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.

Plexus brachialis strain and compression deformation in the costo-axillary-brachial region: a cadaveric study.

OBJECTIVE: The aim of this study was to clarify the role of different mechanisms in nerve injury during arm abduction positions. The tasks were to determine the strain deformation of the plexus brachialis during arm abduction, to measure the pressures in the neurovascular bundle in the cervico-costoclavicular-axillary area, and evaluate the histological changes of nerve after the stretch test. MATERIAL AND METHODS: During the cadaveric study on 7 specimens 7-20 h after death, strain deformation of plexus brachialis as well as compression deformation caused by the surrounding structures of the neurovascular bundle were investigated in the arm abduction position of 0°, 90°, 12°, 150°, and 180°. One nerve sample was studied histologically after 15% stretch on the bench. RESULTS: The relative strain deformation of 3%-23% was documented during 0° to 180° abduction tests. The strain deformation from 0° to 90° was significant (P<0.001). The mean pressure change in the bundle was 13.6 mm Hg at 90°, 53.7 mm Hg at 120°, 73.4 mm Hg at 150°, and 89.0 mm Hg at 180° arm abduction. An increase in pressure was significant in the intervals: 0°-90° (P<0.001), 91°-120° (P<0.001), 121°-150° (P<0.001) and 151°-180° (P<0.05). CONCLUSIONS: Nerve traction and tissue compression arising during the arm abduction above 90° were found to be sufficient to induce lesions in neural bundles of the plexus brachialis.

Effect of body mass index on the ED50 volume of bupivacaine 0.5% for supraclavicular brachial plexus block.

BACKGROUND: The aim of this study was to determine whether the ED(50) dose of bupivacaine 0.5% for supraclavicular brachial plexus block increases with increasing body mass index (BMI). METHODS: This double-blind, non-randomized trial followed an up-and-down sequential allocation design. Adult patients undergoing elective upper limb surgery under ultrasound-guided supraclavicular brachial block were recruited. A preliminary study was used to guide the dosing schedule for the main study in which patients were divided into three groups according to their BMI (Group A, BMI >27 kg m(-2); Group B, BMI 24-27 kg m(-2); Group C, BMI <24 kg m(-2)). The study design and analysis followed Dixon's small sample model using a 'nominal' sample size of six per group. RESULTS: Twenty-one patients were recruited to the preliminary study. Using isotonic regression, the ED(50) for bupivacaine 0.5% was estimated to be 8.9 ml [95% confidence interval (CI) 7.8-15.9]. In comparison, the ED(50) volume was found to be 10.8 ml (95% CI 5.9-19.7) using the Dixon-Massey formula. In the main study, six patients were recruited in each group with mean (range) BMI of 31.5 (27.2-38.8) kg m(-2) in Group A, 25.6 (24.4-26.3) kg m(-2) in Group B, and 21.6 (19.7-23.8) kg m(-2) in Group C. The ED(50) (95% CI) for Groups A, B, and C were 8.9 (6.2-12.7), 10.7 (7.5-15.4), and 13.4 (9.3-19.1) ml, respectively (P=0.05 for Group A vs Group C). CONCLUSIONS: Our study demonstrates that the ED(50) of bupivacaine 0.5% does not increase with an increase in BMI. We found evidence of a possible inverse relationship between ED(50) and BMI.

Systematic evaluation of the highest current threshold for regional anaesthesia in a porcine model.

BACKGROUND: The purpose of this study was to determine systematically the highest minimal stimulation current threshold for regional anaesthesia in pigs. METHODS: In an established pig model for regional anaesthesia, needle placements applying electric nerve stimulation were performed. The primary outcome was the frequency of close needle to nerve placements as assessed by resin injects and subsequent anatomical evaluation. Following a statistical model (continual reassessment method), the applied output currents were selected to limit the necessary number of punctures, while providing guidance towards the highest output current range. RESULTS: Altogether 186 punctures were performed in 11 pigs. Within the range of 0.3-1.4 mA, no distant needle to nerve placement was found. In the range of 1.5-4.1 mA, 43 distant needle to nerve placements occurred. The range of 1.2-1.4 mA was the highest interval that resulted in a close needle to nerve placement rate of > or =95%. CONCLUSIONS: In the range of 0.3-1.4 mA, all resin deposition was found to be adjacent to nerve epineurium. The application of minimal current intensities up to 1.4 mA does not obviously lead to a reduction of epineural injectate contacts in pigs. These findings suggest that stimulation current thresholds up to 1.4 mA result in equivalent needle tip localisation in pigs.

