Brachial Plexus injuries are one of the most important topics, its pathogenesis investigation and management are to be known.
Anatomy of brachial plexus
C5 – C8 nerve roots are lateral to scalene muscles
Branches from roots
- Dorsal Scapular nerve (C5): Rhomboids and levator scapulae
- Nerve to subclavius (C5, C6): Subclavius
- Long thoracic nerve (C5, C6, C7): Serratus anterior
Branches from the Upper trunk
Lower and middle have no branches
- Suprascapular nerve (C5, C6): Supraspinatous and Infraspinatous
Branches from Lateral Cord (LML)
- Lateral pectoral nerve (C6): Upper half of pectoralis major
- Lateral head of median nerve (C6, C7)
- Musculocutaneous nerve (C5, C6, C7)- BBC
- Biceps
- Brachialis
- Coracobracialis
Branches from Medial Cord (4MU)
- Medial pectoral nerve: Sternocostal fibres of pectoralis major
- Medial cutaneous nerve of arm
- Medial cutaneous nerve of forearm
- Medial head of median nerve
- Ulnar nerve (C7, C8, T1)
Branches of Posterior Cord (ULNAR)
- Upper subscapular nerve (C6, C7): Subscapularis
- Lower subscapular nerve (C6, C7): Subscapularis and teres major
- Nerve to latissmus dorsi
- Axillary nerve (Deltoid and teres minor)
- 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) | Postganglionic | Preganglionic |
---|---|---|
Sensation | – | – |
Wallerian degeneration | + | – |
Sensory NCV | – | + |
Motor NCV | – | – |
Paracervical EMG | – | + |
Myelogram | – | + |
Diaphragm paralysis | – | + |
Tinel Erbs point | + | – |
Horner’s syndrome | – | – |
Repairable | Yes | No |
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