---

THYROID CASE - COMPLETE VIVA GUIDE (MS Surgery / DNB)

---

SECTION 1: EMBRYOLOGY

Origin of the Thyroid Gland

• Thyroid arises from two anlages - median and lateral - that follow separate embryologic paths before fusing into a single gland.
• Median thyroid anlage: Originates at the foramen cecum at the base of the tongue (floor of the primitive pharyngeal anlage), around the 3rd week of gestation.
• It descends anterior to the hyoid bone and larynx, connected to the foramen cecum via the thyroglossal duct (epithelial-lined tube).
• Median anlage gives rise to thyroid follicular cells (from endoderm).
• Lateral anlage: Originates from the 4th branchial pouch (ultimobranchial bodies), fuses with median anlage at ~5th week.
• Lateral anlage is neuroectodermal in origin - provides parafollicular C cells (calcitonin-secreting), which lie in the superposterior region of the gland.
• Thyroid follicles appear by 8 weeks; colloid formation begins by 11th week.

Thyroglossal Duct (TGD)

• Duct starts obliterating at 5th week, disappears by 8th week.
• Remnants lead to thyroglossal duct cysts - the most common congenital cervical anomaly.
• 80% are found juxtaposed to the hyoid bone.
• Histologically lined by pseudostratified ciliated columnar epithelium + squamous epithelium, with ectopic thyroid tissue in 20%.
• Sistrunk operation: En bloc cystectomy + excision of the central hyoid bone - mandatory to prevent recurrence.
• ~1% of TGD cysts contain cancer, usually papillary (85%).
• MTCs are never found in TGD cysts (C cells don't migrate through the duct).

Lingual Thyroid

• Failure of median anlage to descend - may be the only thyroid tissue present.
• Presents with choking, dysphagia, airway obstruction.
• Must rule out normal neck thyroid before any ablation or excision.

Lateral Aberrant Thyroid

• Thyroid tissue lateral to carotid sheath / jugular vein - almost always metastatic PTC in lymph nodes, NOT true ectopic tissue. (Crile's fallacy debunked)

---

SECTION 2: ANATOMY

Gross Anatomy

• Weight: ~20 g (varies with body weight and iodine intake).
• Color: Brown, firm consistency.
• Two lobes joined by an isthmus lying just inferior to the cricoid cartilage.
• Pyramidal lobe present in ~50% of people - extends cephalad from isthmus, usually left of midline. Palpable only in thyroid disease (Graves', diffuse goiter, Hashimoto's).
• Located posterior to strap muscles; lobes lie adjacent to carotid sheaths laterally.
• Extends from midthyroid cartilage superiorly to 5th-6th tracheal ring inferiorly.

Capsule and Ligament

• True capsule: Thin, densely adherent fibrous layer; sends septa inward forming pseudolobules.
• Berry's ligament (posterior suspensory ligament): Condensation of capsule near the cricoid cartilage and upper tracheal rings - attaches thyroid to trachea; this is where the RLN is at most risk.

Blood Supply

Nerve Relations (MOST IMPORTANT VIVA TOPIC)

• Left RLN: loops around arch of aorta, ascends in the tracheoesophageal groove.
• Right RLN: loops around right subclavian artery, ascends more laterally and obliquely than the left, a few mm away from the tracheoesophageal groove.
• Innervates all intrinsic laryngeal muscles EXCEPT cricothyroid.
• Enters larynx at the inferior border of the inferior constrictor, posterior to the cricothyroid joint.
• Injury causes: unilateral - hoarseness; bilateral - respiratory distress (stridor, may need tracheostomy).
• Non-recurrent inferior laryngeal nerve: ~0.5% incidence; associated with aberrant right subclavian artery arising directly from aorta (arteria lusoria). Runs near-transverse behind thyroid - high injury risk if not anticipated. Diagnose pre-op with ultrasound or CT.

• Innervates cricothyroid muscle - controls high-pitched voice and voice projection.
• Runs close to the superior thyroid artery.
• Cernea Classification (most common viva classification):
  • Type 1: Crosses >1 cm above superior pole - low injury risk
  • Type 2A: Crosses within 1 cm above superior pole - moderate risk
  • Type 2B: Crosses below the superior border of superior pole - highest injury risk
• Injury causes: loss of high-pitch voice, vocal fatigue (the "singer's nerve").

