The nerve pathway is traceable as a line between the axilla and the medial condyle of the humerus. The nerve touches the coracobrachialis muscle and the medial area of the brachial biceps. The nerve may have functional abnormalities in the absence of direct trauma, if anatomical abnormalities are present, such as accessory coracobrachialis muscle or biceps brachialis.

There are many anatomic variants in the course of the medial brachial cutaneous nerve.  In most individuals, proximal to the medial epicondyle, there is an arborization of two to three cutaneous branches, although few have been found to have four or five.[3] The number of distal branches on average ranges from two to four.[3] In one study, the mean distance from the medial epicondyle to the distal branches was 7.8 cm, with specimens ranging from 6.5 cm to 8.6 cm. The mean distance from the medial epicondyle to the proximal branches was 15.3 cm, with specimen ranging from 13.0 cm to 16.2 cm, where it sends branches across the ulnar nerve.[3]

The variability in the course of this nerve is important for surgical dissections of the medial part of the arm. The course of the medial brachial cutaneous nerve is quite variable. One study done on ten fresh cadaver specimens showed that in 9 out of 10 cadavers (18 arms), there was a link to the intercostobrachial cutaneous nerve (ICBCN).[2] This relation was rendered in the form of an ansa. The nerve travels medially and posteriorly to the ulnar nerve as it courses distally. There is a wide variety of single branches from the medial brachial cutaneous nerve to the medial part of the limb. A terminal arborization of two to five branches begins at the level of 2 to 3 cm proximal to the medial epicondyle.[2] In 40% of the specimens, the medial brachial cutaneous nerve sent this small branch in an anterolateral direction, which crossed the ulnar nerve 10 to 12 cm proximal to the medial epicondyle. Moreover, in one cadaver (two arms), the medial brachial cutaneous nerve stretched directly over the ulnar nerve for 14 cm from the root of the ulnar nerve at the medial cord before its posteromedial path.[2]

Additionally, research has found some variants in the brachial plexus where there is an absence of the posterior cord, causing the lateral and medial cords connecting with the communicating branches and that course in front of the axillary artery.[8] As the medial brachial cutaneous nerve originates from the medial cord, this would change its course in these individuals. Therefore, caution should always be used in surgery when dissecting the medial aspects of the arm, making a note of individual variations. In some patients, the nerve may be absent.

The medial brachial cutaneous nerve has a significant clinical role in brachioplasty surgeries. With the rise of bariatric surgery procedures, there has also been an increased demand for plastic surgery focusing on the upper arm. Brachioplasty procedures emphasize correcting the soft tissue laxity of the middle to the upper third of the arm. Traditional procedures involve incisions from the axilla to the medial epicondyle, with the elevation of cutaneous tissue proximal to the medial epicondyle. One of the complications of brachioplasty is an injury to cutaneous nerves within the tissues dissected, mainly the ulnar nerve and terminal branches of the medial brachial cutaneous nerve and medial antebrachial cutaneous nerve. Unfortunately, the medial antebrachial cutaneous nerve and medial brachial cutaneous nerve's anatomic path makes it necessary for these nerves to cross the area where the older skin incision is typically placed.[2] Compromise of the medial brachial cutaneous nerve, along with the ulnar and medial antebrachial cutaneous nerves, leads to decreased pressure and pain sensation of the arm and can result in pressure ulcers over the elbow.[3] For plastic surgeons to avoid this and also provide a maximal aesthetic outcome, incisions must be placed more posteriorly on the arm.[3][2][3] The surgeon must also avoid dissecting the deep fat layer near the axilla to avoid injuring this nerve and lymphatic vessels, and the intercostobrachial nerve.[9] This nerve can also suffer an injury during lymph node dissections and breast augmentation, which involves dissection of the axillary fossa.[5]

The medial brachial cutaneous nerve plays a role in upper extremity nerve entrapment syndromes, especially following axillary lymph node dissections and breast augmentation. Entrapment of this nerve should be a consideration with complaints of paresthesia over the upper arm.[5] This condition is diagnosable via ultrasound with the transducer places on top of the teres major and latissimus dorsi muscles. It can be found on the distal arm running parallel to the ulnar nerve. Possible entrapment of the nerve is identifiable by changes in nerve size and echogenicity, as well as hypertrophic scars on adjacent structures causing possible compression.[5]

The medial brachial cutaneous nerve crosses the brachial fascia. The pectoralis major muscle, latissimus dorsi muscle, and the deltoid muscle with some muscle fibers manage and influence the tension of the brachial fascia. Each arm movement influences the force vectors on the band.[10] If there is fascial dysfunction, such as adherence, a scar, a previous trauma, the brachial fascia can abnormally draw the medial brachial cutaneous nerve causing an entrapment syndrome. The nerve can be the subject of sports injuries, in particular, due to continuous movements of the elbow (extension).[11]