An unusual relationship between the axillary artery and brachial plexus in a cross-breed dog cadaver: a proposal for revising the terminology for nerve loops

In the left axilla of a formalin-embalmed adult female cross-breed dog, an unusual course of the axillary artery in relation to the brachial plexus was noted. A part of the axillary artery after the origin of the subscapular artery coursed through the loop formed by the contributions of the caudal pectoral and lateral thoracic nerves and then between the median and ulnar nerves. Thus, the common trunk for the latter two nerves was missing. Instead, in the proximal brachium, they communicated with each other in both directions. A communicating branch between the cranial and caudal pectoral nerves forming a nerve loop, ansa pectoralis lacked the axillary artery and was instead traversed by the subscapular artery. This is a variation in the relationship between the axillary artery and brachial plexus in the domestic dog and has not been reported in the literature yet. The axillary artery entrapped by the contributions of the caudal and lateral thoracic nerves may be considered as a risk factor for the neuroarterial compressions with non-specific signs and should be taken into account both in surgery and imaging.

Muscle-tendon arrangement and intramuscular nerve distribution of flexor digitorum superficialis in the siamang (Symphalangus syndactylus), western lowland gorilla (Gorilla gorilla gorilla), western chimpanzee (Pan troglodytes verus), and Japanese macaque (Macaca fuscata)

Flexor digitorum superficialis (FDS) shows diverse muscle-tendon arrangements among primates. The intramuscular nerve distribution pattern is a criterion for discussing the homology of FDS. In this study, the muscle-tendon arrangement and intramuscular nerve distribution of FDS were examined in the siamang, western lowland gorilla, western chimpanzee, and Japanese macaques. The FDS had muscle bellies to digits II-V. FDS had proximal belly and intermediate tendon except for siamang. Distal belly to digit II (in the western lowland gorilla and western chimpanzees) or distal bellies to digits II and V (in Japanese macaque) originated from the intermediate tendon. In all specimens, nerve branches within digit III belly extended into digit IV belly, and nerve branch(es) within digit IV belly extended into digit V belly. This consistent pattern suggested that each muscle belly to digits III-V is interspecifically homologous. The digit II belly in the siamang and the distal belly to digit II in the western lowland gorilla, western chimpanzees, and Japanese macaques could be homologous based on their similar innervating patterns. The proximal belly was innervated by branches from the communicating nerve between median and ulnar nerves in the western lowland gorilla or branches from median and ulnar nerves in western chimpanzees. In the siamang and Japanese macaque, the whole FDS was innervated by median nerve. The proximal belly in the western lowland gorilla, western chimpanzees, and Japanese macaques could be classified into different groups from the other part of the FDS.

Morphological significance of the medial brachial cutaneous nerve: An anatomical study of the brachial plexus in primates

The medial brachial cutaneous nerve (MBC) originates from the medial cord of the brachial plexus and innervates the skin sensory in the medial posterior surface of the upper arm. Considering previous reports of the primate brachial plexus, the MBC appeared to be the sole branch in the brachial plexus that only some primates possess. However, the detailed descriptions and records regarding the morphology of the MBC and related nerves, their origins and distributions (dermatomes) in particular, were frequently lacked in the previous reports, and it remains unclear why the difference in the MBC appearance exists among primates. In this study, the brachial plexus and its branches were first re-evaluated and certainly identified in several primates, humans, chimpanzee, macaque monkey, lutung, tamarin, squirrel monkey, and spider monkey. The MBC was identified in humans, chimpanzee, spider monkey, and squirrel monkey. In the other species, the intercostobrachial nerve (ICB) originating from some of 1st to 3rd intercostal nerves developed and distributed instead of the MBC. According to the kinesiological and behavioral studies, the former species possessing MBC show high shoulder joint mobility associated with their locomotive patterns. We speculate that the MBC corresponds to transformed ICB; specifically, where it originates presumably transfers from the 1st and/or 2nd intercostal nerves to the brachial plexus, which allows it to reach the upper arm by coursing the shortest distance even if the forelimb is raised high. Therefore, MBC may embody phylogenetic morphogenesis of the nerve associated with the locomotive evolution and adaptation in primate forelimb.

