Anatomical variations of the cords of brachial plexus and the median nerve

Brachial plexopathy as a result of anatomical prone position in COVID-19 patients-Systematic review

In patients with COVID-19 different methods improving therapy have been used, including one of the anatomical position-prone position, to support ventilation. The aim of this review was to summarize the cases of brachial plexopathy as a consequence of the prone position in COVID-19 patients, and thus bring closer the issue of the brachial plexus in the face of clinical aspects of its function, palsy, and consequences. The Preferred Reporting Items for Systematic Reviews and Meta-analyses statement was followed, inclusion criteria were created according to Patients, Interventions, Comparisons, Outcomes (PICO). PubMed and Scopus were searched until April 1, 2023 by entering the key term with Boolean terms. The risk of bias was assessed using JBI's critical appraisal tools. Fifteen papers with 30 patients were included in the review. This study showed that brachial plexopathy after the prone position occurs more often among males, who are at least 50 years old with comorbidities like hypertension, overweight, and diabetes mellitus. The most common symptoms were weakness, pain, and motion deficits. Duration of the prone position session and the number of episodes were different as well as the modification of positioning. Brachial plexopathy is a significant problem during prone position, especially when hospitalization is prolonged, patients are males, have comorbidities, and changes in body weight. Attention should be drawn to understand the anatomy of the brachial plexus, correct positioning, avoiding factors worsening the prognosis, and proper nutrition of the patients.

The Coexistence of the Superficial Brachial Artery With the Common Origin of the Posterior Circumflex Humeral Artery and the Deep Brachial Artery

The brachial artery (ΒΑ) represents the axillary artery's extension as it distally progresses to the teres major muscle or beneath the tendon of the latissimus dorsi muscle. Throughout its course, the BA maintains continuous proximity to the median nerve. Occasionally, an artery located in front of the arm muscles may exhibit a slightly more lateral position than the BA, following a convoluted path, referred to as the superficial brachial artery (SBA). SBA variants are not uncommon and can impact neural structures as well. In the course of routine dissection on a formalin-embalmed donated cadaver through the Body Donation Program, the following notable findings were identified: a) a BA bilateral trifurcation, below the tendon of the latissimus dorsi muscle; b) a posterior circumflex humeral artery of low origin (brachial artery); c) the coexistence of an SBA with the main BA; d) a subscapular artery of high origin (second part of the axillary artery); e) an anterior circumflex humeral artery duplication. These BA variants, particularly those related to the SBA, hold significance in upper limb surgery and everyday clinical practice. In such cases, meticulous surgical dissection is crucial to prevent arterial injury, and in complex situations, preoperative imaging might be advisable. Additionally, it's important to note that concurrent neural variants may also be present, potentially complicating the surgical approach.

Coracobrachialis muscle morphology and coexisted neural variants: a cadaveric case series

PURPOSE

The current cadaveric case series evaluates the coracobrachialis muscle morphology, the related musculocutaneous nerve origin, course, and branching pattern, as well as associated adjacent neuromuscular variants.

MATERIALS AND METHODS

Twenty-seven (24 paired and 3 unpaired) cadaveric arms were dissected to identify the coracobrachialis possible variants with emphasis on the musculocutaneous nerve course and coexisted neural variants.

RESULTS

Four morphological types of the coracobrachialis were identified: a two-headed muscle in 62.96% (17/27 arms), a three-headed in 22.2% (6/27), a one-headed in 11.1% (3/27), and a four-headed in 3.7% (1 arm). A coracobrachialis variant morphology was identified in 37.04% (10/27). A three-headed biceps brachii muscle coexisted in 23.53% (4/17). Two different courses of the musculocutaneous nerve were recorded: 1. a course between coracobrachialis superficial and deep heads (in cases of two or more heads) (100%, 24/24), and 2. a medial course in case of one-headed coracobrachialis (100%, 3/3). Three neural interconnections were found: 1. the lateral cord of the brachial plexus with the medial root of the median nerve in 18.52%, 2. the musculocutaneous with the median nerve in 7.41% and 3. the radial with the ulnar nerve in 3.71%. Duplication of the lateral root of the median nerve was identified in 11.1%.

