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Block 4 > Upper Limb Nerve Injury > Flashcards

Upper Limb Nerve Injury Flashcards

1
Q

Why does the resting position of limbs change when there is nerve damage?

A

Due to unopposed pull of muscles that remain innervated

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2
Q

Sensory loss with nerve root damage will be ____.

A

Dermatomal

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3
Q

What would be the affects of musculocutaneous nerve damage?

A

Loss of most anterior arm compartment muscles but not part of brachialis (radial n.) so there will be:

  • Weakened elbow flexion
  • Weakened supination
  • Weak flexion as brachioradiialis affected but part of brachialis (radial n.) and forearm flexors from common flexor origin (media and ulnar n.) are not
  • Weakened biceps tendon (C5/6) reflex
  • Sensory loss over lateral forearm (C6)
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4
Q

How could the axillary nerve be damaged? What would be the affects?

A

Dislocation of shoulder or surgical neck humerus # (may also damage circumflex humoral vessels which can lead to compartment syndrome and pain, colder and weaker limbs)

Loss of deltoid and teres minor so patient will not be able to adduct arm and shoulder becomes relatively immobile

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5
Q

What would be the affects of median nerve damage?

A

Loss of most anterior compartment forearm muscles, thenar muscles and lumbricals 1 and 2 resulting in the hand of benediction but also sensory changes/loss of lateral 3.5 digits on palmar side inc. thumb

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6
Q

What would be the affects of damaging the radial nerve?

A

Loss of posterior arm and posterior forearm compartment muscles

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7
Q

What would be the affects of ulnar nerve injury?

A

Loss of most small muscles of hand and a couple forearm muscles leading to an ulnar claw where the lateral 3 fingers are extended but the medial 2 are flexed

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8
Q

How/where is the median nerve injured?

A
  • Median arm or cubital fossa puncture wound/laceration
  • Trapped between 2 heads of pronator teres
  • Forearm prior to carpal tunnel (e.g. defence wound or suicide attempt)
  • CTS
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9
Q

What does the median nerve supply?

A

Everything in anterior forearm except FCU and FDP to digits 4 and 5 along with the thenar muscles and lumbricals to digits 2 and 3

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10
Q

What would be the effects of damaging the median nerve at the elbow or proximal?

A
  • Cant make fist with digits 2 and 3
  • No active flexion of IP joints of digits 1, 2 and 3
  • Weaker flexion of digits 4 and 5 because you have no FDS but FDP from ulnar nerve
  • No forearm pronation
  • Weak wrist flexion that deviates to adduction as FCU is ulnar nerve
  • Plus issues seen with wrist injury
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11
Q

What would be the effects of damaging the median nerve at the wrist?

A
  • Thenar wasting and thumb opposition not possible
  • Thumb laterally rotated and adducted looking like a finger
  • Digits 2 and 3 lag in fist making as lumbricals 1 and 2 are paralysed
  • Sensory changes: palm spared in CTS but inc. with volar distal forearm laceration
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12
Q

How/where is the ulnar nerve injured?

A
  • Medial epicondyle by # or compression (e.g. haematoma as a result)
  • Cubital tunnel compression
  • Penetrating injury on anterior wrist near at pisiform
  • Wrist compression superficial to flex`ior retinaculum (Guyon’s canal)
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13
Q

What does the ulnar nerve supply?

A

FCU and FDP to digits 4 and 5 along with all intrinsic hand muscles except the thenar and lumbricals to digits 2 and 3

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14
Q

What is the difference between the ulnar claw hand and hand of benediction?

A

Ulnar claw hand: MCP joints of the 4th and 5th fingers are extended and the IP joints of the same fingers are flexed passively due to tone of extensor expansion often accompanied with difficult ad/abducting 2nd, 3rd, 4th and 5th digits - most prominent at rest or when patient extends fingers

Hand of benediction: hyper-extension of MCPs from the unopposed extensor digitorum as well as weakened extension and flexion of the IP joints of the 2nd and 3rd digits often accompanied by difficulty opposing thumb - most prominent when patient asked to make a fist

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15
Q

Where will you see wasting with ulnar nerve and median nerve lesions?

A

Ulnar: 1st dorsal interosseous muscle of hand

Median: thenar eminence

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16
Q

How does the extensor expansion work?

A

Anything pulling from behind it will extend the digits however, anything pulling in front of MCP joint, will flex MCP joint but passively extend the IP joints

17
Q

How are the metacarpophalangeal (MCP) joints finely controlled?

A

Interossei and lumbricals balance the crude powerful pull of the long extensors and flexors essentially acting as antagonists

18
Q

What would happen if there was a lack of refined metacarpophalangeal (MCP) flexion by lumbrical contraction?

A

MCP extension at rest

19
Q

What would be the effects of ulnar nerve damage at the elbow or proximal?

A
  • No flexion of DIP joints of digits 4 and 5 due to lack of FDP
  • Weaker wrist flexion where wrist will abduct on flexion due to lack of FCU
  • No digit ab/adduction (exc. thumb abduction)
  • Plus damage seen with wrist injury EXCEPT clawing is less as FDP no longer works = ULNAR PARADOX
  • Sensory loss in ulnar territory of hand
20
Q

What would be the effects of ulnar nerve damage at the wrist?

