Evidence-Based Approach to a “Missing” Parathyroid Gland During Thyroid or Parathyroid Surgery

Rodrigo Arrangoiz MS, MD, FACS, FSSO
  • Failure to identify a parathyroid gland during cervical exploration:
    • Is most commonly explained by:
      • Ectopic location rather than true absence
  • Large anatomic and surgical series demonstrate that approximately 15% to 16% of parathyroid glands are ectopic:
    • With predictable distributions:
      • Based on embryologic origin (Taterra et al., Surg Radiol Anat, 2019):
        • Consequently, a structured search strategy:
          • Guided by embryology and prevalence data is recommended
  • General intra-operative principles:
    • Careful inspection of the orthotopic field:
      • Is mandatory before declaring a gland ectopic
    • Approximately 80% to 90% of parathyroid glands are located within a few millimeters of the posterior thyroid capsule (Taterra et al., 2019):
      • Gentle subcapsular dissection along the posterior surface of the thyroid should be completed before expanding the field
  • Intrathyroidal parathyroid glands:
    • Account for 2% to 3% of all glands and up to 20% to 22% of ectopic glands, particularly inferior glands (Phitayakorn & McHenry, Am J Surg, 2006):
      • For this reason, inspection and palpation of the thyroid specimen is considered standard practice in experienced centers (Noussios et al., Exp Clin Endocrinol Diabetes, 2012)
  • Reoperative series demonstrate that most “missed” glands:
    • Are found in standard embryologic locations:
      • Most commonly the tracheoesophageal groove, thyrothymic ligament, or superior mediastinum:
        • Emphasizing the importance of a systematic rather than random exploration (Silberfein et al., Arch Surg, 2010)
  • Superior parathyroid gland – Evidence-Based search pattern:
    • Typical location:
      • Superior parathyroid glands:
        • Fourth pharyngeal pouch origin:
          • Exhibit limited migration and are therefore relatively constant in position
      • They are typically located on the posterior aspect of the upper thyroid pole:
        • Approximately 1 cm above the intersection of the recurrent laryngeal nerve (RLN) and the inferior thyroid artery:
          • Frequently within the tracheoesophageal groove (Scharpf et al., Surg Oncol Clin N Am, 2016)
    • Common ectopic locations:
      • When ectopic:
        • Superior parathyroid glands are most often displaced posteriorly, rather than inferiorly:
          • Tracheoesophageal or para-esophageal groove the most common ectopic site for superior glands (Noussios et al., 2012; Taterra et al., 2019)
          • Retro-esophageal or retro-pharyngeal space, particularly in undescended glands (Scharpf et al., 2016)
          • Posterior mediastinum, where enlarged glands may descend along the esophagus but remain posterior in relation to the RLN (Phitayakorn & McHenry, 2006)
    • Stepwise surgical approach:
      • If a superior gland is not identified in its orthotopic location, the recommended sequence is:
        • Systematic exploration of the tracheoesophageal groove following the RLN superiorly
        • Blunt dissection of the para- and retro-esophageal spaces
        • Evaluation of the high posterior neck for undescended glands
        • Inspection of the thyroid specimen for an intrathyroidal gland (Noussios et al., 2012; Silberfein et al., 2010)
  • Inferior parathyroid gland – evidence-based search pattern:
    • Typical location:
      • Inferior parathyroid glands:
        • Third pharyngeal pouch origin
        • Descend with the thymus and demonstrate significantly greater variability
        • Orthotopically, they are most often located near the lower thyroid pole, anterior to the RLN, frequently within or adjacent to the thyrothymic ligament (Scharpf et al., 2016)
    • Common ectopic locations:
      • Inferior glands account for the majority of ectopic parathyroids:
        • Intrathymic or within the cervical thymus:
          • Approximately 30% of ectopic inferior glands (Phitayakorn & McHenry, 2006)
        • Anterosuperior mediastinum, often contiguous with thymic tissue (Noussios et al., 2012)
        • Intrathyroidal:
          • Accounting for ~ 20% to 22% of ectopic inferior glands (Phitayakorn & McHenry, 2006)
        • High cervical or carotid sheath locations, representing failed embryologic descent (Noussios et al., 2012)
    • Stepwise surgical approach:
      • When an inferior gland is not identified at the lower pole:
        • The thyrothymic ligament should be followed inferiorly toward the thymus
        • A limited cervical thymectomy should be performed when clinically appropriate:
          • Given the high incidence of intrathymic glands
        • The lower thyroid pole and specimen should be inspected for intrathyroidal tissue
        • The carotid sheath and high cervical region should be explored in cases suspicious for undescended glands (Phitayakorn & McHenry, 2006; Silberfein et al., 2010)
  • Lessons from re-operative surgery:
    • In contemporary re-operative parathyroidectomy series, previously missed glands were most commonly located in the:
      • Tracheoesophageal groove
      • Thyrothymic ligament
      • Superior mediastinum
    • Confirming that failure is usually related to incomplete exploration of predictable embryologic sites rather than unusual anatomy (Silberfein et al., Arch Surg, 2010)
  • Key references:
    • Taterra D, et al. The prevalence and anatomy of parathyroid glands: a meta-analysis. Surg Radiol Anat. 2019.
    • Phitayakorn R, McHenry CR. Incidence and location of ectopic abnormal parathyroid glands. Am J Surg. 2006;191:418–423.
    • Noussios G, et al. Ectopic parathyroid glands and their anatomical, clinical and surgical implications. Exp Clin Endocrinol Diabetes. 2012.
    • Silberfein EJ, et al. Reoperative parathyroidectomy: location of missed glands. Arch Surg. 2010.
    • Scharpf J, et al. Anatomy and embryology of the parathyroid glands. Surg Oncol Clin N Am. 2016.
Unknown's avatar

Published by Rodrigo Arrangoiz MS, MD, FACS, FSSO

My name is Rodrigo Arrangoiz I am a breast surgeon/ thyroid surgeon / parathyroid surgeon / head and neck surgeon / surgical oncologist that works at Center for Advanced Surgical Oncology in Miami, Florida. I was trained as a surgeon at Michigan State University from (2005 to 2010) where I was a chief resident in 2010. My surgical oncology and head and neck training was performed at the Fox Chase Cancer Center in Philadelphia from 2010 to 2012. At the same time I underwent a masters in science (Clinical research for health professionals) at the University of Drexel. Through the International Federation of Head and Neck Societies / Memorial Sloan Kettering Cancer Center I performed a two year head and neck surgery and oncology / endocrine fellowship that ended in 2016. Mi nombre es Rodrigo Arrangoiz, soy cirujano oncólogo / cirujano de tumores de cabeza y cuello / cirujano endocrino que trabaja Center for Advanced Surgical Oncology en Miami, Florida. Fui entrenado como cirujano en Michigan State University (2005 a 2010 ) donde fui jefe de residentes en 2010. Mi formación en oncología quirúrgica y e n tumores de cabeza y cuello se realizó en el Fox Chase Cancer Center en Filadelfia de 2010 a 2012. Al mismo tiempo, me sometí a una maestría en ciencias (investigación clínica para profesionales de la salud) en la Universidad de Drexel. A través de la Federación Internacional de Sociedades de Cabeza y Cuello / Memorial Sloan Kettering Cancer Center realicé una sub especialidad en cirugía de cabeza y cuello / cirugia endocrina de dos años que terminó en 2016.

Leave a comment