Analgesic Effects and Neuropathology Changes of Electroacupuncture on Curing a Rat Model of Brachial Plexus Neuralgia Induced by Cobra Venom.

BACKGROUND: Electroacupuncture (EA) is widely applied to treat neuropathic pain. Brachial plexus neuralgia (BPN) is a common form of chronic persistent pain. Few studies have evaluated the analgesic effects and mechanism of EA using the novel animal model of BPN. OBJECTIVE: To observe the curative effects of repeated EA on curing BPN induced by administration of cobra venom to the lower trunk of the right brachial plexus. STUDY DESIGN: Controlled animal study. SETTING: Department of Anesthesiology, Pain Medicine & Critical Care Medicine, Aviation General Hospital of China Medical University. METHODS: Sixty-six adult male Sprague-Dawley rats were equally and randomly divided into the following groups: normal control (NC), brachial plexus neuralgia (BPN), BPN with sham EA stimulation, BPN with EA stimulation starting on postoperative day 1 (EA1), and BPN with EA stimulation starting on postoperative day 12 (EA12). The BPN model was established by administration of cobra venom to the lower trunk of the right brachial plexus. On postoperative day 1 or day 12, EA (constant aquare wave, 2 Hz and 100 Hz alternating frequencies, intensities ranging from 1 - 1.5 - 2 mA) was applied to the right "Shousanli" (LI10) and "Quchi" (LI11) acupoints for 30 minutes, once every other day for 12 times in both groups. Mechanical withdrawal thresholds (MWT) were tested with von Frey filaments. Video recordings were conducted to analyze the spontaneous exploratory behaviors. Moreover, the organizational and structural alterations of the right brachial plexus and cervical cord (C8-T1) were examined via light and electron microscopy. RESULTS: Following the production of the BPN model, the MWT of both ipsilateral and contralateral paws demonstrated a profound decrease (P < 0.05). But after EA interventions, the MWT showed a significant increase (P < 0.05). In comparison to the EA12 group, the analgesic effects of the EA1 group were more significant, and similar results were observed in exploratory behaviors. However, grooming behaviors did not demonstrate significant differences. Meanwhile, on day 12 after surgery it was observed under light microscopy that the inflammatory response in the right brachial plexus and cervical cord (C8-T1) were significantly attenuated after EA stimulation. Furthermore, the demyelination of the brachial plexus and cervical cord (C8-T1) were also reversed. LIMITATIONS: Limitations include the fact that there was demyelination of the cervical cord (C8-T1) in the control group because of inappropriate manipulation. CONCLUSION: Repeated EA contributes significant analgesic effects in the treatment of BPN.

A GABAergic projection from the central nucleus of the amygdala to the parabrachial nucleus: an ultrastructural study of anterograde tracing in combination with post-embedding immunocytochemistry in the rat.

To determine whether axonal terminals emanating from the central nucleus of amygdala (Ce) to the parabrachial nucleus (PBN) contain gamma-aminobutyric acid (GABA) as their neurotransmitter, an electron microscopic study was performed employing the combined techniques of WGA-HRP anterograde tracing and post-embedding immunocytochemistry for GABA. Our analysis distinguished a large population of GABA immunopositive axonal terminals from the Ce that exhibited symmetrical synaptic contacts with neurons in the lateral parabrachial nucleus. Additionally, most retrogradely labeled dendrites and perikarya received synaptic contacts from GABA immunoreactive terminals, with some of them originating from the Ce. The present study provides the first direct ultrastructural evidence for a monosynaptic, GABAergic link between Ce axons and neurons of the parabrachial nucleus via classical symmetrical synapses.

Comparison of two techniques for ultrasound-guided axillary brachial plexus blockade in cats.

