Int J Anat Res 2015, 3(2):1008-10. ISSN 2321-4287 1008
Case Report
M EDIAN NERVE AS A NERVE OF ANTERIOR COM PARTM ENT OF
ARM W ITH ITS VARIANT FORM ATION
Charushila D. Shinde* , Rekha M ane.
ABSTRACT
Address for Correspondence: Dr. Charushila D. Shinde, Assistant Professor, Dept . of Anat omy, M GM M edical College, Navi M umbai, M aharasht ra, India. M obile No.: +919420112269
E-M ail: charushila29@gmail.com
Assistant Professor, Dept . of Anat omy, M GM M edical College, Navi M umbai, M aharasht ra, India.
Absence of M usculocut aneous nerve and unusual form at ion and innervat ion of M edian nerve w ere not ed in left upper lim b during anat om ical dissect ion of 60 yr old fem ale cadaver. M edian nerve norm ally does not give any br anch in ar m but in t his case it innervat es all t he m uscles of ant er ior com part m ent of arm in place of M usculocut aneous nerve. Here w e discussed it s em bryology. It is im portant t o be aw are of such possible anat om ical variat ions in rout ine clinical pract ice.
KEY W ORDS:Brachial plexus, M edian ner ve, M usculocut aneous nerve, Flexor m uscles, lat eral cord, M edial
cord.
INTRODUCTION
Int ernat ional Journal of Anatomy and Research,
Int J Anat Res 2015, Vol 3(2):1008-10. ISSN 2321- 4287 DOI: ht t p:/ / dx.doi.org/10.16965/ ijar.2015.146
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Received: 23 M ar 2015 Accept ed: 16 Apr 2015 Peer Review : 23 M ar 2015 Published (O): 30 Apr 2015 Revised: None Published (P): 30 June 2015
Int ernat ional Journal of Anat omy and Research ISSN 2321-4287
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DOI: 10.16965/ ijar.2015.146
M usculocut aneous nerve (C5-7) is a branch of l at er al co r d o f b r ach i al p lexu s an d i s i t s con t i nu at io n . It is t he n er v e o f an t er i o r compart ment of t he arm. It s muscular branches are t o Cor acobr achialis, Biceps Br achii and Brachialis and it cont inues as Lat eral Cut aneous nerve of forearm w hich supplies lat eral aspect of forearm t ill t he base of t henar eminence.
M edian nerve is form ed in axilla by union of lat eral root (C5-7) and medial root (C8, T1) of l at er al & m ed ial co r d o f br achi al p l exu s respect ively [1].
Know ledge of anat om ical variat ion of t hese nerves in axilla and arm are very import ant for surgical purpose.
CASE REPORT
During t he routine dissect ion of 60 yr old female cadaver at M GM M edical College, Navi M umbai, in left upper limb w e not iced:
1. Absence of M usculocut aneous nerve
2. M edian nerve receives IIIrd addit ional root
from medial cord of brachial plexus Ant erior t o IInd part of Axillary artery.
3. Lat eral root of M edian nerve gives a branch t o Coracobrachialis.
4. Lat eral root of M edian nerve gives a common t runk w hich supplies t
o-a. Lo ng and sho r t h ead o f Bi cep s Br achi i individually
Int J Anat Res 2015, 3(2):1008-10. ISSN 2321-4287 1009
Charushila D. Shinde, Rekha M ane. M EDIAN NERVE AS A NERVE OF ANTERIOR COM PARTM ENT OF ARM W ITH ITS VARIANT FORM ATION.
c. And it cont inues as Lat eral Cut aneous nerve of forearm
5. M edian nerve is formed in middle of t he arm.
In low er half of arm, in cubit al fossa, in forearm and in hand it s course and branches are normal.
Fig 1: LC,M C-Lat eral and M edial Cord of brachial plexus.
1- lat er al root of M edian nerve, 2- m edial root of m edian ner ve, 3-3rd root of m edian ner ve, 4- br. To coracobrachialis, 5- com m on t runk, 6- M edian nerve, 7- 2nd part of axillar y art er y.
Fig . 2: diagram m at ic represent at ion of var iat ion Show ing var iat ion in form at ion of M edian nerve and it s supply t o ant erior com part m ent m uscles.
5- com m on t r unk, 8,9- Br. To short & long head of biceps, 10- Br. To brachialis, 11-Lat eral cutaneous nr.
DISCUSSION
M edi an n er v e as r ep or t ed i n lit er at ur e is associat ed wit h several variat ions which include abnormal communicat ion wit h other nerves such as M u scu locut aneo us ner ve, Ulnar n er v e, spl i t t i n g o f M ed i an n er v e an d u n u su al innervat ion of flexor muscles in arm by median nerve [2].
