongue mass consistent with a lingual thyroid and an absent cervical thyroid gland. 400x156mm (96 x 96 DPI)
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Head & Neck
Figure 2: A transoral robotic assisted incision is carried through the mucosa and submucosa at the anterior border of the lingual thyroid. Posterior traction on the lingual thyroid helps delineate the plane between the lingual thyroid and lingual musculature. The plane is carefully dissected anteriorly and is carried through posteriorly along a broad plane until the lingual thyroid is circumferentially free from the underlying musculature. 179x197mm (150 x 150 DPI)
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