Atypical branching of the musculocutaneous and median nerves with associated unusual innervation of muscles in the anterior compartment of the arm: case report and plea for extension of the current classification system.

PURPOSE: Variations of the peripheral nervous system in the upper limb, especially of the musculocutaneous and median nerves, are common, but closer attention to the knowledge of the variant anatomy should be paid to avoid iatrogenic injury or to understand the unusual clinical signs. METHODS: During a routine dissection course, bilateral variations were observed in a Central European male cadaver. RESULTS: Variable branching of the musculocutaneous and median nerves associated with atypical innervation of the muscles in the anterior compartment of the arm and other concomitant variations were found bilaterally. In both cases, the musculocutaneous nerve innervated only the coracobrachialis muscle and terminated inside the muscle belly. Branches to the biceps brachii and brachialis muscles arose either directly from the median nerve or its branches. On the right side, two communicating branches between the roots of the median nerve were noted, and a common medial cutaneous trunk originated from the lateral cord. On the left side, a communicating branch extended from the lateral cord to the medial root of the median nerve and a tributary to the axillary vein passed through a window formed by the roots of the median nerve and the communicating branch. CONCLUSION: There exist only few cases in the literature describing similar variations, but the present arrangement has not yet been reported to the best of our knowledge. With the proposed extension to the existing classification system, we aim to provide clearer orientation in the variability of the musculocutaneous and median nerves.

Hypoplastic superficial brachioradial artery coexisting with atypical formation of the median and musculocutaneous nerves: a rare combination of unusual topographical relationships.

The use of the term "brachioradial artery" was introduced for the high origin of the radial artery. Although the prevalence of the brachioradial artery reported by different authors varies from 4.67 to 15.6%, the presence of the hypoplastic brachial segment of the brachioradial artery is rare with an occurrence rate of 0.83%. Moreover, in just 0.6% of cases the loop of the median nerve may be placed near half of the length of the brachial artery, as in the case described in our report. A comprehensive understanding of anatomical variations of neurovascular structures in the upper limb is of great clinical significance. The presented case report illustrates a rare manifestation of persistent primitive developmental relationships in the arterial pattern of the upper limb (persistent, hypoplastic brachial segment of the superficial brachioradial artery), coexisting with atypical formation of the median and musculocutaneous nerves. Anatomical variations of vessels and nerves may coexist which should be taken into account when performing vascular, reconstructive or orthopedic surgery.

Anatomical study of the musculocutaneous nerve branching pattern: application for selective neurectomy in the treatment of elbow flexors spasticity.

PURPOSE: Spastic flexion deformity of the elbow is mainly mediated by the biceps brachii and the brachialis muscles, innervated by the musculocutaneous nerve. Selective neurectomy of the musculocutaneous nerve showed promising results to relieve excessive spasticity in the long term but lacks of a consensual surgical strategy. The aim of the study was to describe the distal branching pattern of the motor branches of the musculocutaneous nerve in an attempt to develop guidelines for surgery. METHODS: Sixteen arms of fresh cadaver specimen were dissected. We recorded the site of each primary and terminal motor branch as a percentage of the distance from the coracoid process to the lateral epicondyle. RESULTS: The biceps muscle was innervated by one to five primary motor branches. The first branch emerged from the nerve at an average of 37.1% of the arm length, and the most distal terminal branch at 55.7%. The brachialis muscle received one to three primary branches. The first branch exited the nerve at an average of 51.7% of the arm length and the last terminal branch at 69.3%. The average number of terminal branches dedicated to the biceps and the brachialis muscles were, respectively, 7.9 and 6.5. CONCLUSIONS: According to our findings, we recommend to dissect the musculocutaneous nerve between 18 and 75% of the distance between the coracoid process and the lateral epicondyle to identify the motor terminal branches to the biceps brachii and the brachialis muscle, sparing sensory branches.

A new anatomical variation of the musculocutaneous and the median nerve anastomosis.

Variations of the brachial plexus and its terminal branches are not uncommon.Therein, the anatomical variations of the musculocutaneous and the median nerve are classified into 5 types, while the communicating branches between the musculocutaneous and the median nerve are classified into 3 types, depending on their position related to the coracobrachial muscle. The case reviewed in this paper presents a variation similar to that of the second variety, but is significantly different due to the appearance of the proximal musculocutaneous nerve and its communicating branching, the site rising from the communicating branch (through the coracobrachial), and important clinical implications of this new variation. Despite the communicating branch being located in the upper third of the upper arm, it should not be considered as being a double lateral root of the median nerve.

Bifurcated distal biceps brachii tendon coexisting with separated bicipital aponeurosis: a complex variational case report.

