Musculocutaneous nerve

Musculocutaneous nerve
Nerves of the left upper extremity. (Musculocutaneous labeled at upper right.)
Details
From	lateral cord (C5-C7)
To	lateral cutaneous nerve of forearm
Innervates	anterior compartment of the arm
Identifiers
Latin	nervus musculocutaneus
Dorlands /Elsevier	n_05/12566256
TA	A14.2.03.024
FMA	37064
Anatomical terms of neuroanatomy []

The musculocutaneous nerve arises from the lateral cord of the brachial plexus, opposite the lower border of the pectoralis major, its fibers being derived from C5, C6 and C7.

It penetrates the coracobrachialis muscle and passes obliquely between the biceps brachii and the brachialis, to the lateral side of the arm; a little above the elbow it pierces the deep fascia lateral to the tendon of the biceps brachii and is continued into the forearm as the lateral cutaneous nerve of the forearm.

In its course through the arm it innervates the coracobrachialis, biceps brachii, and the greater part of the brachialis.

The musculocutaneous nerve presents frequent variations.

Although rare, the musculocutaneous nerve can be affected through compression due to hypertrophy or entrapment between the biceps aponeurosis and brachialis fascia or it may be injured through stretch as occurs in dislocations and sometimes in surgery.

Isolated injury causes weakness of elbow flexion and supination of the forearm.

A discrete sensory disturbance is present on the radial side of the forearm. The biceps reflex is also affected.

The nerve is usually involved in an upper brachial plexus palsy.

Injury can occur before entering the coracobrachialis due to dislocation or apparently due to stretch due to throwing injury

Heavy backpacks can cause damage to the upper trunk of the brachial plexus – dysfunction can be severe and prolonged with similar injury as occurs with Erb's palsy from breech deliveries. Early detection is important – the combination of time, avoidance of wearing a backpack, and strengthening of the shoulder muscles will probably be effective.