Medial Cord Research Articles

Unusual formation of the median nerve associated with the third head of biceps brachii

Unilateral variations in the formation of the median nerve, with the presence of the third head of the biceps brachii entrapping the nerve are very rare. These variations were observed on the right side, of a 30-year-old male cadaver during routine dissection at the Department of Human Anatomy, University of Nairobi. The median nerve was formed by the union of three contributions; two from the lateral cord and one from the medial cord. An additional head of the biceps brachii looped over the formed median nerve. On the left side, the median nerve was formed classically by single contributions from the medial and the lateral cords. These variations are clinically important because symptoms of high median nerve compression arising from similar formations are often confused with more common causes such as radiculopathy and carpal tunnel syndrome.

Anatomical variation in the formation of median nerve - A case report.

During routine dissection of an adult male cadaver in the Department of Anatomy, Prathima institute of medical sciences, Kariminager, India, the right median nerve was found to be formed by four roots . The finding was noted after thorough and meticulous dissection of the upper limbs of both sides (axilla, arm, forearm and palm). Out of the four roots forming the anomalous median nerve, three were from lateral cord and one from medial cord of brachial plexus. However, the distribution of the anomalous median nerve was normal in arm, forearm and palm. The arterial pattern in the arm (axillary and brachial arteries) was also normal.

Surgical anatomy of the pectoral nerves and the pectoral musculature

The pectoral nerves (PNs) may be selectively injured through various traumatic mechanisms such as direct trauma, hypertrophic muscle compression, and iatrogenic injuries (breast surgery and axillary node dissection, pectoralis major muscle transfers). The PN may be surgically recovered through nerve transfers. They may also be used as donors to the musculocutaneous, axillary, long thoracic, and spinal accessory nerves and for reinnervation of myocutaneous free flaps. Thus, in this article, we reviewed the surgical anatomy of PN. A meta-analysis of the available literature showed that the lateral pectoral nerve (LPN) arises most frequently with two branches from the anterior divisions of the upper and middle trunks (33.8%) or as a single root from the lateral cord (23.4%). The medial pectoral nerve (MPN) usually arises from the medial cord (49.3%), anterior division of the lower trunk (43.8%), or lower trunk (4.7%). The two PN are usually connected immediately distal to the thoracoacromial artery by the so-called ansa pectoralis. The MPN may also show communications with the intercostobrachial nerve. In 50%-100% of cases, it may pass, at least with some branches, through the pectoralis minor muscle. The LPN supplies the upper portions of the pectoralis major muscle; the MPN innervates the lower parts of the pectoralis major and the pectoralis minor muscle. Among the accessory muscles of the pectoral girdle, the LPN may also innervate the tensor semivaginae articulationis humero-scapularis, pectoralis minimus, sternoclavicularis, axillary arch, sternalis, and infraclavicularis muscles; the MPN may innervate the pectoralis quartus, chondrofascialis, axillary arch, chondroepitrochlearis, and sternalis muscles.

Nerve transfers for restoration of upper extremity motor function in a child with upper extremity motor deficits due to transverse myelitis: Case report

Transverse myelitis (TM) may result in permanent neurologic dysfunction. Nerve transfers have been developed to restore function after peripheral nerve injury. Here, we present a case report of a child with permanent right upper extremity weakness due to TM that underwent nerve transfers. The following procedures were performed: double fascicle transfer from median nerve and ulnar nerve to the brachialis and biceps branches of the musculocutaneous nerve, spinal accessory to suprascapular nerve, and medial cord to axillary nerve end-to-side neurorraphy. At 22 months, the patient demonstrated excellent recovery of elbow flexion with minimal improvement in shoulder abduction. We propose that the treatment of permanent deficits from TM represents a novel indication for nerve transfers in a subset of patients.

A four trunked brachial plexus and a post fixed brachial plexus: A conjunction or a co‐incidence?: Report of three cases

The anatomical variations of the brachial plexus in humans have clinical significance for surgeons, radiologists, and anatomists. In a study of 60 brachial plexuses, four trunked brachial plexuses were encountered in three limbs (two female and one male), all of them being post fixed and on left side of cadavers. The third trunk in all these limbs gave rise to two anterior divisions (upper and lower) and one posterior division. In two limbs belonging to the female sex, the upper anterior division joined with the anterior division of the second trunk to form the lateral cord while its lower anterior division joined with the anterior division of the fourth trunk to form the medial cord. In the sole male limb, along with the third trunk, the fourth trunk also divided into upper and lower anterior divisions. Upper anterior divisions of the third and fourth trunks joined to form the medial root of the median nerve while lower anterior divisions joined to form the ulnar nerve. No medial cord was formed as such. Further, it is inferred that in postfixed brachial plexus, there is a tendency to failure on part of T1 and T2 to join C8 which continues as the third trunk while T1 and T2 continue as the fourth trunk. Since it was seen in all postfixed brachial plexuses of the present study, it is emphasized to be given a place in the textbooks of anatomy or to conduct a study on a larger database.

