Friday, March 12, 2021

Superior Vena Cava Syndrome Case File

Posted By: Medical Group - 3/12/2021 Post Author : Medical Group Post Date : Friday, March 12, 2021 Post Time : 3/12/2021
Superior Vena Cava Syndrome Case File
Eugene C. Toy, MD, Lawrence M. Ross, MD, PhD, Han Zhang, MD, Cristo Papasakelariou, MD, FACOG

CASE 11
A 48-year-old man complains of swelling of the neck and shortness of breath of 1-week duration. He has noticed some nasal stuffiness with hoarseness of his voice for about 3 weeks and had attributed these symptoms to an upper respiratory infection. He denies the use of alcohol but has smoked two packs of cigarettes per day for 30 years. Lately, he feels as though something is pushing against his throat. On physical examination, the patient’s face appears ruddy and swollen. The jugular veins are distended.

What is the most likely diagnosis?
 What is the most likely cause?
 What are the anatomical structures involved?


ANSWER TO CASE 11:

Superior Vena Cava Syndrome
Summary: A 48-year-old heavy smoker has a 1-week history of neck swelling, dyspnea, and the sensation of something pushing on his throat. Three weeks ago, he developed nasal stuffiness and voice hoarseness. He has facial plethora, edema, and jugular venous distention.
Most likely diagnosis: Superior vena cava (SVC) syndrome
Most likely cause: Bronchogenic lung cancer
Anatomical structures likely involved: SVC, trachea, and right mainstem bronchus


CLINICAL CORRELATION
The SVC receives venous drainage from the head, neck, upper limb, and thorax. Located in the upper mediastinum, this thin-walled vessel is susceptible to pressure from external sources. The most common cause of such external compression is malignancy, usually from a right-side bronchogenic carcinoma. Such tumors can also compress the trachea, producing dyspnea, and may involve the recurrent laryngeal nerve, producing hoarseness, as in this patient. The stellate sympathetic ganglion may be compressed, leading to Horner syndrome, the clinical triad of unilateral miosis (constricted pupil), facial anhydrosis (dryness), and ptosis (drooping eyelid). The development of SVC syndrome is often an emergency because the trachea may be obstructed, leading to respiratory compromise. The priority in treatment is directed toward the airway, with oxygen and possibly diuretic agents, and corticosteroid agents to relieve the edema. A chest radiograph, computed tomographic (CT) scan, and a tissue biopsy, in that order, would be the next diagnostic steps. Most patients who have lung cancer are treated with radiotherapy. Although patients who have SVC syndrome often respond well to the radiation treatment, the overall prognosis is nearly always poor due to the advanced extent of the cancer.


APPROACH TO:
The Mediastinum

OBJECTIVES
1. Be able to describe the divisions of the mediastinum and the contents of each
2. Be able to describe the lymphatic drainage of the thoracic organs


DEFINITIONS 
Superior vena cava syndrome: Engorgement of the vessels of the head, neck, and upper limbs accompanied by cough and respiratory difficulty due to compression of the SVC or its main tributaries by a benign or malignant mass.
Bronchogenic carcinoma: A malignant tumor arising from the mucosal epithelium of the large bronchi.
Mediastinum: The central region of the thorax between the two pleural cavities.


DISCUSSION
The mediastinum is the central portion of the thoracic cavity, and it lies between the two pulmonary cavities. It is bounded laterally by the mediastinal pleura. It contains all the thoracic viscera except the two lungs. Superior and inferior divisions are described, with the latter further divided into anterior, middle, and posterior divisions.

The superior mediastinum extends from the superior thoracic aperture bounded by the superior border of the manubrium, first rib, and T1 vertebral body. The inferior boundary is a horizontal line from the sternal angle posterior to the intervertebral disk between T4 and T5. The superior mediastinum contains the following structures, from anterior to posterior: adipose tissue with remnants of the thymus gland, right and left brachiocephalic vein, SVC, aorta with its brachiocephalic trunk, left common carotid and left subclavian arterial branches, trachea, esophagus, and thoracic duct. Related to these structures are the phrenic, vagus, left recurrent laryngeal and cardiac nerves, and anterior mediastinal lymph node group (Figure 11-1).

Superior vena cava syndrome anatomy

Figure 11-1. The superior mediastinum and root of the neck. (Reproduced, with permission, from Lindner HH. Clinical Anatomy. East Norwalk, CT: Appleton & Lange, 1989:226.)

The inferior mediastinum is bounded anteriorly by the sternum, posteriorly by vertebral bodies T5 through T12, and the diaphragm inferiorly. The anterior mediastinum portion lies between the sternum and the pericardial sac and contains small branches of the internal thoracic artery and a few nodes of the parasternal lymph node group. The thymus gland is present during childhood. The middle mediastinum contains the pericardial sac with the heart, terminations of the SVC, inferior vena cava (IVC), pulmonary veins, the ascending aorta, the pulmonary trunk and its bifurcations into the right and left pulmonary arteries, lung roots, phrenic nerve, and bronchial lymph nodes. The posterior mediastinum lies between the pericardial sac and vertebral bodies T5 through T12. It contains the esophagus, descending thoracic aorta and right intercostals and esophageal arteries, azygous venous system, thoracic duct, vagus and splanchnic nerves, and posterior mediastinal lymph nodes.