Axillary blockade of the brachial plexus (BP) is advocated in humans and dogs for surgical procedures carried out on the foot, carpus and elbow as it provides complete analgesia distally from above the elbow joint. The aim of this study was to develop an ultrasound (US)-guided approach to block the BP in cats. Two groups of 12 feline cadavers each were used to compare two different techniques to block the BP at the axillary level. The reliability of the techniques was assessed by anatomical and computed tomography (CT) studies. Cadavers of the first group were positioned in dorsal recumbency with the forelimb to be blocked adducted (thoracic limbs flexed and orientated caudally) (FAD technique). The second group was positioned in dorsal recumbency with the forelimb abducted 90° (FAB technique). The accuracy of the techniques was determined by US after injecting 1 ml blue ink along the BP nerves, and by CT after injecting 1 ml of an iodinated contrast medium. The anatomical and CT studies confirmed the accuracy of the US location of the BP nerves. Staining of the axillaris, musculocutaneous, radialis, medianus and ulnaris nerves was observed in 100% of cats using the FAB technique and in 66% of the cats using the FAD technique. Rate of complications was higher in the FAD technique. In conclusion, a US-guided axillary approach to the BP by the use of a FAB technique is a safe and feasible procedure to block the BP in the cat. Further studies are needed to ascertain whether the technique can be applied in a clinical setting.

The fine structure of the cervical spinal cord, ventral root and brachial nerves in the wobbler (wr) mouse.

Much indirect evidence supports the prevailing concept that the wobbler mouse represents an inherited form of lower motor neuron degeneration, with resultant neurogenic muscular atrophy, due to an autosomal recessive gene (wr). This report, which emphasizes the fine structural changes in the wobbler mouse cervical spinal cord, ventral root and brachial nerves, both extends and modifies previously published data concerning the ultrastructural changes in this disorder. In addition to the more obvious neuronal cytoplasmic vacuolization known to occur, studies extended to a broader age range of wobbler mice have revealed neuronal alterations such as nonvacuolar dissolution of granular endoplasmic reticulum, proliferation of cytoplasmic microtubules and neurofilaments, proliferation of branched tubules resembling smooth endoplasmic reticulum, development of lipid droplets, and increased numbers of pleomorphic dense and lamellar cytoplasmic bodies. The spectrum of pathological changes in this murine form of motor neuron disease thus appears more complex and varied than has hitherto been appreciated, and may be relevant to the formulation of pathogenetic hypotheses.

Morphology of brachial segments in mudpuppy (Necturus maculosus) spinal cord studied with confocal and electron microscopy.

The isolated brachial spinal cord of Necturus maculosus is useful for studies of neural networks underlying forelimb locomotion, but information about its cellular morphology is scarce. We addressed this issue by using confocal and electron microscopy. Remarkably, the central region of gray matter was aneural and consisted exclusively of a tenuous meshwork of glial fibers and large extracellular spaces. Somata of motoneurons (MNs) and interneurons (INs), labeled by retrograde transport of fluorescent tracers from ventral roots and axons in the ventrolateral funiculus, respectively, were confined within a gray neuropil layer abutting the white matter borders, whereas their dendrites projected widely throughout the white matter. About one-third of labeled INs were found contralaterally, with axons crossing ventral to a thick layer of ependyma surrounding the central canal. Lateral MN dendrites proliferated under the pial surface to form a dense, thin (1-2 microm) plexus immediately beneath a thin layer of glial fibrillary acidic protein-positive glia limitans. The latter contained arrays of unusual tubular structures (diameter 200-400 nm, length 3 microm) that resembled mitochondria but lacked double membranes or cristae. Dorsal roots (DRs) produced dense presynaptic arbors within a wedge-shaped afferent termination zone medial to the dorsal root entry, within which dendrites of MNs and INs mingled with dense collections of synaptic boutons. Our data suggest that a major fraction of synaptic interactions takes place within the white matter. This study provides a detailed foundation for designing electrophysiological experiments to study the neural circuits involved in locomotor pattern generation.

Chick wing innervation. I. Time course of innervation and early differentiation of the peripheral nerve pattern.