Variations appearing in biceps brachii muscle are common with accessory head, different origins, variant insertion, and different pattern of nerve innervation. However, variations appearing in both origin and insertion, and with other anomalous morphology at the same time are seldom. Here we report a complex variational case on the right arm of a 91-year-old Japanese female cadaver. The complex variations included (1) the biceps brachii muscle bifurcated at its distal ending; (2) the long head had its own tendon, which divided into two parts, i.e., a lateral part fused into the fascia between the brachioradialis and extensor carpi brevis, and a medial part attached to the radius about one centimeter ahead of the radial tuberosity; (3) the short head had an accessory origin from the shoulder capsule; (4) the bicipital aponeurosis was of two parts with an anterior superior layer formed by the long head and a posterior deep one formed by the short head; (5) the musculocutaneous nerve was especially underdeveloped that only innervated the coracobrachialis; (6) the existence of communicating branch between the musculocutaneous and median nerves, and the median nerve issued muscular branches to the biceps brachii and brachialis muscles, and (7) the brachioradial muscle had two accessory muscular bundles that originated from the fascia of the brachial muscle (proximal one) and from the bicipital aponeurosis (distal one).

Accessory coracobrachialis: a case report with its morphological and clinical significance.

METHOD: During the routine dissection of a male cadaver for teaching undergraduate medical students, a variation was seen in the morphology of coracobrachialis muscle. RESULTS: The presence of an anomalous head of coracobrachialis muscle which had muscular origin from an abnormal site on coracoid process and thin tendinous insertion at the junction of brachialis and triceps muscle in common with insertion of coracobrachialis muscle to the medial surface of the middle of the shaft of the humerus. CONCLUSION: Coracobrachialis muscle can have variant origin related to its embryogenesis with its clinical and surgical significance.

Asymmetric bilateral variations in the musculocutaneous and median nerves with high branching of brachial artery.

Brachial Plexus is formed by the union of the anterior rami of cervical 5, 6, 7, 8 and thoracic 1 nerves. These nerves unite and divide to form the key nerves innervating the upper limb. Variations in the course of these nerves are clinically important to anesthetists, neurologists and orthopedicians. We report bilateral variations in the arterial and neural structures in the upper limb of a 65 year old cadaver. The muscles of the arm on one side were innervated by the median nerve with absence ofmusculocutaneous. While on the other side the musculocutaneous nerve contributed to the formation of the median nerve. There was a presence of high bifurcation of brachial artery on both sides. Knowledge of such variations in the innervations of muscles and the arterial supply of the limbs are important to remember before performing any reconstructive procedures or interventions on the limb.

Absence of the musculocutaneous nerve associated with a supernumerary head of biceps brachii: a case report.

Unusual neural and muscular variations in the right upper limb were noted during anatomical dissection of a 54-year-old male cadaver. The absence of the musculocutaneous nerve was correlated with a three-headed biceps brachii muscle. The distribution of muscular branches innervating the anterior compartment of the muscles of the arm was different to the cases described in literature hitherto. This report contains a comparison of various instances where the musculocutaneous nerve is absent. We discuss the embryological explanation for this anomaly and its clinical results. It is important to be aware of such possible anatomical variations during clinical practice.

[Absence of the musculocutaneous nerve and its distribution from median nerve: About two cases and literature review]. / Absence du nerf musculocutané et distribution à partir du nerf médian : à propos de deux cas et revue de la littérature.

Musculocutaneous nerve arises mostly from the lateral cord of brachial plexus. Nevertheless, variations have been reported and, among them: the total absence of musculocutaneous nerve (from 1.4 to 15%), the absence of its passage through the coracobrachial muscle, its variable level of penetration as measured from the tip of the coracoid process, and its communicating branches with the median nerve. We report two cases of unilateral musculocutaneous nerve absence in a 66-year-old male and a 95-year-old female cadavers, on the right and the left side, respectively. The nerve fibers normally coming from musculocutaneous nerve emerged from the median nerve. The knowledge of this anatomical variation is important specially when performing plexus bloc or Latarjet's procedure.

Is the musculocutaneous nerve really in the coracobrachialis muscle when performing an axillary block? An ultrasound study.