Parathyroid Gland Relations

• 4 glands total (2 superior, 2 inferior) - located posterior to thyroid.
• Superior parathyroids: Lie posterior to the RLN plane - more anatomically constant, ~2-5 mm from the nerve.
• Inferior parathyroids: Lie anterior to the RLN plane - more variable, ~7-10 mm from nerve; derived from 3rd branchial pouch (same as thymus - hence may be found in thymus!).
• Ectopic parathyroids: 15% of cases - retroesophageal, intrathyroidal, intrathymic, mediastinal.

---

SECTION 3: HISTOLOGY & PHYSIOLOGY

Histology

• Composed of follicles (spherical units lined by follicular epithelial cells).
• Follicles contain colloid (stored thyroglobulin).
• Follicular cells: cuboid in inactive state, columnar when active.
• Parafollicular C cells (between follicles): secrete calcitonin - source of MTC.

Thyroid Hormone Synthesis

1. Iodide trapping: Active transport via NIS (sodium-iodide symporter) - inhibited by perchlorate, thiocyanate.
2. Oxidation of I- to I2: By thyroid peroxidase (TPO) - blocked by PTU, carbimazole.
3. Organification: Iodination of tyrosine residues on thyroglobulin (Tg) → MIT and DIT.
4. Coupling: MIT + DIT → T3; DIT + DIT → T4.
5. Storage as colloid.
6. Secretion: Tg reabsorbed by endocytosis → proteolysis → T3 and T4 released.

• Wolff-Chaikoff effect: High doses of iodine temporarily inhibit thyroid hormone synthesis (exploited by Lugol's iodine preoperatively).
• Jod-Basedow effect: Excess iodine given to iodine-deficient patient → hyperthyroidism.

Thyroid Hormone Axis

• Hypothalamus → TRH → Pituitary → TSH → Thyroid → T3/T4 (negative feedback on TRH and TSH).
• T4 (inactive) is peripherally converted to T3 (active) by 5'-monodeiodinase in liver, kidney, muscle.
• Reverse T3 (rT3) = inactive; rises in severe illness (sick euthyroid / euthyroid sick syndrome).
• PTU (unlike carbimazole) also blocks peripheral conversion of T4 to T3.

---

SECTION 4: EVALUATION / INVESTIGATIONS

Thyroid Function Tests

• TSH is the most sensitive single test for thyroid function.
• Free T4 is preferred over total T4 (not affected by binding proteins).

Thyroid Autoantibodies

Thyroglobulin (Tg)

• Used as tumor marker for differentiated thyroid cancer (PTC, FTC) post-thyroidectomy.
• Should be undetectable after total thyroidectomy + RAI ablation.
• Rising Tg = recurrence / metastasis.
• Tg levels meaningless if anti-Tg antibodies are present (interfere with assay).

Calcitonin

• Tumor marker for medullary thyroid carcinoma (MTC).
• Baseline calcitonin screening indicated in all thyroid nodules before surgery (in some guidelines).
• Pentagastrin stimulation test used to unmask subclinical MTC.

Imaging

• First-line investigation for any thyroid swelling.
• Gives: size, number, echogenicity, vascularity, calcification, lymph nodes.
• Features of malignancy on USG: Hypoechoic, microcalcifications (psammoma bodies in PTC), irregular/ill-defined margins, taller-than-wide shape, increased central vascularity, absent halo sign.
• ACR TIRADS / K-TIRADS: Risk stratification system for thyroid nodules on USG.
• TIRADS 1 (benign) → TIRADS 5 (high suspicion malignancy).

• Gold standard for evaluating thyroid nodules.
• Bethesda System for Reporting Thyroid Cytopathology (BSRTC) - 6 categories:

• Uses Tc-99m pertechnetate (for structure) or I-123/I-131 (for function).
• Hot nodule (hyperfunctioning): RAI uptake increased in nodule, suppressed in rest - low risk of malignancy; seen in toxic adenoma.
• Cold nodule (hypofunctioning): No uptake - 10-15% malignancy risk; requires FNAC.
• Warm nodule: Equal uptake to rest of gland.
• RAI scan essential before RAI therapy for DTC (to assess remnant and metastases).