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.

Schwannoma of Brachial Plexus

Brachial plexus tumours are a rare entity. Schwannomas are benign nerve sheath tumours and only about 5% arise from the brachial plexus. Due to its rarity and complex anatomical location they can pose a formidable challenge to surgeons. We present a case of a young patient who presented with an axillary swelling three months after a lymph node biopsy from the same axilla, which turned out to be a Schwannoma arising for the medial cord of the brachial plexus.

Thoracic Outlet Syndrome: A Primer on Objective Methods of Diagnosis

Thoracic outlet syndrome (tos) is a disabling symptomatic condition that arises from injury to nerves of the brachial plexus and the subclavian vessels as these structures pass from the neck and thorax into the upper limb. 1 Sanders R. Thoracic outlet syndrome: a common sequela of neck injuries. JB Lippincott, Philadelphia1991 Google Scholar , 2 Atasoy E. Thoracic outlet compression syndrome. Orthop Clin N Am. 1996; 27: 265-303 PubMed Google Scholar , 3 Luoma A. Nelems B. Thoracic outlet syndrome: thoracic surgery perspective. Neurosurg Clin North Am. 1991; 2: 187-225 PubMed Google Scholar , 4 Heughan C. Thoracic outlet compression. Can J Surg. 1984; 24: 35-36 Google Scholar The condition usually presents with pain, fatigue, and deep muscle aching suggesting a nonspecific nocicentric type of injury signal. Neuropathic reports suggesting direct nerve injury may localize symptoms to the medial cord of the plexus or ulnar innervated area of the upper limb. Arterial insufficiency may produce overlapping chronic or acute symptoms such as ischemic pain in the limb, coldness, or blanching in the hand during exercise. A subclavian artery aneurysm may produce emboli and distal digital ischemia. 1 Sanders R. Thoracic outlet syndrome: a common sequela of neck injuries. JB Lippincott, Philadelphia1991 Google Scholar Venous obstruction may be associated with chronic swelling in the limb. Acute venous thrombosis may be experienced after vigorous exercise in patients with costoclavicular compression. 1 Sanders R. Thoracic outlet syndrome: a common sequela of neck injuries. JB Lippincott, Philadelphia1991 Google Scholar , 5 Machleder H.I. Evaluation of a new treatment strategy for treatment of Paget-Schroeder syndrome: spontaneous thrombosis of the subclavian vein. J Vasc Surg. 1993; 17: 305-317 Abstract Full Text Full Text PDF PubMed Scopus (223) Google Scholar •Discuss the different signs and symptoms between neurologic, arterial, and venous thoracic outlet syndrome. •Describe the Wright's and Adson’s tests. •Discuss the role of plain x-rays in the diagnosis of thoracic outlet syndrome. •Compare and contrast the various vascular imaging studies for thoracic outlet syndrome. •State the role of Botox in thoracic outlet syndrome. •Discuss the test of selective symptom provocation associated with oxygen saturation in the diagnostic algorithm of thoracic outlet syndrome. Earn up to 2 hours of CME credit per JHS issue when you read the related articles and take the online test. To pay the $20 fee and take this month's test, visit http://www.assh.org/professionals/jhs. •Discuss the different signs and symptoms between neurologic, arterial, and venous thoracic outlet syndrome. •Describe the Wright's and Adson’s tests. •Discuss the role of plain x-rays in the diagnosis of thoracic outlet syndrome. •Compare and contrast the various vascular imaging studies for thoracic outlet syndrome. •State the role of Botox in thoracic outlet syndrome. •Discuss the test of selective symptom provocation associated with oxygen saturation in the diagnostic algorithm of thoracic outlet syndrome. Earn up to 2 hours of CME credit per JHS issue when you read the related articles and take the online test. To pay the $20 fee and take this month's test, visit http://www.assh.org/professionals/jhs. Journal CME QuestionsJournal of Hand SurgeryVol. 35Issue 9Preview Full-Text PDF

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.

