Brachial Plexus Flashcards

1
Q

What is the most common mechanism for brachial plexus injuries?

A

Closed injury (traction, compression, or combination of the two).

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2
Q

What is the most common location of brachial plexus injuries?

A

Supraclavicular, root and trunks.

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3
Q

What is the typical mechanism of a C8-T1/lower trunk traction injury?

A

Forceful abduction of the arm overhead.

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4
Q

What brachial plexus injury is typically produced by violent lateral bending of the head and neck?

A

Traction injury of C5, C6/upper trunk.

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5
Q

What is a common site for brachial plexus compression injuries?

A

Between clavicle and first rib, near the coracoid process.

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6
Q

What are the demographics of the majority of patients with brachial plexus injuries?

A

Male, aged 15 to 25.

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7
Q

What proportion of brachial plexus injuries occur in motor vehicle accidents?

A

70%.

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8
Q

What type of vehicle is most commonly implicated in brachial plexus injuries?

A

The motorcycle (70% of motor vehicle accidents). Snow mobiles in colder climates.

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9
Q

At what level do most root avulsions occur?

A

Lower roots (C7, C8, T1)

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10
Q

How many nerve roots form the brachial plexus?

A

Five (C5–8, T1).

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11
Q

What term describes a contribution of the C4 nerve root to the brachial plexus?

A

Prefixed plexus

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12
Q

What phenomenon is described by the term “postfixed” brachial plexus?

A

T2 contribution to the plexus

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13
Q

What are the five separate sections of the brachial plexus?

A

Roots, trunks, divisions, cords, terminal branches.
(Robert Taylor Drinks Coffee Black)

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14
Q

What structure is formed by coalescence of the ventral and dorsal rootlets?

A

The nerve root.

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15
Q

What vascular structure is associated with the C7 root in the exposure of the cervical region of the brachial plexus?

A

Transverse cervical artery.

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16
Q

The medial cord of the brachial plexus receives contributions from which nerve roots?

A

C8 and T1.

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17
Q

Where does the nerve root leave the spinal canal?

A

Through the neuroforamen.

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18
Q

What is contained in the dorsal root ganglion?

A

The cell bodies of the sensory nerves.

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19
Q

Where do the motor nerves travel?

A

In the volar root ganglion. (V-volar, Vroom!!)

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20
Q

What is described by the term preganglionic brachial plexus lesion?

A
  1. lesion proximal to the dorsal root ganglion
  2. intradural rupture of the rootlets
  3. avulsion from spinal cord
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21
Q

How are the upper, middle, and lower trunk typically formed?

A

Upper trunk by C5 and C6.
Middle trunk by C7.
Lower trunk by C8 and T1.

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22
Q

What is Erb point?

A

Point where C5 and C6 merge to form upper trunk.

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23
Q

What structures join to become the posterior cord?

A

All three posterior divisions.

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24
Q

What is formed by the anterior divisions of the upper and middle trunk?

A

The lateral cord.
(Imagine a football announcer, “Number 34 runs up [upper trunk] the middle [middle trunk] and throws a lateral [lateral cord]!”)

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25
Q

What continues as the medial cord?

A

The anterior division of the lower trunk.

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26
Q

The cords are named after their location in relation to which structure?

A

The axillary artery.

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27
Q

What part of the brachial plexus crosses underneath the clavicle?

A

The divisions.

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28
Q

What muscles are innervated by the dorsal scapular nerve?

A

Rhomboid major/minor and levator scapulae.

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29
Q

What are the terminal branches of the posterior cord?

A

Proximal to distal:
1. upper subscapular n. 2. thoracodorsal n.
3. lower subscapular n. 4. axillary n.
5. radial n.

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30
Q

What branches originate at the C5 root level?

A
  1. phrenic n. contribution
  2. long thoracic n. contribution
  3. dorsal scapular n. (levator scapulae, rhomboids)
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31
Q

What are the terminal branches of the medial cord?

A

Four “medial (or median)” structures and the ulnar nerve.
Medial pectoral n.
medial brachial cutaneous n. medial antebrachial cutaneous n. contribution to the median n. ulnar n.

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32
Q

What are the branches of the lateral cord?

A
  1. lateral pectoral n.
  2. contribution to the median n. 3. musculocutaneous n.
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33
Q

What branches originate from the upper trunk?

A

Suprascapular n. nerve to the subclavius.

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34
Q

Where is the inferior cervical sympathetic ganglion located?

A

In proximity of the T1 nerve root.

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35
Q

What is Horner syndrome?

A
  1. ptosis
  2. miosis
  3. anhydrosis
  4. enophthalmos
    This constellation indicates a lesion of the cervicothoracic sympathetic ganglion (adjacent to C8, T1) disrupting the oculosympathetic pathway.
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36
Q

How is muscle strength graded?