CONCLUSIONS

The knowledge of the morphology of the muscles of the anterior arm compartment, especially the coracobrachialis variant morphology and the related musculocutaneous nerve variable course, is of paramount importance for surgeons. Careful dissection and knowledge of relatively common variants play a significant role in reducing iatrogenic injury.

Variations in the Branching Pattern and Course of the Left Axillary Artery: A Cadaveric Case Report

The axillary artery is the primary arterial supply of the upper limb and functions as a key landmark in the region of the axilla. Anatomical variations in the axillary artery may arise from abnormal angiogenesis in the upper limb bud during embryological development. The routine dissection of the upper limb of an 88-year-old male cadaver revealed unilateral variations in the left axillary artery, including an abnormal anteromedial course with respect to the divisions and cords of the brachial plexus, while no variations were observed in the right axillary artery. Variations in branching were observed in each part of the artery. In the first part of the artery, variations included an accessory branch coursing towards the clavicle and another to the subscapularis muscle. A total of four branches arose from the second part of the artery: a thoracoacromial artery, an accessory pectoral branch, and two common trunks. The first common trunk gave off the alar thoracic artery, an accessory lateral thoracic artery, and the subscapular artery, which further gave off the thoracodorsal and lateral thoracic arteries, prior to continuing as the circumflex scapular artery. The second common trunk yielded the anterior and posterior circumflex humeral arteries prior to continuing as the profunda brachii artery. No branches arose from the third part of the artery. Awareness of variations in the course and branching patterns of the axillary artery as observed in this cadaveric donor is essential for anesthetic, radiographic, surgical, and other interventional procedures of the upper limb.

A Cadaveric Study to Define the Variant Patterns of Median Nerve Formation

The median nerve is one of the important nerves of the upper limb which supplies the muscles of the front of the forearm, muscles of the hand, and skin of the hand. Many works of literature mentioned its formation by the fusion of two roots, the medial root from the medial cord and the lateral root from the lateral cord. But multiple variations in the median nerve formation have clinical importance from surgical and anesthetic points of view. For the study purpose, we dissected 68 axillae of 34 formalin-fixed cadavers. Out of 68 axillae, two (2.9%) showed median nerve formation by a single root, 19 (27.9%) showed median nerve formation by three roots, and three (4.4%) showed median nerve formation by four roots. A normal pattern of median nerve formation by fusion of two roots was seen in 44 (64.7%) axilla. The knowledge of variant patterns of median nerve formation will be helpful to surgeons and anesthetists while performing surgical or anesthetic procedures in the axilla to avoid any injury to the median nerve.

Branching patters of the vascularization and innervation of the primate forelimb

In this study, we investigate the branching patterns of the vascularization and innervation of the primate forelimb by performing detailed dissections of five unembalmed nonhuman primate specimens belonging to five different species, i.e., rhesus macaque (Macaca mulatta), white-handed gibbon (Hylobates lar), Western gorilla (Gorilla gorilla), chimpanzee (Pan troglodytes), and bonobo (Pan paniscus). Results are compared with five embalmed human specimens (Homo sapiens), and anatomical data of previous studies on nonhuman primates are also included to provide a broader comparative framework. The results show that the overall configuration of the forelimb blood vessels and nerves of the different primate species is similar, although some apparent interspecific differences are found. In all nonhuman primates, in contrast to humans, the superficial vena basilica is absent. Moreover, in gorilla, chimpanzee, and bonobo the superficial v. cephalica is confined to the forearm. In humans, both an arteria interossea anterior and posterior are present, while in the nonhuman primates only an a. interossea anterior is present, which migrates to the posterior side at the level of the musculus pronator quadratus. For the innervation, the nervus medianus and n. ulnaris connect in the forearm of the gorilla and macaque. In the gibbon, the brachial plexus shows some differences in the branching pattern at the fasciculus level compared to the other primates. We conclude that the forelimb innervation branching pattern shows some minor differences between the nonhuman primate species, compared to a higher plasticity in the vascularization. However, the exact functional implications of these differences still remain unclear. Therefore, more research in a broader range of primate species and sampling more specimens for each taxon is needed. This article is protected by copyright. All rights reserved.