Selective Local Anesthetic Placement Using Ultrasound Guidance and Neurostimulation for Infraclavicular Brachial Plexus Block

In this study, we performed the infraclavicular block with combined ultrasound guidance and neurostimulation to selectively target cords to compare the success rates of placing a single injection of local anesthetic either in a central or peripheral location. Two hundred eighteen patients were enrolled in a consecutive, prospective study. Patients were randomized to injection of local anesthetic either centrally (posterior cord) or peripherally (medial or lateral cord) using ultrasound guidance and neurostimulation. Supervised senior anesthesiology residents or attending anesthesiologists performed the blocks. Both intent-to-treat and treatment-received analyses were used to compare central and peripheral placement efficacy. The overall success rate was significantly higher for the central placements than peripheral placements (96% vs 85%, P = 0.004). Individual cord success rates were as follows: posterior 99%, lateral 92%, and medial 84% (P = 0.001). The central group required attending physician intervention more frequently (27% vs 6%, P < 0.001). Postoperative pain scores of < or =3 were more likely with central placement (100% vs 94%, P = 0.012). Central placement of a single injection of local anesthetic targeted at the posterior cord resulted in a higher success rate for infraclavicular block.

Extracerebellar progenitors grafted to the neurogenic milieu of the postnatal rat cerebellum adapt to the host environment but fail to acquire cerebellar identities

Stem or progenitor cells acquire specific regional identities during early ontogenesis. Nonetheless, there is evidence that cells heterotopically transplanted to neurogenic regions of the developing or mature central nervous system may switch their fate to adopt host-specific phenotypes. Here, we isolated progenitor cells from different germinative sites along the neuraxis where GABAergic interneurons are produced (telencephalic subventricular zone, medial ganglionic eminence, ventral mesencephalon and dorsal spinal cord), and grafted them to the prospective white matter of the postnatal rat cerebellum, at the time when local interneurons are generated. The phenotype acquired by transplanted cells was assessed by different criteria, including expression of region-specific transcription factors, acquisition of morphological and neurochemical traits, and integration in the cerebellar cytoarchitecture. Regardless of their origin, all the different types of donor cells engrafted in the cerebellar parenchyma and developed mature neurons that shared some morphological and neurochemical features with local inhibitory interneurons, particularly in the deep nuclei. Nevertheless, transplanted cells failed to activate cerebellar-specific regulatory genes. In addition, their major structural features, the expression profiles of type-specific markers and the laminar placement in the recipient cortex did not match those of endogenous interneurons generated during the same developmental period. Therefore, although exogenous cells are influenced by the cerebellar milieu and show remarkable capabilities for adapting to the foreign environment, they essentially fail to switch their fate, integrate in the host neurogenic mechanisms and adopt clear-cut cerebellar identities.

White Matter Organization in Cervical Spinal Cord Relates Differently to Age and Control of Grip Force in Healthy Subjects

Diffusion tensor imaging (DTI) can be used to elucidate relations between CNS structure and function. We hypothesized that the degree of spinal white matter organization relates to the accuracy of control of grip force. Healthy subjects of different age were studied using DTI and visuomotor tracking of precision grip force. The latter is a prime component of manual dexterity. A regional analysis of spinal white matter [fractional anisotropy (FA)] across multiple cervical levels (C2-C3, C4-C5, and C6-C7) and in different regions of interest (left and right lateral or medial spinal cord) was performed. FA was highest at the C2-C3 level, higher on the right than the left side, and higher in the lateral than in the medial spinal cord (p < 0.001). FA of whole cervical spinal cord (C2-C7) was lower in subjects with high tracking error (r = -0.56, p = 0.004) and decreased with age (r = -0.63, p = 0.001). A multiple regression analysis revealed an independent contribution of each predictor (semipartial correlations: age, r = -0.55, p < 0.001; tracking error, r = -0.49, p = 0.003). The closest relation between FA and tracking error was found at the C6-C7 level in the lateral spinal cord, in which the corticospinal tract innervates spinal circuitry controlling hand and digit muscles. FA of the medial spinal cord correlated consistently with age across all cervical levels, whereas FA of the lateral spinal cord did not. The results suggest (1) a functionally relevant specialization of lateral spinal cord white matter and (2) an increased sensitivity to age-related decline in medial spinal cord white matter in healthy subjects.

