Head & Neck Surgery Course Surgical anatomy of thyroid and parathyroid glands Dr Pierfrancesco PELLICCIA Pr Benjamin LALLEMANT Service ORL et CMF CHU de Nîmes CH de Arles Thyroid glands Dr Pierfrancesco PELLICCIA Pr Benjamin LALLEMANT Service ORL et CMF CHU de Nîmes CH de Arles Introduction • Thyroid gland includes 2 lobes and isthmus • Endocrine gland – T3, T4, CT Thyroid region • Boundaries – Superior: hyoid – Lateral: carotid sheath – Inferior: manubrium – Anterior: strap muscles and their fascia – Posterior : prevertebral fascia Infrahyoid muscles 5 Middle layer of deep cervical fascia Thyroid region: anterior view Thyroid region: anterolateral view Thyroid region: right lateral view Thyroid region: left lateral view Arterial supply • Sup. & inf. thyroid arteries • Superior and posterior anastomotic arch • Anatomy variant: thyroid ima artery, in 1.5% to 12%, in front of the trachea. Arterial supply Venous supply – Superior and middle thyroid v. drain into the internal jugular – Inferior thyroid v. drains into the brachiocephalic trunk Nodular goiter and superior mediastinum • Prevascular • Retrovascular Lymph vessels • 1st echelon nodes: prelaryngeal, pretracheal and paratracheal nodes (level VI) • 2nd echelon nodes: – Level VII – Level IIa-III-IV-Vb Lymph vessels Recurrent Laryngeal Nerve (RLN) • Sim’s triangle – Carotid artery – Trachea – Inferior pole of thyroid • Left RLN runs parallel with the tracheoesophagel groove • Right RLN runs diagonal with the TEG RLN RLN is seen, in order of decreasing frequency: - As a single nerve - bifurcated (posterior branch=anastomotic branch with the sympathetic or branch to esophagus) - Trifurcated - Plexiform. RLN RLN RLN and inferior thyroid artery • RLN crosses branches of the artery in 75% of cases, the trunk in 14% and division in 11%. • RLN is posterior to the artery in 47% of cases, anterior in 28% of cases, between the branches in 25%. • So, 75% of RLN crosses the branches of artery, but is between them just in 25% of cases. RLN and inferior thyroid artery • RLN crosses the trunk of the artery the most often on the right side, the branches or division the most often on the left side. • RLN is found anteriorly the artery the most often on the right side, and posteriorly on the left side. RLN and inferior thyroid artery RLN and inferior thyroid artery Non recurrent inferior laryngeal nerve • Right side (<<1%) • Aberrant right subclavian artery • Dysphagia lusoria • Situs inversus Non recurrent inferior laryngeal nerve Berry ligament Berry ligament Posterior thyroid tubercle of Zuckerkandl Posterior thyroid tubercle of Zuckerkandl Superior Laryngeal Nerve Parathyroid glands Parathyroid glands Dr Pierfrancesco PELLICCIA Pr Benjamin LALLEMANT Service ORL et CMF CHU de Nîmes CH de Arles Introduction • 4 endocrine glands (PTH) • Autopsy studies suggest that four parathyroid glands are virtually always present. • Supernumerary glands can be identified in up to 15% of patients, most often in association with the thymus. Embriology of parathyroids •The superior parathyroid gland (P4) arises from the fourth pharyngeal pouch in conjunction with the lateral thyroid • the inferior gland (P3) arises from the third pouch along with the thymus. •The derivatives of each pouch then migrate together. P4 and P3 are supposed to migrate down the neck to end up next to and around the thyroid gland Embriology of parathyroids •P4 usually remains in close association with the upper pole of the thyroid •It may occasionally be loosely attached by a long vascular pedicle, migrating caudad along the esophagus into the posterior mediastinum •Occasionally, a gland may be totally embedded in the thyroid parenchyma. Embriology of parathyroids •P3 descends with the thymus, but this migration is extremely variable. •Regardless of their location, they usually adhere to the thymus or are within the thyrothymic ligament. •Inferior glands can be found anywhere from the pharynx to the mediastinum. Blood supply of parathyroids • Branches of the inferior thyroid artery • Great variation exists, supply by the superior thyroid arteries, the thyroid ima artery, the laryngeal arteries, tracheal arteries or oesophageal arteries has been documented. • The glands drain into the plexus of veins on the anterior surface (front) of the thyroid comprising the superior, middle and inferior thyroid veins. Blood supply of parathyroids Parathyroid glands: intraoperative view Ectopic parathyroid glands • If the gland does not migrate down it will be found high in the neck under the jaw (sestamibi scans!) • If the parathyroid gland migrates too far, it will end up in the chest (about 15 times more common than parathyroid glands that don’t migrate far enough and end up high in the neck) Inferior Parathyroid Locations Superior Parathyroid Locations Where to look for parathyroid glands ? • 1) 80 % of glands • 2) 98 % Where to look for parathyroid glands ? • Look on the posterolateral aspect of thyroid first (1) • Then look on the posteromedial aspect of thyroid, around RLN (2) • Then look in the thyrothymic ligament and around the thymus (3) Where to look for P3 ? • A. Usual location = 80 % of P3 • B. Usual location + most often encountered ectopic locations = 98 % of P3 • C. Same as B + less often encountered ectopic locations = 100 % of P3 Where to look for P4 ? • D. Usual locations. • E. Usual + ectopic locations Distribution of 220 parathyroid specimens of patients who underwent reoperative neck surgery because of persistent hyperparathyroidism 136 parathyroid glands (61.8%) located in their normal anatomical positions 84 ectopic parathyroid glands (38.2%) Sites of ectopic location of 104 parathyroid glands found at reoperation for primary hyperparathyroidism (From Wang C-A. A clinical and pathological study of 112 cases. Ann Surg 1977;186:140-145.) .