2. HISTORY Term 'thyroid' was coined by Thomas Warton in 17th
century Emil Theoder Kocher is considered as the Father of Modern
Thyroid surgery First thyroidectomy is considered to be done more
than 1000 years ago by Abu-al-Qasim The earliest account of
thyroidectomy was probably given by Roger Frugardi, 1170 3.
EMBRYOLOGY Thyroid gland develops from the median anlage and two
lateral anlagen Median anlage starts as a thickening of endodermal
epithelium in foregut between 1st and 2nd branchial arches at base
of tongue cells proliferate thyroid bud and then a diverticulum
expands and migrates to lie in anterior to trachea (4-7 wks of
gestation) The track usually disappears by birth 4. Two lateral
anlagen (ultimobranchial bodies) develop from caudal aspect of 4th
pharyngeal pouch fuse with median anlage as thyroid gland descends
in the neck Median anlage follicular cells Lateral anlagen
parafollicular cells 5. ANATOMY Thyroid gland 6. Thyroid gland is
composed of follicles which are secreting functional units of the
gland, together with a rich vascular, lymphatic and neural network
The gland comprises of two lobes connected by isthmus, lying in
midline on trachea at level of 2nd-3rd tracheal ring Gland is
invested in a fascial capsule 'Surgical capsule' derived from the
pretracheal fascia of deep cervical fascia. It is thin and closely
related to external surface of gland 7. Capsule is deficient in
posterior aspect of isthmus and most of posteromedial surface of
lobe where gland lies in close relation to trachea Along upper part
of posterior border of thyroid lobe and adjacent posteromedial
surface fascia is thick and firmly attached to trachea 'Ligament of
Berry' It binds gland firmly to trachea and must be freed while
releasing a lobe surgically RLN lies behind ligament of Berry just
before it disappears in larynx behind cricothyroid joint 8.
Posteriorly capsule extends to blend with prevertebral fascia
Laterally with carotid sheath Superiorly envelopes upper lobe of
gland and extends upwards around superior pedicle Along upper
border of isthmus fascia attaches to outer surface of trachea and
cricoid Inferiorly fascia passes into mediastinum anterior to
trachea and contains inferior thyroid veins 9. Each lobe of the
gland resides in a bed between trachea and larynx medially &
carotid sheath and SCM laterally. Strap muscles lie anterior to the
thyroid lobes Parathyroids and RLN are associated with posterior
surface of each lobe Superior pole lies posterior to sternothyroid
muscle and lateral to inferior constrictor & posterior thyroid
lamina Inferior pole may extend to level of 6th tracheal ring 10.
About 40% may have a 'pyramidal lobe' arising from either lobe or
isthmus and extends superiorly. It represents remnants of embryonic
thyroglossal duct and lie on surface of thyroid cartilage Tubercle
of Zukerkandl 75% Pyramidal enlargment of lateral edge of thyroid
lobe formed from fusion of median and lateral anlages Closely
related to RLN, inferior thyroid A, ligament of Berry and superior
parathyroid gland 11. Arterial supply 12. Superior thyroid artery
First branch of external carotid artery Course along inferior
constrictor muscle and enters upper pole of thyroid, and divides
into superior and inferior branches Superior branch runs along
medial surface of upper pole and along upper border of isthmus to
anastose with its fellow on opposite side Inferior branch descends
along posterior border of thyroid to anastomose with upper branch
of inferior thyroid artery Superior thyroid A lies posterolateral
to external branch of SLN 13. Inferior thyroid artery Arises from
thyrocervical trunk Lies deep to common carotid artery and as it
nears gland divides into upper and lower branches Upper branch
anastomoses with inferior branch of superior thyroid artery Lower
branch runs downwards towards inferior pole of thyroid 14. Inferior
thyroid artery provides an important surgical landmark for RLN In
almost 70% of patients inferior thyroid artery lies anterior to the
RLN. Thyroidea ima artery is occasionaly present arising from
aortic arch / carotid artery 15. VENOUS DRAINAGE Superior thyroid
vein accompanies the superior thyroid artery and joins IJV Middle
thyroid vein originate from anterolaterla surface of gland and pass
laterlally to join IJV Division of this vein permits adequate
rotatiom of thyroid lobe to identify RLN and parathyroid glands
Inferior thyroid vein comes from inferior boeder of gland and drain
mainly to left brachiocephalic vein, but also into IJV 16. NERVES
Thyroid gland is innervated by symphatetic fibres from middle
cervical ganglia, fibres pass into gland along with principal
arteries to the gland Recurrent laryngeal nerve Provides motor
supply to larynx and some sensory fibres to upper trachea and
subglottis Right RLN arise from vagus (CN X) at base of neck, loops
around subclavian artery and ascends behind right lobe of thyroid.