Anterograde transport of horseradish peroxidase was used to map the initial projection patterns of motor and sensory axons innervating the wing of the chick embryo. Injections which resulted in labeling large numbers of motor and sensory axons, separately or in combination, were used to define the time course of innervation and to visualize the progressive morphogenesis of the peripheral nerve pattern. Motor axons emerged from the spinal cord and accumulated near the ventromedial border of the myotome where they remained for up to 16 hours before growing into the plexus region and limb bud. Despite the known later time of sensory neuron production, the first sensory axons projected to the wing at the same time as motor axons. When axons first entered the wing bud, they were distributed in two loosely organized sheets of axon fascicles, one projecting to dorsal muscle mass, the other to ventral muscle mass. The width of the sheets was between one-third to one-half the width of the wing bud, and this distance was more than twice the diameter of the proximal nerve trunks measured at stage 28. In the proximal limb the basic pattern of peripheral nerves emerged gradually from stages 26 to 28. During these stages, the loosely organized sheets of axonal fascicles seen at younger stages were progressively transformed into several coherent nerve trunks and muscle nerves extended from common nerve trunks. The implication of these observations is that many outgrowing axons appear not to follow preformed pathways corresponding to the mature peripheral nerve branching pattern. This pattern may instead result from axonal recognition of cues within a largely undifferentiated limb bud, and from the subsequent bundling together of loosely organized axon fascicles. These events occur concurrently with limb growth and differentiation.

Synaptogenesis in the brachial and lumbosacral enlargements of the spinal cord in the postnatal opossum, Monodelphis domestica.

Synaptic proteins were localized in light microscopy on sections of the brachial and lumbosacral enlargements of the spinal cord of postnatal opossums, Monodelphis domestica, to determine whether their expression correlates with the development of major motor pathways and simple motor behaviors. The tissues were fixed, cryoprotected, frozen, cut in 15-micrometer sections, and processed immunohistochemically using antibodies against synaptophysin, synaptotagmin-I, or SNAP-25. Immunolabeling was observed in the presumptive white matter before the presumptive gray matter, suggesting that the proteins are evidenced in growing axons before the onset of synaptogenesis, and it was observed in presumed propriospinal axons before most presumed descending axons of supraspinal origin. In the newborn opossum, the immunolabeling was scant in the gray matter and was limited to the periphery of the ventral horn, and indeed few synapses were seen in electron microscopy in nonexperimental material. Labeling increased in intensity and spread throughout the gray matter until 5-7 weeks, when it was no longer found in the white matter and resembled the adult pattern of labeling. Considering the location and relative intensity of the immunolabeling for the three proteins over time in the two enlargements, synaptogenesis occurs according to three general gradients: rostrocaudal, ventrodorsal, and lateromedial. These gradients match those of spinal cord and limb development, and of the growth of descending axons into the cord. Synaptogenesis is most intense when the spinal sensorimotor reflexes begin to be expressed.

Morphometrical analysis of types and sub-types of neurons in dorsal root ganglia of the lizard Podarcis sicula.

In the present study, we conducted a morphometrical analysis of the different types and sub-types of lizard DRG neurons at various spinal levels. This analysis demonstrated significant differences in size distribution among the various neuron types and sub-types, as well as a significant shift to greater values in neurons from the dorsal root ganglia at the cervical and the lumbar spinal levels. The results are critically evaluated in relation to methodological issues, and the implications of these findings are discussed.

Motor blockade and absence of local nerve toxicity induced by liposomal bupivacaine injected into the brachial plexus of rabbits.

Bupivacaine has been encapsulated into multilameller liposomes in order to reduce its systemic toxicity and to lengthen its action. Low, constant and sustained plasma levels have been observed after epidural injection and brachial plexus administration to rabbits. The present experiment was performed in order to study the motor block effect and the possible neurotoxicity of bupivacaine encapsulated in multilamellar liposomes applied in vivo to intact peripheral nerve bundles. Five milliliters of sterile solutions containing 0.75% bupivacaine encapsulated in 42.5 and 85 mg of lipids (phosphatidylcholine and cholesterol in a molar ratio 4:3) were administered to 4 rabbits at the level of the brachial plexus. A motor blockade of the forelimb lasting for 10 hours was measured immediately after injection of the liposomal drug. Light microscopic analyses of the nerves after 2 and 7 days revealed weak inflammatory perineural infiltration. Electron microscopy showed no changes of the myelin sheaths and no alteration of unmyelinated fibers. It may be concluded that the pharmacologically active liposomal formulation of bupivacaine did not induce alterations of the nerve tissues.

[Transmission electron microscope observation of morbid nerve segments in neurocausalgia].