• For large goiters, retrosternal extension, tracheal compression, lymphadenopathy assessment.
• CT neck with contrast for preoperative planning of large/invasive thyroid cancers.
• MRI superior for soft tissue invasion assessment.

• Pre-operative indirect/direct laryngoscopy mandatory when:
  • Voice change present
  • Previous anterior neck surgery
  • Large/invasive thyroid lesion
  • Malignancy
• Documents RLN function pre-operatively.

---

SECTION 5: BENIGN THYROID DISORDERS

Goiter - Classification

• Non-toxic goiter (euthyroid)
• Toxic goiter (hyperthyroid)

• Diffuse goiter
• Nodular (MNG)
• Solitary nodule

• Simple (colloid) goiter
• Endemic goiter (iodine deficiency - most common worldwide)
• Sporadic goiter
• Physiological (puberty, pregnancy)
• Inflammatory (Hashimoto's, de Quervain's, Riedel's)
• Dyshormonogenetic (enzyme defect in hormone synthesis)
• Drug-induced (lithium, amiodarone)
• Malignant

• Grade 0: No goiter
• Grade 1: Goiter palpable but not visible (even with neck extended)
• Grade 2: Goiter visible with neck in normal position

Retrosternal Goiter

• Extension of thyroid mass below the thoracic inlet (plane of superior thoracic aperture).
• 80-90% are secondary/descending (from cervical goiter extending substernally - surgical plane intact).
• 10-20% are primary intrathoracic (aberrant thyroid tissue in mediastinum - no connection to cervical thyroid, separate blood supply from internal mammary / aorta).
• Symptoms: Dyspnoea, stridor (tracheal compression), dysphagia (esophageal compression), superior vena cava (SVC) syndrome (facial oedema, dilated neck veins), Horner's syndrome.
• Pemberton's sign: Facial congestion / plethora on raising both arms above head (internal jugular vein compression at thoracic inlet).
• CT chest essential for preoperative planning.
• Treatment: Surgical - cervical incision is usually sufficient for secondary RS goiter; sternotomy / thoracotomy for primary intrathoracic goiter.

Hashimoto's Thyroiditis (Lymphocytic Thyroiditis)

• First described by Hashimoto in 1912 as "struma lymphomatosa."
• Most common inflammatory thyroid disorder; leading cause of hypothyroidism.
• Autoimmune - CD4+ T cells activated against thyroid antigens, recruit CD8+ cytotoxic T cells.
• Antibodies: Anti-TPO (most sensitive), Anti-Tg.
• Histology: Lymphocytic infiltration, germinal center formation, Hurthle cell (oxyphilic) change, follicular atrophy.
• Can present as goiter ± hypothyroidism.
• Increased risk of thyroid lymphoma (B-cell NHL) and PTC.
• Treatment: Thyroxine (LT4) replacement for hypothyroidism.
• Surgical indications: Compressive symptoms, suspected lymphoma, suspicious nodule on FNAC.

de Quervain's Thyroiditis (Subacute Painful)

• Viral / post-viral etiology; strong association with HLA-B35.
• Tender thyroid, elevated ESR (>100 mm/hr), low RAIU (<2% at 24 hours).
• 4 phases: Hyperthyroid → Euthyroid → Hypothyroid (20-30%) → Resolution (>90%).
• Treatment: NSAIDs/aspirin, steroids for severe cases; beta-blockers for symptoms.

Riedel's Thyroiditis

• Rare fibro-inflammatory condition - thyroid replaced by dense fibrosis extending into surrounding structures (trachea, esophagus, carotid sheath, nerves).
• Associated with systemic IgG4-related disease (sclerosing cholangitis, retroperitoneal fibrosis).
• Presents as rock-hard, fixed thyroid - must distinguish from anaplastic carcinoma.
• Treatment: Tamoxifen, steroids; wedge resection of isthmus for tracheal decompression.