A

By the British Medical Research Council grading system:
M0: no evidence of contractility
M1: evidence of contractility but no motion
M2: complete range of motion with gravity eliminated M3: complete range of motion against gravity
M4: complete range of motion against some resistance M5: normal power

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37
Q

Examination of which upper extremity functions will test for the condition of the posterior cord?

A
  1. wrist extension (radial n.)
  2. elbow extension (radial n.)
  3. shoulder abduction (axillary n. via deltoid)
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38
Q

How can the condition of the suprascapular n. be tested?

A
  1. shoulder elevation (supraspinatus)
  2. external rotation (infraspinatus)
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39
Q

What is a strong indicator for a preganglionic lesion at the C8 and T1 nerve roots?

A

Presence of a Horner syndrome (indicating a lesion of the cervicothoracic sympathetic ganglion [adjacent to C8,
T1]).

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40
Q

Dysfunction of which nerve will result in scapular winging with forward elevation of the shoulder?

A

Long thoracic nerve via serratus anterior (SALT—serratus anterior long thoracic).

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41
Q

What is the significance of transverse process fractures on the cervical spine x-rays in brachial plexus patients?

A

May indicate root avulsion.

42
Q

What findings on a chest x-ray may point toward a brachial plexus lesion?

A

Fractures of the first and second rib.

43
Q

What is the significance of pseudomeningoceles on a cervical CT myelogram?

A

Indicates root level injury.

44
Q

What finding would be expected on the chest x-rays of patients with phrenic nerve injury?

A

Elevation of ipsilateral hemidiaphragm.

45
Q

What do fibrillation potentials in the EMG indicate?

A

Denervation of the tested muscles (just like the heart fibrillates when it is dying).

46
Q

After acute brachial plexus injury, how soon would muscles exhibit fibrillations in the EMG?

A

10 to 14 days for proximal muscles and 3 to 4 months for distal muscles.

47
Q

What evidence can be found in electrodiagnostic studies of preganglionic lesions?

A

Preservation of sensory nerve action potentials (SNAPs).

48
Q

What is the significance of the appearance of nascent potentials in follow-up EMGs?

A

Early sign of reinnervation.

49
Q

What does the presence of intraoperative nerve action potentials (NAPs) across a lesion indicate?

A

Intact axons.

50
Q

How many patients with detectable NAPs across a lesion will make a clinically useful recovery?

A

90%.

51
Q

What pattern of NAPs would be expected in a preganglionic plexus lesion?

A

Accelerated conduction velocity with increased amplitude.

52
Q

What do motor evoked potentials assess?

A

Integrity of motor pathway via the ventral root (remember Vroom)

53
Q

How can the integrity of the sensory pathway via the dorsal roots be tested?

A

Somatosensory evoked potentials.

54
Q

When is immediate exploration and primary repair of brachial plexus injuries indicated?

A

Sharp, open injuries.

55
Q

What is the preferred treatment for low-velocity gunshot wounds of the brachial plexus?

A

Observation, local would management.

56
Q

What type of nerve injury is typically associated with low-velocity gunshot wounds?

A

Neuropraxia.

57
Q

What is the recommended time frame for brachial plexus exploration in stretch injuries that fail to recover?

A

3 to 6 months.

58
Q

What is the order of priority for restoration of function to the flail extremity?

A
  1. elbow flexion
  2. shoulder abduction/stability
  3. hand sensibility
  4. wrist extension/finger flexion
  5. wrist flexion and finger extension
59
Q

What type of injury is preferably addressed with primary nerve repair?

A

Sharp laceration, not possible in stretch injuries.

60
Q

What procedure needs to be performed to facilitate intraoperative nerve conduction studies?

A

External neurolysis.

61
Q

What is the treatment for electrically silent ruptures or neuromas of the brachial plexus that are electrically
silent?

A

Interpositional nerve grafting (eg, sural cable graft).

62
Q

What upper extremity function should be targeted if interpositional nerve grafting from a functioning C5 nerve root is performed?

A

Shoulder abduction (suprascapular, axillary nerves).

63
Q

What nerve root (when available) should be used to restore elbow flexion by interpositional sural nerve grafting?

A

C6 (musculocutaneous n.).

64
Q

How can triceps function be restored in a patient with a brachial plexus injury at the trunk level?

A

By interpositional grafting from C7 across the zone of injury.

65
Q

What is the likely etiology of neuropathic pain after brachial plexus reconstruction?

A

Regenerating axons from non-avulsed nerve roots.

66
Q

What type of brachial plexus injuries requires the use of nerve transfer (neurotization) to restore function?

A

Preganglionic injuries.

67
Q

How can a nerve transfer accelerate recovery of function?

A

By decreasing the distance between the nerve repair site and the end organ (muscle).

68
Q

What is the Oberlin transfer?

A

Transfer of select ulnar nerve fascicles in the upper arm to motor branches of the musculocutaneous nerve to the
biceps to restore elbow flexion.

69
Q

What nerve has been used successfully to neurotize the serratus anterior muscle to address scapular winging?

