June 20, 2024

Brachial Plexus injuries are one of the most important topics, its pathogenesis investigation and management are to be known.

Anatomy of brachial plexus

anatomy of brachial plexus
Anatomy of brachial plexus

C5 – C8 nerve roots are lateral to scalene muscles

Branches from roots

  1. Dorsal Scapular nerve (C5): Rhomboids and levator scapulae
  2. Nerve to subclavius (C5, C6): Subclavius
  3. Long thoracic nerve (C5, C6, C7): Serratus anterior

Branches from the Upper trunk

Lower and middle have no branches

  1. Suprascapular nerve (C5, C6): Supraspinatous and Infraspinatous

Branches from Lateral Cord (LML)

  1. Lateral pectoral nerve (C6): Upper half of pectoralis major
  2. Lateral head of median nerve (C6, C7)
  3. Musculocutaneous nerve (C5, C6, C7)- BBC
    • Biceps
    • Brachialis
    • Coracobracialis

Branches from Medial Cord (4MU)

  1. Medial pectoral nerve: Sternocostal fibres of pectoralis major
  2. Medial cutaneous nerve of arm
  3. Medial cutaneous nerve of forearm
  4. Medial head of median nerve
  5. Ulnar nerve (C7, C8, T1)

Branches of Posterior Cord (ULNAR)

  1. Upper subscapular nerve (C6, C7): Subscapularis
  2. Lower subscapular nerve (C6, C7): Subscapularis and teres major
  3. Nerve to latissmus dorsi
  4. Axillary nerve (Deltoid and teres minor)
  5. Radial nerve

Etiopathogenesis of brachial plexus injury

Traction or over stretching

The Head is flexed laterally towards the opposite side, and the shoulder is depressed (Birth trauma, breech delivery)

Shoulder dislocation, Mild overstretching of nerve fibers to avulsion of the nerve root from cords or through the intervertebral foramen

Meninges have torn away, membrane heals with the formation of empty meningocele which extends through rupture foramen

Rupture of nerve fiber is most frequently in that portion of the plexus that is subjected to the greatest stretch (C5, C6)

Rupture of C5 and C6 group of roots will paralyze following groups of muscles:

  • Subclavius, Supraspinatus, and infraspinatus
  • Deltoid and teres minor
  • Brachioradialis, biceps brachii, and brachialis

Compression

  • Fracture of the clavicle and its callus formation
  • Infections
  • Subsequent scar contracture
  • Tumor
  • Hemorrhages
  • Consequence cicatrix
  • Direct blow to the side of the neck

Penetrating trauma

Includes stab or gunshot wound

Interruption of function is immediate

Positive Tinel signs in supraclavicular region is a strong indicator of nerve rupture as opposed to an avulsion.

Horner’s Syndrome:

A strong indicator of avulsion of one or both lower nerve root

Disruption of sympathetic supply of ipsilateral eye and face

Miosis, ptosis and anhydrosis

Preganglionic vs postganglionic injury

Features (SWS MED THR)PostganglionicPreganglionic
Sensation
Wallerian degeneration+
Sensory NCV+
Motor NCV
Paracervical EMG+
Myelogram+
Diaphragm paralysis+
Tinel Erbs point+
Horner’s syndrome
RepairableYesNo

Investigation of brachial plexus injury

A. Radiological Study

X-Ray

Complete radiological of cervical spine, clavicle, shoulder, and chest

Transverse process fracture of the cervical spine: Root avulsion

Rib fracture: Could indicate intercostal nerve: Potential source of nerve transfer

Full inspiration and expiration: Chest radiograph (Upper trunk of plexus injury): Diaphragmatic paralysis

CT/ Myelography

Gold standard for evaluating the root avulsion

Consistent with preganglionic lesion

  • Presence of pseudomeningocele
  • Obliteration of root pouch
  • An absence of nerve root
  • Shifting of cord away from the midline
  • Cystic accumulation of cerebrospinal fluid

MRI

Another modality to visualize plexus injury

Good visualization of the plexus more distally can help establish plexus of injury distally

Still not as reliable as CT/Myelography

B. Electrophysiological Studies

EMG and NCS

Localization as well as monitoring of post-injury progress

Should be evaluated with clinical pictures

Paraspinal muscle testing with EMG should be performed to determine whether the corresponding roots are

  • Ruptured (post-ganglionic)
  • Avulsed (pre-ganglionic)

If these muscles are denervated, finding include corresponding root avulsion

If these muscles are intact, the injury is most likely infra-ganglionic more distal, and repairable

A disruption in the axon will produce time-related electrical changes that will represent the pathophysiological of the denervation.

Denervation potential will appear around 3 weeks after injury: Wallerian denervation

Along with the motor, sensory conduction studies must be performed because insensible arm testing produces normal sensory conduction velocities indicating root avulsion.

The purpose of the EMG study is to access the nature of the lesion and to determine the severity according to the Sunderland classification.

