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FRCS Revision > Upper Limb: Brachial Plexus and Peripheral Nerve injury > Flashcards

Upper Limb: Brachial Plexus and Peripheral Nerve injury Flashcards

1
Q

What are the roots of the brachial plexus?

A

C5-T1
Enter post triangle between Scalenus anterior and Scalenus medius

The roots are surrounded by the fascial sheath known as the axillary sheath from the prevertebral fascia.

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2
Q

What forms the Lateral Cord of the brachial plexus?

A

Anterior divisions from upper and middle trunks

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3
Q

What forms the Medial Cord of the brachial plexus?

A

Anterior divisions from the Lower trunk

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4
Q

What forms the Posterior Cord of the brachial plexus?

A

All 3 Posterior divisions

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5
Q

What are the myotomes associated with C5?

A

Shoulder abduction

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6
Q

Which myotomes are responsible for shoulder adduction?

A

C6, C7, C8

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7
Q

What myotomes are involved in elbow flexion?

A

C5, C6

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8
Q

What myotomes are responsible for elbow extension?

A

C7, C8

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9
Q

Which myotomes control wrist movements?

A

C6, C7

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10
Q

What myotomes are associated with finger movements?

A

C7, C8

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11
Q

What myotome is responsible for intrinsics of the hand?

A

T1

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12
Q

Where do the cords of the brachial plexus lie in relation to the axillary artery?

A

At the first part of the axillary artery, the lateral and posterior cords lie superolateral, whereas the medial cord lies posteriorly. A loop connecting the medial and lateral pectoral nerve also lies anterior to axillary artery.

At the second part of the axillary artery, the posterior, lateral and medial cord are related to the axillary artery as named (ie medial cord lies
Medially)

At the third part of the axillary artery, the cords branch into their branches

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13
Q

How does the Medial cord of the brachial plexus relate to the axillary artery?

A

Crosses behind the artery to lie to the medial side of the 2nd part of the artery under pec minor

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14
Q

Where is the Posterior cord located in relation to the axillary artery?

A

Behind the artery

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15
Q

What is the function of sensory nerves in the brachial plexus?

A

Skin and joints

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16
Q

What is the motor function of the brachial plexus?

A

Muscles

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17
Q

What is the sympathetic vasomotor function associated with the brachial plexus?

A

Diameters of blood vessels

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18
Q

What is the sympathetic secretomotor function associated with the brachial plexus?

A

Sweat glands

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19
Q

What does the suprascapular nerve supply?

A

Supraspinatus and infraspinatus

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20
Q

What does the lateral pectoral nerve supply?

A

Pec Major

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21
Q

What muscle does the thoracodorsal nerve supply?

A

Latissimus dorsi

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22
Q

What is the medial root of the median nerve a continuation of?

A

Medial Cord

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23
Q

What muscles does the median nerve eventually supply?

A
  • Pronator teres
  • Flexor carpi radialis
  • Palmaris longus
  • Flexor digitorum superficialis
  • Thenar muscles
  • 1st 2 lumbricals
  • Digital nerves
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24
Q

What is the axillary nerve responsible for supplying?

A

Shoulder joint, deltoid, and teres minor

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25
Q

What does the upper and lower subscapular nerves supply?

A

Upper and lower parts of the subscapularis muscle

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26
Q

What does the dorsal scapular nerve supply?

A

Levator scapulae and rhomboids

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27
Q

What does the nerve to subclavius supply?

A

Subclavius

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28
Q

What does the musculocutaneous nerve supply?

A
  • Coracobrachialis
  • Biceps
  • Brachialis
  • Elbow joint
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29
Q

What is the largest branch of the plexus?

A

Radial Nerve

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30
Q

What muscles does the radial nerve supply?

A
  • Long head of triceps
  • Medial head of triceps
  • Extensor compartment
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31
Q

What does the ulnar nerve supply in the forearm?

A
  • Flexor carpi ulnaris
  • Flexor digitorum profundus (medial)
  • Palmar cut branch
  • Posterior cut branch
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32
Q

What does the medial cutaneous nerve of the arm supply?

A

Sensation of medial side of arm

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33
Q

What does the medial pectoral nerve supply?

A

Pec Minor and Pec Major

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34
Q

What muscle does the long thoracic nerve supply?

A

Serratus anterior

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35
Q

What is Thoracic Outlet Syndrome?

A

Results from compression of the subclavian vessels and brachial plexus in the base of the neck

36
Q

What anatomical structures constrict the thoracic outlet?

