J Korean Med Sci.  2010 Mar;25(3):454-457. 10.3346/jkms.2010.25.3.454.

Anatomical and Electrophysiological Myotomes Corresponding to the Flexor Carpi Ulnaris Muscle

• Pyun SB
• Kang S
• Kwon HK

• KMID: 1778043
• DOI: http://doi.org/10.3346/jkms.2010.25.3.454

Abstract

This study was designed to investigate the incidence of lateral root of the ulnar nerve through cadaveric dissection and to analyze its impact on myotomes corresponding to the flexor carpi ulnaris (FCU) assessed by electrodiagnostic study. Dissection of the brachial plexus (BP) was performed in 38 arms from 19 cadavers, and the connecting branches between the lateral cord and medial cord (or between lateral cord and ulnar nerve) were investigated. We also reviewed electrodiagnostic reports from January 2006 to May 2008 and selected 106 cases of single-level radiculopathy at C6, C7, and C8. The proportion of abnormal needle electromyographic findings in the FCU was analyzed in these patients. In the cadaver study, branches from the lateral cord to the ulnar nerve or to the medial cord were observed in 5 (13.1%) of 38 arms. The incidences of abnormal electromyographic findings in the FCU were 46.2% (36/78) in C7 radiculopathy, 76.5% (13/17) in C8 radiculopathy and 0% (0/11) in C6 radiculopathy. In conclusion, the lateral root of the ulnar nerve is not an uncommon anatomical variation of the BP and the FCU commonly has the C7 myotome. Needle EMG of the FCU may provide more information for the electrodiagnosis of cervical radiculopathy and brachial plexopathy.

Keyword

Brachial Plexus; Ulnar Nerve; Electromyography; Radiculopathy

MeSH Terms

Brachial Plexus/anatomy & histology/physiology
Brachial Plexus Neuropathies/diagnosis
Cadaver
Electrodiagnosis/methods
Electrophysiology/*methods
Female
Forearm/*anatomy & histology
Humans
Male
Muscle, Skeletal/*innervation/physiology
Radiculopathy/diagnosis
Ulnar Nerve/*anatomy & histology/physiology

Figure

• 

  Fig. 1 Five cases of anatomical variations observed in cadaver dissection of 38 upper extremities. Four cases (A-D) show connecting branches (arrow) from the lateral cord to the ulnar nerve (lateral root of the ulnar nerve), and one case (E) shows a connection (arrow) between the lateral cord and the medial cord. Lat C, lateral cord; M, median nerve; MC, musculocutaneous nerve; Med C, medial cord; U, ulnar nerve.

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