The authors report the observations by TEM of morbid nerve segment from 3 cases of typical neurocausalgia. It was discovered that a lot of collagen fibrils proliferation, myelin sheaths compressed partly or completely disintegrated and exposed axons. A great number of no myelinic nerve fibers, remained and a great number of macrophages were present, which are morphological characteristics of neurocausalgia.

Sex-related macrostructural organization of the deer's brachial plexus.

We describe the morphological organization of the deer brachial plexus in order to supply data to veterinary neuroclinics and anaesthesiology. The deer (Mazama gouazoubira) brachial plexus is composed of four roots: three cervical (C6, C7 and C8) and one thoracic (T1). Within each sex group, no variations are observed between the left and the right brachial plexus, though sex-related differences are seen especially in its origin. The origin of axillary and radial nerves was: C6, C7, C8 and T1 in males and C8-T1 (radial nerve) and C7, C8 and T1 (axillary nerve) in females; musculocutaneous nerve was: C6-C7 (males) and C8-T1 (females); median and ulnar nerves was: C8-T1 (males) and T1 (females); long thoracic nerve was: C7 (males) and T1 (females); lateral thoracic nerve was: C6, C7, C8 and T1 (males) and T1 (females); thoracodorsal nerve was: C6, C7, C8 and T1 (males) and C8-T1 (females); suprascapular nerve was: C6-C7 (males) and C6 (females) and subscapular nerve was: C6-C7 (males) and C7 (females). This study suggests that in male deer the origin of the brachial plexus is more cranial than in females and the origin of the brachial plexus is slightly more complex in males, i.e. there is an additional number of roots (from one to three). This sexual dimorphism may be related to specific biomechanical functions of the thoracic limb and electrophysiological studies may be needed to shed light on this morphological feature.

Incidence of humeral head of biceps brachii muscle: anatomical insight / Incidencia de la cabeza humeral del músculo bíceps braquial - visión anatómica

Biceps brachii is stated as one of the muscles that shows most frequent anatomical variations. Its most commonly reported anomaly is the presence of an accessory fascicle arising from the humerus which is termed as the humeral head of biceps brachii. Evidence shows a clear racial trend in the incidence of the humeral head of biceps brachii. Therefore, detailed knowledge of this variation in different populations is important for surgical interventions of the arm, nerve compression syndromes and in unexplained pain syndromes in the arm or shoulder region. The goal of this study was to elucidate the incidence and morphological features of this muscle in an adult Sri Lankan population. Upper extremities of the total of one hundred thirty five cadavers were dissected and studied for the presence of accessory heads of the biceps brachii muscle. The proximal and distal attachments of the humeral heads as well as their cranio-caudal, antero-posterior and medio-lateral dimensions were recorded. The incidence of humeral head of biceps brachii was found to be 3.7 percent. In all cases, it was found unilaterally and only in male subjects. The humeral head originated from the antero-medial aspect of the humeral shaft and descended and merged with the other two heads to form a common tendon. The results of the present study further highlight the racial variations in the incidence of humeral head of biceps brachii among Sri Lankans. Knowledge of the occurrence of humeral head of biceps brachii may facilitate preoperative diagnosis as well as the surgical procedures of the upper limb thus avoiding iatrogenic injuries.

El músculo bíceps braquial se conoce como uno de los músculos que muestra las variaciones anatómicas más frecuentes. Su anomalía más común es la presencia de un fascículo accesorio proveniente del húmero, que se denomina cabeza humeral del músculo bíceps braquial. La evidencia muestra una clara tendencia racial en la incidencia de la cabeza humeral del músculo bíceps braquial. El conocimiento acabado de esta variación, en las diferentes poblaciones, es importante para las intervenciones quirúrgicas del brazo, en los síndromes de compresión nerviosa y en los síndromes de dolor inexplicable en la región del brazo o del hombro. El objetivo de este estudio fue determinar la incidencia y las características morfológicas de este músculo en una población adulta de Sri Lanka. Fueron estudiados los miembros superiores en 135 cadáveres, disecados para evaluar la presencia de las cabezas del músculo bíceps braquial accesorio. Fueron registrados el origen e inserción de la cabeza humeral del músculo bíceps braquial, así como su dimensión cráneo-caudal, anteroposterior y mediolateral. La incidencia de la cabeza humeral del músculo bíceps braquial se encontró en el 3,7 por ciento de los miembros estudiados. En todos los casos, su presencia era unilateral y sólo presente en hombres. La cabeza humeral se originó en la región antero-medial de la diáfisis del húmero, descendió y se fusionó con las otras dos cabezas para formar un tendón común. Los resultados de este estudio resaltan aún más las variaciones raciales en la incidencia de la cabeza humeral del músculo bíceps braquial, entre los habitantes de Sri Lanka. El conocimiento de la presencia de la cabeza humeral del músculo bíceps braquial puede facilitar el diagnóstico preoperatorio, así como los procedimientos quirúrgicos del miembro superior, evitando las lesiones iatrogénicas.

