Intramuscular innervation patterns of the brachialis muscle

Abstract

The aim of this study was to provide accurate anatomical descriptions of the patterns of innervation of the brachialis muscle by the musculocutaneous, radial, and median nerves. Sihler's staining method was applied to 20 brachialis muscles from 10 cadavers to reveal the intramuscular distribution patterns of the musculocutaneous, radial, and median nerves. Three patterns of innervation of the brachialis muscle by the three studied nerves were found: single, double, and triple. These innervation patterns were categorized into four types: Type I--only the musculocutaneous nerve; Type II--double innervation by the musculocutaneous and radial nerves; Type III--double innervation by the musculocutaneous and median nerves; and Type IV--triple innervation by all three nerves. Single, double, and triple innervation patterns occurred 25%, 70% (Type II, 55%; Type III, 15%), and 5% of the samples, respectively. The brachialis muscle is not solely innervated by the musculocutaneous nerve but also by the radial and median nerves, thus making it a potentially triply innervated muscle. Double innervation of this muscle with either the musculocutaneous and median nerve or the musculocutaneous and radial nerves was also observed.

The Italian master Leonardo da Vinci and his early understanding of the brachial plexus

“…The brachial plexus continues to be of significant clinical interest [8][9][10][11][12][13] and thus our current knowledge of this structure was begun by the works of da Vinci in the fifteenth century. …”

Intramuscular nerve distribution pattern of ankle invertor muscles in human cadaver using sihler stain

“…) and underwent Sihler staining, as modified by Liem and Douwe van Willigen . This method involves many steps to obtain a visual representation of the neural arborization pattern . After completing the Sihler staining, the vertical lengths of the FHL, TP, and FDL were divided into 10 equal divisions by transverse lines, each representing 10% increments of the total length.…”

“…Previous studies assumed that the MEP zone was located at the center of a muscle belly . However, intramuscular nerve distribution varies within muscles, as revealed by Sihler staining of forearm muscles, hip adductor muscles, and calf muscles . Still, no anatomical studies have been conducted on the tibialis posterior (TP), flexor hallucis longus (FHL), and flexor digitorum longus (FDL), which are the muscles targeted for releasing equinovarus foot and toe clawing…”

Accessory Branch of Median Nerve Supplying the Brachialis Muscle: A Case Report and Clinical Significance

“…Extremely rare cases in which distinct branches of the median nerve supply the inferior portion of the BM have been cited in the literature. Hur et al, [14] observed such a branch originating from the upper edge of the median nerve innervating the infero-medial portion of BM, whereas Won et al, [15] noticed the median nerve supplying the lower quarter of the BM in 15% and the BM's uppermost quarter in 5% of the specimens. Our case, that corresponds to type III according to Won's et al, classification, resembles with that of Hur et al, with the difference of branching site that was located at the limit between middle and inferior portion of the median nerve.…”