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.

Anatomical and Electrophysiological Myotomes Corresponding to the Flexor Carpi Ulnaris Muscle

This study was designed to investigate the incidence of lateral root of the ulnar nerve through cadaveric dissection and to analyze its impact on myotomes corresponding to the flexor carpi ulnaris (FCU) assessed by electrodiagnostic study. Dissection of the brachial plexus (BP) was performed in 38 arms from 19 cadavers, and the connecting branches between the lateral cord and medial cord (or between lateral cord and ulnar nerve) were investigated. We also reviewed electrodiagnostic reports from January 2006 to May 2008 and selected 106 cases of single-level radiculopathy at C6, C7, and C8. The proportion of abnormal needle electromyographic findings in the FCU was analyzed in these patients. In the cadaver study, branches from the lateral cord to the ulnar nerve or to the medial cord were observed in 5 (13.1%) of 38 arms. The incidences of abnormal electromyographic findings in the FCU were 46.2% (36/78) in C7 radiculopathy, 76.5% (13/17) in C8 radiculopathy and 0% (0/11) in C6 radiculopathy. In conclusion, the lateral root of the ulnar nerve is not an uncommon anatomical variation of the BP and the FCU commonly has the C7 myotome. Needle EMG of the FCU may provide more information for the electrodiagnosis of cervical radiculopathy and brachial plexopathy.

In Response:

In Response: Although we concur with Chin et al.1 that it “would have been useful to know the distribution of sensory loss and its correlation with the site of surgical pain,” we disagree that we failed to “specify if the motor response used as the endpoint for catheter placement was random, standardized or matched to the site of surgery.” As noted in the Methods section,2 the catheter-placement protocol was identical to that previously published (Ref. 1 of article under discussion)3; and the protocol specified that the catheter insertion was standardized with the preferred stimulation-induced muscular motion correlating with the medial cord.3 Our reasoning for targeting the medial cord is that when using the coracoid technique and the Stimucath (Arrow International, Reading, PA) stimulating catheter, we have found it difficult to keep the catheter tip along the posterior and lateral cords when inserting the catheter past the needle tip (probably for anatomic reasons). Thus, although the specific muscle response and correlation with the surgical site was not investigated/recorded, the insertion protocol was standardized and the overwhelming majority of catheters placed along the median cord. Chin et al. also noted that “it is also possible that patients in this group [0.4% concentration] self-administered more boluses of local anesthetic in an attempt to improve analgesia, and hence received a larger mass and volume of local anesthetic.” We agree with their assessment and specifically noted among the study limitations that, “although each patient-controlled bolus dose delivered the same ropivacaine dose for both treatment groups (8 mg available every 30 min), the actual delivered doses for each group are unavailable. Therefore, it is possible that patients assigned to 0.4% ropivacaine self-administered a greater number of bolus doses resulting in a higher total dose of delivered ropivacaine. This methodological weakness decreases confidence in the rejection of our null hypothesis.”1 We are thus retesting the original hypothesis in a new study involving hospitalized patients, which gives us access to the important bolus-dose use information. But whatever the mechanism may be, our study conclusions remain clinically useful. “In other words, regardless of the total amount of local anesthetic delivered to each treatment group, providing a 0.2% ropivacaine infusion at a basal rate of 8 mL/h resulted in a lower incidence of patient-identified insensate limbs relative to a 0.4% ropivacaine infusion at a basal rate of 4 mL/h.”1 Brian M. Ilfeld, MD, MS Edward R. Mariano, MD, MAS Vanessa J. Loland, MD Department of Anesthesiology University of California San Diego San Diego, California [email protected] Daniel I. Sessler, MD Department of Outcomes Research Cleveland Clinic Cleveland, Ohio For the PAINfRE™ Investigators

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.