Morphology of Schmidt-Lanterman incisures of human shoulder plexus nerves.

Morphological studies of peripheral human nerves have shown that the number o of Schmidt-Lanterman incisures in an internode is proportional to the fibre diameter. Quantitative and ultrastructural examinations of incisures in the shoulder plexus nerves of the juvenile have proved some common features in the distribution and structure of incisures, characteristic for the nerves of both mammals and people. However, in all probability, in the peripheral nerves of man under certain condition there is a mechanism, leading to a sharp increase of the number of incisures in the internodal segment.

[Ultrastructural dynamics of the muscular branches of the normal brachial plexus and in exposure to reflexotherapy]. / Dinamika ul'trastruktury myshechnykh vetvei plechevogo spleteniia v norme i pri vozdeistvii refleksoterapii.

The changes in the ultrastructure of myelinic fibers of branchial plexus muscular branches have been studied during exposure to acupuncture of different duration. The studies were performed using muscular branches obtained from the forelegs of sexually mature white rats, weighing 150-170 g. The nerves were processed for electron microscopy according to a conventional technique. It is demonstrated that myelinic conductors react to the exposure by a complex of structural changes of a reactive, non-specific nature.

The perineural sheath in the urodele amphibian.

The perineural epithelial cells of the peripheral nerve sheath in triturus are elongated flat cells with long and thin cytoplasmic processes. Structural characteristics of the processes include a relative absence of common cytoplasmic organelles of the perinuclear cytoplasm but an abundance of vesicular profiles similar to fully formed pinocytotic vesicles. Unlike pinocytotic vesicles, vesicles of the processes often contain an 8-nm thick filament attached to their cytoplasmic face. Vesicles are also interconnected by similar filaments or by tubules. In addition, almost all vehicles appear to have openings at the cell surface, a feature not seen for pinocytotic vesicles. The concentration of exogenous peroxidase in the vesicles, and the subsequent appearance of peroxidase in the endoneural fluid, myelin sheath and axon, support the notion that the vesicles function in the exchange of substances between extraneural and endoneural fluids.

Origen y trayecto anómalos del nervio musculocutáneo / Anomalus origin and traject of musculocutaneous nerve

El nervio musculocutáneo se origina del fascículo lateral en el plexo braquial y sus fibras emergen principalmente de las raíces nerviosas anteriores de C5 y C6. Durante la disección de rutina del plexo braquial en un cadáver formolizado, fue encontrada una variación del origen y trayecto de este nervio. El nervio musculocutáneo se originaba de la cara lateral del nervio mediano y después del origen, cruzaba anteriormente al músculo coracobraquial, sin perforarlo, de medial hacia lateral y de proximal hacia distal, para después ramificarse. Las variaciones anatómicas encontradas contribuyen para el estudio de la anatomía y sirven para el cirujano en intervenciones en la fosa axilar y en la parte anterior del brazo, previniendo, así, complicaciones operatorias.

The musculocutaneous is originated from the lateral fascicle in the brachial plexus and its fibers emerge mainly from the anterior nervous roots C5 and C6. During the routine dissection of the brachial plexus in a formolized corpse, its origin variation and passage was found. The nerve was originated on the lateral face of the median nerve and after its origin, crossed anteriorly to the coracobrachial muscle, without perforating it, from medial to lateral, proximal to distal, after to branch off. The anatomical variations found contribute to the anatomy study and they serve as alert for the surgeon in interventions in the axillary's cavity and in the previous store of the arm, preventing, thus, operational complications.