CN VII, Facial Nerve, VII, 7th Cranial Nerve

(12) A 45-year old woman develops a tumor of the left parotid gland. On physical exam, what sign might you see in this patient due to compression of a cranial nerve in the region of the tumor? 

Explanation

Correct Answer: 
Drooping of the mouth on the left
Take-Home Message: 
The facial nerve, which is the major motor nerve to the muscles of facial expression, passes through the parotid gland to reach the face.
Explanation of Correct Answer: 
The facial nerve, cranial nerve 7, exits the skull via the internal auditory canal in company with the 8th cranial nerve (acoustic or auditory). In the petrous bone, it has a tortuous course, traveling first in the facial canal and finally exiting the skull via the stylomastoid foramen, just medial to the mastoid process. After this point, it travels forward within the substance of the parotid gland, where it divides into its terminal branches that are distributed to all of the muscles of facial expression. Because of this complex course, the facial nerve is at risk of damage by any process that involves the parotid gland, including tumors as well as surgery on the parotid.
Explanation of Incorrect Answers: 
The masseter muscle, a muscle of mastication, is supplied by the trigeminal nerve, not the facial nerve Taste to the posterior 1/3 of the tongue is supplied by the glossopharyngeal nerve, not the facial nerve Motor fibers to the parotid gland are supplied by parasympathetic fibers in the glossopharyngeal nerve, not the facial nerve
Clinical Pearls: 
Bell’s palsy is due to loss of function of the facial nerve, leading to facial drooping. It is idiopathic, but may be due to viral infection or Lyme disease.
For more information on this topic, please click on the following link(s): 
(While these web sources have been vetted by our content experts, please use them with caution --- the peer-reviewed literature should be the ultimate source of medical information.) 
http://library.med.utah.edu/neurologicexam/html/cranialnerve_anatomy.html#09 
http://www.cancer.org/docroot/CRI/content/CRI_2_4_1X_What_is_salivary_gland_cancer_54.asp?sitearea 

Diaphragm, phrenic nerve

: 

labeled CT: 

Explanation

The structure outlined in red is the diaphragm, or the thoracic diaphragm (to distinguish it from other diaphragms, such as the urogenital or pelvic diaphragm).  It is the primary muscle of respiration, pulling the lungs downward like a piston when it contracts, leading to inspiration.  The innervation of the diaphragm is primarily the phrenic nerve, which arises from C3, C4 and C5, passing along the lateral margins of the mediastinum to reach the lower chest.  Some innervation is also supplied from intercostal nerves to the peripheral portions of the diaphragm.

brachiocephalic artery

labeled CT: 

unlabeled CT:

Explanation

The labeled CT images show the course of the ascending aorta, aortic arch, and descending aorta, along with the three major branches that arise from the aortic arch.  The branch outlined in blue is the brachiocephalic artery.

The aorta is outlined in red, the left common carotid artery in purple, and the left subclavian artery in yellow. The only branches that arise from the ascending aorta are the coronary arteries.  The descending aorta gives off the bronchial arteries, the esophageal arteries, mediastinal arteries and the posterior intercostal arteries.  After the thoracic aorta enters the abdomen via the aortic hiatus of the diaphragm, it becomes the abdominal aorta.  Two of the midline branches of the upper abdominal aorta are also labeled:  the celiac artery (in green) and the superior mesenteric (in dark blue).

Image A shows an abnormality of the branches off the aorta:

Image B shows the aortic arch and its branches outlined:

The aorta is outlined in red.  The first branch, the brachiocephalic artery, is shown in green.  There is a rounded outpouching near the origin of this vessel that protrudes from the anterior side of the vessel.  A contour abnormality of this type is called a saccular aneurysm, and in this patient this abnormality was visible on the lateral chest radiograph, simulating an anterior mediastinal mass.  The normal left common carotid artery is shown in yellow and the normal left subclavian artery is shown in blue.

labeled CT: 

unlabeled CT: 

Explanation

The labeled CT shows the main pulmonary artery and its two branches, the right and left pulmonary arteries outlined in blue.

Figure A shows an abnormality of the right pulmonary artery.

The main, right and left pulmonary arteries are outlined in blue. There is a large right mediastinal mass of relatively low attenuation (a liposarcoma) that is compressing the right pulmonary artery.

Figure B shows a different abnormality of the pulmonary artery.

In this case, a small cell lung carcinoma (outlined in red) has directly invaded the right pulmonary artery  (outlined in purple), producing complete obstruction of flow to the right lung.  Only bronchial artery branches remain patent to supply blood to the right lung tissues.

Clavicles

eled CT: 

labeled CT: 

Explanation

The right and left clavicles are outlined in blue.  They are positioned obliquely for a chest CT scan because the patient's arms are raised overhead.  This rotates the scapulae and lifts the lateral ends of the clavicles from the usual resting position. The patient's arms are overhead for this study because it decreases artifacts in the upper portion of the chest due to excessive bone.  If patients are scanned with their arms at their sides, the course of the beam in the coronal plane must pass through the humeri, scapulae, and spine, and this produces streak artifact.

Pulmonary Artery or Pulmonary Trunk

eled CT: 

labeled CT: 

Explanation

The right and left clavicles are outlined in blue.  They are positioned obliquely for a chest CT scan because the patient's arms are raised overhead.  This rotates the scapulae and lifts the lateral ends of the clavicles from the usual resting position. The patient's arms are overhead for this study because it decreases artifacts in the upper portion of the chest due to excessive bone.  If patients are scanned with their arms at their sides, the course of the beam in the coronal plane must pass through the humeri, scapulae, and spine, and this produces streak artifact.

Explanation

The labeled CT shows the main pulmonary artery and its two branches, the right and left pulmonary arteries outlined in blue.

Figure A shows an abnormality of the right pulmonary artery.

The main, right and left pulmonary arteries are outlined in blue. There is a large right mediastinal mass of relatively low attenuation (a liposarcoma) that is compressing the right pulmonary artery.

Figure B shows a different abnormality of the pulmonary artery.

In this case, a small cell lung carcinoma (outlined in red) has directly invaded the right pulmonary artery  (outlined in purple), producing complete obstruction of flow to the right lung.  Only bronchial artery branches remain patent to supply blood to the right lung tissues.

left subclavian artery

abeled CT: 

labeled CT: 

What is outlined in yellow on the labeled CT images? Be specific!

Explanation

The labeled CT images show the course of the ascending aorta, aortic arch, and descending aorta, along with the three major branches that arise from the aortic arch.  The branch outlined in yellow is the left subclavian artery.

The aorta is outlined in red, the left common carotid artery in purple, and the left subclavian artery in yellow. The only branches that arise from the ascending aorta are the coronary arteries.  The descending aorta gives off the bronchial arteries, the esophageal arteries, mediastinal arteries and the posterior intercostal arteries.  After the thoracic aorta enters the abdomen via the aortic hiatus of the diaphragm, it becomes the abdominal aorta.  Two of the midline branches of the upper abdominal aorta are also labeled:  the celiac artery (in green) and the superior mesenteric (in dark blue).

Image A shows an anomaly of the aortic branches:

Image B shows labels on the structures in these CT images.

The aorta is outlined in red.  The right subclavian artery has an anomalous origin, coming off as the last branch of the aortic arch and passing posterior to the trachea and esophagus.  This is called an aberrant right subclavian artery.  The aberrant vessel is shown in pink.  The right common carotid artery (there is no brachiocephalic artery in this case, since the right common carotid artery and right subclavian artery do not arise from a common trunnk) is shown in blue, the left common carotid artery in yellow and the left subclavian artery in green.