Thyroid tutorial by our dedicated Dr. Lohith [BMJH]

1. THYROID
Dr Lohith S
DNB Resident
Department of General Surgery
BMJH,Bangalore

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. The thyroid glandThe thyroid gland
ANATOMY AND EMBRYOLOGY
Lobes
Position
Blood supply
Development
Parathyroid glands

4.  The thyroid gland
derives its name
from the
thyroid cartilage
which resembles a
shield
(G. thyreos = shield)

5. Function
 The thyroid gland is
an endocrine gland
that is responsible for
the secretion of
thyroxin and
thyrocalcitonin

6. Lobes
 The thyroid gland
consists of two lobes
united in front of the
second, third and
fourth tracheal rings
by an isthmus of
gland tissue.
isthmusisthmus

7. Lobes
 Each lobe is pear-
shaped consisting of
a narrow upper pole
and a broader lower
pole
upper poleupper pole
lower polelower pole

8. Thyroid scan
 This nuclear scan uses
an injectable radioactive
compound. When
injected into the
bloodstream the
compound will be
concentrated in the
thyroid gland resulting in
an image of the gland
 The test can be useful in
diagnosis of thyroid
tumor

9. Position
 It lies under cover of sternothyroid and
sternohyoid muscles on the side of the larynx
and trachea
sternothyroid
sternohyoid

10. Position
 The upper pole of the thyroid cannot normally
rise above the level of the oblique lineoblique line of the
thyroid cartilage
Thyroid, upper pole
sternothyroid
thyrohyoid
cricothyroid

11.  The thyroid gland is
caught in the pocket
of sternothyroid
thyroid
cricoidthyroidcartilage
sternothyroidsternothyroid
thyrohyoid
cricothyroid
Position

12.  The lower pole of the
thyroid gland extends
along the side of the
trachea as low as the
sixth tracheal ring
1
2
3
4
5
6
Position

13.  Because of the proximity of the thyroid gland to the trachea
and esophagus, goiter causes compression of the trachea
and esophagus resulting in dyspnea and dysphagia
respectively
esophagusesophagus

14. Retro-sternal goitre with tracheal deviationRetro-sternal goitre with tracheal deviation

15. Retro-sternal goitreRetro-sternal goitre
with esophagealwith esophageal
deviationdeviation

16. Pyramidal lobe
 In about 40% of
people, there is a
small upwards
extension of the
isthmus called the
pyramidal lobe.

17. Levator glandulae thyroidae
 The pyramidal lobe may
be attached to the hyoid
bone by fibrous or
muscular tissue (levator
glandulae thyroidae).

18. Variations
 Bifurcation of the
lower end of the
pyramidal process,
one part going to
each lateral lobe

19. Variations
 Pyramidal process
attached to the left
lobe of the gland,
isthmus absent.

20. Variations
 Both pyramidal
process and isthmus
are absent.

21. Pre-tracheal fascia
 The thyroid gland is
surrounded by a
fibrous capsule and is
enclosed in the pre-
tracheal fascia

22. Pre-tracheal fascia
 The pre-tracheal
fascia attaches the
thyroid gland to the
trachea and larynx
 thus the thyroid
moves upwards on
swallowing, an
important diagnostic
feature for lumps in
the neck
thyroid
larynx

23. Blood supply
 The thyroid gland is very
vascular
 The vessels lie
between the capsule
and the pre-tracheal
fascia.
 In some pathological
conditions such as
thyrotoxicosis, owing to
its high vascularity, the
blood flow can be heard
with a stethoscope as a
bruit

24. Thyroid arteries
 The main arteries are
the superior and
inferior thyroid
arteries.
superiorsuperior
thyroid a.thyroid a.
inferiorinferior
thyroid a.thyroid a.

25. Superiorthyroidartery
 Arises from the
anterior surface
of the external
carotid
immediately
distal to the
carotid
bifurcation.
externalexternal
carotid a.carotid a.
carotidcarotid
bifurcationbifurcation

26. Superior thyroid artery
 Arches downwards,
giving a
sternomastoid
branch and a
superior laryngeal
branch that enters
the larynx with the
nerve of the same
name
superior
laryngeal
a. & n.

28. Superior thyroid artery
 enters deep to
sternothyroid
sternothyroid
Superior thyroid vessels

29. Superior thyroid artery
 before reaching the
upper pole of the
gland, and within the
pre-tracheal fascia, it
divides into two main
branches one for
either surface of the
gland
anterior posterior

30. Superior thyroid artery
 the posterior branch
anastomoses with the
inferior thyroid artery
posterior br.
of superior
thyroid a.
inferior
thyroid a.

