12.7 Neural Conditions of the Upper Limb

Question 1

Describe the 6 stages of the Seddon classification of nerve injury

Answer 1

1: Neuropraxia
2: Axonotmesis
3: Ax. + endoneurium
4: Ax. + endo + perineurium
5: Neurotmesis
6: Mixed (multiple sites)

Question 2

List two common traumatic injuries that can cause damage to the axillary nerve (Where does it wrap around the humerus?)

Answer 2

1. Shoulder dislocation
2. Proximal humeral shaft fracture

Question 3

Where does the radial nerve run through the arm? Therefore, what proximal traumatic injury can damage the radial nerve?

Answer 3

• Radial nerve runs in radial groove, wrapping posteriorly from medial to lateral.
• Then emergres anterioly at elbow joint, and runs down, dividing into superficial/posterior interosseus
• Can be damaged in humeral shaft fractures (since it wraps around)

Question 4

List three kinds of surrounding traumatic injuries that can damage the median nerve

Answer 4

• Supracondylar humeral fracture
• Elbow dislocation
• Perilunate dislocation (hand)

Question 5

List two kinds of traumatic injuries that can cause ulnar nerve damage

Answer 5

• Hamate fracture
• Medial epicondyle fracture (why does this make sense?)

Question 6

What is a physical exam test for ulnar nerve cubital tunnel compression? How might we treat it conservatively, and - if required - less conservatively?

Answer 6

Test: Tinnel’s test

Treat: Night splints and activity modification

Less conservative: surgical decompression

Question 7

Where is the ligament of struther’s? Does everyone have it? How might it compress the median nerve?

Answer 7

• Ligament that runs from the anteromedial humerus to the anteriormedial proximal ulna.
• Only about 13% prevalence
• Median nerve passes under; can get compressed by it

Question 8

What is radial tunnel syndrome often confused with? How might we test for it/treat it?

Answer 8

• Often confused with lateral epicondylitis
• Test: resisted middle finger extension
• Treat: Corticosteroid injection (surgical release if needed)

Question 9

What are some risk factors for carpal tunnel syndrome?

Answer 9

• Occupation
• Diabetes
• Obesity
• Pregnancy
• Hypothyroidism (think back to the clin case with the woman with a sore wrist)

Question 10

What are the boundaries of the carpal tunnel (roof vs others)? How can carpal tunnel syndrome occur?

Answer 10

• Roof is transverse carpal ligament (part of the flexor retinaculum)
• Others borders are carpal bones
• If all tendons are inflamed, small increase in size is magnified by 9x tendons, so median nerve can become compressed

Question 11

How will patients classically describe carpal tunnel?

Answer 11

• Paraesthesia, weakness, numbness of hand (thenar eminence is often preserved; palmar cutaneous branch is superficial to the flexor retinaculum)
• Waking up with shooting pain; need to shake it out

Question 12

List three special tests that can be used for carpal tunnel

Answer 12

1. Durkan’s: push down on median nerve at the level of the wrist
2. Tinel’s: T for Tap: Tap on wrist
3. Phalen’s: Flex wrists 90°, and press dorsal aspects of hands together for 30secs symptoms?

Question 13

What are the mechanics of NCS. How might they differ in neuropraxia vs neurotmesis if we’re diagnosing, say, carpal tunnel?

Answer 13

• Measures amplitude/latency of electrical impulse conduction
• In neuropraxia, we’d expect higher latency and lower amplitude
• In neurotmesis, we’d expect absent of both, since axon is transected completely

Question 14

What is the most commonly recommended treatment for carpal tunnel? How might this change if the patient is pregnant/wants as conservative a treatment as possible?

Answer 14

• Surgery is highly effective in the treatment of carpal tunnel
• Corticosteroid injections can also be given if the patient is pregnant (probably transient CTS)