---

SECTION 6: HYPERTHYROIDISM - SURGICAL ASPECTS

Causes

1. Graves' disease (most common, ~70-80%)
2. Toxic multinodular goiter (Plummer's disease)
3. Toxic adenoma (Plummer's adenoma)
4. TSH-secreting pituitary adenoma (rare)
5. Factitious hyperthyroidism
6. Struma ovarii
7. Amiodarone-induced thyrotoxicosis
8. de Quervain's (transient)

Graves' Disease

• Autoimmune hyperthyroidism due to TRAb (TSH receptor-stimulating antibodies).
• Triad: Goiter + Ophthalmopathy + Pretibial myxedema (= Graves' disease).
• Graves' ophthalmopathy (thyroid eye disease / Graves' orbitopathy): Exophthalmos, lid retraction, lid lag (von Graefe's sign), extraocular muscle myopathy, optic neuropathy. Mediated by TSH receptor antibodies acting on orbital fibroblasts.
• Key clinical signs:
  • Bruit over thyroid (high vascularity)
  • Thyroid thrill (palpable)
  • Pyramidal lobe often palpable

Medical Treatment

• Thionamides: Carbimazole (CBZ) / Methimazole (MMI) - block TPO, inhibit organification.
• PTU additionally blocks peripheral T4→T3 conversion (preferred in thyroid storm, pregnancy 1st trimester).
• Beta-blockers: Propranolol (blocks peripheral effects, inhibits T4→T3 conversion at high doses) - symptomatic relief.
• Lugol's iodine (potassium iodide solution): Wolff-Chaikoff effect - reduces thyroid hormone synthesis and release; makes gland firm and less vascular; used 7-14 days pre-operatively in Graves' patients.

Surgical Treatment of Hyperthyroidism

• Reasons: Eliminates autoimmune stimulus, prevents recurrence, allows definitive RAI surveillance.

1. Patient must be biochemically euthyroid (T3/T4 normal) before surgery - to prevent thyroid storm.
2. Thionamide therapy for 4-8 weeks.
3. Propranolol (beta-blockade).
4. Lugol's iodine for 7-14 days pre-op (reduces vascularity and hormone release).

• Failure of / non-compliance with antithyroid drugs
• Recurrence after drug therapy
• Large goiter with compressive symptoms
• Suspected malignancy in a hot gland
• Pregnancy (2nd trimester) where drugs are contraindicated
• Patient preference
• Child/young patient (avoid lifelong RAI/drugs)
• Graves' ophthalmopathy (total thyroidectomy stops antigen supply to orbit)

• Stop thionamides and Lugol's immediately after surgery.
• Start levothyroxine replacement (1.5-1.7 mcg/kg/day).
• Check TSH at 6-8 weeks, then every 1-2 months until stable.
• After lobectomy for toxic adenoma: check TSH + free T4 at 4-6 weeks.

---

SECTION 7: SOLITARY THYROID NODULE (STN)

Definition

Prevalence

• Clinically palpable nodules: ~5% of population.
• On ultrasound: >50% of adults have thyroid nodules.
• Risk of malignancy in a solitary nodule: ~5-15%.

Features Suggesting Malignancy (History)

• Male sex
• Age <20 or >60 years
• Hard, fixed, rapidly growing nodule
• History of radiation to neck (especially childhood radiation)
• Family history of thyroid cancer / MEN
• Hoarseness, dysphagia, dyspnoea (RLN / tracheal invasion)
• Associated cervical lymphadenopathy
• Previous thyroid surgery

Features Suggesting Benign (History)

• Female sex, young age
• Soft, smooth, mobile nodule
• Painful / tender nodule (colloid, hemorrhagic, thyroiditis)
• Sudden increase in size (cystic hemorrhage)

Investigation Algorithm

1. TSH - if low → scintigraphy (hot nodule = unlikely malignant).
2. USG neck - characterize nodule, assess lymph nodes, guide FNAC.
3. FNAC - classify per Bethesda.
4. CT chest if retrosternal extension, tracheal deviation, lymphadenopathy.
5. Laryngoscopy if hoarseness.

