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J. Anat. Soc. India 52(1) 66-68 (2003)

J Anat. Soc. India 52(1) 66-68 (2003)

Inter-Communications Between Median And MusculocutaneousNerves With Dual Innervation of Brachialis Muscle-A Case Report.Arora, J; Kapur, V; Suri, R.K., Khan, R.Q.Department of Anatomy, Maulana Azad Medical College, N. Delhi, INDIA

Abstract. — Inter-communications between peripheral nerves deserve special attention in view of their clinical significance. Thepresent article pertains to a case displaying two sites of communications between median and musculocutaneous nerves in the left arm ofa 60-years old male cadaver. The proximal communicating trunk coursed between musculocutaneous and median nerves. It was given offbefore the musculocutaneous nerve pierced the coracobrachialis muscle. The distal communicating trunk carried fibres from median tomusculocutaneous nerve and joined the latter after it had supplied coracobrachialis and biceps brachii. From the site of union of the distalcommunicating branch and the musculocutaneous nerve, branches were given off to the brachialis muscle.

Key words : — Median nerve, communications, musculocutaneous nerve, brachialis.

Introduction :

Connections at the arm level between themusculocutaneous (MCN) and median nerves (MN)have been reported by many authors (Turner, 1864;Le Minor, 1990; Choi et al, 2002). The most frequentof these variations consists of the presence of acommunicating branch that bifurcates from the MCNand goes distally to join the MN. (Venieratos andAnagnastopoulou, 1998). The opposite situationnamely the presence of a communicating branchfrom MN to MCN is rarely encountered (Ferner,1938; Venieratos and Anagnostopoulou, 1998).

In the present case, we recorded two commu-nications between MN and MCN. Such incidence oftwo communicating branches between MN and MCNis uncommonly reported in literature (Vallois, 1922;Yang et al, 1995) and presents great variability. In-terestingly, the brachialis muscle was innervated bynerve fibres from the site of union of the distal com-municating branch and the MCN.

In the present article we have discussed thetopography, morphology and clinical aspects ofthese variations.

Case Report :

The present obsevation was encountered dur-ing routine dissection of the left side of the upperlimb of a 60 year old male cadaver. The MCN andMN had inter-communications at two sites. Theproximal communicating trunk was 2.5cm in lengthand was given off by the MCN before the latterpierced the coracobrachialis (CB) muscle. This trunkcoursed distally to join the MN 4.6 cms from thecoracoid process. The length of distal communicat-ing branch was 10.7cm. it emerged from the MN,

12.4 cms from the coracoid process, and courseddistally to join the MCN after the latter had piercedthe CB and had supplied branches to biceps brachii.From the site of union of the distal communicatingbranch and the MCN, branches were given off to thebrachialis muscle. The MCN continued distally asthe lateral cutaneous nerve of the forearm. (Photo-graph 1, 2 & 3)

Discussion :

The communications between MN and MCNhave been classified by earlier workers (Le Minor,1990; Kosugi et al, 1986; Venieratos andAnagnastopoulou, 1998). In the most recent obser-vations reocrded by Choi et al, 2002 such commu-nications have been broadly classified into 3 pat-terns. In pattern I, the MCN and MN were fused. Inpattern 2, There was one connecting branch be-tween the MCN & MN. In pattern 3, two connectingbranches were present between the MCN and MN.The incidence of this variant was 6.8%. The patternof communication recorded in the present case canbe placed in type 3 of classification advocated byChoi et al, 2002, since there were two communicat-ing branches between MN and MCN. In most ofthese cases reported by Choi et al 2002, the com-municating branches were from MCN to MN. How-ever, in our case, the proximal communicatingbranch emerged from MCN to MN while the distalcommunicating branch was given off in the oppositedirection i.e. from MN to MCN and coursed distallyto join the latter in the middle one third of the arm.Such connections from the MN to the MCN, in theopposite direction are rarely found (Vallois, 1922;Hirasawa, 1931; Ferner, 1938; Kosugi et al, 1992;Venieratos & Anagnostopoulou, 1998).

