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

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

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

Absence of musculocutaneous nerve associated with variations of distribution patterns of the median nerve / Ausencia del nervio musculocutáneo asociada con variaciones de los patrones de distribución del nervio mediano

Variations in the brachial plexus and the distribution patterns of its branches are not uncommon. A communicating branch, which is the most frequent variation, often arises from musculocutaneous nerve to median nerve. However, the branches arising from lateral cord of the brachial plexus and median nerve instead of musculocutaneous nerve are very rare. Detailed description of the abnormalities is important for surgical procedures. Our case study reports the musculocutaneous nerve was absent, a branch from the medial cord innervated the coracobrachialis muscle and two branches from the median nerve innervated the biceps and brachialis muscles, respectively. Moreover, the median nerve gave off the lateral antebrachial cutaneous nerve. This report provides evidence of such possible anatomical variations to surgeons, anesthetists and neurologists during clinical practice.

Las variaciones en el plexo braquial y los patrones de distribución de sus ramos no son infrecuentes. Un ramo comunicante, que es la variante más frecuente, a menudo surge desde el nervio musculocutáneo al nervio mediano. Sin embargo, los ramos que surgen del fascículo lateral del plexo braquial y nervio mediano en vez de nervio musculocutáneo son muy raros. La descripción detallada de las anomalías es importante para procedimientos quirúrgicos. En nuestro caso el nervio musculocutáneo estaba ausente, un ramo del fascículo medial inervó el músculo coracobraquial y dos ramos del nervio mediano inervaron los músculos bíceps y braquial, respectivamente. Por otra parte, el nervio mediano originó al nervio cutáneo antebraquial lateral. Este informe proporciona evidencia de algunas variaciones anatómicas útiles para cirujanos, anestesistas y neurólogos durante la práctica clínica.

Incidences and clinical implications of communications between musculocutaneous nerve and median nerve in the arm: a cadaveric study / Incidencias e implicaciones clínicas de las comunicaciones entre el nervio musculocutáneo y nervio mediano en el brazo: un estudio cadavérico

OBJECTIVES: Variations such as communications between the median nerve and musculocutaneous nerve or in their abnormal branching pattern constitute a major concern in clinical and surgical field. Knowledge of these variations not only provides the clinician with a proper interpretation of the case, but also minimizes the complication in surgical approaches in this region. METHOD: We examined 50 isolated upper limbs to investigate the possible incidences of various types of communications between these two neighbouring peripheral nerves. RESULT: Twenty-eight per cent of limbs were found to have communication between these two nerves. When categorized according to Venieratos and Anagnostopoulou's classification method, 11 out of 14 cases (79%) showed type I communications, two out of 14 (14%) showed type II and the remaining one (7%) showed type III communication pattern. CONCLUSION: Prior knowledge of communications between these two neighbouring nerves, both in terms oftheir incidences and pattern ofcommunications, may be ofconsiderable significance to neurologists and orthopaedic surgeons in dealing with nerve entrapment syndromes in the upper limb of patients.

OBEJTIVOS: Las variaciones tales como las comunicaciones entre el nervio mediano y el nervio musculocutáneo o en su patrón de ramificación anormal constituyen un interés principal en el campo clínico y quirúrgico. El conocimiento de estas variaciones no sólo proporciona una interpretación adecuada del caso clínico, sino que también minimiza la complicación en abordajes quirúrgicos en esta región. MÉTODO: Se analizaron 50 miembros superiores aislados para investigar las posibles incidencias de diversos tipos de comunicaciones entre estos dos nervios periféricos vecinos. RESULTADO: Se halló que el veintiocho por ciento de los miembros tenía comunicación entre estos dos nervios. Cuando fueron categorizados según el método de clasificación de Venieratos y Anagnostopoulou, 11 de 14 casos (79%) mostró comunicaciones de tipo I, dos de 14 (14%) mostraron el tipo II, y el restante (7%) mostró un patrón de comunicación de tipo III. CONCLUSIÓN: El conocimiento previo de las comunicaciones entre estos dos nervios vecinos, en términos tanto de sus incidencias como patrones de comunicación, puede ser de una importancia considerable para los neurólogos y ortopédicos a la hora de tratar con el síndrome del atrapamiento del nervio en la extremidad superior de los pacientes.

Comunicación masiva del ramo superficial del nervio radial con el nervio cutáneo antebraquial lateral, un análisis morfométrico: 1+1 < 2 / Massive communication between the superficial branch of radial nerve and the lateral cutaneous nerve of the forearm, a morphometric study: 1+1 < 2

La distribución de los ramos nerviosos sensitivos en el borde lateral y en el dorso de la mano han sido descritos con mayor exactitud en las últimas décadas, debido al avance de nuevas técnicas de diagnóstico, las cuales han permitido detectar que alrededor del 40 por ciento de la población examinada presenta algún grado de variación anatómica en el territorio de distribución de los nervios involucrados. Conocer el número de fibras que componen un ramo nervioso cutáneo de la región de la mano, ha adquirido mayor relevancia con el desarrollo de técnicas de microcirugía y de ultrasonografía, procedimientos que han demostrado la utilidad de este conocimiento en el diagnóstico y tratamiento de las lesiones nerviosas. Así, la arquitectura fascicular, el área adiposa y el área vascular de un ramo nervioso determinado constituyen datos que se ha demostrado se modifican con la edad y, en consecuencia, van condicionar la conducta terapéutica y el pronóstico de las lesiones nerviosas. En este caso presentamos una variación anatómica bilateral extremadamente rara, que involucra al ramo superficial del nervio radial y al nervio cutáneo lateral antebraquial; situación que aparece descrita en la literatura especializada sólo una vez y que modifica notablemente la inervación sensitiva del borde radial de la mano...