Anatomical variation of median nerve: cadaveric study in brachial plexus

Median nerve is formed by lateral root from lateral cord and medial root from medial cord of brachial plexus. Formation of median nerve occur in front or lateral to axillary artery in axilla. In the present study we observed anatomical variations of median nerve formation in the brachial plexus. We examined formalin fixed 60 upper limbs from 30 adult cadavers (15 males and 15 females) which were above the age 40 years from the department of Anatomy. All the cadavers were dissected on both sides according to Cunningham's Manual of Practical Anatomy. Normal formation of median nerve by two roots noted in 42 (70.0%) of upper limb specimen. Variation of median nerve formation noted in 18 (30.0%) upper limb specimen. Three roots taking part in the formation of median nerve in 13 (21.7%) upper limb specimen where additional root coming from lateral cord of brachial plexus. Four roots taking part in formation of median nerve in 3 (5.0%) upper limb specimen, where additional roots coming from lateral cord and posterior cord of brachial plexus. Lateral root crossed the axillary artery anteriorly to join with medial root lying medial to axillary artery. The median nerve formed medial to third part of axillary artery. Additional communication with musculocutaneous nerve with median nerve seen in 2 (3.3%) upper limb specimen. Knowledge of such anatomical variations is of interest to the anatomist and clinician alike. Surgeons who perform procedures involving neoplasm or repairing trauma need to be aware of these variations. Median nerve variation may lead to confusions in surgical procedures and axillary brachial plexus nerve block anesthesia.

Variations of Median Nerve Formation in North Indian Population

Introduction: The median nerve is usually formed by two roots contributed from the medial and lateral cords of the brachial plexus. Morphological variations of the median nerve can have clinical implications from the anesthetic and surgical points of view. In this cadaveric observation study, we report the variations of median nerve formation in the North Indian population.

Methods: We observed the formation of the median nerve in 40 human cadaveric upper limb specimens. The specimens belonged to 20 right and 20 left upper limbs. Variations in the formation of the median nerve were noted.

Results: Of the 40 dissected specimens, six (15%) had triple roots including a supernumerary root contributing to the medial nerve formation. The supernumerary root was a branch of the lateral cord in five cases, and it had an additional contribution from the medial cord in one case. The median nerve formation and continuation were located anterior or laterally in 39 specimens (97.5%) and medial in one (2.5%) in relation to the axillary artery.

Conclusion: We observed supernumerary roots of varying morphology contributing to the median nerve formation. These variations should be considered during the administration of regional anesthesia and during the management of brachial plexus injuries. Further large multi-region studies will help in a better understanding of these variations.

Relationship Between Gender, Age, BMI and Side of Body on the Size and Position of Nerves of the Brachial Plexus in Axilla: Pilot Study

Background and Objectives

Studies demonstrate variations in the size and position of the nerves in the brachial plexus. The objective of this pilot study was to determine the effect of age, gender, BMI and side of body on the size and position of these nerves and to determine the feasibility of a further study.

Methods

Twenty healthy volunteers were recruited. The ultrasound position of the nerves was confirmed by a dynamic scan. The size of the nerves was calculated using the freehand calliper tool. A graph was designed to study the position of the nerves. ImageJ was used to analyse the position of the nerves. Student's t-tests were carried out to compare the gender and side of arm with the size of the nerve. Pearson's correlation coefficients were calculated to determine the correlation between BMI and age with the size of the nerves. The position of the nerves was compared between male and female, and left and right sides of the body.

Results

The mean size of the median nerve, musculocutaneous nerve, radial nerve and ulnar nerve was 0.099, 0.032, 0.179 and 0.076 cm2 (males) and 0.091, 0.022, 0.128 and 0.026 cm2 (females), respectively. There were significant differences between the size of nerves and gender in the musculocutaneous, radial and ulnar nerves (P <0.05). The correlations between the sizes of the nerves with BMI and age were not significant. The position of the radial nerves was found to be variable within the same genders and between males and females. The position of the nerves was variable between the left and right hand side.