31. Inferior thyroid artery
 Is a branch
of the
thyrocervical
trunk from
the
subclavian artery
. subclavian a.subclavian a.
thyrocervicalthyrocervical
trunktrunk
inferiorinferior
thyroid a.thyroid a.

32. Inferior thyroid artery
 Ascends and
turns medially
at the level of
the cricoid
cartilage to
enter the back
of the gland
some distance
above the
lower pole.

33. Inferior thyroid artery
 The tortuous course of
the inferior thyroid artery
is due to the fact that in
every swallow the thyroid
gland ascends a few
centimeters and must
naturally drag its blood
supply with it.
 If this artery has no
capability to elongate, it
would be traumatized

34. Inferior thyroid artery
 Divides outside the
pre-tracheal fascia
into four or five
branches that pierce
the fascia separately
to reach the lower
pole of the gland.
Remember that the superior thyroidRemember that the superior thyroid
artery divides within the pretrachealartery divides within the pretracheal
fasciafascia

35.  The recurrent laryngeal nerve lies normally behind the
branches of the inferior thyroid artery

36.  The recurrent laryngeal nerve lies normally behind the
branches of the inferior thyroid artery
 but it is common for the nerve to pass between the
artery branches before they pass through the fascia.

37.  The recurrent
laryngeal nerve
always lies
behind the pre-
tracheal fascia
and if this
structure
remains intact
during
thyroidectomy
the nerve will
not have been
divided
recurrent laryngeal n.
inferior thyroid a.

38.  Both thyroid arteries are
related to nerves which
must be avoided when
tying the arteries.

39.  A little distance
behind the superior
thyroid artery is the
external laryngeal
nerve.
superior thyroid a.
external laryngeal n.
external laryngeal n.
internal laryngeal n.
superior laryngeal n.

40. Superior laryngeal nerve variations
vagusvagus
internalinternal
externalexternal

41.  To avoid injury to the
external laryngeal
nerve, the superior
thyroid artery is
ligated and sectioned
near the superior
pole of the thyroid
gland where it is notnot
so closely related to
the nerve as it is at
its origin.

42.  Section of the
external laryngeal
nerve produces
weakness of voice,
since the vocal fold
cannot be tensed.
 The cricothyroid
muscle is paralyzed Cricothyroid tenses the vocal cordCricothyroid tenses the vocal cord

43.  The recurrent laryngeal nerve has a variable
relationship to the inferior thyroid artery
 because of its proximity to the inferior thyroid
artery and the pre-tracheal fascia it may be
injured while ligating the artery during
thyroidectomy

44.  hence the advisability of
ligating the inferior
thyroid artery well lateral
to the gland before it
begins to divide into its
terminal branches.
 the inferior thyroid artery
gives off esophageal
and inferior laryngeal
branches before its
terminal distribution into
the thyroid gland
site of
inferior
thyroid a.
ligation
site of
superior
thyroid a.
ligation

45.  The variable relationship of the inferior thyroid
artery to the recurrent laryngeal nerve makes
thyroid surgery a potential risk to normal
speech
 The recurrent laryngeal nerve supplies all the
intrinsic muscles of the larynx

46.  it is advisable that a
surgeon about to perform
a thyroidectomy
examines the vocal cords
prior to operation, so that
if there is any problem
postoperatively one
knows at least the origin
of the lesion.

47. Recurrent laryngeal nerve damage
 Is a complication of
thyroid surgery that
causes paralysis of
the vocal cords
 When bilateral the
voice is almost
absent as the two
vocal folds cannot be
adducted.

48. Recurrent laryngeal nerve damage
 A unilateral recurrent
laryngeal nerve injury
may not be noticed in
normal speech but
would be very
detrimental to a
singers career.

49.  The thyroid arteries
anastomose freely
with each other and
with tracheal and
esophageal arteries.

50.  In operations
of partial or
sub-total
thyroidectomy,
all four arteries
are tied

51.  In operations of
partial or sub-
total
thyroidectomy,
all but the
posterior part of
the gland
excised
remaining
thyroid
tissue

52.  the dangerous
anatomy lies in the
posterior lateral lobes
(recurrent laryngeal
nerve and the
parathyroid glands)
Recurrent
laryngeal n.
parathyroid
gland

53.  The remains of
the gland are
located
alongside the
trachea and
contain the
parathyroid
glands, the
whole being
supplied with
blood by the
anastomosis

54. Thyroidae ima artery
 In about 10% of
individuals, an unpaired
artery, the thyroidae ima
(L. ima = lowest) is a
small occasional artery
from the brachiocephalic
trunk, or left common
carotid artery, or direct
from the arch of the
aorta

55. Thyroidae ima artery
 Ascends anterior to
trachea and supplies
the isthmus of the
thyroid gland.

56. Thyroidae ima artery
 The possible presence of
the thyroid ima artery
must be remembered
when incising the trachea
inferior to the isthmus.
 As the thyroidae ima runs
anterior to the trachea, it
is a potential source of
serious bleeding

57. Thyroid veins
 The veins are three in
number on each side
 the superior
thyroid vein from
the upper pole follows
the artery and enters
the internal jugular
vein or the
common facial
vein
Superior thyroid v.
Internal jugular v.

