16. Limb neuropathies - Carpal Tunnel Syndrome, Wrist drop, Claw hand, Foot drop

Question 1

What is the structure of the carpal tunnel?

Answer 1

Floor: carpal arch
Roof: flexor retinaculum (AKA transverse carpal ligament)
Contains 9 flexors + the median nerve

Question 2

Define carpal tunnel syndrome.

Answer 2

A nerve entrapment disorder that results in the median nerve being compressed, which makes its way into the wrist via a narrow entry called the carpal tunnel, causing pain + numbness in the median nerve distribution in the hand.

The most common mononeuropathy and entrapment
neuropathy.

Question 3

What nerve is affected in carpal tunnel syndrome?

Answer 3

Palmer digital cutaneous branch of the median nerve.

Question 4

What is the function of the nerve affected in carpal tunnel syndrome?

Answer 4

Palmar digital cutaneous branch of the median nerve.

1. Sensory function to first 3.5 fingertips
   -> (not the palm though, this is a different branch that doesn’t go through the carpal tunnel)
2. Thumb motor function (thenar muscles)
   -> Abductor pollicis brevis
   -> Opponens pollicis
   -> Flexor pollicis brevis
   (Not the adductor!)

Question 5

Give 3 diseases carpal tunnel syndrome is associated with.

Answer 5

1. Diabetes mellitus.
2. Acromegaly.
3. Hypothyroidism.
4. Amyloidosis.
5. Rheumatoid disease.

Question 6

Give 5 risk factors/causes/associations for carpal tunnel syndrome.

Answer 6

1. Pregnancy (3rd trimester).
2. Obesity.
3. RA.
4. Hypothyroidism.
5. Acromegaly.
6. Diabetes mellitus.
7. Amyloidosis including in dialysis patients.
8. Myxodema.
9. Idiopathic.
10. Repetitive strain.

Question 7

Describe the clinical presentation of carpal tunnel syndrome.

Answer 7

Symptoms character:
- Gradual onset, intermittent, worst at night, wakes you up.

1. Aching pain in first 3.5 fingers and arm
2. Sensory changes to first 3.5 fingers - numbness, parasthesia, burning, pain
3. Motor symptoms of carpal tunnel syndrome affect the thenar muscles, with:
   - Weakness of thumb movements
   - Weakness of grip strength
   - Difficulty with fine movements involving the thumb
   - Wasting of the thenar muscles (muscle atrophy)
   - Reduced thumb grip strength/difficulty with fine movements

Question 8

Why is there no sensory loss in the palmer region of the hand in carpal tunnel syndrome?

Answer 8

Palmer branch of the median nerve innervates it, before branches off before going through the carpal tunnel.

Question 9

What relieves carpal tunnel syndrome?

Answer 9

Shaking the hand
- Relieved by dangling the hand over the edge of the bed - “wake
and shake”

Question 10

What investigations might you do in someone who you suspect has carpal tunnel syndrome?

Answer 10

1. Electromyography (EMG) - GOLD STANDARD
   * See slowing of conduction velocity in the median sensory nerves
   across the carpal tunnel
   * Prolongation of the median distal motor latency
   * Helps to confirm lesion site and severity
2. Phalen’s test:
   * Patient can only maximally flex wrist for 1 minute
3. Tinel’s test:
   * Tapping on the nerve at the wrist induces tingling - but non-specific

Question 11

What is Phalen’s test?

Answer 11

Ask patient to hold wrists in full flexion (reverse prayer position) for 30-60s (press on wrist if needed).

Positive = gets tingling sensation/pain (sensory symptoms).

Question 12

What is Tinel’s test?

Answer 12

Lightly tap over the wrist at the location where the median nerve travels through the carpal tunnel.
This is in the middle, at the point where the wrist meets the hand.

Positive = gets paraesthesia and sensory symptoms.

Question 13

What is the Kamath and Stothard carpal tunnel questionnaire (CTQ)?

Answer 13

• Gives a score based on the symptoms.
• Can be used to predict the likelihood of a diagnosis of carpal tunnel syndrome.

A high score on the questionnaire may replace the need for nerve conduction studies to confirm the diagnosis.

It scores based on questions such as:
- Do symptoms wake you at night?
- Do you have trick movements (e.g., shaking the hand) to improve symptoms?
I- s your little finger affected? (Answering yes scores negatively, making carpal tunnel syndrome less likely)

Question 14

Management of carpal tunnel syndrome.