It enters larynx behind cricothyroid muscle between arch of cricoid
cartilage and inferior cornua of thyroid cartilage 17. Left RLN
arise from left vagus at level of arch of aorta, loops posteriorly
around it and ascends in tracheo-oesophageal groove, posterior to
left lobe of thyroid and enters larynx. Left RLN is in close
relationship with inferior thyroid artery (70%) Non RLN may occur
rarely seen on right side 18. External laryngeal nerve Subdivision
of SLN SLN arises beneath nodose gangion of upper vagus and
descends medial to carotid sheath, dividing into external and
internal branches about 2cm above superior pole of thyroid Internal
branch travels medially and enters posterior thyrohyoid membrane
supplying sensation to supraglottis External branch extends
medially along inferior constrictor muscle to enter cricothyroid
muscle 19. LYMPHATICS Lymphatic drainage of thyroid gland has been
proposed by Taylor. His studies shows clinically relevant lymphatic
spread in thyroid malignancy Central compartment of neck - Tracheal
LN Chain of LN which lie in tracheo-oesophageal groove One or more
LN lying above isthmus 'delphian nodes' B/L central LN dissection
(level 6 dissection) Clears all LN from carotid artery to other and
down into superior mediastinum 20. Lateral compartment of neck A
constant group of LN lies along IJV on each side (level 2,3,4). LN
in supraclavicular fossa or more laterally level 5 LN may also be
involved in thyroid malignancy Thoracic duct on left side of neck
arches up out of mediastinum and passes forwards and laterally to
drain into left subclavian vein / IJV Lateral LN dissection removal
of level 2, 3, 4 and 5 LN. Vagus N, symphatheticc ganglia, phrenic
N, brachial plexus and spinal accessory N are preserved 21.
PARATHYROID GLANDS They are small semilunar shaped, ochra coloured
glands,situated in a pad of fat generally outside surgical capsule
secreting PTH, which controls serum Ca metabolism Gland are usually
4 in numbers, two on each side, occasionally 3-6. Superior
parathyroid glands - Develops from 4th pharyngeal pouch and descend
only slightly during devvelopment and their position remains
constant in adult life 22. Generally found at level of
pharyngo-oesophageal junction behind and seperate from posterior
border of thyroid gland Supplied by branch from upper division of
inferior thyroid artery Inferior parathyroid glands Arise from 3rd
pharyngeal pouch along with thymus Descend along with thymus and
have a wide range of distribution in adults Usually located short
distance from lower pole of thyroid Supplied by inferior terminal
branch of inferior thyroid artery 23. Thyroidectomy INDICATIONS As
therapy for patients with thyrotoxicosis To treat benign and
malignant thyroid tumours To alleviate pressure symptoms
(respiratory distress, dysphagia) with benign/ malignant process
Cosmetic purpose To establish a definitive diasgnosis of a mass
within thyroid gland, especialy when cytological analysis is either
non diagnostic or indeterminate 24. TYPES Thyroid lobectomy /
Hemithyroidectomy Subtotal thyroidectomy Near total thyroidectomy
Total thyroidectomy Completion thyroidectomy 25. PRE OPERATIVE
EVALUATION Ultrasonography Fine needle aspiration cytology FNAC
Thyroid function tests TFT CT scan Thyroid uptake scan Laryngoscopy
Serum Calcium, Parathormone (PTH) 26. PRE OPERATIVE PREPARATION
Hypothyroidism Hyperthyroidism 27. PRE OPERATIVE CONSENT Scar
Airway obstruction Voice changes Hypoparathyroidism Hypothyroidism
28. OPERATIVE STEPS Anaesthesia, Positioning & Draping 29. Skin
incision and creation of flaps 30. Exposure of thyroid gland 31.
Mobilization and dissection of upper pole 32. Identification of RLN
33. Identification of parathyroid glands 34. Dissection of ITA and
removal of gland 35. Closure 36. POST OPERATIVE CARE Look for signs
of bleeding, respiratory distress Serum Calcium Removal of drain
Reassessment of vocal cord mobility and thyroid function tests 37.
COMPLICATIONS Wound hemmorhage Wound infection Superior laryngeal N
injury Recurrent laryngeal N injury Unilateral RLN injury Bilateral
RLN injury Hypocalcemia Thyroid storm 38. POST OPERATIVE MANAGEMENT
Thyroid hormone replacement Radioactive iodine treatment External
beam radiotherapy and chemotherapy 39. RECENT ADVANCES Minimally
invasive thyroidectomy Robotic transaxillary thyroid surgery
Transoral thyroidectomy 40. THANK YOUTHANK YOU