EMG is unable to differentiate whether the peripheral nerve is intact (neuropraxia) or is completely divided and needs surgical repair

If it detects minimal residual innervation suggests continuity of nerve for conservative treatment that increases amplitude and frequency with voluntary muscle contraction

Somatosensory evoked potential

Repeatedly stimulating a peripheral sensory nerve (mild electric shock): record from scalp for summated response

Look for :

  • Latency
  • Amplitude
  • Waveform

Complete interruption of conduction: Waveform to become flat

Partial interruption of conduction:

  • Increase latency
  • Decrease amplitude
  • Abnormal waveform

If the waveform is flat (early days): Myelography shows no evidence of avulsion : Early exploration is advisable

Direct Electrical Stimulation

Brachial plexus can be electrically stimulated at Erb’s Point

Axonal Response

Accurately distinguish the preganglionic and postganglionic lesion

Stimulus

  • (eg. histamine (1:100)/ cold (5oC)– applied over skin — Reflex (vasodilation response )
  • Ninhydrin/ Iodine starch printing methods

Angiography

Condition of subclavian, and axillary vessels before surgery

Treatment Options for brachial plexus injury

Treatment should be initiated immediately and continuously for a long time (months to years)

The lesion is localized with help of paralyzed muscle (A brief waiting period of recovery is done)

In suspected avulsion: Myelography (outpouching from dural sac) which is rare but required immediate surgery

Delay surgery will result in poor result due to

  • Constricting scar
  • Muscle scar
  • Joint contracture

Excision of scar tissue and neuromas

Experimentally autogenous nerve grafts have been used to bridge a gap.

Sometimes middle 1/3rd of the clavicle is necessary to resect to explores the distal plexus

Compression should be relieved

Offending callus or tumor is removed

In aneurysm formation, ligation of the subclavian artery has been done without untoward affects

Indication for surgery

Immediate exploration

  • Sharp penetrating wound
  • Associated with vascular injury: Potential limb/ life-threatening
  • Otherwise not recommended without workup

Early surgery exploration (3 -12 weeks)

Total and near-total palsy

This duration further delineates nerve injury and better assessment of nerve injury

Partial plexus injury/ lower velocity injury (Best prognosis for spontaneous repair)

Serial examination is done every 3-6 months: To determine the need for surgical intervention

Proximal muscles are more likely to repair from surgical intervention than distal muscles

Advancing Tinel Sign:- Useful parameter to follow nerve recovery

A negative Tinel sign is a poor indicator

Absence of Tinel’s sign in the supraclavicular fossa is a contraindication to early exploration in brachial plexus injury

Intraoperative Evoked potential

Direct stimulation: Produces cortical somatosensory evoked potential (Unlikely if nerve avulsion present)

Surgical Goals:

Focus in proximal muscle groups, less distance for nerve regeneration: Better prognosis

1st Priority: Elbow flexion then shoulder stabilizer

For patients with Total brachial plexus palsy

  • Elbow flexion (reinnervation of biceps and brachialis)
  • Shoulder abduction + ER ( innervation supra and infraspinatus)
  • Restoration of brachio-thoracic pinch mechanism (pectoralis major)
  • Sensation in C6-C7 distribution
  • Restoration of wrist extension and finger flexion

Surgical Procedure/ Options for brachial plexus injuries

A. Neurolysis

B. Direct nerve repair

C. Nerve grafting

Indications:

  • Post-ganglionic rupture
  • Post-ganglionic neuromas with conduction block to nerve action potential

(If the proximal nerve is available (healthy) and length < 10 cm)

Options:

  • Sural nerve
  • Medial brachial cutaneous nerve
  • Medial antebrachial cutaneous nerve
  • Vascularized ulnar nerve graft

C. Nerve transfer(Neurotization)

If C5 and C6 avulsed:-

  • Transfer spinal accessory nerve: Suprascapular nerve
  • 2/3 intercostal nerve: Most commonly used to transfer to musculocutaneous, thoracodorsal , serratus anterior, pectoral nerves, or as donor axons for free muscle graft

If one C5 or C6 avulsed:-

  • available root grafted on the lateral cord of the plexus ( Elbow flexion, Finger flexion, Radial sensation)

In complete loss (pre-ganglionic)

  • Contralateral C7 root transfer across the chest

Other options:

  • Thoracic intercostal nerve (Most commonly used to transfer to musculocutaneous, thoracodorsal , serratus anterior , pectoral nerves or as donor axons for free muscle graft)
  • Medial and lateral pectorals
  • Distal spinal accessory
  • Descending cervical plexus

Others:

  • Phrenic nerve transfer (not used if significant chest injury)
  • Contralateral Hemi- C7 transfer
  • Hypoglossal nerve transfer

D. Tendon transfer

  • Elbow flexors: Pectoralis muscle (Clarke’s transfer)
  • Common flexor origin (Steindler transfer)
  • Lattismus Dorsi or triceps

E. Free functional muscle transfer (FFMT)

  • Gracialis
  • Rectus
  • Contralateral lattissmus muscle

F. Salvage surgery

  • Shoulder arthrodesis
  • Wrist arthrodesis

Principles of peripheral nerve repair

Previous Post