Nerves of Arm
Objectives
At the end of the lecture, the student should be able to:
1. To know the nerve supply to arm
2. To know the course of the nerves
3. To know the branches of the nerves
4. To know the clinical correlates of the nerves
Following nerve supply upper arm
- Musculocutaneous nerve
Nerve of anterior compartment of arm
- Radial nerve
Nerve of posterior compartment of arm
Other nerves are passing through the arm but they are not supplying the arm
e.g. Median nerve
ulnar nerves
Musculocutaneous nerve
It is main nerve that supply the front of arm.
It is branch of lateral cord of brachial plexus
Root value c5, c6, c7
Course
In axilla
It arises from lateral cord in axilla.
In axilla it lies lateral to 3rd part of axillary artery
Relation in axilla
· Anteriorly
o pectoralis major
· Posteriorly
o subscapularis
· Medially
o axillary artery
o Lateral root of median nerve
· Laterally
o coracobrachialis
· It leaves the axilla and enters the front of arm by piercing the coracobrachialis.
In arm
It runs downward and laterally between the biceps and brachialis to reach the lateral side of the tendon of the biceps piercing the deep fascia 2cm above the bent of fore arm and continue as lateral cutaneous nerve of fore arm.
Branches
· Muscular branches
o Coracobrachialis
o Biceps
o Brachialis
· Cutaneous branches
o Through lateral cutaneous nerve of fore arm it supplies the skin of lateral side of fore arm from elbow to wrist.
· It also supplies elbow joint through its branch to brachialis.
Radial nerve
· Main nerve that supplies the back of the arm
· It is largest branch of posterior cord of brachial plexus.
Root value
C5, c6, c7, c8, t1
Course
In axilla
· It lies posterior to third part of axillary artery.
· It rests on subcapularis, latissimusdorsi from axilla.
· It passes posteriorly with profunda brachii vessel through lower triangular space, below teres major, between long head of triceps and humerus.
· It then enters the radial groove with profunda vessel.
In radial groove
· It runs downward and laterally between lateral and medial head of triceps.
· At the lower end of groove, 5cm below the deltoid tuberosity the nerve pierces the lateral intermuscular septum and passes into anterior compartment of arm.
Branches
In axilla
· muscular branches to
1. Long head of triceps
2. Medial head of triceps
· cutaneous branch
1. Posterior cutaneous nerve of arm.
In radial groove
· Muscular branches
1. Lateral head of triceps
2. Medial head of triceps
3. Anconeus
· Cutaneous branches
1. Lower lateral cutaneous nerve of arm
2. Posterior cutaneous nerve of fore arm
· Articular branch
1. To elbow joint
Clinical correlates
Radial nerve is very commonly damaged in the region of radial groove.
Cause of injury
-intramuscular injection in triceps instead of deltoid
-fracture of shaft of humerus
Clinical features
-weakness or loss of power of extension at wrist (wrist drop)
-sensory loss over back of lateral part of the dorsum of the hand