Brief Summary
This video provides a detailed guide on examining the thyroid gland, covering anatomy, history taking, and clinical examination techniques relevant for NEET PG and INI CET aspirants in India. It emphasises the importance of anatomical knowledge, history taking skills and clinical examination.
- Importance of anatomical knowledge for clinical case understanding.
- Detailed explanation of history taking for thyroid swellings, including key questions to ask.
- Step-by-step guide to clinical examination of the thyroid, including inspection, palpation, and other relevant tests.
Introduction
The session will cover examination of the thyroid, including history taking, clinical examination, and basic concepts. It's important to have a strong understanding of anatomy before discussing clinical cases. Any queries can be posted in the chat box.
Anatomy of Thyroid Gland
The thyroid gland gets its name from the Greek word "thyrus," meaning shield, because of its proximity to the thyroid cartilage, which protects neck structures. The thyroid gland itself doesn't shield anything directly. It's a butterfly-shaped gland attached to the trachea via the isthmus, with two lobes (right and left). For surgeons, understanding the blood supply and related nerves is crucial. The superior thyroid artery originates from the external carotid artery and divides into branches within the gland. The inferior thyroid artery, a branch of the thyrocervical trunk from the subclavian artery, divides into multiple branches before entering the gland. A third, less common artery, the arteria thyroidia ima, can arise from the arch of the aorta.
Thyroid Veins and Theodore Cocker
The superior thyroid vein corresponds to the superior thyroid artery and joins the internal jugular vein. The middle thyroid vein also joins the internal jugular vein. The inferior thyroid vein drains into the brachiocephalic vein. A fourth vein, Cocker's vein, has variable drainage. Theodore Cocker, the first surgeon to receive the Nobel Prize, significantly reduced mortality rates in thyroid surgery from 40% to less than 1%. He is known as the father of thyroid surgery.
Nerve Supply of Thyroid
The superior laryngeal nerve divides into the internal laryngeal nerve (purely sensory, supplying mucosa above the vocal cords) and the external laryngeal nerve (purely motor, supplying the cricothyroid muscle, which is a tensor of the vocal cord). Injury to the external laryngeal nerve results in huskiness or loss of pitch in the voice. Injury to the internal laryngeal nerve leads to paroxysmal cough and aspiration, especially when lying down. The most commonly injured nerve during thyroid surgery is the external laryngeal nerve.
Recurrent Laryngeal Nerve
The recurrent laryngeal nerve, a branch of the vagus nerve, "recurs" or loops around major vessels before reaching the thyroid. The right recurrent laryngeal nerve hooks around the right subclavian artery, while the left hooks around the arch of the aorta, giving it a longer course. In 2% of individuals, the right recurrent laryngeal nerve may be non-recurrent, directly supplying the thyroid gland. During surgery, superior thyroid artery ligation should be close to the gland to avoid injury to the external laryngeal nerve. Inferior thyroid artery ligation is now done close to the gland to preserve blood supply to the parathyroid glands.
Surgical Anatomy and Parathyroid Glands
The right and left inferior thyroid arteries are ligated close to the gland to preserve blood flow to the parathyroid glands. The superior thyroid artery is ligated close to the gland to prevent injury to the external laryngeal nerve. The inferior parathyroid gland is located superior to the recurrent laryngeal nerve, while the superior parathyroid gland is posterior to it. During parathyroidectomy for hyperplasia, the inferior parathyroid gland is often left to allow future removal without disturbing the recurrent laryngeal nerve.
Recurrent Laryngeal Nerve Injury and Berry's Ligament
The most common site of recurrent laryngeal nerve injury is in Beer's triangle, bounded by the tracheoesophageal groove, inferior thyroid artery, and common carotid artery. The right recurrent laryngeal nerve hooks around the right subclavian artery, and the left hooks around the arch of the aorta. The right recurrent laryngeal nerve can be non-recurrent in 2% of people. The recurrent laryngeal nerve supplies mucosa below the vocal cords and provides motor function to all laryngeal muscles, including the posterior cricoarytenoid, the safety muscle of the larynx. Injury causes hoarseness. Beer's triangle is the same location where Berry's ligament attaches.
Pre-Tracheal Fascia and Thyroid Movement
The deep cervical fascia extends from the arch of the aorta, becoming the pre-tracheal fascia, which engulfs the thyroid gland and attaches to the hyoid bone. Berry's ligament is a posterior medial thickening of this fascia. This attachment causes the thyroid gland to move with deglutition (swallowing). Thyroid enlargement can extend into the mediastinum up to the arch of the aorta but not above the hyoid bone, explaining retrosternal extensions.
History Taking in Thyroid Examination
When taking a history for thyroid issues, focus on the presenting illness (swelling and pain), pressure effects, toxic features, and potential signs of cancer. For swelling, ask about duration, onset, and progress. Short duration swellings are often associated with cancer or thyroiditis, while long duration is seen in colloid goiters. Rapidly progressing swellings may indicate cancer or thyrotoxicosis. Painful thyroid swellings can be due to post-FNAC pain, thyroiditis, or nerve infiltration by cancer.
Painful vs. Painless Thyroid Swellings and Pressure Effects
Most thyroid swellings are painless. Painful swellings can occur post-FNAC, with thyroiditis, or with cancers infiltrating nerves (especially anaplastic cancer). Riedel's thyroiditis is a painless exception. Follicular cancer, arising from colloid goiters, can have a long duration followed by rapid growth. Inquire about pressure effects like dysphagia (esophageal compression), dyspnea (tracheal compression), syncopal attacks (carotid artery compression), and hoarseness of voice (recurrent laryngeal nerve compression).