In our st udy, M usculocutaneous nerve is absent and all f lexor gr oup of m uscles in ar m ar e supplied by M edian nerve.
Uzan (2001) found t hat 3 root s of lat eral cord and 1 root of medial cord form M edian nerve [3].
In our st udy, 2 root s from medial cord and 1 root fr om lat eral cor d t ook part in f or m at ion of M edian nerve.
Jah ansh ali (2003) f o u nd t h at , ab sence o f M usculocut aneous nerve, and muscles supplied by it w ere supplied by M edian nerve. Here t he format ion of M edian nerve is normal i.e lat eral and medial root from lat eral and medial cord of brachial plexus respect ively [4].
In our study, M usculocutaneous nerve is absent , and m uscles supplied by it are supplied by M edian nerve (Lat eral root ) w hich is formed at middle arm level and also receives IIIrd root from
medial cord anterior t o 2nd part of axillary artery.
Sat yanarayana (2009), described 3 unilat eral cases of variat ion of format ion of M edian nerve. In 1st case he described M edian nerve formed
on medial side of Axillary art ery at higher level. Lat er median nerve cont inued behind brachial art ery and receives a com m unicat ing branch from lat eral cord. In t he 2nd case -format ion of
M edian nerve by t hree root s- 2 from lat eral and 1 from medial cord of brachial plexus. In 3rd case
Int J Anat Res 2015, 3(2):1008-10. ISSN 2321-4287 1010
Charushila D. Shinde, Rekha M ane. M EDIAN NERVE AS A NERVE OF ANTERIOR COM PARTM ENT OF ARM W ITH ITS VARIANT FORM ATION.
In our case, lat eral root receives addit ional communicat ing root from medial cord in front of IInd par t of Axi llary art ery. M edian ner ve
form at ion t ake place at m idd le of t he ar m . Additional t o it it supplies flexor group of muscles in arm as M usculocut aneous nerve is absent .
Combinat ion of absence of M usculocut aneous nerve, M edian nerve receives 3rd root ant erior
t o 2nd part of axillary art ery and form at ion of
M edian Nerve at low er level (at middle of t he arm) as seen in our case, is rare occurrence.
Kn ow l edge of v ar i abl e p at t er n s of n er v e format ion and nerve supply t o muscles, joint s skin is essent ial t o explain t he unexpect ed clinical signs and sympt oms. It is also helpful dur ing surgical int er v ent ions li ke shoulder r eco n st r u ct i on s, i n ci si on and dr ai nage o f abscesses, block dissect ion of axilla, axillary lymph nodes, reconst ruct ive flab surgeries et c.
Presence of such variat ions should always kept i n m i nd w hi l e t est i n g a m uscl e, af t er adm inist rat ion of neurom uscular block. It is import ant for surgeon, clinician and anat omist t o be aw are of possible anat omical variat ions t o avoid unexpect ed complicat ions.
Embryology: The embryological development of upper lim b m ay help in explaining t hese anat omical variat ions.
Significant variat ions in nerve pat t erns may be r esu l t o f al t er ed sign ali n g b et w een mesenchymal cells and neuronal grow t h cones [6] or circulat ory fact ors at t he t ime of fusion of brachial cords [7].
The axons of somat ic mot or fibers in dorsal and vent ral rami seek out specific muscle or bundle of muscles fibers and form synapses w it h t he m uscle fibers. The specific signals t hat guide mot or fibers to t heir t argets are unknown. Axons h ave r em ar kab l e ab il i t y t o r each t hei r appropriate t arget s.
The mot or axons t hat innervate t he limb perform an int ricat e feat of pat h finding t o reach t heir t arget m uscles. The axons dest inat ed for t he limb apparent ly t ravel t o t he base of limb bud by grow ing axon permissive pat hways. Once the mot or axons arrive at t he base of limb bud, t hey mix in specific pat t ern t o form brachial plexus in upper limb. This zone const it utes t he decision
making region. Once axons have sort ed out in plexus, growt h cones cont inue int o the limb bud, t ravelling along permissive pat hw ays t hat lead in general dir ect ion of appr opr iat e m uscle compart ment [8].
In our case, t he grow t h cone of vent ral column m ot or axons com ing f or M usculocut aneous nerve takes different pat h t o t ravel t o target organs; it passes t hrough lat eral root of M edian nerve. Growth cone recognize their target organs and innervat e t hem . M edian nerve has t w o m edial root s as fibers from C8 and T1 spinal segm ent passes separ at ely t o form M edian nerve.
CONCLUSION
The variat ion in M edian nerve format ion and it ’s innervat ion, and absence of M usculocut aneous nerve have no effect on t he funct ions of upper limb but knowledge of various pattern of brachial plexus is essent ial for medical professionals w ho explores axilla for t reat ment , int ervent ions’ or block dissect ion.
Conflicts of Interests: None
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