Conclusion

The position and size of brachial plexus branches in axilla is very variable. This pilot study highlights the need for further research with larger sample sizes to fully understand the extent and implication of this variability.

A meta-analysis on the anatomical variability of the brachial plexus: Part I - Roots, trunks, divisions and cords

INTRODUCTION

The brachial plexus is a complex anatomical structure that gives rise to all the nerves of the upper limb. Its variability is frequently observed and represents a challenge for interventions in the lower neck and axilla. The aim of this study was to present a comprehensive and evidence-based review with meta-analytic techniques on the variability of roots, trunks, divisions and cords of the brachial plexus.

MATERIALS AND METHODS

Major medical databases were searched to identify all anatomical studies investigating the variability in the formation of the brachial plexus. Data extracted consisted of demographic information, morphometric parameters, the arrangement of the brachial plexus at the level of the roots, trunks, divisions and cords and the relationship of the brachial plexus to the axillary artery and scalene muscles. The different configurations of the brachial plexus were put into a new classification, and the pooled prevalence of each case was calculated using a random effects model. A sub-analysis on age and geographical location was also performed.

RESULTS

A total of 40 studies (3055 upper limbs) were included in the meta-analysis. The regular arrangement of roots forming trunks was identified in 84% (95% CI 79-89%) of cases. The overall prevalence of the prefixed and postfixed brachial plexus was 11% (95% CI 6-17%) and 1% (95% CI 0-1%), respectively and in less than 0.1% of cases the brachial plexus received a branch from both C4 and T2. For divisions forming cords, the regular arrangement was observed in 96% (95% CI 93-98%) of cases. Additional communicating branches between the components of the brachial plexus appeared in 5% (95% CI 3-7%) of cases. The relationship of the brachial plexus to the axillary artery and scalene muscles was considered regular in 96% (95% CI 89-100%) and 86% (95% CI 66-98%) of cases, respectively. Analysis of the morphometric parameters revealed the proportional consistency between the components forming the plexus during aging.

CONCLUSIONS

Knowledge of anatomical variations of the brachial plexus is important for examinations and interventions in the lower neck and axilla. The variability was observed especially in the roots forming trunks, while divisions forming cords showed quite stable appearance. The results of this evidence-based review and meta-analysis can be applied in many different medical disciplines.

Evaluation of Brachial Plexus Using Combined Stereological Techniques of Diffusion Tensor Imaging and Fiber Tracking

Background  Brachial plexus (BP) is composed of intercommunications among the ventral roots of the nerves C5, C6, C7, C8, and T1 in the neck. The in vivo and in vitro evaluation of axons of the peripheral nervous system is performed using different techniques. Recently, many studies describing the application of fiber tractography and stereological axon number estimation to peripheral nerves have been published. Methods  Various quantitative parameters of nerve fibers, including axon number, density, axonal area, and myelin thickness, can be estimated using stereological techniques. In vivo three-dimensional reconstruction of axons of BP can be visualized using a combined technique of diffusion tensor imaging (DTI) and fiber tracking with the potential to evaluate nerve fiber content. Conclusion  It is concluded that terminal branches of BP can be successfully visualized using DTI, which is a highly reproducible method for the evaluation of BP as it shows anatomical and functional features of neural structures. We believe that quantitative morphological findings obtained from BP will be useful for new experimental, developmental, and pathological studies in the future.

Axillary Sonography of the Shoulder: An Adjunctive Approach

Sonography of the shoulder is widely used to assess various disorders, including tendinous diseases of the rotator cuff and the long head of the biceps brachii muscle. The shoulder is commonly explored through anterior, superior, and posterior approaches, but the inferior axillary approach is rarely considered in the literature. However, this technique allows the direct visualization of relevant anatomic structures. The aim of this pictorial essay is, first, to technically describe this approach and the normal musculoskeletal sonographic anatomy of the region and, second, to present the sonographic findings of shoulder disorders that may be helpfully explored this technique.