Toxic Features and Hypothyroidism
Ask about toxic features such as weight loss despite increased appetite, diarrhea, hypomenorrhea, heat intolerance, palpitations, tremors, and sleeplessness. For hypothyroidism, inquire about weight gain, hair loss, loss of appetite, constipation, lethargy, and cold intolerance.
Cancer-Related History and Past History
Inquire about other swellings, weight loss, bony swellings, hemoptysis (lung mets), and abdominal swelling (liver mets). Papillary cancer commonly metastasizes to the lungs, follicular cancer to the skull (pulsatile skull secondaries), and medullary cancer to the liver. Ask about past irradiation, which increases the risk of papillary cancer, and any goitrogenic drugs. Family history of thyroid problems, especially iodine deficiency and medullary thyroid cancer (RET oncogene mutation), is important.
Local Examination: Inspection
During inspection, note the site, size, shape, and surface of the swelling. Describe the location and dimensions of the swelling. Determine the plane of the swelling by assessing its relationship to the strap muscles and pre-tracheal fascia. The swelling becomes less prominent when the strap muscles are contracted and more prominent when the neck is extended. Thyroid swellings move with deglutition but not with tongue protrusion.
Trial Sign, Pemberton Sign, and Palpation
Trial sign refers to the prominence of the sternocleidomastoid muscle due to tracheal deviation. If the lower border of the swelling is not visible, perform Pemberton's sign to check for retrosternal extension causing SVC compression. Palpation should be done from behind with the neck slightly flexed. Confirm the size, shape, surface, and extent of the swelling.
Carotid Artery Palpation and Berry Sign
Palpate the carotid artery unilaterally against the Chassaignac tubercle. In benign swellings, the carotid artery can be pushed laterally. Berry's sign indicates malignancy if the carotid artery is not palpable due to infiltration. Carcass test involves lateral compression of the thyroid gland to check for tracheal compression, indicated by stridor.
Laggies Test, Krills Test, and Consistency
Laggies test involves pushing the thyroid gland with three fingers and palpating with the other three from the front. Krills test involves keeping the thumb on the thyroid swelling and asking the patient to swallow. Soft consistency is seen in Graves' disease, firm in colloid goiters, and hard in Riedel's thyroiditis and cancer.
Auscultation and Palpation of Nodes
Auscultate for thyroid bruits, especially in the superior pole, indicative of Graves' disease. Percuss over the manubrium sterni to check for retrosternal extension. Palpate for nodes in the neck, including submental, submandibular, upper jugular, middle jugular, lower jugular, posterior group, pre-laryngeal (Delphian), pre-tracheal, and upper mediastinal nodes.
Eye Signs: Exophthalmos and Proptosis
Examine for eye signs, starting with exophthalmos, confirmed by Navzigal's test (examining from above to see protruding eyeball). Differs test assesses the ability to avert the upper eyelid, which is not possible in Graves' disease due to Muller's muscle spasm. Differentiate exophthalmos (thyroid pathology) from proptosis (retro-orbital pathology).
Specific Eye Signs and Other Examinations
Demonstrate eye signs like Von Graefe's (lid lag), Joffroy's (absent wrinkle sign), Moebius' (absent convergence), Dalrymple's (lid retraction), and Stellwag's (staring look). Look for loss of eyebrows. Examine the mouth for fasciculations and lingual thyroid. Palpate for nodes in the neck systematically. Assess for fine tremors in the hands, acropachy, and pre-tibial myxedema. Check ankle and knee reflexes, looking for hung-up reflexes in hypothyroidism.
Grading of Exophthalmos and Systemic Examination
Grade exophthalmos as mild (Stellwag's, Von Graefe's, Dalrymple's), moderate (Joffroy's), or severe (Moebius'). Severe exophthalmos is due to intraorbital accumulation and paralysis of muscles. In malignant cases, look for keratitis, epiphora, chemosis, and orbital hemorrhage. Examine other systems, especially for cardiac failure features in secondary thyrotoxicosis.
Primary vs. Secondary Thyrotoxicosis
Primary thyrotoxicosis (Graves' disease) involves thyroid enlargement with toxic features due to long-acting thyroid-stimulating antibodies. Eye signs and CNS features (tremors, exaggerated reflexes) are prominent. Secondary thyrotoxicosis occurs in older patients with long-standing multinodular goiters, leading to toxic features. CVS manifestations (atrial fibrillation) are more common, and eye signs are less pronounced. Thyroid storm can occur in both.
Hypothyroid Features and Malignancy Examination
Hypothyroid features include obesity, dry inelastic skin, macroglossia, mask-like faces, loss of hair, hoarseness, and pseudomyotonic reflexes (hung-up reflexes). In malignancy, examine the spine, lungs, and cranium for pulsatile skull metastasis.
Diagnosis of Solitary Nodule Thyroid
Diagnose solitary nodule thyroid by providing an anatomical diagnosis (e.g., left side nodule), a functional diagnosis (e.g., euthyroid, hypothyroid, or thyrotoxic), and assessing for pressure effects. Provide a pathological diagnosis based on differential diagnoses, such as colloid goiter, dominant nodule of multinodular goiter, thyroiditis, cystic swelling, thyroglossal cyst, or malignant thyroid swellings.
Differential Diagnosis and Final Points
The most common cause is colloid goiter. Differentiate between benign and malignant causes. Toxic adenoma is a differential diagnosis if toxic features are present. Secondary thyrotoxicosis involves a solitary or multinodular goiter going for toxicosis, with more CVS manifestations and fewer eye signs. The pathological diagnosis should indicate whether the swelling is benign or malignant.
