FrontalCortex, Inc. is a non-profit corporation dedicated to neurology education.

Nerve Injuries Affecting the Upper Extremity

Topic: Pharmacology

Created on Thursday, December 21 2006 by jdmiles

Last modified on Thursday, December 21 2006.

A Greek female deity was gouged in the axilla by a Narwhal yesterday. She presents to your clinic today complaining of numbness in the area shaded in green in the image above. She also, as pictured, is unable to extend her arm at the elbow. Abduction at the shoulder has been spared. Of the following options, which is the most likely site of the lesion?

 
        A) Posterior interosseous nerve
 
        B) Radial nerve
 
        C) Right cranial nerve VI
 
        D) Axillary nerve
 
        E) Musculocutaneous nerve
 

 


Back to the question = Go back to the top of the page.
See another question like this one = Reload a different version of this question ().
Click here for a random question = Load a random question from the database.
Clone this question = Use this question as a template to create a totally NEW question.
Rate this question = Enter detailed rating for this question!
Average user rating for this question = 5 = How users like you have rated this question.
This question was created on December 21, 2006 by jdmiles.
This question was last modified on December 21, 2006.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ANSWERS AND EXPLANATIONS




A) posterior interosseous nerve

This answer is incorrect.


The posterior interosseous nerve is a distal motor branch of the radial nerve. It branches off the radial nerve distal to the elbow, and does not affect arm extension. It does affect finger flexion. A lesion of this nerve would not cause numbness.   (See References)

Back to the questionSee another question like this oneClick here for a random questionClone this question Rate this questionAverage user rating for this question = 5
Please log in if you want to rate questions.

 

 

 

 

 

 

 

 

 




B) radial nerve

This answer is correct.


The sensory distribution shown, with weakness of the triceps (inability to extend the arm at the elbow) could be consistent with a posterior cord lesion, or a radial nerve lesion. Abduction of the shoulder is intact, however, suggesting that the innervation of the deltoid is not affected. The deltoid is innervated by the axillary nerve, which comes off the posterior cord. Therefore, this is most likely a radial nerve lesion.   (See References)

Back to the questionSee another question like this oneClick here for a random questionClone this question Rate this questionAverage user rating for this question = 5
Please log in if you want to rate questions.

 

 

 

 

 

 

 

 

 




C) right cranial nerve VI

This answer is incorrect.


A lesion affecting the abducens nerve (CN VI) would result in impaired abduction of the eye ipsilateral to the lesion. This answer is just plain silly.   (See References)

Back to the questionSee another question like this oneClick here for a random questionClone this question Rate this questionAverage user rating for this question = 5
Please log in if you want to rate questions.

 

 

 

 

 

 

 

 

 




D) axillary nerve

This answer is incorrect.


A lesion of the axillary nerve would result in weakness of the deltoid. This would impair abduction at the shoulder. The distribution of the sensory component of the axillary nerve is limited to a small patch on the lateral surface of the upper arm. An axillary nerve lesion could not explain the motor or sensory symptoms this patient has.   (See References)

Back to the questionSee another question like this oneClick here for a random questionClone this question Rate this questionAverage user rating for this question = 5
Please log in if you want to rate questions.

 

 

 

 

 

 

 

 

 




E) musculocutaneous nerve

This answer is incorrect.


A lesion of the musculocutaneous nerve would result in impaired flexion at the elbow, but would not affect extension. The sensory distribution of the musculocutaneous nerve is located on the lateral forearm; it does not normally innervate the hand or the upper arm.   (See References)

Back to the questionSee another question like this oneClick here for a random questionClone this question Rate this questionAverage user rating for this question = 5
Please log in if you want to rate questions.

 

 

 

 

References:

1. Preston, D.C., and Shapiro, B.E. (2005). Electromyography and Neuromuscular Disorders: Clinical-Electrophysiologic Correlations, 2nd Edition. Elsevier, Philadelphia. Pp. 663-666.
2. Leigh, R.J., and Zee, D.S. (2006). The Neurology of Eye Movements, 4th Edition. Oxford University Press, Oxford.
3. Bickley, L.S., and Hoekelman, R.A. (1999). Bates' Guide to Physical Examination and History taking, 7th Edition. Lippincott, Philadelphia. Pp. 163-244.
Back to the questionSee another question like this oneClick here for a random questionClone this question Rate this questionAverage user rating for this question = 5
Please log in if you want to rate questions.

 

FrontalCortex.com -- Neurology Review Questions -- Neurology Boards -- Board Review -- Residency Inservice Training Exam -- RITE Exam Review
pharmacology
Nerve Injuries Affecting the Upper Extremity
Question ID: 12210600
Question written by J. Douglas Miles, (C) 2006-2009, all rights reserved.
Created: 12/21/2006
Modified: 12/21/2006
Estimated Permutations: 201600

User Comments About This Question:

1 user entries
 

jdmiles
physiology Comment Dec 29, 2008 @ 08:29

Venus



 
Please log in if you'd like to add a comment.