Journal of Neurosciences in Rural Practice
 


 
CASE REPORT
Year : 2010  |  Volume : 1  |  Issue : 1  |  Page : 51-53 Table of Contents     

Unilateral variant motor innervations of flexure muscles of arm


Department of Anatomy, Jawaharlal Nehru Medical College, Sawangi (Meghe), Wardha, Maharashtra, India

Date of Web Publication10-May-2010

Correspondence Address:
A S Yogesh
Department of Anatomy, JN Medical College, Sawangi Meghe, Wardha, Maharashtra
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0976-3147.63107

Rights and Permissions
   Abstract 

The musculocutaneous nerve usually branches out from the lateral cord of brachial plexus. It innervates the corcobrachialis, biceps brachii and brachialis muscles and continues as the lateral cutaneous nerve of forearm without exhibiting any communication with the median nerve or any other nerve. We report unilateral variation in motor innervations of the left arm in a 58-year-old male cadaver. The musculocutaneous nerve was found to be absent. A muscular branch of the median nerve was supplying the coracobrachialis muscle. In the middle of arm, the median nerve was found to be branching out, bifurcating and supplying the long and short head of biceps. The median nerve was found to be giving a separate branch, which supplied the brachialis muscle and continued as the lateral cutaneous nerve of forearm. The right sided structures were found to be normal. Surgeons should keep such variations in mind while performing arm surgeries.

Keywords: Anatomical variant, lateral cutaneous, musculocutaneous nerve, median nerve, nerve of forearm


How to cite this article:
Yogesh A S, Joshi M, Chimurkar V K, Marathe R R. Unilateral variant motor innervations of flexure muscles of arm. J Neurosci Rural Pract 2010;1:51-3

How to cite this URL:
Yogesh A S, Joshi M, Chimurkar V K, Marathe R R. Unilateral variant motor innervations of flexure muscles of arm. J Neurosci Rural Pract [serial online] 2010 [cited 2019 Apr 23];1:51-3. Available from: http://www.ruralneuropractice.com/text.asp?2010/1/1/51/63107


   Introduction Top


As per the medical and surgical aspects, the nerve supply of arm is very important. The musculocutaneous nerve (MCN) branches out from the lateral cord of brachial plexus. It passes through the Corcobrachialis muscle to innervate it and the biceps brachii muscle. Then it passes between the biceps brachii and brachialis muscle, gives a branch to supply later and continues as the lateral cutaneous nerve of forearm without exhibiting any communication with the median nerve (MN) or any other nerve. The MN passes through the anterior compartment of arm without innervating any flexure muscle of arm. [1]

Variations in the formation and branching pattern of the brachial plexus and the nerves supplying upper limb are common and have been reported continuously since the 19 th century. [2] The anatomical variations of peripheral nerves are important to orthopedic surgeons, neurophysicians, physiotherapist and radiologists. Such comprehension is useful in nerve grafting, neurophysiological evaluation for diagnosing peripheral neuropathies. [3] The present variation was observed during routine dissection at the Anatomy department of Medical College of rural hospital.


   Case Report Top


In a 58-year-old male cadaver, the unilateral variation in motor innervations of the left arm is reported. The pectoralis major and pectoralis minor muscles were removed to expose the brachial plexus. Skin, superficial and deep fascia, was excised to get a view of the arm contents. The musculocutaneous nerve was found to be absent. A branch of the MN was found to be supplying the coracobrachialis muscle. This branch of MN, arising from its lateral side, entered the substance of the coracobrachialis muscle [Figure 1]. In the middle of the arm, the MN was found to be giving the second branch from its lateral side. This branch of MN bifurcated and supplied the long and short head of biceps brachii muscle separately [Figure 2]. The MN was found to be giving a third branch in the arm, running downward and laterally in between the biceps brachii and brachialis muscle. This third branch was supplied the brachialis muscle and continued as the lateral cutaneous nerve of forearm. Dissection was continued to expose the entire brachial plexus from the origin and it was found to be normal. The right sided structures were found to be normal.


   Discussion Top


In this case report, the motor branches of flexure muscles of the left arm were found to be arising from the MN. The MN branch supplying the brachialis muscle was found to be continuing as the lateral cutaneous nerve. Thus, the MCN was replaced by the MN branches. The origin of brachial plexus was found to be normal. Variants of the branching pattern of MCN and MN have been well described by many authors. [4],[5] Le Minor (1992) classified these variations into five types: [6]

Type 1: No communication between MN and MCN.

Type 2: The fibers of the medial root of the MN pass through the MCN and join the MN in the middle of the arm.

Type 3: The fibers of the lateral root of the MN pass through the MCN and after some distance leave it to form the lateral root of the MN.

Type 4: The MCN fibers join the lateral root of the MN and after some distance the MCN arise from the MN.

Type 5: The MCN is absent and all the MCN fibers pass through lateral root of MN; fibers to the muscles supplied by MCN branch out directly from MN. In this type, the MCN does not pierce the coracobrachialis muscle.