The body’s main lymphatic vessel, the thoracic duct, originates in the abdomen at the level of L1 as a highly variable dilation called the cisterna chili. It enters the posterior mediastinum through the aortic hiatus and lies on the right anterior surface of the thoracic vertebral bodies, posterior to the esophagus between the azygous venous system and the thoracic aorta. By the level of the sternal angle, the duct completes a shift to the left side, traverses the superior mediastinum, and terminates by emptying into the venous system near the junction of the left internal jugular and subclavian veins. The thoracic duct receives lymph drainage from the lower limbs, abdomen and left hemithorax, upper limb, and head and neck. A small right lymphatic duct receives lymph drainage from the right hemithorax, upper limb, and head and neck. The thoracic and right lymphatic ducts are described as receiving lymph from jugular, subclavian, and bronchomediastinal trunks, although these trunks may variably unite or empty into veins independently.

Lymph node groups that drain lymph from the thoracic wall include the parasternal, intercostals, and several diaphragmatic groups. Lymph nodes that drain thoracic viscera include anterior mediastinal nodes in the anterior region of the superior mediastinum and those located on the anterior surfaces of the brachiocephalic veins, SVC, and the aortic arch and its branches. These nodes receive lymph from the thymus, inferior part of the thyroid gland, heart, pericardium, mediastinal pleura, lung hilum, and parasternal and diaphragmatic nodes. Vessels from the anterior mediastinal help form the right and left bronchomediastinal trunks. Posterior mediastinal nodes lie along the esophagus and thoracic aorta and drain lymph from the esophagus, pericardium, diaphragm, and superior surface of the liver. The vessels from this group empty into the thoracic duct or tracheobronchial nodes (Figure 11-2).

The largest number of visceral nodes are associated with the lungs and airways. The lungs have superficial and deep lymphatic plexuses that drain into the bronchopulmonary (hilar) lymph node. The deep plexuses, however, first drain through pulmonary nodes along the bronchi within the lung, from which the lymph passes to the bronchopulmonary nodes. Lymph then drains to inferior and superior tracheobronchial nodes (below and above the tracheal bifurcation) and tracheal nodes located along the sides of the trachea. The tracheobronchial nodes on the right side are closely related to the SVC and receive lymph from the right lung and the inferior part of the left lung. Vessels from these node groups form the right and left bronchomediastinal trunks.

Lymphatic flow through the chest

Figure 11-2. Lymphatic flow through the chest.


COMPREHENSION QUESTIONS

11.1 A thoracic surgeon has entered the right pleural cavity and excised two suspicious lymph nodes at the hilum of the right lung for frozen-section pathological study. These nodes belong to which of the following lymph node groups?
A. Parasternal
B. Paratracheal
C. Superior tracheobronchial
D. Inferior tracheobronchial
E. Bronchopulmonary

11.2 During a surgical procedure, a surgeon has reflected the fat pad containing the thymic remnants and notes a large venous structure crossing the midline from the left and apparently emptying into the SVC. This vessel is most likely which of the following?
A. Right brachiocephalic vein
B. Left brachiocephalic vein
C. Left internal jugular vein
D. Left subclavian vein
E. Azygous vein

11.3 A pediatric heart surgeon has just divided the sternum in a child to repair a cardiac malformation. A lobulated gland-like structure is seen immediately obscuring the heart. This is most likely which of the following?
A. Lung
B. Thyroid gland
C. Thymus
D. Lymph nodes
E. Liver


Answers

11.1 E. The bronchopulmonary lymph node group is located at the hilum of each lung, and it receives lymph from the superficial and deep lymphatic plexuses.
11.2 B. The left brachiocephalic vein crosses the midline to unite with the almost vertical right brachiocephalic vein to form the SVC.
11.3 C. The anterior mediastinum lies immediately posterior to the sternum and contains the thymus in children.


ANATOMY PEARLS
 The surface landmark for the boundary between the superior and inferior (anterior, middle, and posterior) mediastinum is the sternal angle.
 The thoracic duct is found in the posterior and superior mediastina.
 The right tracheobronchial nodes drain lymph from the right lung and inferior portion of the left lung.
 Much of the lymph from the thorax and its contents will drain into the bronchomediastinal trunk.

References

Gilroy AM, MacPherson BR, Ross LM. Atlas of Anatomy, 2nd ed. New York, NY: Thieme Medical Publishers; 2012:78−79, 85, 89, 114, 127. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy, 7th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:117−118, 127−128, 133, 160−166. Netter FL. Atlas of Human Anatomy, 6th ed. Philadelphia, PA: Saunders; 2014: plates 203, 205.

0 comments:

Post a Comment