---

SECTION 8: THYROID MALIGNANCY

Classification

Papillary Thyroid Carcinoma (PTC)

• Most common thyroid malignancy.
• Risk factors: Childhood radiation exposure (strongest known risk factor), family history, Hashimoto's.
• Macroscopy: Unencapsulated, irregular, white-gray, with calcification.
• Histology: Characteristic nuclear features (pathognomonic):
  • Nuclear grooves
  • Orphan Annie eye nuclei (ground-glass, empty-looking nuclei)
  • Nuclear pseudoinclusions
  • Psammoma bodies (concentrically calcified spherules - seen in ~50%)
• Molecular: BRAF V600E mutation most common (>60% of PTC) - associated with more aggressive behavior; also RET/PTC rearrangements (esp. radiation-induced).
• Spread: Primarily lymphatic (cervical lymph nodes - central Level VI first, then lateral).
  • Lateral aberrant thyroid = metastatic PTC in lymph node (not ectopic tissue).
• Variants:
  • Tall cell variant - more aggressive
  • Columnar cell variant - aggressive
  • Diffuse sclerosing variant
  • Cribriform-morular variant (associated with FAP/APC mutation)
  • NIFTP (Non-invasive follicular thyroid neoplasm with papillary-like nuclear features): Encapsulated follicular variant of PTC, now classified separately - benign behavior; lobectomy alone sufficient.

Follicular Thyroid Carcinoma (FTC)

• Second most common thyroid malignancy.
• Cannot be distinguished from follicular adenoma on FNAC - requires histological evidence of capsular invasion or vascular invasion.
• Molecular: RAS mutations, PAX8/PPARγ rearrangement.
• Spread: Primarily hematogenous (lung, bone - osteolytic lesions; brain).
• FNAC shows Bethesda IV (Follicular Neoplasm) → proceed to hemithyroidectomy (diagnostic + therapeutic).
• Minimally invasive FTC (capsular only): Lobectomy may suffice.
• Widely invasive FTC: Total thyroidectomy + RAI.

Hurthle Cell Carcinoma

• Variant of FTC composed of >75% oxyphilic (Hurthle / Askanazy) cells.
• Less responsive to RAI than conventional FTC.
• Less favorable prognosis.

Medullary Thyroid Carcinoma (MTC)

• Arises from parafollicular C cells (secrete calcitonin).
• 25% are hereditary - associated with MEN 2A / MEN 2B or familial MTC (FMTC).
• 75% sporadic.
• Marker: Serum calcitonin (screening, diagnosis, follow-up) ± CEA.
• Molecular: RET proto-oncogene mutation on chromosome 10.
  • Hereditary MTC: germline RET mutation → genetic testing of ALL first-degree relatives mandatory.
  • Sporadic MTC: somatic RET mutation in ~40%.
• Histology: Amyloid stroma (positive for Congo red) - derived from procalcitonin.
• Does NOT take up RAI (C cells have no iodine-concentrating mechanism).
• Treatment: Total thyroidectomy + central neck dissection (Level VI) - always.
• If hereditary: lateral neck dissection based on calcitonin levels.
• Prophylactic thyroidectomy in RET mutation carriers based on risk stratification:
  • Highest risk (MEN 2B, codon 918) → thyroidectomy before age 6 months.
  • High risk (codon 634) → by age 5 years.
  • Moderate risk → by age 5 years or when calcitonin elevated.

MEN 2A vs MEN 2B

Anaplastic Thyroid Carcinoma (ATC)

• Most aggressive thyroid malignancy; median survival 3-6 months.
• Usually arises from dedifferentiation of pre-existing PTC or FTC.
• Presents in elderly with rapidly enlarging, rock-hard thyroid mass with tracheal/esophageal invasion.
• p53 mutations + BRAF + TERT mutations.
• All ATC classified as Stage IVA, IVB, or IVC at presentation.
• Treatment: Multimodal - surgery (debulking if resectable), external beam radiotherapy, chemotherapy (doxorubicin-based), targeted therapy (dabrafenib + trametinib for BRAF V600E-mutant ATC).
• Distinguish from Riedel's thyroiditis (FNAC / biopsy essential).

