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Surgical Anatomy Thyroid and Parathyroid Glands Bastaninejad Shahin MD, ORL&HNS, TUMS, Amiralam Hospital Presentation outlines • Thyroid Gland: – General measures – Vascular supply – Important proximities – Surgical approaches and important Landmarks • Parathyroid glands: – General measures – Surgical localization Thyroid Gland General measures • • • • • • Two lateral lobes connected with isthmus Total weight is about 15 to 25 g Each lobe: 4 x 1.5 x 2cm (height/width/depth) Extends from C5 to T1 vertebra Isthmus is over 2nd & 3rd tracheal ring Approximately 40% of patients have a pyramidal lobe that arises from either lobe or the midline isthmus 40% present General measures... • Cervical Fascia: – True Thyroid Capsule – Surgical Capsule – Berry’s Ligament (connecting the lobes of the thyroid to the cricoid cartilage and the first two tracheal rings) • Surgical Approaches regarding to the Fascia: – Intracapsular Thyroidectomy – Extracapsular Thyroidectomy Berry’s Ligament Vascular Supply • Two pairs of arteries • Three pairs of veins • Connecting vessels within the thyroid true capsule • In less than 10%, there is a midline arterial supply to the gland, named as Thyroid Ima artery Important proximities About 12cm About 5-6cm Non-recurrent LN, Less than 1% Can be find in only 10-30% of the times 1 cm Surgical approaches and Landmarks • The course of the inferior laryngeal nerve is highly variant • Incidence of nerve paralysis is three to four times greater in cases in which the recurrent nerve was not localized compared with cases in which it was • Try to seek, expose and identifying the nerve, instead of avoiding it! • Extracapsular approach with nerve identification is the method of choice The most common course of Incidence is the nerve ismore within TEinGroove higher Revision cases (48.5% - not depicted here) 42.2% 5.4% 3.9% Extralaryngeal Branching (35.5% in some reports up to 80%!) Surgical approaches and Landmarks • Lateral Approach – Inferior Thyroidal Artery – Tubercle of Zuckerkandl (ZT) • Inferior Approach – Lore’s triangle – Tracheoesophageal Groove • Superior Approach – Posterolateral aspect of the Cricoid – Berry’s ligament – Inferior border of the inferior Constrictor – Inferior horn of the thyroid cartilage ...Lateral Approach • Used most commonly • RLN is identified typically at the thyroid midpole level (less nerve dissection required) • This approach is less useful for Revision ZT is Present in 63-80% of the patients ...Inferior Approach • Used for Revision cases and Goiter surgery (not substernal) • Problem: Longer nerve dissection and probability of Parathyroid glands ischemia • Benefit: nerve will be find before any extralaryngeal branching ...Superior Approach • Used for large substernal Goiters • Nerve is at the lower edge of the lateral aspect of the cricoid cartilage • Nerve should be identified just caudal to the lowest fibers of the inferior constrictor Parathyroid Glands General measures • • • • Two pairs: Superior and Inferior Weight is about 50 to 70 mg Size 5 x 3 x 1 mm Color of normal parathyroid glands ranges from yellowish brown to reddish brown • 87% there are four glands (super numerary glands are usually in the mediastinum or thymus gland) • Their Arterial supply is usually from Inferior Thyroid artery (80%) Surgical Localization • Superior Parathyroid Glands – 80% they are at the cricothyroid junction approximately 1 cm cranial to the juxtaposition of the recurrent laryngeal nerve and the inferior thyroid artery. – Ectopic glands: it cloud be intrathyroid, paraesophageal, retroesophageal and mediastinal (posterior superior compartment) ...Surgical Localization • Inferior Parathyroid Glands: – More variable location – More than 50% of the inferior parathyroid glands are situated near the lower pole of the thyroid gland – Ectopic glands: it could be situated in thyrothymic ligament (28%) or mediastinum (Anterior superior compartment)