58.  The middle thyroid
vein is short and
wide, it enters the
internal jugular
vein
Thyroid veins
middle thyroid v.
Internal jugular v.

59.  From the isthmus and
lower pole of the gland
the inferior thyroid
veins form a plexus
within the pre-tracheal
fascia that descends in
front of the trachea to
reach the left
brachiocephalic vein
Thyroid veins
inferior thyroid vv.
brachiocephalic v.

60.  As the inferior thyroid
veins cover the anterior
surface of the trachea
inferior to isthmus, they
are potential sources of
bleeding during
tracheotomy (also
remember the
situation of the
thyroidae ima artery).
Inferior thyroid
veins

61. Development of the thyroid gland
 The gland begins as
a diverticulum from
the floor of the
embryonic pharynx

62. Development of the thyroid gland
 The diverticulum
grows caudally
superficial to the
hyoid before dividing
into two lobes
 The stem of the
diverticulum, the
thyroglossal duct,
normally disappears
hyoid
Thyroglossal duct

63. Development of the thyroid gland
 After the tongue has
developed, it can be seen
that the point of
outgrowth of the
thyroglossal duct is the
foramen cecum (of
Morgagni) [Morgagni,
Giovanni Battista, 1682-1771, a
Padua anatomist and pathologist,
also known for hydatid of
Morgagni (appendix testis) and
anal columns (of Morgagni)].

65. Thyroglossal cyst
 cysts derived from the
duct may also appear
anywhere between
the foramen cecum
and the normal
position in the midline
of the neck
1. Beneath foramen cecum
2. Floor of the mouth
3. Suprahyoid
4. Subhyoid
5. On thyroid cartilage
6. At level of cricoid cartilage

66. Thyroglossal cyst
 Can be diagnosed
because
characteristically
it moves upwards
as the patient puts
his tongue out.

67.  Infection of a
thyroglossal cyst
may spread to a
persistent
thyroglossal duct
which must be then
excised

68.  Although the
duct lies
ventral to the
hyoid bone,
it passes up
for a short
distance
behind the
body, which
therefore
has to be
excised with
the duct

69. Accessory thyroid gland
 Aberrant thyroid
tissue may appear
between the foramen
cecum and the
normal position

70. Lingual thyroid
 Rarely the thyroid
fails to descend
during development
resulting in the
development of a
lingual thyroid

71. Ectopic thyroid
 Failure of descent
mar result in a
superior cervical
thyroid in the region
of the hyoid bone
 the thyroid may
sometimes
descended too far
and be found in the
superior mediastinum

72. Parathyroid glands
 Two on each side
 They are yellow-brown
endocrine glands, about
the size of a small pea
(about 0.5x0.8 cm
ovoids)
 They are important
because of their role in
calcium metabolism.
They secrete
parathormone that
mobilizes bone calcium
and increases gut and
kidney calcium
absorption

73. Parathyroid glands
 Are located posterior
to the thyroid gland
between its capsule
and fascial sheath

74. Superior parathyroid glands
 more constant in
position
 embedded in the
posterior surface of
the thyroid gland, a
short distance above
the entry of inferior
thyroid artery (and the
level of the cricoid
cartilage).

75. Inferior parathyroid
glands
 variable in position
 usually embedded
behind the lower pole
but is often found
elsewhere (they may
even present in the
superior
mediastinum).

76. Parathyroid
development
 The parathyroids develop from the endoderm of
the third (inferior gland) and fourth (superior
gland) pharyngeal pouches

77.  The thymusthymus also develops from the third pouch and
may therefore carry the inferior parathyroidparathyroid with it
when it descends into the thorax.
Parathyroid
development

78. Parathyroid glands, blood supply
 The glands are
usually supplied by
the inferior thyroid
arteries but may also
be supplied by both
superior and inferior
thyroid arteries
posterior br.
of superior
thyroid a.
inferiorinferior
thyroid a.thyroid a.