A

Triangle formed by:
* Scalenus anterior (anteriorly)
* Scalenus medius (posteriorly)
* 1st rib (inferiorly)

37
Q

What are some abnormal anatomical conditions that can lead to Thoracic Outlet Syndrome?

A

Conditions include:
* Cervical rib or rudimentary 1st rib
* Abnormal scalenes
* Clavicle fracture

38
Q

What percentage of normals have cervical ribs?

A

0.5% of normals

39
Q

What percentage of Thoracic Outlet Syndrome cases are associated with cervical ribs?

A

10% of thoracic outlet cases

40
Q

What are common causes of Thoracic Outlet Syndrome?

A

Causes include:
* Cervical ribs
* Rudimentary 1st ribs
* Abnormal scalenes
* Bone or soft tissue tumors
* Trauma (e.g., clavicle fracture)
* Poor posture

41
Q

What are the symptoms of Thoracic Outlet Syndrome?

A

Symptoms can be:
* Neurogenic (90% of cases): pain, paraesthesia, weakness, sympathetic symptoms
* Vascular (10%): claudication, splinter haemorrhages, digital emboli, venous engorgement

42
Q

What activities can provoke symptoms of Thoracic Outlet Syndrome?

A

Activities such as carrying heavy loads or working with arms overhead

43
Q

What are the key components of the examination for Thoracic Outlet Syndrome?

A

Key components include:
* Assess sensation and motor function
* Auscultate over the subclavian artery with arms dependent then raised
* Differential blood pressure between limbs
* Specific provocation tests such as Roos test

44
Q

What imaging investigations are used for Thoracic Outlet Syndrome?

A

Investigations include:
* Chest and C spine x-ray
* CT/MRI scanning
* Angiography or venography

45
Q

What medical management options are available for Thoracic Outlet Syndrome?

A

Medical management includes:
* Analgesics
* Carbamazepine
* Amitriptyline
* Benzodiazepines
* NSAIDs

46
Q

What percentage of patients improve with physiotherapy for Thoracic Outlet Syndrome?

A

75% of patients improve with physiotherapy

47
Q

What are the surgical management options for Thoracic Outlet Syndrome?

A

Surgical options include:
* Exploration and decompression
* Supraclavicular (Adson)
* Transaxillary (Roos)
* Posterior parascapular (Claggett)
* Transthoracic

48
Q

What is the pathophysiology of nerve injury

A
  1. electrochemical gradient (conduction loss)
  2. demyelination
  3. axonal disruption (traction injury), Wallerian degeneration (re-growth)
  4. apoptosis - secondary to compression/ischaemia and unable to repair/recover
49
Q

What classification systems are you aware of for peripheral nerve injury?

A

Seddon + Sunderland

Grade 1: Neuropraxia (‘compression’: transient block - mildest form. localised degeneration of myelin sheath. good prognosis if insult removed)

Grade 2: axonotmesis (‘crush’: lesion in continuity, complete interruption of axons and loss of conduction in nerve distal to injury. preservation of surrounding structures - Schwann tubes, epineurium, perineurium; can have good prognosis - wallarian degeneration (regrowth 2-4mm/day)

GRade 3: Neurotmesis (‘‘cut nerve”: myelin sheath and endoneurium are disconnected, loss of axonal continuity, recovery incomplete and variable (months) 1-2mm/day. can get axonal misdirection (mixed sensory/motor cross over)

Grade 4: Neurotmesis (grade 3+ perineurium injury; recovery often incomplete and variable (months-years); little regeneration <1mm/day, little motor or sensory recovery

Grade 5: Neurotmesis (Grade 4+ epineurium injury; recovery often unpredictable, and requires surgery - complete transection of nerve or rupture of nerve trunk!)

50
Q

Describe the types of physiological conduction blocks in PNI

A

Lundenburg Classification:

Type A: The insult has caused intraneural circulatory arrest. This is a form of metabolic block with no nerve fibre pathology. It is immediately reversible (as the insult is transient).

Type B: There has been greater degree of insult to the nerve such that there is intraneural oedema. There is increased endoneurial fluid pressure. It is reversible within days or weeks (after removal of the insult). ie compression/traction injury (recovery days-weeks)

51
Q

What are the symptoms implying axonal disturbance (ie not just a Neurapraxia)?

A

Tinnels +ve
Neuropathic pain
Autonomic dysfunction (dry skin etc)
loss of all modality within nerve (including deep pressure)

52
Q

Describe the surgical options to restore shoulder function following significant PNI

A

Axillary (C5/6) injury -
-deltoid and teres minor (shoulder abduction/ext. rotation)
Suprascapular nerve (C6/7)

Restoration of movement with:

  1. medial triceps (branch of radial nerve) to axillary nerve transfer (preserves long head of triceps function -shoulder stability), easier dissection, longer donor nerve
  2. long head triceps br. to axillary (Somsak/Bangkok)
  3. Spinal accessory nerve to suprascapular nerve (via ant or post approach - **preserve upper trapezius branches)
53
Q

What are the options for reducing a nerve gap for reconstruction?