---

SECTION 9: THYROID CANCER SURGERY

Extent of Surgery

• Removal of all thyroid tissue.
• Indicated for:
  • PTC >1 cm
  • Bilateral / multifocal PTC
  • FTC (widely invasive)
  • MTC (always)
  • ATC (if resectable)
  • Graves' disease (preferred over subtotal)
  • Toxic MNG (preferred)

• For: Follicular neoplasm (Bethesda IV), NIFTP, low-risk PTC ≤1 cm (unifocal, no extrathyroidal extension, no LN involvement).
• Some small PTCs (<1 cm) = papillary thyroid microcarcinoma (PTMC) - can be managed with active surveillance in selected patients.

• Leaves <1 g of tissue near Berry's ligament to protect RLN. Less favored now.

Lymph Node Dissection

• Central neck dissection (CND) = Level VI: Prelaryngeal (Delphian), pretracheal, paratracheal nodes.
  • Therapeutic CND: Indicated when central nodes are clinically/radiologically positive.
  • Prophylactic CND: Controversial for PTC; recommended for MTC, high-risk PTC, T3-T4 tumors.
• Lateral neck dissection: For radiologically confirmed lateral node involvement (Levels II-V). Never a "berry-picking" dissection - must be a formal compartmental dissection.

AMES / MACIS / TNM Staging (PTC)

• ATA (American Thyroid Association) risk stratification:
  • Low risk: Intrathyroidal PTC, no LN mets, no vascular invasion
  • Intermediate risk: Minor extrathyroidal extension, microscopic LN mets, aggressive histology
  • High risk: Gross extrathyroidal extension, incomplete resection, distant mets

Radioactive Iodine (RAI / I-131) Therapy

• Used for: Remnant ablation after total thyroidectomy for differentiated thyroid cancer (PTC, FTC).
• NOT effective for MTC or ATC.
• Pre-RAI: TSH should be elevated (>30 mIU/L) to stimulate iodine uptake.
  • Method 1: Withdraw levothyroxine for 4-6 weeks (hypothyroid stimulation).
  • Method 2: rhTSH (Thyrogen) injection - preferred (avoids hypothyroid symptoms).
• Low iodine diet for 2 weeks before RAI.
• Indications for RAI ablation (ATA guidelines): High or intermediate risk; not routinely for low-risk microcarcinoma.

TSH Suppression Therapy

• Post-thyroidectomy levothyroxine given at supraphysiological dose to suppress TSH.
• TSH drives differentiated thyroid cancer growth (via TSH receptor on cancer cells).
• High risk DTC: TSH suppressed to <0.1 mIU/L.
• Low risk DTC: TSH 0.1-0.5 mIU/L.

---

SECTION 10: THYROIDECTOMY - SURGICAL TECHNIQUE

Incision

• Kocher's transverse collar incision: 2-3 cm above the suprasternal notch, along Langer's lines (skin creases).
• Length: ~4-6 cm for routine thyroidectomy.

Steps of Thyroidectomy (Standard)

1. Skin incision - Kocher's collar incision.
2. Subplatysmal flaps raised superiorly to thyroid notch, inferiorly to sternal notch.
3. Midline (linea alba cervicis) divided, strap muscles separated (NOT cut unless enlarged gland).
4. Middle thyroid vein ligated and divided early (allows medial rotation of lobe).
5. Superior pole dissected - superior thyroid artery ligated individually on the capsule (to protect EBSLN).
6. Inferior thyroid artery ligated away from capsule or individual branches on capsule (to protect RLN and parathyroids).
7. RLN identified - followed from its entry into Berry's ligament / tracheoesophageal groove upward.
8. Parathyroid glands identified and preserved (superior first - more constant). If devascularized, autotransplant to sternocleidomastoid or brachioradialis.
9. Berry's ligament divided close to trachea.
10. Isthmus divided ± pyramidal lobe excision.
11. Drain placed (optional - not routine; used for large thyroidectomies).
12. Strap muscles reapproximated, platysma, skin closure.

Key Surgical Principles

• Always ligate superior thyroid artery on the capsule - protects EBSLN.
• Always identify and visualize the RLN throughout its course (not just palpate).
• Preserve parathyroid blood supply (branches of inferior thyroid artery to posterior capsule).
• Intraoperative nerve monitoring (IONM): Electromyographic monitoring of RLN via endotracheal tube electrodes - reduces RLN injury risk, helps identify nerve.
• Autotransplantation of parathyroid: If parathyroid inadvertently removed or devascularized - mince into 1mm3 fragments, implant into pocket in SCM or brachioradialis.

