Peripheral Nerve Entrapment

Question 1

What are the Sunderland classifications of nerve injury?

Answer 1

Type 1: neuropraxia = damage to local myelin only
Type 2 : axonotmesis = axon severed but endoneurium intact (optimal for regeneration)
Type 3 : axonotmesis = axon discontinuity, endoneurial tube discontinuity, perineurium and fascicular arrangement preserved.
Type 4: axonotmesis = loss of continuity of axons, endoneurial tubes, perineurium and fasciculi, perineurium intact
Type 5: neurotmesis = complete physiologic disruption of entire nerve trunk

Question 2

What are the most common compression neuropathies in upper limb?

Answer 2

Carpal tunnel syndrome
Cubital tunnel syndrome

Question 3

what is the pathology of carpal tunnel syndrome?

Answer 3

Nerve entrapment disorder - compression of wrists median nerve (median nerve passes through carpal tunnel)
Repetitive stress injury in susceptible people = inflammation = oedema = fluid in narrow space compresses structures = nerve injury, impaired neuronal transport/vessel compression, nerve ischaemia.

Question 4

What is the anatomy of the carpal tunnel?

Answer 4

Formed by two layers: a deep carpal arch and a superficial flexor retinaculum.
Carpal arch - concave on plamar side, forming base and side of tunnel. Formed laterally by scaphoid and trapezium tubercles. Formed medially by hook of hamate and pisiform.
Flexor retinaculum - thick connective tissue from the roof of the carpal tunnel. Bridges the space between the medial and lateral parts of the arch. Span etween the hook of hazmat and pisiform (medially) and the scaphoid and trapezium (laterally).

Question 5

What are the causes of carpal tunnel syndrome?

Answer 5

Tendonitis
Oedema
Repetitive stress injury (typing)

Question 6

What are the risk factors for carpal tunnel syndrome?

Answer 6

Obesity
Pregnancy
Other underlying conditions - RA
Trauma
Genetic predisposition
Occupation
Acromegaly
Myxoedema

Pneumonic TRAMP (trauma, RA, acromegaly, myxoedema, pregnancy)

Question 7

What is a key complication of carpal tunnel syndrome?

Answer 7

The article muscle atrophy

Question 8

What are the symptoms of carpal tunnel syndrome?

Answer 8

Usually unilateral symptoms
Individual may awake with numbness, tingling (after day of use = worse at night.
Initially dull ache. Discomfort, paraesthesia sharp pain extending to forearm.
Pain, numbness, tingling in thumb, index finger, middle finger, thumb side of ring finger on palmar side of hand.
Clumsiness, dropping small objects.
No sensation loss in palms central region - palmar branch of median nerve innervates it, branches off before going through carpal tunnel.

Question 9

What other diagnostics are used for carpal tunnel syndrome?

Answer 9

EMG - identifies neuropathic changes - sharp waves, increased insertion all activity
NCS - reduced response amplitude
Physical exam:
- phalen manoeuvre: pressing of upper hands together while flexing writs induces pain
- tinel’s signs: tapping on wrist over median nerve elicits pain
- durkan’s test: pressing of median nerve for 30s worsens symptoms
- thenar eminence atrophy

Question 10

What is the treatment for carpal tunnel syndrome?

Answer 10

Medications - corticosteriod injection to reduce inflammation
Surgery - cut transverse ligament to relive pressure
Behaviour modifications - adjusting typing position, weight loss
Wrist supports, splints
Physio - relive wrist strain so reduce symptom severity.

Pneumonic WRIST (wear splints at night, rest, inject steroid, surgical decompression, take directs)