SM 231a - Peripheral Neuropathies of the Upper Limb Flashcards
What is the difference in the “Pope’s blessing/hand of benediction” in ulnar vs. median nerve injury?
- In a median nerve injury the “Pope’s blessing” hand occurs when the patient is asked to make a fist
- In an ulnar nerve injury, the “Pope’s blessing” hand occurs when the patient is asked to extend their fingers
Which of the following is most likely to result in injury to the musculocutaneous nerve?
- Mastectomy operation
- Fracture of the humeral surgical neck
- Forceful upward pull of the shoulder during birth
- Fracture of the humeral shaft
- Fracture of the supracondylar humerus
A. Mastectomy operation
What sensory deficits will result from damage to the median nerve?
Loss of sensation in the blue areas
Which nerves innervate the lumbricals?
What do the lumbricals do?
The lumbricals simultaneously flex the MCP joints and extend the DIP and PIP joints
- 1st and 2nd: Median nerve
- 3rd and 4th: Ulnar nerve
Damage to which nerve causes “ape hand?”
Median nerve
- Loss of innervation to thenar muscles -> thumb cannot be flexed or abducted
- Stays pressed against the lateral side of the hand
Loss of the thenar muscles results in which characteristic sign? Which nerve is damaged?
Ape hand
Median nerve (proximal or distal lesion)
What kind of injury might occur during this maneuver?
What is the effect?
Upper brachial plexus injury (C5, C6)
- Affects lateral cord and therefore the musculocutaneous nerve
- Results in water’s tip arm
- Loss of shoulder flexion, abduction, lateral rotation
- Weakness in forearm flexion, supination
- Weakness in wrist extension
What causes an upper brachial plexus injury (Erb’s palsy)?
Which nerves and functions are affected?
Excessive separation of the neck and the shoulder
Supply from spinal nerves C5 and C6 are interrupted
- Results in “waiter’s tip” arm position due to…
- Loss of shoulder flexion, abduction, lateral rotation
- Weakeness of elbow flexion, supination
- Weakness of wrist extenstion
How do newborns typically acquire an upper brachial plexus injury?
What is the effect?
Pulling on the head when the arm is caught in the birth canal, causing excessive separation of the neck and the shoulder
-> Loss of C5, C6 supply -> waiter’s tip arm
- Loss of shoulder flexion, abduction, lateral rotation
- Weakness in forearm flexion, supination
- Weakness in wrist extension
How is the musculocutaneous nerve most commonly injured?
What are the consequences?
Pentrating wounds in the axilla
Loss of innervation to biceps brachii, brachialis, and coracobrachialis
- Weakness of forearm flexion (brachialis, biceps brachii)
- Saved by anterior deltoid (axillary nerve) and pectoralis major (lateral and medial pectoral nerves)
- Weakness of supination (biceps brachii)
- Saved by supinator (radial nerve)
- Weakness of arm flexion (coracobrachialis, biceps brachii)
- Saved by brachioradialis (radial nerve)
Loss of abduction and adduction of the fingers results from damage to which nerve?
Ulnar nerve
What are the common causes of injury to the axillary nerve?
Fractures of the humeral surgical neck - can sever the nerve
Dislocations of the shoulder joint - can stretch the nerve
Which of the following is most likely to result in injury to the radial nerve?
- Mastectomy operation
- Fracture of the humeral surgical neck
- Forceful upward pull of the shoulder during birth
- Fracture of the humeral shaft
- Fracture of the supracondylar humerus
D. Fracture of the humeral shaft
Which of the following is most likely to result in injury to the upper brachial plexus (C5, C6)?
- Mastectomy operation
- Fracture of the humeral surgical neck
- Forceful upward pull of the shoulder during birth
- Fracture of the humeral shaft
- Fracture of the supracondylar humerus
C. Forceful upward pull of the shoulder during birth
What causes a lower brachial plexus injury (Klumpke’s palsy)?
Tearing of the lower trunk of the brachial plexus (C8, T1)
Caused by excessive abduction of the arm
- Grabbing onto something as you’re falling
- Compression by the cervical rib
- Forceful upward pull of the shoulder when the head is caught in the birth canal
Which nerve is most likely damaged in this patient?
How do you know?
Long thoracic nerve
Normally innervates serratus anterior to protract the scapula
Loss of innervation to serratus anterior -> retraction, upward rotation of the scapula. This causes winging
Distal lesions in the median nerve result in…
- Loss of 1st and 2nd lumbricals
- Cannot flex MCP
- Cannot extend PIP and DIP
(Long flexors and extensors are still intact but not strong enough to oppose each other without lumbricals?)
This hand position is caused by damage to which nerve?
Distal lesion in the median nerve
What are the functions of the interossei?
What is their innervation
Adduct and abduct the fingers
Flex the MCP joints
Ulnar nerve (lower brachial plexus)
What are the common causes of distal lesions in the ulnar nerve?
- Nerve compression or cut in the tunnel of Gunyon
- Fracture of the hook of the hamate (falling onto an outstretched hand) can cut the nerve
What are the effects of injury to the radial nerve?