Answer 14

1. Rest and altered activities
2. Wrist splints - 1st line
   - Maintain a neutral position of the wrist can be worn at night (for a minimum of 4 weeks)
3. Steroid injections - 2nd line
4. Decompression Surgery
   - Cut the flexor retinaculum to reduce pressure

Question 15

Define ‘Wrist drop’.

Answer 15

A disorder caused by radial nerve palsy.

Because of the radial nerve’s innervation of the extensor muscles of the wrist and digits, those whose radial nerve function has been compromised cannot actively extend them.

Question 16

Wrist drop indicates damage to which nerve?

Answer 16

Radial nerve (C5 - T1)

Functions:
- For spreading hands and opening fist
- Sensation to dorsal thumb

Question 17

Which muscles are involved in radial nerve damage/wrist drop?

Answer 17

Muscles involved - BEST:
* Brachioradialis
* Extensors
* Supinator
* Triceps

Question 18

What is otherwise known as ‘Saturday night palsy’?

Answer 18

Radial nerve compression - causes wrist drop and weakness of brachioradialis and finger extension, sensory loss in anatomical snuff box

Question 19

Define ‘Claw Hand’ (AKA Ulnar claw/Spinster’s claw).

Answer 19

A disorder caused by ulnar nerve palsy.

Deformity where the fingers are bent into a position that looks like a claw.
- Results in hyperextension at the metacarpophalangeal joints and flexion of the interphalangeal joints

Question 20

What nerve is damaged in elbow trauma and what functions does this nerve provide?

Answer 20

Ulnar nerve
(C7-T1 via brachial plexus)

Functions:
For wrist flexion, crossing fingers, sensory to little and 4th fingers.

Lesion = claw hand

Question 21

List the muscles involved in precision grip.
What nerve controls it and what are its spinal roots?

Answer 21

Median nerve - C6-T1.

LOAD:
2 Lumbricals
Opponens pollicis.
Abductor pollicis brevis
Flexor pollicis brevis

Question 22

Describe the patterns of sensory loss seen in the hand.

Answer 22

Median nerve damage - loss of radial 3.5 fingers and palm.
Ulnar - medial/ulnar 1.5 fingers.

Question 23

Give a sign of radial nerve damage and an example of how this may occur.

Answer 23

Wrist and finger drop.
Compression against humerus.

Question 24

Give a sign of ulnar nerve damage and how it may occur.

Answer 24

Weakness/wasting of ulnar side wrist flexors, interossei (can’t cross fingers) and medial two lumbricals (claw hand).

Hypothenar eminence wasting.

Question 25

Lung cancer, thymoma and TB commonly damage which nerve?

Answer 25

Phrenic nerve

Question 26

How would brachial plexus damage present?

Answer 26

Pain/paraesthesiae and weakness in affected arm.

Question 27

A heavy rucksack or broken rib commonly causes damage to the ___.

Answer 27

brachial plexus

Question 28

What happens when the phrenic nerve (C3-5) is damaged?

Answer 28

Loss of innervation to diaphragm
= orthopnoea and diaphragm is raised on CXR

Question 29

Define ‘Foot drop’.

Answer 29

A result of weakness of the foot dorsiflexors.

Caused by common peroneal branch of sciatic nerve.

Question 30

Foot drop indicates damage to which nerve?

Answer 30

Common peroneal (branch of sciatic), aka common fibular nerve

Question 31

Pelvis fracture commonly damages which nerve?

Answer 31

Sciatic nerve (L4 - S3)

Question 32

Common peroneal nerve is from which spinal levels and could be damaged by what?

Answer 32

L4-S1
Trauma to fibular head

Question 33

Which nerve innervates plantar flexion and sensation on the sole of the foot?

Answer 33

Tibial nerve

Question 34

Damage to what nerve causes burning thigh pain?

Answer 34

Lateral cutaneous L2-L3

Question 35

What nerve controls the ankle jerk reflex?

Answer 35

S1

Question 36

A slim female yoga instructor comes to see her doctor complaining that her left foot keeps dragging on the floor.

What do you think could be causing her problem?

Answer 36

Common peroneal palsy - her symptoms are due to weakness of ankle inversion and extension.

She probably also has numbness over anterolateral border of dorsum of foot and lower shin

Question 37

A patient comes in having had an accident on the rugby pitch with a suspect elbow fracture, he’s now complaining of sensory loss over his little finger and medial side of his hand.

What do you think could be causing his symptoms and if left untreated? What could he go on to develop?

Answer 37

Ulnar nerve compression

Could go on to develop weakness/wasting of medial wrist flexors, interossei, medial 2 lumbricals and hypothenar eminence.

Question 38

Mononeuropathies of the hand/wrist.

Answer 38