Preparatory Mindset
Cervical/thyroid disease is a core surgical topic — goiter classification, thyrotoxicosis, thyroid nodules & cancer, and thyroidectomy (CM exam tested). The exam tests: the thyroid anatomy & blood supply (see Anatomy notes), the indications for thyroidectomy, the complications of thyroid surgery (recurrent laryngeal nerve, hypocalcemia, hemorrhage), and thyroid cancer types (papillary > follicular > medullary > anaplastic). The past paper asks "Which is NOT an indication of thyroidectomy?" — a classic MCQ.
Exam mindset: thyroidectomy indications (toxic nodule, tumor, large goiter with compression, cosmetic, malignancy suspicion), the surgical complications with their signs, and the differentiated cancer prognosis. Papillary = best prognosis; anaplastic = worst.
Core Concepts
1. Thyroid anatomy recap (MUST KNOW)
- Position: front of the neck, below the larynx; isthmus at tracheal rings 2-3; butterfly shape, two lobes
- Blood supply: superior thyroid artery (ECA) + external laryngeal nerve; inferior thyroid artery (thyrocervical trunk) + recurrent laryngeal nerve; thyroid ima (inconstant)
- Nerves: external laryngeal (cricothyroid — voice); recurrent laryngeal (all intrinsic laryngeal muscles except cricothyroid — vocal cord); left loops under the aorta, right under the subclavian
- Parathyroids (4): behind the thyroid, inferior thyroid artery supply → hypocalcemia if injured
- Surgical relations: ligate superior thyroid artery close to the gland (protect external laryngeal); ligate inferior thyroid artery away from the gland (protect recurrent laryngeal); preserve parathyroids
2. Goiter (甲状腺肿) — classification (MUST KNOW)
- Graves' disease (弥漫性毒性甲状腺肿): autoimmune (TSH receptor antibodies), diffuse goiter + thyrotoxicosis + exophthalmos; the classic - Toxic multinodular goiter (Plummer's): older patients, no eye signs - Toxic adenoma: single hyperfunctioning nodule
- Simple (non-toxic) diffuse goiter (单纯性甲状腺肿): endemic (iodine deficiency), sporadic (puberty/pregnancy); diffuse, euthyroid; may become nodular/multinodular
- Nodular goiter: single vs multinodular goiter (MNG) — benign most common; risk of compression (trachea/esophagus) & malignancy (solitary nodule more suspicious than MNG)
- Toxic goiter (毒性甲状腺肿):
- Thyrotoxicosis vs thyroiditis: thyroiditis (subacute, postpartum) = transient hyperthyroidism from inflammation (↑T3/T4, low uptake)
3. Thyrotoxicosis (甲状腺功能亢进) (MUST KNOW)
- Medical: antithyroid drugs — carbimazole/methimazole, propylthiouracil (PTU); β-blockers (propranolol — symptom control); for Graves may give radioiodine - Surgical (thyroidectomy): for large goiter, compression, suspected cancer, failed medical, pregnancy (2nd trimester), patient preference - Radioiodine (I-131): definitive for Graves/Plummer (avoid in pregnancy, active eye disease)
- Clinical: weight loss, heat intolerance, sweating, palpitations/tachycardia, tremor, anxiety, diarrhea, exophthalmos (Graves), warm moist skin, goiter with bruit
- Investigations: TSH ↓, free T4 ↑, free T3 ↑; TSH-receptor antibodies (Graves); thyroid uptake scan (Graves = diffuse ↑ uptake; toxic adenoma = hot nodule; thyroiditis = low uptake)
- Treatment:
- Preoperative preparation for thyroidectomy (MUST KNOW): render the patient euthyroid — antithyroid drugs (6-8 weeks) then iodine (Lugol's) for 1-2 weeks (reduces vascularity & hormone release) + β-blocker; check vocal cords (RLN function)
4. Thyroidectomy — indications (MUST KNOW — past-paper MCQ)
Which is NOT an indication of thyroidectomy? (past paper: answer = a simple goitre that is small/asymptomatic) Indications:
- Toxic nodule / toxic nodular goiter (failed medical, recurrence, large)
- Thyroid tumour (suspected/confirmed malignancy)
- Large goiter with compression symptoms (dysphagia, stridor, dyspnea) or substernal extension
- Graves' disease (failed medical/radioiodine, pregnancy 2nd trimester, patient choice, large)
- Cosmetic (large disfiguring goiter)
- Retrosternal goiter
- Not an indication: small asymptomatic simple goiter (medical follow-up/iodine)
5. Complications of thyroidectomy (MUST KNOW)
| Complication | Mechanism | Presentation & management |
|---|---|---|
| Recurrent laryngeal nerve injury | Nerve damage | Unilateral: hoarseness, vocal cord paralysis (paramedian); Bilateral: stridor, airway obstruction → reintubate/tracheostomy |
| External laryngeal nerve injury | Cricothyroid paralysis | Weak/breathy voice, inability to shout (no pitch change) |
| Hypocalcemia (parathyroid injury) | Parathyroid removal/ischemia | Perioral/tingling numbness, carpopedal spasm, Chvostek's/Trousseau's signs, tetany → IV calcium gluconate, oral calcium+vitamin D |
| Hemorrhage/hematoma | Bleeding | Neck swelling, airway compromise (1st 24 h) → open wound immediately in ICU/ward |
