Traumatic Brachial Plexus Injuries in Adults

                                  Traumatic Brachial Plexus Injuries in Adults

                                                                 Dr KS Dhillon

 Brachial plexus anatomy

The brachial plexus is formed by the ventral/anterior rami of the C5, C6, C7, C8, and T1 spinal nerve roots. There are normal variations, where the C4 root (prefixed) and the T2 root (postfixed) may contribute to the formation of the plexus. The five roots terminate in five nerves which provide motor and sensory innervation to the upper limb. This 5 nerves include the musculocutaneous, median, ulnar, axillary, and radial nerves. The portion the plexus between the roots and the nerves consists of 3 trunks, 3 divisions and 3 cords (sets of 3).
The trunks include the superior (C5,C6), middle (C7) and inferior (C8,T1). Each trunk divides into two divisions, the anterior (3) and posterior (3) divisions. The divisions form 3 cords, the medial (C8,T1), lateral (C5-C7) and posterior (C5 -T1). Each cord gives rise to 2 branches.The posterior cord divides into the axillary and the radial nerves and the lateral cord divides into the musculocutaneous nerve and the lateral branch of the median nerve. The medial cord divides into the medial branch of the median nerve and the ulnar nerve.
The musculocutaneous nerve (C5,6 and 7) provides motor innervation to the coracobrachialis, biceps and the medial brachialis and sensory innervation to the lateral forearm via the lateral antebrachial cutaneous nerve.
The axillary nerve (C5,C6) supplies the motor innervation to the Deltoid and the Teres Minor muscles and sensation to the lateral shoulder via the superficial lateral cutaneous nerve of arm.                   
The ulnar nerve (C7,C8,T1) provides motor innervations to the following muscles, Flexor carpi ulnaris, Flexor carpi profundus to ring and little finger, adductor pollicis, deep head of flexor pollicis brevis (FPB),interossei (dorsal and palmar), 3rd & 4th lumbricals, abductor digiti minimi, opponens digiti minimi and flexor digiti minimi. It provides sensory innervation to the ulna aspect of the dorsum of the hand and dorsum of the little finger and ulnar  aspect of the ring finger via the dorsal dorsal  aspect of the ring finger via the dorsal dorsal cutaneous branch and hypothenar region of the hand via the palmar cutaneous branch and the palmar aspect of the little finger and ulnar side of the ring finger via the superficial terminal branches.           
The radial nerve (C5-T1) provides motor innervation to the triceps, anconeus, extensor carpi radialis longus and brevis and the brachioradialis.
 The posterior interosseous branch innervates the extensor digitorum, supinator, extensor digitorum minimi, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis longus and brevis and the extensor indicis proprius. The radial nerve provides sensory supply to the posterior aspect of the arm, forearm and the radial aspect of the extensor aspect of the hand and the thumb, index, middle and radial aspect of the ring finger via the posterior cutaneous nerve arm, posterior cutaneous nerve of the forearm, superficial branch radial nerve and the dorsal digital branch.
The median nerve (C5-T1) provides motor innervation to the, Pronator teres, Flexor carpi radialis, Palmaris longus, Flexor digitorum superficialis,  Flexor digitorum profundus (lateral), Flexor pollicis longus, Pronator quadratus, 1st and 2nd lumbricals, Opponens pollicis, Abductor pollicis brevis and the Flexor pollicis brevis. It provides sensory supply to the lateral palm via the palmar cutaneous branch and the radial 3 and half digits (palmar) and can also supply the index, middle, and ring fingers dorsally via the digital cutaneous branches.

Epidemiology

There is a scarcity of literature on the epidemiology of traumatic brachial plexus injuries. Midha reported a 1.2% incidence in 4538 patients with polytrauma [1]. In winter sports injuries the incidence is about 4.8% and after motorcycle collisions it is about 4.2% [1].
The majority of the brachial plexus injuries involve the upper brachial plexus. In about 725 of the cases there is upper plexus palsy and in 26% of the cases there is a complete plexus palsy. Lower plexus palsies are seen in about 2% of the cases [2].