BACKGROUND: In reference textbooks describing axillary block, the ulnar, radial, and median nerves are located in a common sheath surrounding the axillary artery. In contrast, the musculocutaneous nerve is described as lying outside this sheath in the coracobrachialis muscle. In a recent case report of ultrasound-guided axillary block, the musculocutaneous nerve was joined to the median nerve outside this muscle. Our study evaluated the prevalence of atypical musculocutaneous nerve localizations during axillary block. METHODS: All patients undergoing ultrasound-guided axillary block were included from December 2006 to December 2008. Before needle insertion, musculocutaneous, median, ulnar, and radial nerves were localized using ultrasound. Nerve stimulation confirmed atypical nerve localization. After injection of local anesthetics, musculocutaneous and median nerve anatomical relationships were observed. RESULTS: The musculocutaneous nerve was outside the coracobrachialis muscle in 83 of the 387 analyzed blocks (22%). It was near the axillary artery in 22 cases (6%). The musculocutaneous and median nerves appeared as a common neural structure in 61 cases (16%). After local anesthetic injection, a common trunk persisted in 16 of 61 cases (26%), musculocutaneous and median nerves separated in 37 cases (61%), and 2 roots of the median nerve appeared (with or without a separated musculocutaneous nerve) in 6 cases (10%). Two cases (3%) remained undefined. Ulnar nerve location of the 83 patients with atypical musculocutaneous nerve position differed from the ones with a classical musculocutaneous nerve localization. CONCLUSIONS: During axillary block, the musculocutaneous nerve is outside the coracobrachialis muscle in 1 of 5 patients. This atypical location should be considered during performance of axillary blockade to avoid repeated IM puncture.

An unreported pattern of musculocutaneous and median nerve communication with multiple variations of biceps brachii: a case report.

An unreported pattern of communication between musculocutaneous (Mcn) and median nerve (Mn) with multiple variations of biceps brachii (Bb) was observed during the dissection of a male cadaver. The first branch of the Mcn ended in coracobrachialis (Cb). The second was the main Mcn piercing the Cb and giving its motor branches to the muscles of the anterior compartment of the arm. It then continued as the lateral cutaneous nerve of the forearm. The largest third branch also pierced the Cb distal to the main Mcn and communicated with the Mn which was classically formed by relevant roots of the medial and lateral cords. Additionally, a third head of Bb was observed bilaterally. Slips from the pectoralis major were inserted on the tendon of the third head on both sides. The origin of the third head was the greater tubercle to the left and the joint capsule to the right. These extremely rare patterns of both variations which were seen concomitantly in the same subject do not exist in the literature. Lack of awareness of such variations with different patterns of communications between Mcn and Mn might complicate surgical repair of the nerves. Knowing different patterns of Bb variations also have clinical importance as they also may cause compression of neurovascular structures or confuse a surgeon during surgical procedures.

Anomalous Innervation of the Median Nerve in the Arm in the Absence of the Musculocutaneous Nerve.

The brachial plexus innervates the upper extremities. While variations in the formation of the brachial plexus and its terminal branches are quite common, it is uncommon for the median nerve to innervate the muscles of the arm. During the dissection of an elderly male cadaver at the Department of Anatomy, All India Institute of Medical Sciences, New Delhi, India, in 2016, the coracobrachialis muscle was found to be supplied by a direct branch from the lateral root of the median nerve and the musculocutaneous nerve was absent. The branches of the median nerve supplied the biceps brachii and brachialis muscles and the last branch continued as the lateral cutaneous nerve of the forearm. These variations may present atypically in cases of arm flexor paralysis or sensory loss on the lateral forearm. Knowledge of these variations is important in surgeries and during the administration of regional anaesthesia near the shoulder joint and upper arm.

A novel classification of musculocutaneous nerve variations: The relationship between the communicating branch and transposed innervation of the brachial flexors to the median nerve.

The musculocutaneous nerve innervates the brachial flexors; i.e., the coracobrachialis, biceps brachii, and brachialis. The musculocutaneous and median nerve sometimes share a communicating branch and also muscular branches to brachial flexors are sometimes transposed to median nerve. Because these variations constitute a potentially important clinical and surgical issue, we evaluated 130 upper limbs of 65 cadavers and 184 cases of musculocutaneous and median nerve variations in the literature and devised a novel system of classification that covers each pattern of variation. Our proposed classification was applicable in all of our cases and those previously reported. In addition, transposed innervation of the brachial flexors from the musculocutaneous nerve to the communicating branches was observed in one limb in our case series. In this case and all previously reported cases of transposed innervation of the brachial flexors, communicating branches between the musculocutaneous and median nerve were found and no brachial flexor branch arose from the musculocutaneous nerve distal to the communicating branches. Consequently, we established that, as per our novel classification, all patterns of communicating branches could be classified into five types and the patterns of transposed innervation of the brachial flexors into three types.

Absence of the musculocutaneous nerve together with unusual innervation of the median nerve.

During routine anatomical dissections, absence of the musculocutaneous nerve was determined in a 58-year-old male cadaver. Moreover, the biceps brachii and brachialis muscles were innervated by two separate branches which divided from the median nerve instead of the musculocutaneous nerve. From a branch that divides from the main trunk of the median nerve at nearly the middle of the arm a motor branch again divided that innervated the brachialis muscle and a sensory branch that conveyed the sense of the lateral part of the forearm. Furthermore, it was found that the brachial artery divided into its terminal branches, the radial and ulnar arteries. We believe that this rare variation of the median nerve will shed light upon surgical procedures involving the median nerve.