Prevalence of Asymptomatic Neurophysiological Carpal Tunnel Syndrome in 130 Healthy Individuals

Diagnosis of carpal tunnel syndrome (CTS) is frequently confirmed by performing nerve conduction studies. Previous studies demonstrated that abnormal nerve conduction study (NCS) is suggestive of CTS among asymptomatic individuals. However, previous studies included individuals with risk factors for the syndrome. A NCS was performed on the median and ulnar nerves in 130 healthy individuals. About 15% of individuals in this study demonstrated electrodiagnostic evidence of carpal tunnels syndrome. Four cases have shown signs of isolated median neuropathy with normal median sensory component. Results indicated that the most widely used method for confirming diagnosis of CTS may have up to 15% of false positives. However, most of those showed changes of minimal CTS. Isolated prolongation of the median motor latency should be investigated further as they are usually classified as moderate to severe CTS and may undergo unnecessary surgeries.

Variations in brachial plexus with respect to concomitant accompanying aberrant arm arteries

INTRODUCTION

Variations in the brachial plexus are the rule rather than the exception. This fact is of special interest for the anesthetist when planning axillary block of brachial plexus.

MATERIAL AND METHODS

167 cadaver arms were evaluated for variations in brachial plexus, with focus on the cords of the plexus, the loop of the median nerve, and the course of the median, musculocutaneous, ulnar, axillary and radial nerves. In addition, concomitant arterial variations were recorded.

RESULTS

In 167 arms, variations were detected in 60 cases (36%). With 46 arms (28%) most variations concern the median nerve, followed by 13 cases (8%) which involved the musculocutaneous nerve. Ulnar, axillary and radial nerve variations were rare, amounting to 1.2% for each nerve. In median nerve conditions with a shifted loop of median nerve (12%), a hidden position of the loop or a hidden course of the beginning median nerve (8%) and a doubled loop of median nerve (17%) were observed. In musculocutaneous nerve conditions with a non-perforated coracobrachialis (1.8%), a doubled origin of the nerve (1.2%) and a giving back of branches to the median nerve (1.8%) were noted. Variations in ulnar, axillary and radial nerves concerned lower than normal diameters.

CONCLUSIONS

It must be stressed that cases which showed a hidden position or a doubled expression of the loop of the median nerve, a hidden course of its beginning and variable interconnections between musculocutaneous and median nerves are of special interest for anesthetists and surgeons. Hence, it is important to note that variations of arm arteries can be associated with brachial plexus variations. For example, a common trunk of axillary artery followed by a hidden loop and course of the median nerve may result in incomplete axillary block of brachial plexus.

Five Roots Pattern of Median Nerve Formation

An unusual combination of median nerve's variations has been encountered in a male cadaver during routine educational dissection. In particular, the median nerve was formed by five roots; three roots originated from the lateral cord of the brachial plexus joined individually the median nerve's medial root. The latter (fourth) root was united with the lateral (fifth) root of the median nerve forming the median nerve distally in the upper arm and not the axilla as usually. In addition, the median nerve was situated medial to the brachial artery. We review comprehensively the relevant variants, their embryologic development and their potential clinical applications.

Surgical Anatomy of the Supraclavicular Brachial Plexus

BACKGROUND

Brachial plexus exploration is performed in infants when addressing birth palsies and in children and adults following trauma. The upper trunk is most often injured. Traditional drawings of the brachial plexus depict the suprascapular nerve as a branch of the midportion of the upper trunk, with the more lateral branch of the upper trunk as the anterior division. We have not found this orientation to be accurate in clinical practice. The purpose of this study was to determine the branching patterns of the upper trunk and to delineate nerve orientations at the level of the divisions.

METHODS

Bilateral brachial plexus dissections were performed on eight adult cadavers. The length of the upper trunk and distance of the takeoff of the suprascapular nerve from the anterior and posterior divisions was measured. The native positions of the divisions and of the suprascapular nerve from lateral to medial were recorded across all trunks.

