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Nerve Injuries Affecting the Upper Extremity

Topic: Pharmacology

Created on Friday, December 22 2006 by jdmiles

Last modified on Friday, December 22 2006.

A Greek female deity was gouged in the axilla by a Narwhal 6 weeks ago. 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.
Needle EMG is likely to show fibrillations in which of the following muscles?

 
        A) The hypothenar muscles
 
        B) Pectoralis major
 
        C) Flexor carpi radialis
 
        D) Extensor indicis
 
        E) Brachialis
 

 


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This question was created on December 22, 2006 by jdmiles.
This question was last modified on December 22, 2006.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ANSWERS AND EXPLANATIONS




A) the hypothenar muscles

This answer is incorrect.


The sensory and motor deficits this patient complains of are consistent with a radial nerve injury. The the hypothenar muscles is not innervated by the radial nerve. It is innervated by the ulnar nerve.   (See References)

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B) pectoralis major

This answer is incorrect.


The sensory and motor deficits this patient complains of are consistent with a radial nerve injury. The pectoralis major is not innervated by the radial nerve. It receives innervation directly off the brachial plexus.   (See References)

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C) flexor carpi radialis

This answer is incorrect.


The sensory and motor deficits this patient complains of are consistent with a radial nerve injury. The flexor carpi radialis is not innervated by the radial nerve. It is innervated by the median nerve.   (See References)

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D) extensor indicis

This answer is correct.


The sensory and motor deficits this patient complains of are consistent with a radial nerve injury. The extensor indicis is one of the muscles innervated by the radial nerve. As the injury was several weeks earlier, one could now expect to see fibrillations on needle EMG.   (See References)

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E) brachialis

This answer is incorrect.


The sensory and motor deficits this patient complains of are consistent with a radial nerve injury. The brachialis is not innervated by the radial nerve. It is innervated by the musculocutaneous nerve.   (See References)

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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. Bickley, L.S., and Hoekelman, R.A. (1999). Bates' Guide to Physical Examination and History taking, 7th Edition. Lippincott, Philadelphia. Pp. 163-244.
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pharmacology
Nerve Injuries Affecting the Upper Extremity
Question ID: 12220603
Question written by J. Douglas Miles, (C) 2006-2009, all rights reserved.
Created: 12/22/2006
Modified: 12/22/2006
Estimated Permutations: 932083200

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