Wrist drop
- Loss of wrist extension
- Extensor carpi ulnaris
- Extensor carpi radialis
- Loss of finger extension at MCP
- Extensor digitorum
- Loss of forearm supination
- Supinator
A patient is diagnosed with a distal injury of the ulnar nerve. Which of the following would you expect to see in this patient?
- Pope’s blessing upon finger extension
- Claw hand of digits 2 and 3
- Sensory changes on the dorsal and palmar surfaces of the lateral 3 ½ digits and adjacent palm
- Claw hand of all 5 digits
- Anesthesia in the C8 and T1 dermatomes along the medial side of the arm, forearm and hand
A. Pope’s blessing upon finger extension
- Loss of 3rd and 4th lumbricals
- Loss of MCP flexion
- Loss of PIP and DIP extension
- Flexor digitorum profundus is still intact
- Pulls DIP into flexion
Describe the deficits that result from damage to the ulnar nerve
(proximal or distal lesion)
- Loss of finger adduction and abduction
- Palmar and dorsal interossei respectively
- Loss of thumb adduction
- Adductor pollicis
- “Pope’s blessing” hand when the patient is asked to extend all digits
- 3rd and 4th lumbricals
- Note - this will be more severe in distal lesions because flexor digitorum profundus will still be able to flex the DIP = more severe claw
Injury to which nerve causes this hand position?
Radial nerve, distal to the axilla
Results in wrist drop due to:
- Weakness of elbow extension
- Medial head of triceps brachii is affected
- Loss of wrist extension
- Extensor carpi ulnaris
- Extensor carpi radialis
- Loss of finger extension at MCP
- Extensor digitorum
- Loss of forearm supination
- Supinator
If the lesion is proximal to the axilla, elbow extension will be lost (all of triceps brachii will lose supply)
Following a brachial plexus injury a patient presents with a waiter’s tip position of the upper limb. In what areas of skin would you expect to see anesthesia or loss of sensation?
- C8, T1 dermatomes
- Medial side of the hand and medial 1 ½ digits
- C5, 6 dermatomes
- Lateral side of the hand and lateral 3 ½ digits
- Medial side of the forearm and hand
C. C5, 6 dermatomes
Waiter’s tip = upper brachial plexus injury, C5, C6 spinal nerve outflow is compromised
Damage to the median nerve results in what hand position?
“Ape hand” regardless of lesion location
- Loss of supply to the recurrent branch of the median nerve
- Loss of thumb flexion, abduction, and opposition
- Loss of 1st and 2nd lumbricals
Plus:
“Pope’s blessing” hand if proximal lesion
- Loss of finger and wrist flexors
- Can still flex ring and pinkie finger, due to ulnar nerve innervation of flexor digitorum profundus
Claw hand of the 1st and 2nd finger if distal lesion
- Loss of 1st and 2nd lumbricals = loss of extension of PIP and DIP, loss of flexion of MCP
- Flexor digiotrum supericialis and profundus are unopposed in finger flexion
- Extensor digiorum is unopposed in MCP extension
Partial results from a patient’s MSK exam:
Wrist flexion deviates to the radial side, hand is shown in the picture.
Which nerve is most likely injured? Where?
Ulnar nerve, proximal lesion
Claw hand is more mild because the medial half of flexor digitorum profundus has lost its supply from the ulnar nerve
It cannot pull the DIP joints into flexion; only the PIP joints are flexed
PIP flexion and MCP extension results from loss of 3rd and 4th lumbricals
Which nerve is most likely damaged in this patient?
Axillary nerve
Results in loss of innervation to and atrofy of the deltoid
(and teres minor, but not shown)
In an upper brachial pelxus injury, where would you expect to find sensory loss?
Lateral arm, forearm, and hand
A patient is asked to make a fist and the following hand position results.
Which nerve is most likely damaged?
Median nerve - proximal lesion
What might occur if one pulls on the arm?
What is the effect?
Lower brachial plexus injury (C8, T1)
- Klumpke’s total claw hand
- Affects the medial cord -> ulnar and median nerves
- Loss of innervation to interossei and lumbricals
- Loss of flexion of MCP joints
- Loss of extension of PIP and DIP joints
- Loss of innervation to thenar and hypothenar muscles
Sensation to which parts of the upper limb will be compromised if the ulnar nerve is damaged?
Medial 1.5 fingers and the palm and back of hand adjacent
What injury may result in loss of sensation in the lateral arm, lateral forearm, lateral hand, and thumb?
Upper brachial plexus - C5 and C6 dermatomes
Proximal lesions in the medial nerve will cause…
- Pope’s blessing/hand of benediction when the patient is asked to make a fist
- Deviation to the ulnar side upon wrist flexion
- Loss of pronation
What nerves are most likely injured in this child?
Upper brachial plexus (C5, C6)
- Waiter’s tip arm
- Loss of shoulder flexion, abduction, lateral rotation
- Weakness in elbow flexion, supination
- Weakness in wrist flexion
This guy is most likely to injure which nerve?
What is the result?
Radial nerve
Loss of wrist, and MCP extension
Weakness of elbow extension
Loss of senation in the posterior arm, forearm, and lateral hand
