the medial antebrachial cutaneous nerve ( macn ) arises from the medial cord of the brachial plexus and is derived from segments c8 and t1 .
it courses on the upper arm , pierces the brachial fascia with the basilic vein , about 10 cm above the medial epicondyle , and emerges most commonly as two branches , the anterior and the posterior , which continue downward as far as the wrist .
its function is to provide sensory innervation to the skin of the medial forearm and the skin over the olecranon .
the authors report a variation in which the macn provides four branches to the medial , inferior half of the arm . although the cases in the literature describing variations of the branches of the brachial plexus are abundant , there is not any similar case describing brachial branches of the macn in this specific area .
the presence of this anatomic variation can be used to explain unexpected clinical , neurological signs and symptoms , such as hypoesthesia or dysesthesia in the area of the arm .
after removing the skin and revealing the subcutaneous tissue , the macn was isolated from the adipose tissue and examined .
in addition , the brachial fascia was removed to study the brachial course of the nerve from its origin , the brachial plexus , to its emersion from the brachial fascia .
one of them , the one of the female cadaver was providing branches to the skin of the medial , inferior half of the arm , in the area that is commonly innervated by the medial brachial cutaneous nerve ( mbcn ) .
the authors isolated the nerve from the basilic vein and examined the number , the thickness , the length , and the allocation of the brachial cutaneous branches .
there were four branches , about 1.02.0 mm in diameter and 4.310.5 cm in length , in the area of the medial , inferior half of the arm [ figures 1 and 2 ] .
the most superior branch was separated from the macn 14.2 cm above the medial epicondyle , the second one 12.4 cm , the third one 7.6 cm , and the most inferior one 5.6 cm above the medial epicondyle .
. 1 - 4 : brachial branches of the medial antebrachial cutaneous nerve , bb : biceps brachialis , bv : basilic vein , macn : medial antebrachial cutaneous nerve , mn : median nerve , un : ulnar nerve brachial course and separation into anterior and posterior branch of the right medial antebrachial cutaneous nerve of a female cadaver . 1 - 4 : brachial branches of the medial antebrachial cutaneous nerve , bb : biceps brachialis , cv : cephalic vein , bv : basilic vein , macn : medial antebrachial cutaneous nerve , mn : median nerve , un : ulnar nerve , abmacn : anterior branch of medial antebrachial cutaneous nerve , pbmacn : posterior branch of medial antebrachial cutaneous nerve
the brachial plexus is a network of nerves that is formed by the anterior rami of the lower four cervical nerves and first thoracic nerve ( c5c8 , t1 ) .
it is divided into five roots , three trunks , six divisions , and three cords and innervates the upper limb . to be more specific
, the macn originates from the medial cord and is derived from segments c8 and t1 . at the area of the arm , it courses distally with the median nerve , the ulnar nerve , the brachial artery , and the basilic vein until it pierces the deep fascia 10 cm above the medial epicondyle where it emerges as two branches , the anterior ( volar ) and the posterior ( ulnar ) branch .
its function is to provide sensory innervation in the medial forearm and the skin over the olecranon .
knowledge of nerve variations in anatomy is of high significance for anatomists , neurologists , and surgeons . in our study
, we found an unusual variation of the macn in which the macn provides sensory innervation to the medial , inferior half of the arm .
that probably means that the percentage of appearance may be lower than we expect it to be .
we have to study this variation on a bigger population to have a reliable result .
paresthesia , numbness , dysesthesia , and acute pain are the neurological problems mentioned in the literature when an macn injury exists .
injury to macn could happen to the nerve itself , to its branches , to the medial cord , or to segments c8 to t1 .
the literature states that macn neuropathy causes neurological disorders on the medial forearm and the anteromedial aspect of the elbow . in the case of our study , a possible injury to the macn would also cause numbness , pain , and other disorders in the medial , inferior half of the arm , in a specific area that is innervated from the mbcn .
an unaware neurologist that does not have this case in his / her mind would suppose that injury in the mbcn also exists except from the macn injury .
the differential diagnosis can become difficult because according to the literature , electrophysiological examination of macn nerve is not an everyday upper extremity electrodiagnostic examination and that explains why some macn injuries may remain undiagnosed . even though it is rarely reported
the possible causes are local anesthesia , injuries by injection needles during brachial plexus block procedures , tumor , and routine venipuncture .
the macn might also been harmed during nerve repair operations , as the branches of the macn are used as the  cable graft  for peripheral nerve repair .
damaging of the volar branch might cause mild ( or none ) , often temporary , sensory , neurological problems .
the most frequent symptoms are dysesthisia , numbness , pain in the medial forearm , and painful paresthesia .
things become more complicated if the macn provides branches in the area of the medial arm , as the mbcn provides branches at the same area at about 15.3 cm proximal to the medial epicondyle . to avoid inevitable confusion
this case could also be interesting for plastic surgeons who undertake arm operations in the medial part of the arm .
a good example could be brachioplasty because the traditional brachioplasty procedure involves incision running from the medial epicondyle to the axilla .
it is very important to avoid injuring the mbcn in the medial arm and the interocostobrachial nerve in the axilla .
brachial branches from the macn could raise the possibilities of nerve injuries and appearance of neurological problems as the branches in the surgical area would be more in amount .
medical - surgical specializations that are not directly related to the nerves , such as vascular surgeons , may also find useful and necessary the knowledge of the macn variations . in case of vascular surgery ,
peripheral nerves can be damaged during vascular access operations , and this fact causes neurological dysfunctions .
a new method , in which axial splitting of macn branches takes place , facilitating second - stage elevation of basilic and brachial vein in patients with arteriovenous fistula , was described .
 the medial antebrachial cutaneous nerve ( macn ) is a branch of the brachial plexus with a great variation within its branches . 
 knowledge of these variations is critical to neurologists , hand surgeons , plastic surgeons , and vascular surgeons . 
 the aim of this study was to search for variations of the macn and to discuss their clinical significance . 
 for this study , six arm cadavers from three fresh cadavers were dissected and examined to find and study possible anatomical variations of the macn . 
 the authors report a rare case of a variation of the macn , in which there are four brachial cutaneous branches , before the separation to anterior ( volar ) and posterior ( ulnar ) branch , that provide sensory innervation to the medial , inferior half of the arm , in the area that is commonly innervated from the medial brachial cutaneous nerve . to our knowledge 
 , this is the first documented case of this nerve variation . 
 this variation should be taken into serious consideration for the differential diagnosis of patients with complaints of hypoesthesia , pain , and paresthesia and for the surgical operations in the medial part of the arm . 
Introduction
Case Report
Discussion
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