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.

Comparative Gross Anatomy of the Forelimb Arteries of the Japanese Monkey (Macaca fuscata) and a Comparative Pattern of Forelimb Arterial Distribution in Primates

Macaca fuscata displays characteristic behaviours, such as stone handling, locomotor behaviour, gait position, and intermittent bipedalism. Differences in characteristic behaviours among primate species/genera could be explained by anatomical details of the body. However, the anatomical details have not been well studied in Macaca fuscata. Arterial models could be one of the anatomical bases for the phylogenetic and functional differences among species, since the arterial supply could be associated with the muscular performance, especially locomotor behaviour. In this study, five thoracic limbs of Macaca fuscata adults were dissected to analyse the vessels. Patterns of arterial distribution in the thoracic limbs of Macaca fuscata were compared with those in other primates. The results indicated that the arterial distribution in the Japanese monkeys was more similar to those in Macaca mulatta and Papio anubis, which is consistent with phylogenetic similarities. However, compared with Papio anubis and other macaques, there were anatomical differences in several points, including (1) the origin of the common, anterior, posterior circumflex, and profunda brachii, and (2) the origins of the collateralis ulnaris artery. The comparative anatomy of the arteries in the forelimb of Macaca fuscata, along with the anatomical studies in other primates, indicated characteristic patterns of brachial artery division and the number of the palmar arches in primates, which is consistent with the phylogenetic division among New World primates, Old World primates, and apes.

BRACHIAL PLEXUS IN THE Leopardus geoffroyi

Abstract Six thoracic limbs from four Leopardus geoffroyi specimens were dissected in order to describe origin and distribution of nerves forming the brachial plexuses. The brachial plexus is a result of connections between ventral branches of the last four cervical nerves (C5, C6, C7 and C8) and the first thoracic nerve (T1). These branches are the origin of the suprascapularis, subscapularis, axillary, musculocutaneous, radial, median and ulnar nerves to the intrinsic musculature, and form the brachiocephalicus, thoracodorsal, lateral thoracic, long thoracic, cranial pectoral and caudal pectoral nerves to the extrinsic musculature. The C7 ventral branch is mainly responsible for formation of nerves (70.5%), followed by C8 (47.4%), C6 (29.5%), T1 (19.2%) and C5 (7.7%). From 78 dissected nerves, 65.4% of nerves resulted from a combination of two or three branches, while only 34.6% of nerves originated from a single branch. Through comparison with other carnivoran species, the origin and innervation area of the Geoffroyi’s Cat brachial plexus were most similar to those of the domestic cat, particularly among those nerves extended to the intrinsic musculature. The results of this study suggest that nerve block techniques currently used in dogs and cats might be efficient in Geoffroyi’s Cat too.

The zonal pattern of arterial supply to the brachial plexus and its clinical significance

PURPOSE

To provide the anatomical basis of blood supply of brachial plexus for the clinical microsurgical treatment of brachial plexus injury.

METHODS

Thirteen adult anticorrosive cadaveric specimens (8 males, 5 females) were dissected in this study. 3 fresh cases (2 males, 1 female) were used to observe the zonal pattern of arteries supplying brachial plexus, and 10 cases (6 males, 4 females) were used to observe the source and distribution of the brachial plexus arteries under microscope.

RESULTS

The brachial plexus is supplied by branches of the subclavian-axillary axis (SAA), and these branches anastomose each other. According to distribution feature, blood supply of the brachial plexus could be divided into three zones. The first zone was from the nerve roots of intervertebral foramina to its proximal trunks, which was supplied by the vertebral artery and the deep cervical artery. The second zone was from the distal nerve trunks of the brachial plexus, encompassing the divisions to its proximal cords, which was supplied by direct branches of the subclavian artery or by branches originating from the dorsal scapular artery. The third zone was from the distal portion of the cords to terminal branches of the brachial plexus, which was supplied by direct branches of the axillary artery.