A
  • Loss of most intrinsic hand muscles
  • Hypothenar and interosseous wasting (guttering on dorsal hand)
  • Pronounced clawing of digits 4 and 5 worse as FDP still work exacerbating IP joint flexion
  • No clawing of digits 2 and 3 as lumbricals 1 and 2 are functional (median n.)
  • Sensory loss may be limited to digits (palm and dorsum spread)
21
Q

What are the roles of lumbricals and interossei muscles?

A

Lumbricals: attach to deep flexor tendon so look like their floating but they contract in front of extensor expansion on palmar side flexing MCP and extending PIPs/DIPs (important position for most dextrous activities of hand)

Interossei: same but also ab/abduction too

22
Q

Why does the ulnar claw hand occur?

A

Lumbricals and interossei of digits 4 and 5 are lost so strong pull of extensor tendons now not resisted so MCP will become extended and PIP/DIP will become flexed passively due to extensor expansion tone

This will not be as severe if injured at elbow as deep flexors for digits 4 and 5 by the FDP of the forearm will be lost so there is less muscle to bring digits into a tighter claw but if they are still working if damaged at wrist, there will be more tone to pull the claw tighter

23
Q

How/where is the radial nerve injured?

A
  • Axilla (shoulder dislocation, crutch or asleep over upper limb)
  • Spiral groove (humeral shaft # or compression due to sleeping arm again)
  • Head/neck of radius issue would dislocation or # due to traction injury would damage PIN e.g. swinging or pulling a childs arm
  • Arcade of Frohse entrapment of PIN between 2 heads of supinator
24
Q

What would be the effects of damaging the radial nerve in the axilla?

A

All function lost:

  • No elbow extension as triceps lost
  • Wristdrop into flexion
  • No digit extension
  • Sensory loss on dorsolateral forearm and hand
25
Q

What would be the effects of damaging the radial nerve in the spiral groove?

A
  • Elbow extension preserved but weaker
  • Wristdrop into flexion
  • No digit extension
  • Weak thumb abduction
  • Sensory loss on dorsolateral forearm and hand
26
Q

What would be the effects of damaging the posterior interosseous nerve (PIN) branch of the radial nerve at the radial head/neck?

A
  • Elbow extension normal
  • Minimal wrist drop as ECR supplies it earlier
  • Digit extension weak/absent
  • Weak thumb abduction
  • No sensory loss as this is a motor nerve
27
Q

If a patient has wrist drop, what cant they do?

A

Make a tight fist at the wrist needs to be neutral or slightly extended to make a fist

28
Q

What reflex can be tested for the radial nerve?

A

Triceps tendon reflex

29
Q

If the radial nerve has been cut, what peripheral nerve can be used as a graft to repair it and why?

A

Sural nerve from lateral lower leg near lateral malleolus can be harvested as a spare part as it doesn’t have a big motor function and only minimal sensory function - can take out the whole nerve or half with only slight sensory loss

30
Q

Can the ends of a cut nerve be stitched together?

A

Yes

31
Q

How/where is the musculocutaneous nerve injured?

A

Rarely damaged but trauma around coracoid process OR associated with C5/6 plexus damage

32
Q

What is the role of the long thoracic nerve? How can it be damaged?

A

Innervates serratus anterior that protracts scapula allowing you to reach out and holds it close to thoracic wall

Damaged in axillary surgery (breast) causing scapula to wing

33
Q

What is Klumpke’s palsy?

A

C8/T1 root damage/compression of brachial plexus that’s less common but caused by upward traction of upper limb or cancer at lung apex/compression via cervical rib affecting parts of ulnar and median nerves causing:

  • Paralysis/wasting of ALL small muscles of hand
  • Clawing of digits 2-5 at rest due to unopposed action of extensors on MCP joint and long flexors on IP joints
  • Sensory loss of medial elbow, forearm and arm
34
Q

What is Erbs palsy?

A

C5/6 upper root/trunk damage of brachial plexus via forced separation of neck from shoulder e.g. in motorcycle accidents or during birth i.e. traction injuries (called shoulder dystocia if occurs to baby in birth) but can also be due to stab wound to neck or iatrogenic causes resulting in a ‘waiters tip’ appearance of upper limb

35
Q

What are the nerves of the brachial plexus mainly formed by C5 and C6 neurons? What would occur if they was damaged?

A
  1. Musculocutaneous: previous
  2. Axillary: previous
  3. Lateral pectoral: loss of clavicular head of pectoralis major
  4. Suprascapular: supraspinatus and infraspinatus affected so shoulder lateral rotation and stability compromised
  5. Dorsal scapula (mainly C5): rhomboid function and levator scapulae affected
36
Q

How can the brachial plexus be damaged at T1 root? What would happen?

A

Lung apex tumour e.g. Pancoast

Wasting of small muscles of hand would show and may be the 1st sign

37
Q

What will be the symptoms of Erb’s palsy?

A

Loss of C5/6 will mean the patient loses axillary, suprascapular, dorsal scapula, lateral pectoral and musculocutaneous nerves so:

  • Loss of supra/infra-spinatus and unopposed medial rotation action from sternal head of pectoralis major = medially rotated shoulder
  • Loss of deltoid = limp and loss of shoulder contour
  • Loss of biceps brachii = pronated forearm
  • Loss of ECR = partial wrist drop/flexion at wrist
  • Sensory loss over C5/6 dermatomes over lateral arm and forearm
38
Q

When cannulating the cephalic vein at the anatomical snuffbox, what is at risk of damage?

A

Cutaneous branch of radial nerve that provides sensory innervation

Block 4 (33 decks)

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