Present findings indicate the presence of Le Minor Type V variant. Surgeons should keep such possible variations of the MCN and the MN surgeon in mind during constructive shoulder arthroplasty and treating shoulder dislocations.

The existence of this variation described in our case report may be attributed to the random factors influencing the mechanism of formation of the limb muscles and the peripheral nerves during the embryonic life. In the context that ontogeny recapitulates phylogeny; it is possible that the variation seen in the current study is the result of developmental anomaly. In the human being, the forelimb muscles develop from the mesenchyme of paraxial mesoderm in the fifth week of the intrauterine life. [7] The regional expression of five Hox D (Hox D 1 to Hox D 5) genes is responsible for upper limb development. [8] The motor axons arrive at the base of the limb bud; they mix to form the brachial plexus in the upper limb. The growth cones of the axons continue in the limb bud. [7] The guidance of the developing axons is regulated by the expression of chemo-attractants and chemo-repulsant in highly coordinated sight specific fission. Tropic substances attract the correct growth cones or support the viability of the growth cones that happen to take the right path. Tropic substances include the brain-derived neurotropic growth factor, c-kit ligand, neutrin-1, neutrin-2 etc. [9] The significant variations in nerve pattern may be the result of altered signaling between the mesenchymal cells and the neuronal growth cones or circulatory factors at the time of fission of brachial plexus cords.

Clinical significance

Meticulous knowledge of possible variations of the MCN and the MN may endow us with valuable help in the management of traumatology of the shoulder joint, specifically constructive shoulder arthroplasty and shoulder dislocations and arm, as well as in circumventing iatrogenic damage during repair operations of these regions.

 
   References Top

1.Standring S, Borley NR, Collins P, Crossman AR, Gatzoulis MA, Healy JC, et al. Gray's Anatomy. Pectoral region, shoulder region and axilla. 40 th ed. London: Churchill Livingstone; 2008. p. 791-822.  Back to cited text no. 1      
2.Linell EA. The distribution of nerves in the upper limb, with reference to variabilities and their clinical significance. J Anat 1921;55:79-112.   Back to cited text no. 2      
3.Wiberg M, Hazari A, Ljungberg C, Pettersson K, Backman C, Nordh E, et al. Sensory recovery after hand reimplantation: A clinical, morphological, and neurophysiological study in humans. Scand J Plast Reconstr Surg Hand Surg 2003;37:163-73.   Back to cited text no. 3      
4.Chauhan R, Roy TS. Communication between the Median and musculocutaneous nerve: A case report. J ASI 2002;51:1-6.  Back to cited text no. 4      
5.Choi D, Rodriguez NM,Vazquez T, Parkin I, Sanudo JR. Patterns of connection between the musculocutaneous and Median nerves in the axilla and in arm. Clin Anatomy 2002;15:11-7.  Back to cited text no. 5      
6.Le MJ. A rare variant of Median and musculocutaneous nerves in man. Ach Anat Histol Embryol 1992;73:33-42.   Back to cited text no. 6      
7.Moore KL, Persaud TV. Before we are born. 7 th ed. The musculoskeletal system. Philadelphia: Saunders Elsevier; 2003. p. 243-4.  Back to cited text no. 7      
8.Morgan BA, Tabin C. Hox genes and growth: early and late roles in limb bud morphogenesis. Dev Suppl 1994:181-6.  Back to cited text no. 8      
9.Larson WJ. Human embryology. 3 rd ed. Development of peripheral nervous system. Pennsylvania: Churchill Livingstone; 2001. p. 115-6.  Back to cited text no. 9      


    Figures

  [Figure 1], [Figure 2]


This article has been cited by
1 Anomalous cutaneous branch of median nerve in arm: a report of anatomical variation with clinical implications
Seema Singh,Neerja Rani,Parul Kaushal,Hitesh Kumar,A. Sharrif,T. S. Roy
Anatomy & Cell Biology. 2014; 47(2): 138
[Pubmed] | [DOI]
2 Brachial plexus variations during the fetal period
Wo{\ęz
Anatomical Science International. 2012; : 1-11
[Pubmed]
3 Brachial plexus variations during the fetal period
Jowita Wozniak,Alicja Kedzia,Krzysztof Dudek
Anatomical Science International. 2012; 87(4): 223
[Pubmed] | [DOI]
4 Musculocutaneous nerve substituting for the distal part of radial nerve: A case report and its embryological basis
Yogesh, A.S., Marathe, R.R., Pandit, S.V.
Journal of Neurosciences in Rural Practice. 2011; 2(1): 74-76
[Pubmed]



 

Top
 
  Search
 
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

 
  In this article
    Abstract
    Introduction
    Case Report
    Discussion
    References
    Article Figures

 Article Access Statistics
    Viewed3002    
    Printed202    
    Emailed7    
    PDF Downloaded205    
    Comments [Add]    
    Cited by others 4    

Recommend this journal