---

SECTION 11: COMPLICATIONS OF THYROIDECTOMY

Immediate (<24h)

1. Primary hemorrhage / hematoma: Most feared immediate complication.
   • Airway compromise from expanding hematoma compressing trachea = surgical emergency.
   • Open wound at bedside (or in emergency) to decompress hematoma → take patient to OR.
2. Respiratory distress: Bilateral RLN injury (rare), tracheomalacia (softened tracheal rings from prolonged goiter compression), bilateral cord palsy.
3. Thyroid storm (if inadequately prepared).

Early (24h - 2 weeks)

1. Hypocalcemia / Tetany (most common early complication after total thyroidectomy):
   • Due to: Inadvertent removal, devascularization, or contusion of parathyroid glands.
   • Also: Hungry bone syndrome - especially in hyperthyroid patients (bones demineralized from high bone turnover; after thyroidectomy, calcium rapidly deposited in bones → severe prolonged hypocalcemia despite normal PTH).
   • Symptoms: Perioral tingling, hand/foot tingling, Trousseau's sign (carpal spasm with sphygmomanometer cuff), Chvostek's sign (facial muscle twitch on tapping facial nerve at zygoma).
   • Treatment: IV calcium gluconate (10 mL of 10% solution over 10 min) for symptomatic, oral calcium + calcitriol for mild.
   • Prophylactic: Routine oral calcium 1g TDS post-total thyroidectomy OR selective (based on post-op PTH level).
   • Intraoperative PTH assay: PTH <10 pg/mL immediately post-thyroidectomy predicts permanent hypoparathyroidism.
2. RLN injury - voice change, hoarseness.

Late (>2 weeks)

1. Hypothyroidism: Expected after total thyroidectomy - managed with lifelong levothyroxine.
2. Permanent hypoparathyroidism: Incidence 1-2% in expert hands; requires lifelong calcium + calcitriol.
3. Permanent RLN palsy: Incidence 1-2% in experienced surgeons. Unilateral - permanent dysphonia; bilateral - may need tracheostomy.
4. Keloid scar / hypertrophic scar.
5. Wound infection, seroma.
6. Recurrence (for cancer / Graves' disease).

Nerve Injury Details

---

SECTION 12: THYROID STORM

• Rare (1-5% of hospitalized thyrotoxicosis patients), mortality up to 25%.
• Precipitants: Surgery (in unprepared patient), infection, trauma, cesation of antithyroid drugs, RAI, DKA.
• Burch-Wartofsky Scoring System (1993): Based on temperature, CNS manifestations (agitation, delirium, coma), GI-hepatic dysfunction (nausea/vomiting/diarrhea/jaundice), cardiovascular (heart rate, AF, CHF), and precipitating factors. Score >45 = thyroid storm.

Treatment of Thyroid Storm (5 Pillars)

1. High-dose PTU: 500-1000 mg loading, then 200-300 mg 6-hourly (blocks synthesis AND peripheral conversion).
2. Lugol's iodine (1 hour AFTER PTU): Blocks hormone release (Wolff-Chaikoff).
3. Propranolol: Controls tachycardia, inhibits T4→T3 conversion.
4. Hydrocortisone 100 mg 8-hourly: Blocks T4→T3 conversion, treats potential adrenal insufficiency (Addison's overlap).
5. Supportive: IV fluids, cooling, treat precipitant, ICU care.

---

SECTION 13: MOLECULAR GENETICS SUMMARY (High Yield Viva)

---

SECTION 14: RAPID VIVA QUESTIONS & MODEL ANSWERS

• Type 1: Crosses >1 cm above the superior pole (safe)
• Type 2A: Crosses within 1 cm above superior pole (at risk)
• Type 2B: Crosses below the superior pole border (highest risk - must carefully ligate superior artery on capsule, not en masse)

• Medullary thyroid carcinoma (C cells don't concentrate iodine)
• Anaplastic carcinoma (dedifferentiated; lost NIS expression)
• Primary thyroid lymphoma
• Follicular adenoma (benign)

---