35. Nerve injuries to the upper limb Flashcards
(39 cards)
Why is there injury to the radial nerve in a mid shaft humeral fracture?
The radial nerve runs in the radial (or spiral) groove on the posterior surface of the shaft of the humerus. It is closely associated with the bone and may therefore be injured in a mid-shaft humeral fracture
Will the patient still be able to actively extend their elbow when radial nerve is injured?
Yes. Extension of the elbow will either be normal or only mildly compromised. The nerve supply to the long and lateral heads of triceps is given off prior to the radial nerve entering the spiral groove. The nerve supply to the medial head of triceps is given off in the spiral groove, but this is generally proximal to the fracture and thus is unaffected. Anconeus is paralysed but this has only a minor role in elbow extension.
If a patient has radial nerve injury, In what position will a their wrist and fingers be when the wrist is pronated? Why?
The wrist and fingers will be flexed. Injury to the radial nerve in the radial groove will result in paralysis of brachioradialis and all extensor muscles of the wrist and fingers. This injury results in “wrist drop” (i.e. inability to actively extend the wrist) and inability to actively extend the fingers. The wrist and fingers are flexed when the forearm is pronated because of unopposed flexor muscles and gravity.
What is the likely distribution of sensory impairment in radial nerve injury?
The posterior cutaneous nerve of the arm branches from the radial nerve above the spiral groove, so is unaffected. The lower lateral cutaneous nerve of the arm and posterior cutaneous nerve of the forearm branch high in the spiral groove and are also usually unaffected. The paraesthesia is therefore usually in the distribution of the superficial branch of the radial nerve
In an injury to the median nerve in the arm, above the level of the elbow (high median nerve injury), which muscles will be affected?
paralysis of pronator teres, flexor carpi radialis, palmaris longus and flexor digitorum superficialis as well as all
of the other muscles supplied by the median nerve in the forearm and hand. In the anterior forearm, both pronators are weak and the flexors of the wrist are paralysed except for flexor carpi ulnaris and the ulnar half of flexor digitorum profundus (both supplied by the ulnar nerve).
Does the median nerve give off and muscular branches to the arm?
The median nerve gives off no muscular branches to the muscles of the arm
In a patient with high median nerve injury, in what position will their forearm be?
The forearm will be supinated (due to the unopposed action of supinator [radial nerve] and biceps brachii [musculocutaneous nerve]). Flexion of the wrist is weak and is often accompanied by adduction, due to the pull of flexor carpi ulnaris
How does high median nerve injury affect the thumb?
In the hand, flexion of the thumb is very weak or absent as FPL is paralysed but the deep head of FPB may have some residual innervation from the ulnar nerve. Opposition (opponens pollicis) and palmar abduction (APB) of the thumb are absent
The interphalangeal joint and MCPJ of the thumb will be extended (due to unopposed action of EPL) and the thumb will be adducted (due to unopposed action of adductorpollicis). Lateral (external) rotation of the thumb occurs due to loss of opponens pollicis (which usually medially rotates the thumb). In long standing lesions, there will be wasting of the thenar eminence.
How does high median nerve injury affect the fingers?
FDS will be paralysed to all four fingers and FDP will be paralysed to the index and middle fingers. The radial two lumbricals (to the index and middle fingers) will also be paralysed but the MCPJs can still flex a little due to the action of the interossei.
What happens when a patient with high median nerve injury attempts to make a fist?
When the patient attempts to make a fist, the ring and little fingers will flex into the palm normally as FDP and the lumbricals are still intact to these digits. However, the index and middle fingers will remain fully extended
What is the name given to the appearance of the hand when trying to make a fist in a patient with high median nerve injury?
Hand of Benediction
When is the Hand of benediction seen in high median nerve injuries?
It is only seen when the patient attempts to make at fist and is not present at rest.
In patients with high median nerve injuries, what may develop in the long term?
in long-standing lesions an Ape Hand Deformity may develop at rest.
Describe the appearance of the Ape Hand Deformity
Deformity with thenar wasting in a high median nerve lesion. The thumb can still be actively flexed by FPB at the MCPJ due to the ulnar nerve supply to the deep
head. (You can tell this is a high lesion as FPL is paralysed with absent flexion of the IPJ of the thumb)
In patients with high median nerve injury, how is sensation affected?
The patient will have sensory loss in the whole of the region supplied by the median nerve
Give an example of an injury that can lead to high median nerve injury?
supracondylar fracture of the humerus
How may the median nerve be injured at the wrist?
The median nerve may be injured at the wrist by a penetrating injury (e.g. from broken glass) or by compression in the carpal tunnel.
What is the difference between high and low median nerve injury?
The presentation differs from the high median nerve injury in that the innervation to the muscles of the common flexor origin at the medial epicondyle (pronator teres, flexor carpi radialis, palmaris longus, and flexor
digitorum superficialis) is intact, as is the innervation to flexor digitorum profundus.
The palmar cutaneous branch of the median nerve, supplying the skin over the thenar eminence, will be spared
Which are the muscles that are paralysed in low median nerve injury?
(remember LOAF):
lumbricals to the index and middle fingers
opponens pollicis
abductor pollicis brevis
flexor pollicis brevis (superficial head)
What is the deformity that results with low median nerve injury? How does it look?
Ape Hand Deformity - after the muscles have atrophied.
The thenar eminence is flattened, and the thumb is adducted and externally (laterally) rotated
Describe the branches of the ulnar nerve
- The ulnar nerve does not supply any muscles in the arm.
- At the level of the elbow, it gives off a branch to flexor carpi ulnaris, which originates from the common flexor origin on the medial epicondyle and from the ulna.
- In the forearm it supplies the ulnar half of flexor digitorum profundus (to the ring and little fingers) and gives off the palmar cutaneous branch (ulnar border of the palm) and the dorsal (posterior) cutaneous branch (ulnar border of
the dorsum plus dorsum of ulnar 1½ digits as far distally as the DIPJ). T
In a patient with ulnar nerve injury at the wrist, which muscles might be affected?
In the hand, the ulnar nerve supplies the muscles of the hypothenar eminence: adductor pollicis, the deep head of flexor pollicis brevis, the interossei, the lumbricals to the ring and little finger, palmaris brevis, and gives off palmar digital branches to the ulnar 1½ digits. Hence, if the nerve is damaged at the wrist, all of these functions may be impaired.
What may lead to ulnar nerve injury at the wrist?
a laceration or by compression in Guyon’s canal
What might long standing injury to the ulnar nerve at the wrist lead to?
‘claw hand’.
The claw affects the little and ring fingers of the hand. These fingers are hyperextended at the metacarpophalangeal (MCP) joint, and flexed at both the
proximal and distal interphalangeal (IP) joints.