Vertical Infraclavicular Brachial Plexus Block

In vertical infraclavicular brachial plexus block, success depends on distal flexion or extension response. Initially, elbow flexion (lateral cord) is generally observed. However, specific knowledge about how to reach the medial or posterior cord is lacking. We investigated the mid-infraclavicular area in undisturbed anatomy and tested the findings in a clinical setting. Along a length of 35 mm around the mid-infraclavicular point, cryomicrotomy sections of 5 shoulders from cadavers were used to determine the topography of the cords in relation to one another and the axillary artery. Based on the findings, the anesthesiologists were instructed on how to elicit a distal motor response after an initial elbow flexion response in single-shot, Doppler-aided, vertical infraclavicular block in a series of 50 consecutive patients. In the mid-infraclavicular area, the lateral cord always lies anterior to either the posterior or the medial cord and cranial to the axillary artery; the posterior cord was always cranial to the medial cord; and both cords were always located dorsal to the artery. In the clinical study, in 98% of the included patients, finger flexion or finger and/or wrist extension was elicited as predicted. The overall success rate was 92%. No vascular or lung puncture occurred. In the clinical study, in 98% of cases, the final stimulation response of posterior or medial cord was found as predicted by the findings of the anatomic study. Once elbow flexion is elicited, a further (ie, deeper) advancement of the needle will result in the proper distal motor response.

Medial pectoral nerve to musculocutaneous nerve neurotization for the treatment of persistent birth-related brachial plexus palsy: an 11-year institutional experience

Medial pectoral nerve (MPN) to musculocutaneous nerve (MCN) neurotization for recovery of elbow flexion by biceps reinnervation is a valid option following traumatic injury to the upper brachial plexus. A major criticism of the application of this technique in infants is the smaller size of the MPN and mismatch of viable axons. We describe our institutional experience utilizing this procedure and critically examine functional outcomes. Office charts and hospital records of children from over an 11-year period beginning January 1997 were reviewed. Of the 53 children of various ages undergoing brachial plexus exploration for traumatic injury of any nature, 20 underwent MPN to MCN neurotization as a part of an overall procedure in the first year of life to treat birth-related brachial plexus palsy and had at least 9 months' follow-up. Medial pectoral nerve to MCN neurotization was chosen if the results of clinical examination and intraoperative electrophysiological evidence were consistent with medial cord function. Functional recovery was defined as the ability of the child to bring their hand to their mouth. Sixteen patients (80%) gained functional recovery. The median age at surgery was 7 months. Median time to first clinic visit documenting recovery was 11.5 months and median overall follow up was 21.5 months. Preoperative hand function was a useful predictor of recovery of elbow flexion. Medial pectoral nerve to MCN neurotization is a valid surgical option for the reinnervation of the biceps muscle for birth-related brachial plexus palsy when the hand is functional preoperatively. Useful elbow flexion can be expected in the majority of these children.

Bilateral multiple complex variations in the formation and branching pattern of brachial plexus

Bilateral variations in the formation and branching of brachial plexus are extremely rare. Multiple bilateral variations in brachial plexus right from divisions to branching pattern were observed during the dissection in an adult male cadaver. Lateral and medial cord formation showed deviation from the usual pattern. Anterior division of upper trunk continued as lateral cord. Medial cord was formed by the union of anterior division of lower trunk and anterior division of middle trunk, thus receiving fibers from both the trunks. Anterior division of middle trunk bifurcated into upper and lower branches. We encountered two lateral roots bilaterally and two medial roots of median nerve on the left side with anomalous origin. There were three upper subscapular nerves on the left and two on the right side with variations in their origin. Anomalous origin of many other branches on both sides was encountered. It is extremely uncommon to find so many variations in one body and bilateral variations are still too rare. Understanding of such variations is clinically important for diagnosing unexplained clinical signs and symptoms as well as during nerve blocks and certain surgical procedures around the neck and proximal arm.

The surgical anatomy of the brachial plexus

The brachial plexus (BP) has a complex structure and risky relations with its neighborhoods. This study was designed to investigate and overcome the morphometric features of the BP and the difficulties regarding surgery of BP lesions. Twelve BP of six adult cadavers were dissected and neural structures, branches, and variations were evaluated. Morphometric measurements were done and surgical approaches were discussed. The length of anterior (ventral) rami of C5-T1 are in decreasing order such as C5 > C6 > C7 > C8 > T1 and the width of them is in decreasing order such as C7 > C8 > C6 > T1 > C5. The length of upper trunk (UT) , middle trunk (MT) and lower trunk (LT) are approximately similar (UT approximately MT approximately LT) , but the width is in decreasing order as LT > UT > MT. The length of the cords are in decreasing order as posterior cord (PC) > lateral cord (LC) > medial cord (MC), whereas their widths are PC > LC > MC . From the ventral rami to the cords, BP has a complex and variable anatomic structure. The selection of surgical procedure to the BP needs to be mastered by having the best knowledge of the relevant anatomy.