A
  1. bone shortening
  2. Joint positioning (ie flex wrist in median nerve repair)
  3. Nerve transposition (ie ulnar nerve at elbow)
54
Q

What are the common nerve autografts used in PNI

A

sural nerve (30-40cm)
lateral cutaneous nerve of forearm (5-8cm)
anterior branch of medial antebrachial cutaneous nerve of arm/forearm(10-20cm)
PIN
superficial radial

55
Q

What are the common caused of graft failure in nerve repair?

A

failure of revascularisation
poor donor or recipient nerve
time from injury to surgery?
disruption of the repair
Poor orientation of the co-aptation - ie failure of the axonal growth into the graft)

56
Q

How can nerve transfers be classified?

A

Intraplexal - donor nerve part of brachial plexus or one of its terminal branches (eg medial pectoral, fascicle of ulnar/thoracodorsal/triceps br etc)

Extraplexal: donor nerve originates from outside of the brachial plexus (eg spinal accessory/intercostal ,phrenic/contralateral C7)

57
Q

Describe the surgical options to restore elbow flexion in significant nerve injury

A

Double fascicular transfer (MacKinnon/intraplexal transfer)
- fascicle of ulnar nerve to FCU transfer to biceps branch of musculocutaneous (Oberlin I)
- fascicle of median nerve to FCR to brachialis branch of musculocutaneous (Oberlin II)

Intercostal nerve (if pan plexus injury - extra-plexal transfer)
- typically use ICN 3-5 to Musculocutaneous nerve
- can harvest additional ICN for triceps if needed.
-maybe unusable after rib fractures or intercostal drain.

58
Q

Describe a surgical approach for scapular stabilisation secondary to a long thoracic nerve injury

A

posterior branch thoracodorsal nerve +/- medial pectoral fasciae of middle trunk to innervate lower strips of serratus

59
Q

What is the Narakas’ rule in relation to epidemiology of brachial plexus injuries

A

‘rule of seven seventies’
1. 70% are RTCs
2. 70% of the RTCs are motorbikes or bikes
3. 70% of the cycle riders have multiple injuries
4. 70% of the injuries in cycle riders are supraclavicular
5. 70% of the supraclavicular injuries have at least 1 root avulsed
6. 70% of the avulsed roots are the lower roots (C7/C8/T1)
7. 70% of the avulsed roots are associated with chronic pain

60
Q

Describe the overall anatomy of the brachial plexus

A

Spinal roots C5-T1 (ventral rami)

5 anatomical zones:
1. Roots (ie ventral rami) (between scalenus anterior and scalenes medius)
2. Trunks (in post.triangle neck)
3. Divisions (behind the clavicle)
4. Cords (in axilla names for position relative to axillary artery)
5. Branches (throughout the plexus)

Trunks:
1. C5+C6 combine to form the upper trunk
2. C7 continues as middle trunk
3. C8 and T1 combine to form the lower trunk

Divisions:
All trunks divide into anterior and posterior division
No peripheral nerves arise at this level

Cords:
1. All posterior divisions combine to form the posterior cord
2. The anterior division of the upper and middle trunk combine to form the lateral cord
3. The anterior division of the lower trunk continues as the medial cord

Branches:
terminal branches are Axillary nerve, Muscluocutaneous nerve, Radial nerve, Ulnar Nerve, Median Nerve. Other branches within plexus also.

61
Q

When considering the brachial plexus, which branches arise from the roots of the plexus and what do they supply?

A
  1. Dorsal scapular nerve( C5) - rhomboids/levator scapulae
  2. Long thoracic nerve (C5-C7)- Serratus
62
Q

When considering the anatomy of the brachial plexus, what are the branches from the upper trunk and what do they supply?

A
  1. suprascapular nerve (C5/6) supraspinatus and infraspinatus
  2. Nerve to subclavius (C5/6) - subclavius
63
Q

When considering the anatomy of the brachial plexus, what are the branches form the lateral cord?

A
  1. Lateral pectoral nerve (C5-C7) - clavicular pec major, pec minor
  2. Musculocutaneous (C5-7) - coracobrachialis, biceps, brachialis
  3. Median (C5-T1) - formed by medial and lateral cords
64
Q

When considering the anatomy of the brachial plexus, what are the branches from the medial cord?

