Ulnar Nerve Flashcards
What is the ulnar nerve?
A major peripheral nerve of the upper limb
What are the spinal roots of the ulnar nerve?
C8-T1
What muscles does the ulnar nerve innervate?
The muscles of the hand (apart from the thenar muscles and two lateral lumbricals), flexor carpi ulnaris and medial half of flexor digitorum produndus
What are the sensory functions of the ulnar nerve?
Innervates the anterior and posterior surfaces of the medial one and a half fingers, and associated palm area
What is the ulnar nerve derived from?
The brachial plexus- is a continuation of the medial cord, containing fibres from spinal roots C8 and T1
What course does the ulnar nerve take?
After arising from the brachial plexus, it descends down the medial side of the upper arm. At the elbow, it passes posterior to the medial epicondyle, entering the forearm
What can be said of the ulnar nerve as it passes posterior to the medial epicondyle?
It is easily palpable and vulnerable to injury
What does the ulnar nerve do in the forearm?
Pierces the two heads of the flexor carpi ulnaruis
Where does the ulnar nerve travel in the forearm?
Alongside the ulna
What branches arise from the ulnar nerve in the forearm?
Muscular branch
Palmar cutaneous branch
Dorsal cutaneous branch
What does the muscular branch of the ulnar nerve do?
Innervates some muscles in the anterior compartment of the forearm
What does the palmar cutaneous branch of the ulnar nerve do?
Innervates the skin of the medial half of the palm
What does the dorsal cutaneous branch of the ulnar nerve do?
Innervates the skin of the medial 1 and a 1/2 fingers, and the associated palm area
Where does the ulnar nerve travel in the wrist?
Superficially, to the flexor retinaculum
How does the ulnar nerve enter the hand?
Via the ulnar canal (or Guyon’s canal)
How does the ulnar nerve terminate?
In the hand it gives rise to superficial and deep branches
What muscles does the muscular branch of the ulnar nerve supply in the anterior forearm?
Flexor carpi ulnaris
Flexor digitorum profundus (medial half)
What does the flexor carpi ulnaris do?
Flexes the hand and adducts the hand at the wrist
What does the flexor digitorum profundus do?
Flexes the fingers
What are the muscles in the anterior forearm that aren’t innervated by the ulnar nerve innervated by?
The median nerve
What does the deep branch of the ulnar nerve innervate?
The majority of the intrinsic hand muscles
What muscles in the hand does the ulnar nerve innervate?
The hypothenar muscles
Medial two lumbricals
Adductor pollicis
Interossei of the hand
What are the hypeothenar muscles?
A group of muscles associated with the little finger
What are the muscles in the hand that aren’t innervated by the ulnar nerve innervated by?
The median nerve
What is responsible for the cutaneous innervation function of the ulnar nerve?
Three branches, the palmar cutaneous branch, dorsal cutaneous branch, and the superficial branch
Where do the palmar and dorsal cutaneous branches arise?
In the forearm
Where does the palmar cutaneous branch of the ulnar nerve innervate?
The skin of the medial half of the palm
Where does the dorsal cutaneous branch of the ulnar nerve innervate?
The skin of the medial one and a half fingers, and the associated palm area
Where does the superficial branch of the ulnar nerve arise?
In the hand
Where does the superficial branch of the ulnar nerve innervate?
The palmar surface of the medial one and a half fingers
Where is the ulnar nerve most susceptible to injury?
The elbow and wrist
Where is the ulnar nerve most vulnerable to injury at the elbow?
At the medial epicondyle
How does ulnar nerve damage at the elbow commonly occur?
Fracture of the medial epicondyle
How are motor functions affected by ulnar nerve damage at the elbow?
Flexor carpi ulnaris and medial half of flexor digitorum profundus paralysed.
Flexion of the wrist can still occur, but is accompanied by abudction
Interossei are paralysed, so abduction and adduction of fingers cannot occur
Movement of little and ring fingers is greatly reduced, due to paralysis of the medial two lumbricals
How are sensory functions affected by ulnar nerve damage at the elbow?
All sensory branches are affected, so loss of sensation over the areas that the ulnar nerve innervates
What are the characteristic signs of ulnar nerve damage at the elbow?
Patient cannot grip paper placed between fingers
How does damage to the ulnar nerve at the wrist commonly occur?
Lacerations to the wrist
How does damage to the ulnar nerve at the wrist affect motor function?
The interossei are paralysed, so abduction and adduction of the fingers cannot occur.
Movement of the little and ring fingers is greated reduced, due to paralysis of the medial two lumbricas.
How does damage to the ulnar nerve at the wrist affect sensory function?
The palmar branch and superficial branch are usually severed (but the dorsal branch unaffected)
Sensory loss over palmar side of medial one and a half fingers
What are the characteristic signs of ulnar nerve damage at the wrist?
Patient cannot grip paper placed between fingers
For long-term cases, ‘ulnar claw’ develops
What does ulnar claw consist of?
Hyper-extension of the metacarpophalangeal joints of the little and ring fingers
Flexion at the interphalangeal joints
Why does the ulnar claw have hyper-extension of the metacarpophalangeal joints of the little and ring fingers?
Because of paralysis of the medial two lumbricals, and the now unopposed action of the extensor muscles
When may flexion at the interphalangeal joints not be apparent?
If the lesion has occurred close to the elbow, as the flexor digitorum profundus will be paralysed