79. Parathyroid glands
 Awareness of the
close relationship
between the
parathyroid glands
and the thyroid gland
is essential to prevent
removal or damage of
the parathyroid
glands during
thyroidectomy.

80.  The parathyroid
glands are
usually safe
during subtotal
thyroidectomy
because the
posterior part of
the thyroid
gland is
preserved

81.  The variability in position of the parathyroid glands may
create a problem during total thyroidectomy; in this case the
parathyroid glands are saved by following their small
vessels which are kept intact before the thyroid is removed.

82. 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.

83. ●
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

85. Investigations

86. USG in Thyroid
-gland enlarged or not
-nodular/diffuse
-single/multiple
-lymphnode assessment
-guide to FNAC
-benign or malignant depending on
vascularity
Peripheral-benign
Central -malignant

87. Disadvntage of USG in
Thyroid
No information about retrosternal thyroid
staging.

88. Radioisotope
 Usually was preferred earlier
 But now avoid as much as possible
 3 indications:
- Toxicity associated with nodularity
- To locate ectopic thyroid
- To locate metastatic
I123 should be avoided because of long t1/2.
Tc99 should be used.

90. Important points
 Most common cause of nodularity in
Thyroid –colloid>follicular adenoma
 80% of thyroid nodule are benign, 20%
are malignant.
 Chance of malignancy
-Euthyroid > hypothyroid > hyperthyroid(<1%)
-Cold > warm> hot
So to summarize cold euthyroid is a deadly
combination.

91. Important points
 IOC for systemic spread of carcinoma
Thyroid –PET scan
 FNNAC(Fine Needle Non Aspiration
Cytology) in this morphology is better
accepted then FNAC.
 Therefore in thyroid gland FNNAC is
preferred more than FNAC.

92. 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
●
Suspicion of malignancy in benign nodule like, hard nodule,
sudden increase in size, involvement of adjacent structures,
enlarged lymphnode and recurrent cyst.

93. TYPES
●
Thyroid lobectomy / Hemithyroidectomy
●
Subtotal thyroidectomy
●
Near total thyroidectomy
●
Total thyroidectomy
●
Completion thyroidectomy

94. Types:
 Sub-total: about 8gms , or a tissue, size of
pulp of finger is retained on lower pole on
both sides and rest is removed. Commonly
done in toxic thyroid, MNG.
 Total: entire gland is removed. Done in
malignancy.

95.  Near-total: both lobes except the lower pole
which is very close to recurrent laryngeal
nerve and parathyroid is removed. Here
<2gm of tissue is left behind.
 Hemi: along with removal of one lobe, entire
isthmus is removed. Done in benign disease
of only one lobe, thyroid cyst, solitary nodule.

96. PRE OPERATIVE
EVALUATION
●
Ultrasonography
●
Fine needle aspiration cytology – FNAC
●
Thyroid function tests – TFT
●
CT scan
●
Thyroid uptake scan
●
Laryngoscopy
●
Serum Calcium, Parathormone (PTH)

97. PRE OPERATIVE
PREPARATION
 Thyrotoxic patient are rendered euthyroid;
 Carbimazole 10-15mg 8hourly, when
patient become euthyroid(in about 4weeks)
they are maintained on 5-10mg
 Propranolol 80mg 6hourly 4-7days before
operation. Symptoms and signs are usually
controlled within 24hours. Continued 8-
10days post op
 Lugol’s iodine; 2weks pre-operatively to
reduce the vascularity of the gland

98. PRE OPERATIVE CONSENT
●
Scar
●
Airway obstruction
●
Voice changes
●
Hypoparathyroidism
●
Hypothyroidism

99. ANAESTHESIA
 Anaesthesia is general with cuffed
endotracheal tube
POSITION
 patient is placed in a supine position
initially with the neck extended by placing a
ring beneath the head and a sandbag roll
beneath the shoulder.
 The table is tilted 20–30 degrees “head up”
to aid in emptying the neck veins.11/26/16 99

100.  The skin is prepped from the chin to the
upper thorax
 Drapes are applied; head scarf, sides of
the neck, chest-abd, large covering the
legs. The are secured with clips
 Surgeon and assistant scrub and gown,
the stands on the opposite side to be
operated upon(usually the larger gland
first)

101. Incision
 Site of incision is indented with suture
 A transverse skin crease incision is placed
2-3cm above the sternal notch about 8cm
long extending to the lateral borders of
sternocleidomastoid.
 The scapel (with size 15 blade) is slanted
to divide the skin and platysma at different
level to give a neater scar
 Hemostasis is controlled with
electrocautary or prior infiltration with
lidocaine and adrenaline11/26/16 101

