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Thyroid Flashcards

1
Q

Risk factors for thyroid cancer

A

Male
Extreme age <20, >60
Family history of thyroid cancer/MEN2
Known MEN2
Hx of neck irradiation

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2
Q

Suspicious features on USG

A

Hypoechogenicity
Microcalcifications
Irregular border/margin
Taller than wide
Disrupted rim calcifications
Extrathyroidal extension
Suspicious cervical LN

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3
Q

Prognostic factors for thyroid cancer (list a few systems) for disease specific mortality

A

AGES
AMES
MACIS
TNM

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4
Q

Complications of thyroidectomy

A

Early:
Wound hematoma
Laryngeal edema
Trachomalacia
Nerve palsy /RLN injury
Hypocalcemia
Thyroid storm
Change in voice
Late:
Hypocalcemia
Hypothyroidism

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5
Q

Arterial supply of thyroid gland

A

Arterial
-Superior thyroid artery from the external carotid artery
-Inferior thyroid artery from the thyrocervical trunk
Thyroid ima artery from the brachiocephalic trunk

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6
Q

Supply of the recurrent laryngeal nerve

A
  • all intrinsic laryngeal muscles except the cricothyroid
  • mucosa below vocal cord
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7
Q

Supply of the external branch of superior laryngeal nerve

A

cricothyroid

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8
Q

Pathway of the LEFT recurrent laryngeal nerve

A

arises left of arch of aorta
crosses the aortic arch
descends in front of aorta
loops under ligaments arteriosum
ascends on side of trachea

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9
Q

Physiological actions of thyroid hormone

A

Metabolic effect: increase BMR, energy (protein, carbohydrate, fat) metabolism
Neurological: cortical arousal
Cardiac: cardiac output, heart rate
GI: gut motility
MSK: catabolic activity of bone=

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10
Q

Choosing between hemithyroidectomy and total thyroidectomy. Risk factors

A

Size >4cm
BRAF mutation +ve
Sonographically suspicious of ETE
Bilateral nodular disease
Familial thyroid carcinoma
Prior neck RT
Patient preference

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11
Q

Advantages of total thyroidectomy over hemithyroidectomy

A
  • Lower risk of recurrence
  • Presence of multifocal disease in contralateral lobe is 35-80%
  • Can perform remnant/adjuvant RAI ablation
  • Surveillance with thyroglobulin levels
  • Low morbidity
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12
Q

Indications for central compartment dissection

A

Positive central LN on palpation/USG/intraoperation
FNAC prevent positive lateral cervical LN
Tumor >4cm
Evidence of extra thyroidal extension

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13
Q

Indications for prophylactic central compartment dissection

A

Tumor >4cm
Evidence of ETE

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14
Q

Indication for modified radical neck dissection

A

FNAC proven lateral cervical LN

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15
Q

Describe the pathway of embryogenic thyroid descent

A

Foramen caecum (floor of pharynx/base of tongue)
Midline descent
Descends in front of hyoid bone
Curves backwards down to larynx

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16
Q

Importance of tubercle of Zuckerkandl

A

1) source of residual thyroid tissue
2) lateral to RLN
3) superior PTH is just cephalic to tubercle

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17
Q

Half life of thyroxine

A

7 days

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18
Q

Half life of T3

A

2.5 days

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19
Q

Pathway of right recurrent laryngeal nerve

A

Branches of at the right subclavian artery
loops behind to artery
ascends on side of trachea behind CCA

20
Q

Pathway of RIGHT recurrent laryngeal nerve

A

Branches from vagus
crosses anteior to right subclavian artery
loops behind artery
crosses behind right CCA
ascends in / near tracheoesophageal grove
enter larynx behind cricothyroid articulation + inferior Cornu of thyroid cartilage

21
Q

What is the mechanism of RAI

A

Radio-iodine 131-I is taken up by thyroid follicular cells and cause acute thyroid cell death by emission of short path length beta particles 1-2mm

22
Q

Short term complications of RAI

A

Radiation thyroiditis
Painless neck edema
Sialadenitits
Tumor hemorrhage/edema
Nausea

23
Q

Long term complications of RAI

A

Secondary malignancy
Gonadal function/fertility
Nasolacrimal duct obstruction
Tumor swelling

24
Q

Preparation of RAI

A

Low iodine diet for 1-2 weeks
No contrast CT within 8 weeks (compromises I-131 uptake)
Avoid amiodarone for 12 months
Increase TSH levels by:
1) withdrawal of thyroid hormone: stop taking 3-6 weeks before RAI
2) recombinant hormone TSH (Thyrogen): injections few days prior to ablation

