Nerves of the Upper Limb Revision Flashcards
What are the roots of the axillary nerve?
C5 and C6
Sensory function of the axillary nerve?
Gives rise to upper lateral cutaneous nerve of arm, which innervates the upper lateral sin of the arm
Motor functions of the axillary nerve?
Innervates deltoid and teres minor
What cord is the axillary nerve formed from?
The posterior cord
In the axilla, where is the axillary nerve located?
Posterior to the axillary artery and anterior to the subscapularis muscle.
Where does the axillary artery exit the axilla?
What is it accompanied by?
Where does it then pass?
At the inferior border of subscapularis via the quadrangular space, accompanied by the posterior circumflex humeral artery and vein
Then passes medially to the surgical neck of the humerus
After passing medially to the surgical neck of the humerus, what happens to the axillary nerve?
Splits into 3 terminal branches:
- Posterior terminal branch
- Anterior terminal branch
- Articular branch
What is the posterior terminal branch of the axillary nerve responsible for?
Provides motor innervation to the posterior aspect of the deltoid muscle and teres minor.
It also innervates the skin over the inferior part of the deltoid as the upper lateral cutaneous nerve of the arm.
What is the anterior terminal branch of the axillary artery responsible for?
Provides motor innervation to the anterior aspect of the deltoid muscle.
How is the sensory component of the axillary nerve delivered?
Via the posterior terminal branch
After the posterior terminal branch of the axillary nerve has innervated the teres minor, what does it continue as?
It continues as the upper lateral cutaneous nerve of the arm –> innervates upper later aspect of arm
What motor functions are affected in axillary nerve injury?
The deltoid and teres minor muscles will be affected, rendering the patient unable to abduct the affected limb.
What sensory functions will be affected in axillary nerve injury?
The upper lateral cutaneous nerve of arm will be affected, resulting in loss of sensation over the upper lateral arm
What are characteristic clinical signs in long standing cases of axillary nerve damage? What muscle atrophies?
The paralysed deltoid muscle atrophies, giving the shoulder a flattened appearance, and the greater tuberosity can be palpated in that area.
What is Erb’s palsy?
Upper brachial plexus injury resulting from damage to C5-C6 (sometimes C7).
The axillary nerve is is affected, and the individual is usually unable to abduct or externally rotate the shoulder joint.
What movement typically causes Erb’s palsy?
Where there is an excessive increase in the angle between the neck and shoulder, which stretches (or even tears) the nerve roots.
What are the roots of the musculocutaneous nerve?
C5-C7
What are the motor functions of the musculocutaneous nerve?
Muscles in the anterior compartment of the arm (coracobrachialis, biceps brachii and the brachialis).
What are the sensory functions of the musculocutaneous nerve?
Gives rise to the lateral cutaneous nerve of forearm, which innervates the lateral aspect of the forearm.
What cord does the musculocutaneous nerve come from?
Terminal branch of the lateral cord
After innervating the anterior arm muscles, describe the route of the musculocutaneous nerve
Emerges lateral to the biceps tendon and brachioradialis.
Continues into the forearm as the lateral cutaneous nerve.
Provides sensory innervation to the lateral aspect of the forearm.
Why is damage to the musculocutaneous nerve uncommon?
It is well protected in the axilla
Injury caused by penetrating trauma (e.g. stabbing) etc
In musculocutaneous nerve injury, how are the motor functions affected?
Coracobrachialis, biceps brachii and brachialis muscles are affected:
- Flexion at the shoulder and elbow are weakened but can still be performed by the pectoralis major and brachioradialis respectively.
- Supination of the forearm is weak, but can still be performed by the brachioradialis.
What are the roots of the median nerve?
C5-T1
Motor function of the median nerve in the upper arm?
None
What cords is the median nerve derived from?
One branch of the lateral cord and one branch of the medial cord
Describe the position of the median nerve in the arm?
Situated medially
How does the median nerve enter the anterior forearm?
Via the cubital fossa
What muscles does the median nerve innervate in the anterior forearm?
- FCR
- PL
- PT
- FDS
What 2 major branches does the median nerve give off in the forearm?
- Anterior interosseous nerve (motor)
2. Palmar cutaneous nerve (sensory)
What does the anterior interosseous branch of the median nerve innervate?
Motor function
The deep muscles of the anterior forearm:
- 1/2 FDP
- FPL
- PQ
How does the median nerve enter the hand?
Carpal tunnel
What branches does the median nerve give off in the hand?
- Recurrent branch (motor)
2. Palmar digital branch (sensory and motor)
What does the recurrent branch of the median nerve innervate?
The thenar muscles (opponens pollicis, flexor pollicis brevis, abductor pollicis brevis)
What does the palmar digital branch of the median nerve innervate?
Motor: lateral two lumbricals
Sensory: innervates palmar surface and fingertips of the lateral 3 and a half digits
What does the palmar cutaneous branch of the median nerve innervate?
Sensory: the lateral aspect of the palm
Overall, what is the sensory innervation of the median nerve?
Lateral aspect of the palm, lateral three and a half fingers on the palmar surface of the hand.
What are the roots of the ulnar nerve?
C8-T1
What are the motor functions of the ulnar nerve?
- FCU
- 1/2 FDP
- Intrinsic muscles of the hand (via the deep branch of the ulnar nerve)
What cord is the ulnar nerve formed from?
Continuation of the medial cord
Describe the route of the ulnar nerve in the upper arm
Descends down the medial aspect of the upper arm. At the elbow, it passes posterior to the medial epicondyle of the humerus.
Where is the ulnar nerve palpable and vulnerable to injury?
At the medial epicondyle.
Does the ulnar nerve pass through the carpal tunnel to enter the hand?
No - travels superficially to the flexor retinaculum
Describe relation of ulnar nerve in relation to ulnar artery as it passes into the hand
Is medial to the ulnar artery
In the hand, how does the ulnar nerve terminate?
terminates by giving rise to superficial and deep branches.
Which muscles in the anterior compartment of the forearm does the ulnar nerve innervate?
- FCU
- Medial 1/2 FDP
What branch of the ulnar nerve innervates the majority of the intrinsic muscles of the hand?
Deep branch
Which intrinsic muscles of the hand does the deep branch of the ulnar nerve inneravte?
- Hypothenar muscles
- Medial 2 lumbricals
- Adductor pollicis
- Palmaris brevis
- Palmar and dorsal interossei
Altogether, what are the sensory functions of the ulnar nerve
Medial one and half fingers and the associated palm area.
In a high ulnar nerve lesion (damage at the elbow), what motor functions are affected?
All the muscles innervated by the ulnar nerve are affected:
- Paralysis of FCU and medial 1/2 FDP –>
…