RESULTS

In six (38%) of the sixteen specimens, a trifurcation was found at the level of the upper trunk. The suprascapular nerve was the most lateral structure at the clavicular level in all specimens, followed by the posterior division and then the anterior division. The mean distance of the takeoff of the suprascapular nerve was 4 mm proximal to the branch point of the divisions; however, in two specimens, the nerve was found to take off from the posterior division proper.

CONCLUSIONS

These findings differ from the standard illustrations and descriptions of the brachial plexus. A thorough understanding of the course of the upper trunk and its branches, such as the suprascapular nerve, is vital to performing nerve transfer surgery or neuroma excision and grafting.

Bilateral single cord of the brachial plexus in an adult female cadaver of South Indian origin

The occurrence of a brachial plexus united into a single cord is very rare. During routine dissection of an elderly female cadaver, the brachial plexus united into a single cord was observed bilaterally. On the left side, C4, C5, and C6 roots combined to form the upper trunk, the C7 root continued as the middle trunk, and C8 and T1 united to form the lower trunk. All three trunks almost immediately fused to form a single cord. On the right side, C5 and C6 roots joined to form the upper trunk, which divided into anterior and posterior divisions. C7, C8, and T1 roots combined to form the lower trunk. The anterior and posterior divisions united with the lower trunk to form a single cord. On both sides, the subclavian artery was superior to the single cord. Supraclavicular brachial plexus injuries in such individuals may have serious clinical manifestations.

Study of sensory and motor fascicles in brachial plexus and establishment of a digital three-dimensional graphic model

To investigate a 3-dimensional (3D) model of human brachial plexus including its topography of sensory and motor fascicles with the assistance of the computer technology, 2 brachial plexus were serially horizontally sliced. Each slice was stained by Karnovsky-Roots acetylcholinesterase histochemical method. The stained sections were scanned, and the image was put into the computer serially. At last, the 3D diagram of brachial plexus was made. The internal structure of the brachial plexus was found to be very complicated. The fascicles bifurcated and recombined with one another with no fixed rules. All fascicles were mixed sensory and motor fibers. Acetylcholinesterase histochemical staining from a serial tissue section is a useful technique to distinguish sensory fibers from motor ones. The 3D visualization of the brachial plexus may help to develop a computerized database of the fascicle topography to provide an anatomical reference in fascicular repair of brachial plexus.

[Absence of the musculocutaneous nerve and its distribution from median nerve: About two cases and literature review]

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.

Motor nerve lengths of twenty-seven muscles in upper extremity

The purpose of this study is to determine the lengths of motor nerves in the upper extremity. Motor nerves of 27 muscles in 10 cadavers (16 extremities) were dissected from their roots at the level of intervertebral foramen to the entry point of the nerves to the corresponding muscles. Distance between acromion and the lateral epicondyle of the humerus was also measured in all cadavers. Nerve length of the coracobrachialis muscle was the shortest (18.26 ± 1.64 cm), while the longest was the nerve of the extensor indicis (59.51 ± 4.80 cm). The biceps brachii, the extensor digitorum communis, and the brachialis muscles showed highest coefficient of variation that makes these nerve lengths of muscles inconsistent about their lengths. This study also offers quotients using division of the lengths of each nerve to acromion-the lateral epicondyle distance. Knowledge of the nerve lengths in the upper extremity may provide a better understanding the reinnervation sequence and the recovery time in the multilevel injuries such as brachial plexus lesions. Quotients may be used to estimate average lengths of nerves of upper extremity in infants and children. Moreover, reliability of the biceps brachii as a determinant factor for surgery in obstetrical brachial plexus lesions should be reconsidered due to its highest variation coefficient.

A rare case of multiple neuromuscular variations in the axilla and arm

During the dissection of a 73-year-old embalmed male cadaver, we noted unusual variations in the flexor compartment of the upper limb-bilateral axillary arch muscles, a three-headed biceps brachii muscle with two supernumerary bellies-and variations in the origin of the musculocutaneous and median nerves from the brachial plexus. The morphological and clinical significance of this unique coexistence of multiple neuromuscular variations are discussed.