A
  1. Medial Pectoral (C8/T1). - sternocostal pec major, pec minor
  2. Medial cutaneous nerve of the arm (C8/T1)
  3. Medial cutaneous nerve of the forearm (C8/T1)
  4. Ulnar (C8/T1) - FCU, FDP ulnar 2 digits, hand intrinsics
  5. Median (C5-T1) - formed by medial and lateral cords
65
Q

Considering the anatomy of the brachial plexus, what are the branches from the posterior cord and what do these nerves supply?

A
  1. upper sub scapular (C5/6) - subscapularis
  2. Thoracodorsal (C6-8) - Lat dorsi
  3. Lower subscapular (C5/6) - subscapularis, teres minor
  4. Axillary (C5/6) deltoid, teres minor
  5. Radial (C5-T1) triceps, atones, brachioradialis, forearm extensor muscles
66
Q

What are the common mechanisms of a closed brachial plexus injury?

A

either individually or a combination of traction/compression/crush

Downward traction causes upper trunk injury.

Traction on abducted arm causes lower trunk injury.

Anterior dislocation of shoulder can be associated with axillary nerve and suprascapular nerve injury.

Compression injury can be secondary to direct compression on plexus or soft tissue oedema/bone fragments/haematoma/pseudoaneurysm etc.

67
Q

Are you aware of any classification system in brachial plexus surgery that addresses aetiology?

A

Lefferts:
Type I: Open (usually stabbing)
Type II: Closed (usually due to RTC)
- IIa: Supraclavicular (preganglionic or post-ganglionic)
-IIb: Infraclavicular
- IIc: Combined
Type III: radiotherapy
Type IV: Obestetric
- IVa: upper roots (Erb’s)
- IVb: lower roots (Klumpkes)
- Ivc: mixed

68
Q

What features on examination of a plexus patient would suggest a preganglionic injury?

A
  1. loss of dorsal scapular and long thoracic nerve (serratus and rhomboids)
  2. Horners (ptosis, mitosis, enophalmos, anhyrosis)
  3. absence of Tinnels sign in posterior triangle of neck
  4. Atrophy of dorsal spinal muscles innervated by dorsal rami
  5. ? partial paralysis of hemi-diaphragm (C3-5)
69
Q

What examination features in a plexus injury patient would be suggestive of a postganglionic lesion?

A
  1. percussion tenderness in supra- or infraclavicular areas
  2. Absence of sweating in territory of injured nerve
  3. Advancing Tinnels, suggesting recovering nerve.
70
Q

What is Acute Brown-Sequard syndrome?

A

Rare, but associated with plexus avulsion
functional distruption of Half spinal cord:
1. ipsilateral UMN lesion below level of injury
2. contralateral deficit in pain and temp sensation

Need urgent C spine MRI to exclude reversible cause of compression (extradural/subdural haematoma)

71
Q

What are the standard investigations in a brachial plexus injury patient?

A

Examination
Electrodiagnostic tests (EMG/NCS)
C spine/chest/shoulder XR - in case of trauma
MRI: can suggest area of plexus injury
CT/MR myelogram help diagnose pseudomeningoceles and root deviations due to root avulsions (must be 1 month post injury)

72
Q

Describe how to interpret nerve conduction studies when considering a patient with brachial plexus injury

A

NCS demonstrates continuity of sensory nerve action potentials (SNAPs)
Combined presence of SNAP, normal sensory conduction velocity in peripheral nerve and paralysed muscle (ie absence motor nerve) indicates ROOT AVULSION (pre-gangionic injury) with preservation of the dorsal root ganglion

this is because although motor axons undergo Wallerian degeneration regardless of the level of injury, because the cell body is in the spinal cord, however, sensory axons do not undergo wallarian degeneration if it is a post-ganglionic injury as the cell body is in the dorsal root ganglion. (therefore SNAPs preserved). Sensory loss occurs because the neuron’s are not connected to the CNS.

Post-ganglionic Injuries do lead to wallarian degeneration so the SNAP is lost.

73
Q

What are the goals of reconstruction in pan-plexus brachial plexus injury

A
  1. resort elbow flexion (hand to mouth)
  2. Stabilse shoulder (to prevent sublimation and support power across elbow) and allow shoulder external rotation
  3. Hand sensitisation
  4. Wrist and finger flexion
  5. Wrist and finger extension
  6. Intrinsic hand muscle function.
74
Q

What are the surgical approaches for access to the brachial plexus?