The distribution of sensory nerve branches in the lateral and the back of the hand have been described more accurately in recent decades due to advances in new diagnostic techniques, which have identified that about 40 percent of the population examined have some degree of anatomical variation in the distribution area of the sensitive nerves involved. The knowledge of the number of fibers forming a sensitive nerve of the hand has become more important with the development of microsurgical techniques and ultrasonography; procedures that have demonstrated the usefulness of this information in the diagnosis and treatment of nerve injuries. Thus, the fascicular architecture, adipose tissue area and the vascular area of a nerve branch, data that has been demonstrated that change with age, will determine the therapeutic and prognosis of nerve injuries. In this case we present an extremely rare and bilateral anatomical variation, involving the superficial branch of radial nerve and the lateral antebrachial cutaneous nerve, a situation that is described in the literature only once and which notably alter the sensory innervations of the radial edge of the hand...

Comunicación bilateral de los nervios músculocutáneo y mediano: aspectos morfológicos e importancia clínica / Bilateral communications of the musculocutaneous and median nerves, morphological aspects and clinical significance

Las comunicaciones entre los ramos terminales de plexo braquial son frecuentes y tienen importancia en la evaluación de traumatismos y procedimientos quirúrgicos de las regiones axilar y braquial. En este artículo presentamos un caso en el que durante la disección de rutina del miembro superior, se observó la presencia de comunicaciones bilaterales entre los nervios musculocutáneo y mediano. Los ramos comunicantes fueron descritos en su trayecto, relaciones y morfometría y se discutió acerca de la prevalencia e importancia clínica de estas comunicaciones.

Communication of the musculocutaneous and median nerves of the brachial plexus is common and is important in the evaluation of trauma and surgical procedures in axillary and brachial regions. This paper presents a case in which during a routine dissection of upper limb the presence of bilateral communication between musculocutaneous and medium nerves was observed. Trajectory of communicating branches was described, relation and morphometry was discussed with regard to prevalence and clinical significance of these communications.

Clinical implications of additional heads of biceps brachii muscle

Biceps brachii is a superficial muscle of the flexor compartment of arm. It is a strong flexor and a supinator of forearm. It is one of the most variable muscles in terms of number of its heads of origin, so the present study proposes to dissect North Indian cadavers to see the frequency of occurrence of more than two heads of biceps brachii and discusses its clinical implications. To determine the prevalence of accessory heads of biceps brachii, their inervation and any anomalous course of neurovascular bundle in the front of arm. Number of heads of biceps brachii muscle were studied in 77 adult human cacdavers [n-154]. Presence of additional heads of biceps brachii and any variation in the course of neurovascular bundle in the front of arm were noted. It was observed that the left upper limb of only one middle aged male cadaver had four heads of origin of biceps brachii i.e. the long head from supraglenoid tubercle of scapula, short head from tip of coracoid process of scapula and the two accessory heads from the anteromedial surface of the humerus between the insertion of coracobrachialis and the origin of brachialis. The musculocutaneous nerve took origin from the lateral cord normally and pierced through coracobrachialis to enter the flexor compartment of forearm. Then it passed between the two accessory heads before supplying brachialis and continued as lateral cutaneous nerve of forearm. Each head of biceps brachii was individually innervated by fibers from musculocutaneous nerve. No other anomalies in the neurovascular bundle were observed. Awareness of the different course of musculocutaneous nerve and origin of supernumerary heads of biceps brachii is of importance to academicians, surgeons, traumatologists, orthopaedicians and plastic

Padrones de inervación y localización biométrica de los puntos motores del músculo bíceps braquial en el hombre / Innervation patterns and biometric localization of the motor points of the brachial biceps muscle in man