Clinical sonopathology for the regional anesthesiologist: part 1: vascular and neural

The use of ultrasound to facilitate regional anesthesia is an evolving area of clinical, education, and research interests. As our community's experience grows, it has become evident that anesthesiologists performing "routine" ultrasound-guided blocks may very well be confronted with atypical or even pathologic anatomy. As an educational resource for anesthesiologists, the following articles present examples of common sonopathology that may be encountered during ultrasound-guided regional anesthesia. This present article describes sonopathology related to blood vessels and nerves.

Unilateral intercordal neural communication coexistent with variant branching pattern of posterior cord of brachial plexus

Variant branching pattern of the cords of brachial plexus coupled with erroneous communications has been an area of concern for surgeons opting to explore this region. Anaesthetic blocks and surgical approaches are the highlights of these interventions, where a keen familiarization of the anatomy of this region is mandatory. The present case description reports a unilateral variant branching pattern of the posterior cord coexistent with a neural communication between lateral and medial cords in an adult male cadaver. This intercordal neural communication between lateral and medial cords was oriented obliquely and measured 2.2 cm in length. Furthermore, the posterior cord revealed a variant branching pattern. It branched into three upper subscapular nerves and a common trunk for the thoracodorsal and lower subscapular nerves. The lowest of the three upper subscapular nerves gave a communicating twig to the thoracodorsal nerve. Inspite of uncountable reports on variations ofbrachial plexus, descriptions regarding anomalous branching patterns hold enormous clinical significance for the radiologists, anesthetists and surgeons, besides being of academic interest for the anatomists.

Branching patterns of the lateral thoracic, subscapular, and posterior circumflex humeral arteries and their relationship to the posterior cord of the brachial plexus

Anatomical variations in the branching pattern of the axillary artery are common and typically include the lateral thoracic, subscapular, and the posterior circumflex humeral (PCHA) arteries. Previous investigations of single specimen dissections demonstrate numerous variations to axillary artery branching, but the frequency of these occurrences is unclear. This study quantifies the frequency of variant branching of the lateral thoracic, subscapular, and posterior circumflex humeral arteries, how it they relate to the posterior cord of the brachial plexus. Axillae of 83 cadavers were dissected to allow examination of the axillary artery and its branches. Data were collected observing the branching pattern of the lateral thoracic, subscapular, and posterior circumflex humeral arteries, as well as those branches spatial relationship to the two terminal branches of the posterior cord of the brachial plexus. Some of the more common variations included the thoracodorsal artery arising from the lateral thoracic artery (LTA) (7.2%) and the subscapular artery (SSA) arising from the LTA (5.4%). The SSA also produced the LTA (4.2%) and the PCHA (12%). The PCHA also originated from the deep brachial artery (8.4%) and traversed the triangular interval to supply the deltoid muscle. These findings are relevant to both the anatomical and clinical fields as provide evidence as to the frequency of variant axillary artery branching and the potential for neurovascular elements to exist in a location other than their classical anatomical description.

Anatomical variation in formation of brachial plexus and its branching

Variant brachial plexus formation with two trunks and two cords is uncommon and has clinical implications as it may result in failure of regional brachial or axillary block. During routine anatomical dissection, unilateral variation in the formation of brachial plexus accompanied by unusual positional relationship with axillary artery was discovered in the left upper extremity of a 52-year-old Indian male cadaver. Brachial plexus showed two trunks formed by ventral rami of C5, C6 and C7, C8, T1 spinal nerves, respectively, which first split and then reunited in an unusual manner to form two cords: posterior and lateral instead of three. Medial cord was absent. The branching pattern of the brachial plexus also showed important variations. Second part of axillary artery was found lying inferomedial to brachial plexus instead of passing between medial and lateral cords. Transverse cervical artery was found to be coursing between two trunks instead of passing superficial to brachial plexus. Median nerve was observed to be formed from a single root, instead of usual two roots. Embryologically, this rare variation may be due to the development of axillary artery from ninth segmental artery instead of usual seventh cervical intersegmental artery. Such rare variation is clinically important as this knowledge may help the anesthesiologists and the surgeons to avoid any inadvertent damage to nerves and axillary artery during blocks and surgical interventions.

