Clinical Case - Anterior Triangle of the Neck

A 30 year old substitute teacher consults her physician, complaining of a swollen neck. She had first noticed the swelling 3 months ago. Over the last three months, it had been increasing in size. She also had some breathlessness. On examination, a solitary swelling of firm consistency was found on the right side of the larynx and trachea. The small mass was not attached to the skin and there were no changes to the overlying skin. The swelling moved upward with swallowing. Further tests showed that the mass was a carcinoma of the thyroid gland. The mass was surgically removed.

Questions to consider:

1. What is the gross form and location of the thyroid gland?

   The thyroid has left and right lobes connected by an isthmus. It extends from the thyroid cartilage to about the fourth or fifth tracheal ring. The isthmus lies anterior to the second, third and fourth tracheal rings. A pyramidal lobe may or may not be present, extending superiorly from the region of the isthmus.

2. Why did the tumor move upward when the patient swallowed?

   The thyroid gland is invested in a sheath derived from the pretracheal fascia. This holds the gland onto the larynx and the trachea, so the thyroid follows the movements of the larynx during swallowing. Any pathological swelling of the thyroid will move upwards with swallowing, distinguishing it from a mass in some other part of the neck.

3. How did the tumor cause breathlessness?

   Since the thyroid is anterior to the trachea, an abnormal mass can push on the trachea and partially occlude the lumen, causing breathlessness.

4. Which lymph nodes should the physician examine for metastases if a malignant tumor is suspected?

   The thyroid gland is drained primarily by the deep cervical lymph nodes.

5. What structures can be damaged during thyroidectomy if the surgeon is not careful?

   The two main arteries supplying the gland are accompanied by nerves that can be damaged during thyroidectomy. The superior thyroid artery is related to the external laryngeal nerve. This nerve supplies the cricothyroid and cricopharyngeus muscles. The inferior thyroid arteries are related to the recurrent laryngeal nerve.

6. Post-operatively, the surgeon carefully ensured that the patient was speaking properly. Why?

   Damage to the external laryngeal nerve can result in the inability to tense the vocal folds, producing weakness of the voice; the cricothyroid muscle is unable to contract. Bilateral damage to the recurrent laryngeal nerves may cause the patient to lose speech completely and cause difficulty in breathing.

A 32-year-old woman, who has been diagnosed with having toxic multinodular goiter for two years, is complaining of increasing shortness of breath and dysphagia that gets worse when lying in bed. Her usual complaint of intolerance to hot atmosphere, sweating, weight loss and emotional irritability has worsened lately. The surgeon assesses her condition and decides that surgery is indicated. He suggests doing bilateral subtotal thyroidectomy to relieve symptoms particularly of the lower parts of the gland. The patient was put on a two-week course of iodine and antithyroid drugs before the operation to reduce the vascularity of the thyroid.

Questions:

1. Why would patients with goiter be likely to have shortness of breath and dysphagia?
   

   The enlarged thyroid will press initially on the trachea. Pressure will increase when it reaches a large size since the sternothyroid muscle will be forced down to the superior mediastinum, and the trachea and esophagus will be compressed.

   
   
2. Which vessels should be ligated before doing lower subtotal thyroidectomy?
   

   The inferior thyroid artery, a branch of the thyrocervical trunk, runs posterior to the carotid sheath to reach the posterior aspect of the gland. It divides into several branches, which pierce the pretracheal fascia to supply the inferior pole of the gland. Other vessels to be dealt with are the middle and inferior thyroid veins.

3. Which structure should be carefully protected from injury during such an operation?
   

   The recurrent laryngeal nerve, because of its intimate relation to the inferior thyroid artery, is susceptible for injury during thyroidectomy.

4. What are the most likely complications that may arise from such an operation?
   

   Bleeding is possible due to the rich blood supply to the thyroid. Injury to the recurrent laryngeal nerve may result in temporary hoarseness of the voice, permanent loss of voice, or even death due to laryngeal spasm. Another possible complication of thyroidectomy is the inadvertent removal of the parathyroid glands, which may cause a severe convulsive disorder known as tetany.