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J. Anat. Soc. India 52(1) 66-68 (2003)

The incidence of 2 communicating branchesbetween MN and MCN has been reported as themost uncommon pattern with great variability owingto the number of possibilities of origin, length anddirection of the supplementary branches. (Choi et al,2002) The presence of such communications maybe attributed to random factors influencing themechanism of formation of limb muscles and theperipheral nerves during embryonic life. Significantvariations in nerve patterns may be a result of al-tered signalling between mesenchymal cells andneuronal growth cones (Sanes et al, 2000) or circu-latory factors at the time of fusion of brachial plexuscords (Kosugi et al, 1986). Studies of comparativeanatomy have observed the existence of such con-nections in monkeys and in some apes; the connec-tions may represent the primitive nerve supply ofthe anterior arm muscles. (Miller, 1934.)

If the surgeon finds it necessary to isolate andtrace the MN and MCN distally, it is essential to bealert to communications that may occur betweenthem. The clinical relevance of such variationsmight be correlated to entrapment syndromes. En-trapment of MCN is rare and has its origin either inphysical activity (Falsenthal et al, 1984) or in violentpassive movements of arm and forearm (Kim &Goodrich, 1984). If this situation coexists with anas-tomosis to MN, it may give rise to symptoms of MNneuropathy (Wertsch et al, 1982). This knowledgemay prove useful for clinicians in order to avoid anunnecessary Carpal tunnel release (Venieratos &Anagnostopoulou, 1998).

The distal communicating branch from MN toMCN coursed between the biceps and brachialismuscles. Presumably, there may be compression ofthe distal communicating branch at this site duringvigorous exercise with flexion of the arm or directinjury. Such compression may be the anatomic ba-sis for nerve compression syndromes of unex-plained etiology.

In the present case, the brachialis muscle wassupplied by branches from the site of union of theMCN and the distal communicating branch from theMN. Branches to the brachialis muscle from connec-tion between MN and MCN are rarely reported(Kosugi et al, 1992; Vallois, 1922; Yang et al, 1995).Such an innervation is of clinical significance since

there is an increased chance of denervating thebrachialis muscle during an anterior surgical ap-proach to the humerus, that includes longitudinallybissecting the muscle (Mahakkanukrauh &Somsoarp, 2002). The clinical implication of such avariant distal communication between MCN & MNmay mislead the physician in cases of nerve injuryin this region of the arm since in such cases flexionat the elbow joint would still be possible due to thepresence of innervation from the MN to brachialis.

Variations that were observed in the presentstudy involving the MN and MCN are important inrepairs for trauma to the shoulder and the under-standing of MN & MCN dysfunction (Sunderland,1978; Flatow et al, 1989; Sonck et al, 1991). Hence,we conclude that variations in the anatomical con-nections between MN and MCN should be consid-ered during surgical procedures and management ofdisorders of the upper limb.

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and Sannudo, JR. (2002) : Patterns of connection betweenthe musculocutaneous and median nerves in the axilla andarm. Clinical Anatomy 15 , 11- 17.

2. Falsenthal, G; Mondell, D.L. Reischer, MA; Mack, RH. (1984): Forearm pain secondary to compression syndrome of thelateral cutaneous nerve of the forearm. ArchaeologicalPhysical Medical Rehabilitation. 65 : 139-141.

3. Ferner, H. (1938) : Der Nervus musculocutaneous, scienceverlaufs varietatien an oberarm and deren Beziehungen ZurEntcoicklung eines caput tertium musculi bicipitis. ZeitschrAnat Ent. Wicklung 108 : 567-586.

4. Flatow, E.L. Bigliani, L.U. April, E.W. (1989) : Ananatomical study of the musculocutaneous nerve and it'srelationship to the coracoid process. Clinical Orthopaedics244 : 166 -171

5. Hirasawa, K. (1931) : Untersuchungen iiber das periphereNervensystem, plexus brachialis und die nerven der oberenExtremitat. Arb Anat. Inst Kai Serlichen Univ Kyoto A2 : 135-136.