CONCLUSIONS

The zonal pattern of arterial supply to the brachial plexus is a systematic and comprehensive modality to improve anatomical basis for the clinical microsurgical treatment for brachial plexus injury.

Brachial Plexus in the Pampas Fox (Lycalopex gymnocercus): a Descriptive and Comparative Analysis

Twenty thoracic limbs of ten Lycalopex gymnocercus were dissected to describe origin and distribution of the nerves forming brachial plexuses. The brachial plexus resulted from the connections between the ventral branches of the last three cervical nerves (C6, C7, and C8) and first thoracic nerve (T1). These branches connected the suprascapular, subscapular, axillary, musculocutaneous, radial, median and ulnar nerves to the intrinsic musculature and connected the brachiocephalic, thoracodorsal, lateral thoracic, long thoracic, cranial pectoral and caudal pectoral nerves to the extrinsic musculature. The C7 ventral branches contribute most to the formation of the nerves (62.7%), followed by C8 (58.8%), T1 (40.0%) and C6 (24.6%). Of the 260 nerves dissected, 69.2% resulted from a combination of two or three branches, while only 30.8% originated from a single branch. The origin and innervation area of the pampas fox brachial plexus, in comparison with other domestic and wild species, were most similar to the domestic dog and wild canids from the neotropics. The results of this study can serve as a base for comparative morphofunctional analysis involving this species and development of nerve block techniques. Anat Rec, 300:537-548, 2017. © 2016 Wiley Periodicals, Inc.

Origens e ramificações do plexo braquial no cachorro-do-mato Cerdocyon thous (Linnaeus, 1766)

Este estudo teve o objetivo de descrever a origem e ramificação dos nervos de vinte plexos braquiais de cachorro-do-mato (Cerdocyon thous). Dez animais da espécie, obtidos post mortem por atropelamento em rodovias, foram utilizados para o estudo, de acordo com a autorização do IBAMA/SISBIO nº33667-1. Depois de coletados, os cadáveres foram fixados em solução de formaldeído a 50% e conservados por pelo menos 14 dias em solução de formaldeído a 10% antes das dissecções. Após remoção da pele, incisões na musculatura peitoral e afastamento dos membros, acessou-se o espaço axilar e os nervos do plexo tiveram seu trajeto dissecados individualmente até sua inserção muscular. Para melhorar a visualização dos ramos ventrais cervicais e torácicos que originavam cada nervo, removeram-se a musculatura que encobria os forames intervertebrais, os processos transversos e os corpos vertebrais ventralmente, expondo inclusive a medula espinhal. Registros fotográficos e desenhos esquemáticos documentaram a origem e ramificação dos nervos. Os vinte plexos braquiais foram resultantes das conexões entre os ramos ventrais dos três últimos nervos espinhais cervicais (C6, C7 e C8) e do primeiro torácico (T1). Estes ramos derivaram os nervos supra-escapular, subescapular, axilar, musculocutâneo, radial, mediano, ulnar para a musculatura intrínseca e os nervos braquiocefálico, toracodorsal, torácico lateral, torácico longo, peitoral cranial e peitoral caudal para a musculatura extrínseca do membro torácico. Constatou-se que os ramos ventrais de C7 foram os que mais contribuíram na formação de nervos (61,5%), seguido de C8 (55,4%), de T1 (41,2%) e de C6 (30,8%). O teste t de comparação entre as médias, ao nível de significância de 5%, não demonstrou diferenças na origem do plexo quando comparados os antímeros e os sexos. Do total dos 260 nervos dissecados, 68,8% foram originados pela combinação de dois ou três ramos, enquanto apenas 31,2% tiveram formação por um único ramo. A combinação entre C8 e T1 foi a que mais formou nervos para o plexo (23,8%) nesta espécie. Quando comparadas a origem, ramificação e área de inervação do plexo braquial do C. thous com outras espécies domésticas e silvestres, verificou-se maior semelhança com o cão doméstico. Os resultados deste estudo podem embasar o diagnóstico de disfunções neuromusculares, as técnicas de bloqueios anestésicos e análises morfofuncionais comparativas envolvendo esta espécie.