# Three-Headed Biceps Brachii Muscle: A Rare Site of Proximal Median Nerve Entrapment

## TL;DR

A rare anatomical variant of the biceps muscle may cause proximal median nerve entrapment, a finding important for diagnosing nerve-related conditions.

## Contribution

Identification of a rare three-headed biceps variant as a potential site of proximal median nerve entrapment.

## Key findings

- A 94-year-old cadaver exhibited a biceps brachii with an additional slip arising from the coracoid process.
- The additional muscular slip crossed over the median nerve and connected to the forearm flexor fascia via aponeurosis.
- This anatomical variant may contribute to proximal median nerve entrapment, beyond the carpal tunnel.

## Abstract

The biceps brachii muscle is a highly variable muscle in the anterior compartment of the arm, and the most common variants include additional heads or slips. The median nerve courses with the brachial artery in the medial arm near the biceps brachii muscle, crosses the elbow, and enters the forearm deep to the bicipital aponeurosis. While entrapment of the median nerve in the carpal tunnel is one of the most common neuropathies, more proximal entrapments by the bicipital aponeurosis or other variants have been reported. In a 94-year-old embalmed female cadaver received through the Humanity Gift Registry of Pennsylvania, a biceps brachii muscle with an additional slip that arose from the coracoid process was found, which bridged over the median nerve and blended with the investing fascia of the forearm flexors via aponeurosis. Because of the course of this muscular slip in the arm and its relationship to the median nerve, this may be an additional site of proximal entrapment of the median nerve. It is important to consider these rare sites of nerve entrapment when diagnosing patients with median nerve neuropathy.