25
Low iodine diet
No iodised salt No dairy products No foods from the sea (seafood) Limited grain products Limited amounts of beef, chicken and turkey Egg yolk
26
What is papillary micro carcinoma
PTC \<= 1 cm
27
Venous supply of thyroid gland
Superior thyroid vein -\> IJV Middle thyroid vein -\> IJV Inferior thyroid vein -\> left brachiocephalic vein All drain the venous plexus
28
What is the result of unilateral recurrent laryngeal nerve injury?\*
Vocal cord is paramedian due to adduction by cricothyroid. Voice is preserved
29
What is Horner's syndrome?
Injury to the cervical sympathetic nerves - pupillary constriction - partial ptosis of the upper eyelid - apart enopthalmos - dilation fo retinal vessesl - flushing and drying of affected facial skins
30
Arterial supply of the parathyroid glands
Inferior thyroid artery
31
Beahrs Triangle
common carotid artery inferior thyroid artery recurrent laryngeal nerve in tracheoesophageal groove
32
Joll's Triangle | (sternothyrolaryngeal triangle)
Aim: to identify the EBSLN Lateral : upper pole of thyroid and superior thyroid vessels Superior: attachment of strap muscles Floor: cricothyroid muscle
33
Capsular dissection technique
Hugging the gland and dividing the tertiary branches of the vessels while dissecting away parathyroid gland and RLN
34
Cernea classification for EBSLN
Type 1: crosses superior thyroid vessels \>1cm above upper edge of superior thyroid pole Type 2a: never crosses \<1cm above the plane Type 2b: below the plane
35
What is Grave's disease?
Autoimmune disease where autoantibodies to TSH receptor (TRAb) cause overstimulation of thyroid gland leading to goiter, hyperthyroidism, orbitopathy and dermopathy
36
What is a thyroid storm?
Life threatening condition due to severe clinical manifestiations of thyrotoxicosis
37
Clinical manifestations of thyroid storm
Hyperpyrexia Cardiovascular: tachycardia, arrhythmia, CHF Mental state: agitation, psychosis, stupor, coma GI: severe nausea, vomiting, diarrhea, abdominal pain
38
Management of thyroid storm
* ABC, ICU * IVF, sedatives * Cooling blankets * Thionamide (PTU 200mg q4H) *block new hormone synthesis* * Oral iodine solution 0.1-0.3ml TDS *block release of thyroid hormones* * Beta blockers *control s/s of increased adrenergic tone* * Glucocorticoids *reduce peripheral conversion of T4 → T3* * Bile acid sequestrants Cholestyramine
39
What cancers metastasize to thyroid
Breast Colon Renal Melanoma
40
Preoperative preparation for thyroidectomy
* Confirm euthyroid status * Laryngoscopy for vocal cord status
41
Thyroidectomy procedure
* Supine, extended neck with shoulder cushion * Collar scar * Develop subplatsymal flaps * Midline raphe open, strap muscles retracted laterally * Middle thyroid vein controlled and ligated * Mobilization of upper thyroid pole by capsular dissection * Superior thyroid vessels controlled and divided, ensure preservation of the external branch of superior laryngeal nerve * RLN identified behind the Zuckerland tubercle * Lower pole mobilized * Isthmus and pyramidal lobe removed enbloc
42
Advantages of hemithyroidectomy over total thyroidectomy
* Lower risk of hypocalcemia * No risk of bilateral RLN injury * Shorter surgery * No need lifelong thyroxine supplements * Trend towards risk adaptive individual management * Increase diagnosis of low risk thyroid cancer
43
**How to prevent EBSLN injury?**
* Routine identification of EBSLN * If unable to identify * Skeletonize superior thyroid vessels * Ligate superior thyroid vessels individually close to thyroid capsule * Never dissect pharyngeal constrictor muscle * Use IONM * meta-analysis shows benefit in EBSLN identification only
44
Routine identification of EBSLN
* Division of laryngeal head of sternothyroid muscle * Retract upper pole laterally and caudally * Enter avascular plane between medial border of upper pole and cricothyroid muscle (Joll's triangle) * Ligate superior thyroid vessels below EBSLN as close to thyroid capsule as possible
45
**How to prevent RLN injury?**
* Routine identification of recurrent laryngeal nerve in Beahr's triangle * Dissect behind Zuckerkandl tubercle (93%) * Be aware of RLN branching (40-80%) *anterior branch smaller but motor* * Be aware fo non-recurrent RLN (R 1%, L0.003%) * Rational use of energey platform + avoid traction injury * Use of IONM -*Cochrane review found no conclusive benefits*
46
Which retrosternal goiters require sternotomy
1. Primary mediastinal goiter 2. Cancer in retrosternal component 3. Iceberg shape 4. Extends below aortic arch 5. Extends into posterior mediastinum
47
**How to operate on retrosternal goiters?**
1. Longer incision 2. Higher incision 3. Do smaller side first 4. Divide strap muscles 5. Divide isthmus 6. Mobilize upper pole first 7. Divide middle thyroid veins 8. Dissect free all lateral attachments 9. Identify and preserve superior parathyroid glands 10. Identify RLN early close to laryngeal entry 11. Delivery of retrosternal component (free fascial attachments, blunt finger dissection, upward traction with other hand, sharp dissection under vision) 12. Additional maneuvers of delivery (use sterile soup spoon or sternotomy)

Endocrine (5 decks)

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