Positional anomaly between the brachial plexus and the scalene muscles, concomitant with an anomalous path of the musculocutaneous nerve: case report and clinical implication / Anomalía posicional entre el plexo braquial y el músculo escaleno anterior, concomitante con un trayecto anómalo del nervio musculocutáneo: reporte de un caso e implicancia clínica

Anatomical variations of the scalene muscles are frequent, as are those of the brachial plexus and its terminal nerves. Nonetheless, these variations are reported separately in the literature. The aim of this work is to present a variation of scalene muscles, concomitant with an abnormal path of the musculocutaneous nerve. During a routine dissection of the cervical region, axilla and right anterior brachial region in an adult male cadaver, a supernumerary muscle fascicle was located in the anterior scalene muscle, altering the anatomical relations of C5 and C6 ventral branches of the brachial plexus. This variation was related to an anomalous path of the musculocutaneous nerve that did not cross the coracobrachialis muscle. It passed through the brachial canal along with the median nerve. It then sent off muscular branches to the anterior brachial region and likewise, communicating branches to the median nerve. The concomitant variations of the brachial plexus and scalene muscles they are not described frequently. Knowledge of these variations improves diagnosis, enhancing therapeutic and surgical approaches by reducing the possibility of iatrogenesis during cervical, axillary and brachial region interventions.

Las variaciones anatómicas de los músculos escalenos son frecuentes, así como también las del plexo braquial y sus nervios terminales. Sin embargo la literatura científica las presenta por separado. El propósito de este trabajo es presentar una variación de los músculos escalenos concomitante con un trayecto anómalo del nervio musculocutáneo. Disección de rutina de región cervical, axila y región braquial anterior derechas realizada en un cadáver adulto de sexo masculino. Se encontró un fascículo muscular supernumerario para el músculo escaleno anterior que alteraba las relaciones anatómicas de los ramos ventrales C5 y C6 del plexo braquial. Esta variación estaba acompañada por un trayecto anómalo del nervio musculocutáneo, el cual no atravesaba al músculo coracobraquial y transitaba por el conducto braquial acompañando al nervio mediano. Desde allí enviaba a la región braquial anterior ramos musculares y al nervio mediano ramos comunicantes. Las variaciones conjuntas del plexo braquial y los músculos escalenos no se presentan con frecuencia. Conocerlas enriquece la capacidad diagnóstica, terapéutica y quirúrgica. Reduciendo la posibilidad de iatrogenia al intervenir en las regiones cervical, axilar y braquial.

A variation of the musculocutaneous nerve absent.

A variation of the brachial plexus, characterized by the absence of the musculocutaneous nerve on the left arm, was found during the dissection of a 28-year old male cadaver. The whole lateral cord was joined to the median nerve, which it met in two points. One was a typical junction of both roots of the median nerve at the level of the coracoid process. The other was a junction of the remaining lateral cord and the median nerve, which was 92 mm away from the typical junction. This case provided some evidence about the absence of the musculocutaneous nerve, rather than a complete fusion of the median and musculocutaneous nerves. As the nerves are named due to their course or innervation, and not from their origin, it is reasonable to assume that the combined nerve was actually the median nerve, and that the musculocutaneous nerve did not exist.

Distribution of median nerve to muscles of the anterior compartment of the arm.

Distribution of the median nerve in the arm is not normally subjected to variation. This report represents a case of complete absence of the musculocutaneous nerve from the lateral cord of the brachial plexus. The innervation of the muscles of the anterior (flexor) compartment of the arm was by direct branches from the median nerve. This variation was present in both the right and left limbs.

Examination of the lateral antebrachial cutaneous nerve: an anatomic study in human cadavers.

Variations in the anatomic course of the cutaneous nerves about the lateral aspect of the elbow are important when surgical exposures and the establishment of arthroscopic portals are considered. The specific anatomic course taken by the lateral antebrachial cutaneous nerve and its relationship to the lateral epicondyle were determined by studying 33 upper extremities in 22 preserved adult cadavers. Considerable anatomic variation was found regarding the location of the lateral antebrachial cutaneous nerve as it crossed the elbow. The nerve pierced the brachial fascia an average of 3.2 cm proximal to the lateral epicondyle and was located an average of 4.5 cm medial to the lateral epicondyle as it crossed the interepicondylar line. In two instances, the nerve passed through the biceps muscle directly, prior to piercing the brachial fascia.

Communicating branch between the musculocutaneous and median nerves in human.

Communicating branch between the musculocutaneous and median nerves was found bilaterally in 1 human cadaver. The topography of vessels was normal.