La inervación del músculo bíceps braquial se torna importante debido a su constitución y a la acción que ejerce a nivel del codo, sobretodo cuando existen lesiones en nervios espinales o médula espinal alta. Con el objetivo de conocer con detalles la disposición de sus nervios y localizar desde el punto de vista biométrico sus puntos motores, se estudiaron 46 miembros superiores de 23 cadáveres formolizados de individuos brasileños, adultos, en los cuales se consideró el número de ramos, longitud, nivel de origen y puntos de penetración en el vientre muscular respecto a una línea trazada entre los epicóndilos humerales (LBE). El nervio musculocutáneo envía un ramo para el músculo en estudio como un ramo común que luego se dividió para sus dos cabezas en 19 casos (41,3%); ramos independientes para cada cabeza se encontraron en las muestras restantes (58,7%). Con respecto al número de ramos, la cabeza larga recibió un ramo (R1) en 35 casos (76,1%), dos ramos (R1 y R2) en 9 casos (19,6%) y tres (R1,R2 y R3) en 2 casos (4,3%); para la cabeza corta se observó un ramo en 39 casos (84,7%), dos en 5 casos (10,9%) y tres en 2 casos (4,3%). Cada uno de los ramos dirigidos a las cabezas del músculo bíceps se dividió en ramos secundarios (RS). Para la cabeza corta, el ramo principal se dividió en 2 RS en 20 casos; en 3 RS en13 casos; en 4 RS en 4 casos, siendo directo sin dividirse en 2 casos. Para la cabeza larga el ramo principal se dividió en 2 RS en 16 casos; en 3 RS en 13; en 4 RS en 3; en 5 RS en un caso y en 6 RS en 1 caso y en una muestra, el ramo principal penetró en el vientre muscular sin dividirse. Los RS penetraron a niveles variables en el vientre muscular. Los resultados obtenidos pueden servir de referencia para procedimientos de punción en los puntos motores o en estudios electromiográficos.

The biceps brachii muscle innervation is important due to its constitution and its function in the elbow joint, mainly when there are in spinal nerves damages or high spinal cord. The purpose of this study was determine with details the nerves disposition of this muscle and locate its motor points. The upper limbs of 23 formolized cadavers of adult Brazilian individuals were studied, in whose it recorded the number of branches, length, origin levels and motor point localization. The localization were recorded using as reference point a line between the humerus epicondyles. The musculocutaneous nerve send a branch for a studied muscle as a common trunk that divides in two branches, each to a different head of the biceps in 19 cases (41.3%); independent branches for each head were observed in the other cases (58.7%). The long head received one branch in 35 cases (76.1%); two branches (B1, B2) in 9 cases (19.6%) and three branches (B1, B2, B3) in 2 cases (4.3%). Each branch divided in secondary branches (SB). In the short head the principal branch divided in two SB in 20 cases; in three SB in 13 cases; in fourth SB in 4 cases and not dividing in 2 cases. In the long head, the principal branch divided in two SB in 16 cases; in three SB in 13 cases; in fourth SB in 3 cases; in five SB in one case and in sixth SB in one case and not dividing in one case. The SB pierce in the muscular belly to different levels. These results can be to use as reference for the puncture procedures in the motor points or in electromyography studies.

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.

Absence of the musculocutaneous nerve: a rare anatomical variation with possible clinical-surgical implications / Ausência do nervo musculocutâneo: uma rara variação anatômica com possíveis implicações clínico-cirúrgicas

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.

CONTEXTO: O nervo musculocutâneo é um dos ramos terminais do fascículo lateral do plexo braquial, sendo responsável pela inervação da musculatura flexora do cotovelo e pela sensibilidade cutânea da face lateral do antebraço. Sua ausência já foi descrita previamente, mas a sua real prevalência é desconhecida. RELATO DE CASO: Este é um relato de caso da ausência do nervo musculocutâneo observada durante a dissecção do membro superior direito de um cadáver do sexo masculino, sendo o seu território de inervação suprido pelo nervo mediano. Deste emergiam três ramos, um para o músculo coracobraquial, outro para o músculo bíceps braquial e o terceiro para o músculo braquial. Este último ramo continuava-se como nervo cutâneo lateral do antebraço. Trata-se de variação anatômica que tem implicações clínico-cirúrgicas, já que a lesão do nervo mediano, neste caso, acarretaria inesperada paralisia da musculatura flexora do cotovelo e hipoestesia da face lateral do antebraço.

A Variation of the Musculocutaneous Nerve Absent

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

A Variation of the Musculocutaneous Nerve Absent

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

Study of the anatomical variations of the musculocutaneous nerve

To study the anatomical variations of the musculocutaneous nerve. Fifty-four arms from embalmed adult cadavers were utilized for this investigation. They were carefully dissected and examined for any anatomical variations of the musculocutaneous nerve. This study was performed at the Department of Anatomy, King Abdul-Aziz University, Jeddah, Kingdom of Saudi Arabia between 2001 and 2003. Four anomalies of the musculocutaneous nerve were found in this study. One case showed that the musculocutaneous nerve pierced the coracobrachialis muscle and passed inside the muscle for some distance. The nerve pierced the coracobrachialis muscle again, and it ran downward and medially and joined the median nerve at the middle of the arm. The brachial artery was sandwiched between the musculocutaneous and the median nerves. Three cases demonstrated that the musculocutaneous nerve did not pierce the coracobrachialis muscle and passed downward and medial to it. The nerve joined the median nerve at the junction of the upper third with the lower two-thirds of the arm. The musculocutaneous nerve was completely absent in one case. In another case, the musculocutaneous nerve originated from the upper part of the median nerve. The knowledge of the anatomical variations of the musculocutaneous nerve may have clinical and surgical implications