(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
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
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