102. 11/26/16 102

103. PROCEDURE
 Elevate the flap of skin with the platysma (the assistant
lifts the skin and the platysma upward with double skin
hooks to allow for the creation of a subplatysmal flap).
 Superiorly to the thyroid cartilage
 Inferiorly to the suprasternal notche
 Place Joll’s retractor to retract the skin flaps
 This procedure should be blood free, because the
superficial veins lie beneath the cervical fascia.
 Divide the deep cervical fascia longitudinally in the
midline, between the anterior jugular veins.
 At the lower part there is usually a transverse cervical vein
that needs to be clamped, divided, and ligated with 3-0 silk
sutures
11/26/16 103

104. 11/26/16 104

105. 11/26/16 105

106.  The strap muscles (sternohyoid, and deeper sternothyroid) are carefully separated to
allow their retraction laterally.
 Assess goiter;
 The loose areolar tissue(capsule) overlying the thyroid gland is divided with
electrocautery.
 After the anterior surface of the thyroid has been thoroughly exposed, the entire
gland is carefully explored and palpated.
 The strap muscles are firmly retracted with a small loop retractor while the thyroid
gland is drawn medially
 Ligate and divide in continuity
 Middle thyroid vein
 Superior thyroid vessels close to the gland(to avoid injury to the external
laryngeal nerve) between two proximal and one distal ligature.
 The recurrent laryngeal nerve and the parathyroids are identified and preserved then
the terminal branches inferior thyroid artery are ligated and divided close to the
capsule. Or the inferior thyroid artery is identified far away from the gland
ligated in continuity to avoid injury to the recurrent laryngeal nerve.
11/26/16 106

107.  The thyroid is then mobilized and removed;
 Divide isthmus and place hemostats around
margin of resection (run with interlocking 3-0
absorbable suture) leaving about 4g of thyroid
from each lobe for subtotal
 If a total thyroidectomy is being performed, the
remaining lobe is removed in a similar fashion,
with division of the middle thyroid vein,
identification of the recurrent laryngeal nerve and
parathyroid glands, and ligation and division of the
superior pole and branches of the inferior thyroid
vessels.11/26/16 107

108. CLOSURE
 Absolute haemostasis
 Suction drain to thyroid bed(beneath
the strap muscles)
 Close loosely in layers with absorbable
sutures
 Close the skin with sutures or clips
 Check vocal cords on extubation by
direct laryngoscopy
11/26/16 bbinyunus2002@gmail.com 108

109. OPERATIVE STEPS
●
Anaesthesia, Positioning & Draping

110. ●
Skin incision and creation of flaps

112. Exposure of thyroid gland

113. Mobilization and dissection of
upper pole

114. Identification of RLN

116. Identification of parathyroid
glands

117. Dissection of ITA and removal
of gland

119. Closure

120. POST OPERATIVE MGT
 Half-hourly observation until conscious
 At the bed side
 Michel clip remover in case of respiratory distress due to hematoma
 10ml of 10% calcium gluconate in case of acute hypocalcamia
 Keep semi-recumbent
 Review indirect laryngoscopy(especially if there is cord
impairment on extubation)
 Serum calcium regularly in the postoperative period
 Thyroid function tests at 6weeks postoperatively
 Remove
 Drain when dry, 24-48hours postoperatively
 Sutures/clips, 2-3days postoperatively
11/26/16 120

121. COMPLICATIONS
 EARLY
 Haemorrhage
 Tetany

In first 3 days from corrected thyrotoxicosis

After 1 week with hypoparathyroidism
 Recurrent laryngeal nerve palsy

95% neurapraxia and resolves

If bilateral, cord adduct to midline so needs immediate reintubation

Thyroid crisis, if throtoxic patient is inadequately prepared rare with modern
technique
 Wound infection
 LATE
 Keloid
 Hypothroidism- 20%
 Recurrent thyrotoxicosis- <5% of patients undergoing
thyroidectomy for grave disease
11/26/16 121

122. RECENT ADVANCES
●
Minimally invasive thyroidectomy
●
Robotic transaxillary thyroid surgery
●
Transoral thyroidectomy

123. QUESTIONS
1. What is the blood supply to the thyroid gland
2. What are the preoperative measures prior to
thyroidectomy for thyrotoxicosis
3. What are the types of thyroidectomy
4. Outline the steps of thyroidectomy
5. What are the complications of thyroidectomy
6. What does the recurrent laryngeal nerve supply
and what is the consequence of it division
7. What does external laryngeal nerve supplies and
what is the consequences of it division
8. What is the Simon’s triangle
11/26/16 123