Origin and antimeric distribution of brachial plexus nerves in Alouatta guariba clamitans Cabrera, 1940 (Primates: Atelidae)

Abstract

The Southern brown howler monkey, Alouatta guariba clamitans, is one of the largest Neotropical primates. The objective of this study was to describe the origin and antimeric distribution of brachial plexus nerves in A. g. clamitans and, thereby, to provide information for comparative anatomy and for anatomy applied to loco-regional anaesthetic blocking in primates. For this purpose, a macrodissection of 10 thoracic limbs of corpses that were collected from highways was performed, and the corpses were stored in 10% formaldehyde solution. The brachial plexus was essentially formed from the ventral spinal branches of segments C5 to T1, although in one specimen the contribution of C4 and in another specimen the contribution of T2 was registered. There was a grouping of ventral branches in cranial, medium and caudal trunks, and branches of C5 and C7 were the ones that mostly contributed to the origin of nerves from the plexus. Comparatively, the brachial plexus from A. g. clamitans reflected characteristics that are typical in the primate order, but also of mammal species that require versatility and precision in movements of the thoracic limbs. On the basis of that similarity, it is proposed that anatomic landmarks for anaesthetic block techniques used in other primate species may be successfully applied to A. g. clamitans.