Nerve loop around the axillary vessels by the roots of the median nerve a rare variation in a south Indian male cadaver: a case report

INTRODUCTION

Median nerve is normally formed by the union of medial and lateral root arising from the medial and the lateral cords of the brachial plexus respectively. However, variations in the formation and its relation with the axillary vessels are not uncommon. Therefore, knowledge of the variations in the nerve formation and course is useful for the clinicians during surgery and for differential diagnosis of uncommon clinical conditions.

CASE PRESENTATION

During the routine dissection in the department of anatomy, Kasturba Medical Collage, Manipal, India, we found unique anatomical variations in the formation and the course of the roots of the median nerve forming the neural loops around the axillary artery and vein.

CONCLUSION

Here we report the detailed description of these variations along with its clinical, embryological relevance and review of literature.

Intersegmental origin of the axillary artery and accompanying variation in the brachial plexus

The wide anatomical variation of the brachial plexus and the axillary artery has been thoroughly explored in previous studies. However, there has been little information reported on the variation in the relationship between the brachial plexus and the axillary artery. The principal feature of this relationship is the passage of the axillary artery through the loop of the median nerve, which occurs in normal arteries derived from the seventh intersegmental artery. In this study, we analyzed the abnormal position and course of the axillary artery related to the brachial plexus in 607 axillae of 306 cadavers. We found 12 unusual axillary arteries that did not pass through the median loop. Eleven arteries were determined to be ninth intersegmental arteries and one as the sixth intersegmental artery. All ninth intersegmental arteries ran caudally to the brachial plexus. In six cases of this type, abnormal connections interfering with the normal arterial position were observed in the brachial plexus. In another five cases of this type, the lateral and medial cords merged and the axillary artery passed anteromedial to the plexus. The sixth intersegmental axillary artery pierced the musculocutaneous nerve which is from the unified lateral and medial cords. This study discussed the how the anomalous structure of the brachial plexus could involve the deterioration of the course of the axillary artery.

Absence of the musculocutaneous nerve: a rare anatomical variation with possible clinical-surgical implications

CONTEXT

The musculocutaneous nerve is one of the terminal branches of the lateral fasciculus of the brachial plexus, and is responsible for innervation of the flexor musculature of the elbow and for skin sensitivity on the lateral surface of the forearm. Its absence has been described previously, but its real prevalence is unknown.

CASE REPORT

A case of absence of the musculocutaneous nerve that was observed during the dissection of the right arm of a male cadaver is described. The area of innervation was supplied by the median nerve. From this, three branches emerged: one to the coracobrachialis muscle, another to the biceps brachii muscle and the third to the brachialis muscle. This last branch continued as a lateral antebrachial cutaneous nerve. This is an anatomical variation that has clinical-surgical implications, considering that injury to the median nerve in this case would have caused unexpected paralysis of the flexor musculature of the elbow and hypoesthesia of the lateral surface of the forearm.

Variations in brachial plexus and the relationship of median nerve with the axillary artery: a case report

Background

Brachial Plexus innervates the upper limb. As it is the point of formation of many nerves, variations are common. Knowledge of these is important to anatomists, radiologists, anesthesiologists and surgeons. The presence of anatomical variations of the peripheral nervous system is often used to explain unexpected clinical signs and symptoms.

Case Presentation

On routine dissection of an embalmed 57 year old male cadaver, variations were found in the formation of divisions and cords of the Brachial Plexus of the right side. Some previously unreported findings observed were; direct branches to the muscles Pectoralis Minor and Latissimus dorsi from C6, innervation of deltoid by C6 and C7 roots and the origin of lateral pectoral nerve from the posterior division of upper trunk. The median nerve was present lateral to axillary artery. The left side brachial plexus was also inspected and found to have normal anatomy.

Conclusion

The probable cause for such variations and their embryological basis is discussed in the paper. It is also concluded that although these variations may not have affected the functioning of upper limb in this individual, knowledge of such variations is essential in evaluation of unexplained sensory and motor loss after trauma and surgical interventions to the upper limb.