| Thyroid storm (crisis) | Preop not euthyroid | Fever, tachycardia, agitation, delirium → β-blockers, antithyroid, iodine, steroids, cooling, ICU |
| Infection, scar (keloid) | — | Wound care |
- Prevention: identify & preserve RLN (routine nerve identification/IONM), preserve parathyroids (autotransplant if devascularized), meticulous hemostasis, drain
6. Thyroid cancer (MUST KNOW)
| Type | % | Features | Prognosis |
|---|---|---|---|
| Papillary (乳头状) | ~80% (most common) | Women, radiation history; spreads lymphatically; slow; psammoma bodies; excellent | Best |
| Follicular (滤泡状) | ~10-15% | Hematogenous spread (bone, lung); capsular invasion distinguishes from adenoma | Good |
| Medullary (髓样) | ~5% | C-cells → calcitonin (marker); MEN2 association; RET mutation | Intermediate |
| Anaplastic (未分化) | <2% | Rapid, aggressive, undifferentiated | Worst (months) |
| Lymphoma/others | rare | MALT lymphoma | variable |
- Presentation: painless neck lump, hoarseness (RLN invasion), lymphadenopathy; incidental on imaging
- Investigation: US + FNA (fine-needle aspiration) cytology (Bethesda classification); calcitonin for medullary; staging CT
- Treatment: total thyroidectomy (for most; lobectomy for small low-risk papillary) + central/lateral neck dissection for nodal disease; thyroxine suppression (TSH <0.1) & radioiodine ablation for high-risk differentiated cancer; medullary: total thyroidectomy + node dissection + calcitonin monitoring; anaplastic: palliative
- Follow-up: thyroglobulin (differentiated), calcitonin (medullary), US
7. Other neck masses (differential)
- Thyroglossal cyst: midline, moves with tongue protrusion; Sistrunk operation
- Branchial cyst: lateral neck, along the anterior border of SCM
- Cervical lymphadenopathy: infection, TB, lymphoma, metastasis (head & neck cancer)
- Parathyroid adenoma → hyperparathyroidism (stones, bones, groans, psychic moans)
High-Yield Points
- Thyroidectomy indications: toxic nodule, tumour, large/compressing goiter, Graves (failed medical), cosmetic, retrosternal — NOT small asymptomatic simple goiter (past-paper MCQ)
- Graves = diffuse toxic goiter + exophthalmos + TSH-R antibodies
- Preop: euthyroid (antithyroid drugs) + Lugol's iodine 1-2 weeks + β-blocker
- Complications: RLN (hoarse/stridor), external laryngeal (weak voice), hypocalcemia (tetany — Chvostek/Trousseau), hematoma (airway — open wound), thyroid storm
- Thyroid cancer: papillary (80%, best, lymphatic), follicular (hematogenous), medullary (calcitonin, MEN2), anaplastic (worst)
- Diagnosis: US + FNA; treatment: total thyroidectomy + thyroxine suppression ± radioiodine
- Thyroglossal cyst: midline, moves with tongue; branchial cyst: lateral
- RLN: left under aorta, right under subclavian; protect with inferior thyroid artery ligation away from gland
Topic Summary
Thyroid disease: goiters (simple/endemic, multinodular, Graves' toxic diffuse with exophthalmos, toxic MNG, toxic adenoma); thyrotoxicosis (TSH↓ T4↑; antithyroid drugs + β-blocker + Lugol's before surgery). Thyroidectomy indications: toxic nodule, tumor, large/compressing goiter, Graves' failure, cosmetic, retrosternal — small asymptomatic simple goiter is NOT an indication (past-paper MCQ). Complications: recurrent laryngeal nerve injury (unilateral hoarseness / bilateral stridor), external laryngeal (weak voice), hypocalcemia from parathyroid injury (tetany — calcium replacement), hematoma (airway — open wound), thyroid storm. Thyroid cancer: papillary (most common, best prognosis, lymphatic spread), follicular (hematogenous), medullary (calcitonin, MEN2), anaplastic (worst). Diagnosis: US + FNA; treatment: thyroidectomy ± node dissection + thyroxine suppression ± radioiodine.
LMCHK OSCE Practice
- Thyroid examination: inspect (goiter, scars, JVP), palpate from behind (lobes, isthmus, consistency, nodules, lymph nodes), auscultate for bruits (Graves), ask the patient to swallow.
- Thyroidectomy indications & consent: list the indications; explain the risks (voice change, hoarseness/stridor from RLN, calcium problems/tetany, bleeding/hematoma, thyroid storm, scar).
- Post-thyroidectomy monitoring: check the wound (hematoma — emergency opening), voice, and calcium (perioral tingling → Chvostek/Trousseau); have IV calcium ready.
- Thyroid nodule workup: thyroid function tests + US + FNA (Bethesda); explain when surgery is indicated (Bethesda IV-VI, compression, suspicious US).
- Thyroid cancer counselling: papillary (excellent prognosis) vs medullary (calcitonin, check MEN2/RET) vs anaplastic (poor); explain thyroxine suppression & radioiodine.
- Neck lump differential: midline moving with tongue = thyroglossal cyst; lateral = branchial cyst; lymphadenopathy workup.
- Graves' vs toxic MNG vs thyroiditis: TSH/T4, uptake scan (diffuse ↑, hot nodule, low uptake), and management differences.