6. Kim, S.M. Goodrich, J.A.; (1984) : Isolated proximalmusculocutaneous nerve palsy : Case report : ArchaeologicalPhysical Medical Rehabilitation. 65 : 735-736.

7. Kosugi, K, Mortia, T; Yamashita, H. (1986) : Branchingpattern of the musculocutaneous nerve 1 case possessingnormal biceps brachii. Jikeakai Medical Journal 33 : 63-71.

8. Le, Minor (1990) : A rare variant of the median andmusculocutaneous nerve in man. Archieves AnatomyHistology embryology 73 : 33 - 42.

9. Mahakkanukrauh P. and Somsarp, V. (2002) : Dualinnervation of the brachialis muscle. Clinical Anatomy 15 :206-209.

10. Miller, R.A. (1934) : Comparative studies upon themorphology and distribution of the brachial plexus, AmericanJournal of Anatomy 54 : 143 -147.

Arora, J. et al

11. Sannes, H.D. Reh, T.A. and Harris, W.A. Development ofthe nervous system In: Axon growth and guidance. AcademicPress New York : pp 189-197 (2000).

12. Sonck, W.A. Franex, M.M; Engels, H.L. (1991) : Innervationanomalies in upper and lower extremities : potential clinicalimplications. Electromyography Clinical Neurophsiology 31 :67 - 80.

13. Sunderland, S. Nerves and nerve injuries 2nd ed. ChurchillLivingstone Edinburgh, London, New York: 656- 727; 796-801. (1978)

14. Turner, W. M. (1864) : On some variations in thearrangement of the nerves of the human body. Natural historyreview 4 : 612 - 617.

15. Vallois, HV. (1922) : Recherches sur le trajet et lesanastomoses du nerf musculocutane au nivcau du bras(etude statistigue) Archieves Anatomy Histology Embryology1 : 184-204

16. Venieratos, D. Anagnostopoulou, S (1998) : Classification ofcommunications between the musculocutaneous and mediannerves. Clinical Anatomy. 11 : 327 - 331.

17. Wertsch, J.J, and Melvin, J. (1982) : Median nerve anatomyand entrapment syndromes : A review. ArchaeologicalPhysical Medical Rehabilitation. 63 623- 627.

18. Williams P.L., Warwick, R., Dyson M., Bannister, L.H. Gray'sanatomy 37th edition, Churchill Livingestone. EdinburghLondon Melbourne, New York, 1130 - 1137. (1989)

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J. Anat. Soc. India 52(1) 66-68 (2003)

Fig-2Photograph of the dissected left upper arm showing

proximal communication between MN and MCN before thelatter pierced the CB.

MN - median nerve, MR -medial root, LR - lateral root,MCN - musculocutaneous nerve, P - proximal communicating

branch, UN -ulnar nerve, CB - coracobrachialis.

Inter-Communications Between Median and Musculocutaneous Nerves

Fig-3Photograph of the dissected left upper arm showing distal

communication and branches to brachialis muscle.MN - median nerve,MCN - musculocutaneous nerve, D- distal

communicating branch, S - site of union of D & MCN,bbc - branches to biceps brachii, bbr- branches to brachialis,UN - ulnar nerve, CB - coracobrachialis, BB - biceps brachii,CP-coracoid process, L- lateral cutaneous nerve of forearm.

Opp. 66

Fig-1Schematic diagram of inter-communications between MN andMCN. Note the branches to brachialis from the site of union of

distal communicating branch and MCN.MN- median nerve, MR & LR-medial and lateral root of MN, P-

proximal communicating branch, MCN-musculocutaneous nerve,D–distal communicating branch, S -site of union of D & MCN, bbc

- branches to biceps brachii, bbr-branches to brachialis,UN -ulnar nerve, CB -coracobrachialis, BB - biceps brachii,

CP - coracoid process, L - lateral cutaneous nerve of forearm,TBc tendon of biceps :