A

Thoracodorsal nerve.

70
Q

What function can be restored by neurotizing the suprascapular nerve with spinal accessory or phrenic nerve?

A

Shoulder abduction/external rotation.

71
Q

What nerve can be targeted in addition to suprascapular nerve to further improve shoulder abduction?

A

Axillary nerve.

72
Q

What nerve transfers are commonly used for restoration of biceps function after upper trunk disruption?

A

Medial pectoral nerve to musculocutaneous nerve or the biceps motor branch Oberlin transfer.

73
Q

What is the advantage of the Oberlin transfer over interpositional nerve grafts from C6 to regain biceps
function?

A

Faster and more predictable recovery of function.

74
Q

In the Oberlin transfer fascicles of the ulnar nerve transmitting which function should preferably be used?

A

Fascicles that stimulate wrist flexion (FCU).

75
Q

What modification of the Oberlin transfer is available to improve recovery of elbow flexion strength?

A

Double fascicular nerve transfer described by MacKinnon et al.

76
Q

What additional muscle is targeted in the double fascicular nerve transfer of the Oberlin transfer?

A

Brachialis muscle.

77
Q

What donor fascicles are used to neurotize the brachialis muscle in the double fascicular nerve transfer?

A

FCR or FDS fascicles of the median nerve.

78
Q

What donor nerves are available for neurotization to restore elbow flexion in a “panbrachial” plexopathy without signs of recovery?

A
  1. intercostal nerves
  2. spinal accessory via nerve grafts
  3. phrenic nerve with interpositional grafts
79
Q

Comparing intercostal and partial ulnar nerve transfers to the biceps branch of the musculocutaneous nerve, which restores elbow flexion more successfully?

A

Partial ulnar nerve (Oberlin).

80
Q

What is the advantage of a vascularized nerve graft?

A

Reinnervation at a faster rate (theoretically)

81
Q

What contralateral nerve root can be used as a donor of large amounts of motor axons?

A

C7—usually half of it.

82
Q

What function is addressed by contralateral C7 transfer via vascularized ulnar nerve to the median nerve?

A

Finger flexion.

83
Q

What overall success rate can be expected with nerve transfers to the musculocutaneous nerve?

A

71% flexion strength > M3, 37% > M4.

84
Q

What is the success rate of the Oberlin transfer?

A

97% for >M3, 94%>M4.

85
Q

How much shoulder abduction can be expected in a good result after nerve transfer?

A

45◦ .

86
Q

What options are available for restoration of elbow flexion in patients that present late (>12 months after
injury)?

A
  1. free functioning muscle transfer
  2. tendon transfer of available, expendable muscles
  3. Steindler flexorplasty (transposition of flexor-pronator origin to anterior humerus) 4. pectoralis major transfer
  4. latissimus dorsi transfer
  5. triceps transfer
87
Q

What are the risk factors for obstetrical brachial plexus palsy?

A
  1. increased birth weight
  2. vertex presentation
  3. births that require instrumentation for delivery 4. shoulder dystocia
88
Q

What are causes for obstetric brachial plexus injury (birth palsy)?

A

Traction injury secondary to
fetal malposition cephalopelvic disproportion forceps use

89
Q

What are the three distributions observed in obstetric brachial plexus palsy?

A
  1. Erb palsy
  2. Panplexus palsy 3. Klumpke palsy
90
Q

What nerve roots are involved in Erb palsy?

A

C5-6—upper roots.

91
Q

What nerve roots are involved in Klumpke palsy?

A

C5-T1—lower roots.

92
Q

What is considered an indication for surgery in obstetric brachial plexus injuries?

A

Absent biceps recovery at age 3 months.

93
Q

What does the Mallet classification assess?

A

Upper extremity function

94
Q

Which root levels are more likely to be affected by root avulsions?

A

Lower levels C8, T1.

95
Q

What is the mainstay for treatment of children with partial lesions?

A
  1. Conservative treatment
  2. ROM exercises
  3. Prevention of contractures
96
Q

What is the typical pattern of contracture of the shoulder in children with brachial plexus birth palsy?

A

Internal rotation
Adduction.

97
Q

What is a common complication due the internal rotation contracture in children with brachial plexus birth palsy?

A

Posterior shoulder dislocation.

98
Q

What nonsurgical treatment can be used to treat early posterior shoulder dislocation due to internal rotation contracture?

A

Closed reduction and Botulinum toxin A injection into the shoulder internal rotators.

99
Q

What tendon transfer can be used to improve external rotation of the shoulder and prevent the development of internal rotation contracture?

A

Transfer of latissimus dorsi and teres major to the humeral greater tuberosity.

100
Q

What deformity of the elbow will frequently develop in children with obstetric brachial plexus palsy?

A

Posterior radial head dislocation. Typically by age 5 to 8 years.

101
Q

What is a typical finding at the forearm in children with obstetric palsy?

A

Supination contracture.