A
  1. supraclavicular: parallel to the clavicle or posterior border of SCM, gives access to the roots, trunks and suprascapular nerve, osteotomy of the clavicle improves exposure
  2. Infraclavicular: incision usually in the deltopectoral groove, gives access to the cords and branches, pectorals minor is detached from the coracoid process to improve exposure
  3. combined: incision may be joined across the clavicle of kept separate
75
Q

What are the surgical strategies in a C5-6 injury?

A
  1. shoulder control (ax and suprascapular reinnervation)
  2. Elbow flexion (MSc reinnervation)
  3. Thoracobrachial pinch (thoracodorsal and pectoral reinnervation)
76
Q

What would be your surgical strategy in a C5-7 injury?

A

as for C5-6:

  1. shoulder control (ax and suprascapular reinnervation)
  2. Elbow flexion (MSc reinnervation)
  3. Thoracobrachial pinch (thoracodorsal and pectoral reinnervation)

Plus:

  1. Wrist extension
  2. Elbow extension
77
Q

What would be your surgical strategy in a C8-T1 injury?

A

Reinnervation is unlikely to success due to the long rein nervation distances
Rely on tendon transfers and free functioning muscle transfers
Aim to restore:
1. flexion/extension of fingers and thumb
2. Opposition
3. Correction of claw deformity

78
Q

Describe the options for a free functioning muscle transfer in a brachial plexus patient. What are the common muscles used? How are suitable muscles defined?

A

Suitable muscles need to have:
1. vascular pedicle amenable to free transfer
2. Sufficient length, contraction and force to fulfil its new function
3. Acceptable donor site morbidity

Common muscles:
LD
Gracilis
Rectus femoris

FFMT can be used acutely (Doi procedure)

  1. Elbow flexion with finger and wrist extension is achieved with one gracilis.
    -gracilis is attached to clavicle, routed under brachioradialis, inset into extensor digitorum tendons
    -anastomosed to thoracoacromial artery, cephalic vein and accessory nerve
  2. a second gracilis can be transferred for finger flexion
    - gracilis is attached to the second and third ribs and to FDP tendons
    - anastamosed to thoracodorsal vessels and intercostal nerves 5 and 6
79
Q

What tendon transfers can be done as a salvage procedure in the case of failed shoulder reinnervation post plexus injury?

A

Tendon transfers for rotator cuff or deltoid function:
- upper trapezius transfer to humerus to stabilse shoulder
- lower trapezius
- LD/teres major rerouting to restore shoulder abduction and external rotation
- Pec major for shoulder abduction

80
Q

What tendon transfers can be done as a salvage procedure in the case of failed restoration elbow flexion post plexus injury?

A

-Pectoralis major
- triceps
- LD
- SCM
- Steindler flexorplasty (transposes the common flexor origin to a more proximal and anterior position on the humerus, increases those muscles’ moment arm for elbow flexion

81
Q

What is the incidence of obstetric brachial plexus injury?

A

0.5-3/1000 live births

82
Q

What are the risk factors for obstetric brachial palsy?

A

Maternal risk factors:
- DM (increased risk fatal macrosomia)
- prev obstetric complications
- multiparous pregnancy

Child risk factors:
- large baby >500g, above average birth weight
- breech

Parturition risk factors:
- prolonged second stage labour
- instrumental delivery
- shoulder or head dystocia

83
Q

What are the common patterns of obstetric brachial plexus palsy?

A

C5-6 (46%)
C5-7 (29%)

(Erbs palsy - upper trunk)

4-5% bilateral

non-plexus causes of palsy: brain injury, limb fractures, congenital causes (arthrogyroposis, synostosis)

84
Q

What is the Narakas classification for obstetric brachial plexus palsy?

A

Group 1: C5-6: paralysis of shoulder and elbow flexion
-spontaneous recovery >80%

Group 2: C5-7, as above with wrist drop
- spontaneous recovery >60%

Group 3: C5-T1, complete flaccid paralysis
- spontaneous recovery 30-50%
- many have a functional hand

Group 4: C5-T1, complete flaccid paralysis with Horner’s
- worst prognosis

85
Q

How are obstetric brachial plexus injuries managed?

A

Most managed non-operatively - passive exercises to maintain ROM until plexus recovers

Surgery usually indicated in Narks group 4 or T1 root avulsion

Repeated examination helps to guide treatment. partial recovers (at least MRC grade M3) within 2 months usually leads to full recovery by age of 2

If some of biceps and shoulder function has not recovered by 6/12 old may recommend reconstruction

Priorities are a bit different in children. -prioritise hand over shoulder. nerve grafting and transfer can reinnervate the hand due to shorter growth distances (unlike in adults)

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