Mechanism of injury

The severity,extent and level of traumatic brachial plexus injuries (BPIs) can vary depending on the degree and direction of the force involved. The
more severe injuries such as rupture of plexal segments or root avulsions are usually associated with higher energy trauma.
High speed vehicular accidents (mostly motorcycle) are responsible for about 83% of traumatic BPIs. A caudally directed force on the  shoulder
predominantly affects the upper brachial plexus and  forced arm abduction (as in grabbing onto something while falling) usually affects lower roots. If the force is severe all roots may be involved [3].

Preganglionic and postganglionic brachial lesions

It is important to locate the level of brachial plexus lesion in relation the ganglion of the dorsal root because the approach to pre and postganglionic injuries is often different. Some postganglionic lesions can recover spontaneously, but preganglionic lesions have no capacity to regenerate and can never heal and they should be identified as soon as possible.
Supraclavicular brachial plexus lesions can be preganglionic or postganglionic but infraclavicular lesions are always postganglionic.
Supraclavicular lesions have a myotome/dermatome distribution whereas postganglionic proximal peripheral distribution. The upper roots (C5,6) are most frequently injured and the upper root lesions are usually postganglionic whereas lower root (C8,T1) are usually preganglionic.
The upper roots are usually protected against avulsion by the branches of the nerves and the the interscalene ligaments. There are fibrous attachments that at the C4 to C7 levels, which tie spinal nerves down to transverse processes, after their exit from intervertebral foramina which
also protect them against avulsion. About 60% of upper root lesions are ruptures and 40% avulsions. The lower roots (C8,T1) lesions are more often preganglionic since the roots are in the direct line of pull to the spinal cord. There is not protection against avulsion for the C8 and T1 roots. Eighty five percent of the lesions are avulsions and about 15% of lower root lesions are ruptures.                           
                           

Root avulsion (preganglionic lesion) should be suspected when the patient reports ‘constrictive or caustic pain in an otherwise insensitive upper limb’ and when clinical examination shows the presence of a Horner’s syndrome and paralysis of the scapular muscles, serratus anterior, and rhomboids. The dorsal scapular as well as long thoracic nerve which supply these muscles are formed just distally to the roots. The presence of Horner’s syndrome (lid ptosis, miosis, enophthalmos, and hemifacial anhidrosis) indicates the that the T1 sympathetic ganglion is injured and this ganglion is close to the T1 root and avulsion injuries occur frequently to both these two structures together [4]. The presences of phrenic nerve injury (paralysis
of the ipsilateral hemidiaphragm) may also be suggestive of a preganglionic lesion since the nerve originates just distal to the roots.         
                           

Clinical diagnosis of brachial palsy

Upper brachial plexus palsy

The upper brachial plexus palsy involving C5, C6 roots has been described as “bad shoulder, good hand” palsy. It is also known as the Erb’s palsy where there is a paralysis of the shoulder abductors (deltoid, supraspinatus), external rotator (infraspinatus), elbow flexors, supinator and the wrist extensor, resulting in ‘waiter’s tip’ upper limb. The rhomboids and serratus anterior is usually spared. There is axillary nerve, suprascapular nerve and radial nerve deficiency due to C5,C6 involvement. The arm is usually held adducted, internally rotated at the shoulder and  extended at the elbow with the wrist flexed.

Intermediate plexus palsy (C7)

Intermediate plexus lesion rarely occur in isolation. They usually occur with upper and lower plexus lesions. C7 lesions in isolation have minimal impact on upper limb function. It usually produces some weakness of wrist extension.

Lower plexus palsy (C8,T1)

Lower plexus palsy involving the C8,T1 roots is often described as the ‘good shoulder, bad hand’ palsy. If it is a preganglionic lesion, a Horner’s syndrome is usually present. Lower plexus lesion produces weakness FCU, FDP to ulnar digits, loss of hand intrinsics function, loss of EIP and EPL function and medial forearm and hand sensory loss.

Panplexus (C5-T1)

In a panplexus palsy all roots of the brachial plexus from C5 to T1 are involved.

Motor testing 

Terminal branches of brachial plexus and their function.

1.Dorsal Scapular nerve (C5).  It supplies the Rhomboids which stabilize the scapula
2.Long Thoracic nerve (C5). It supplies the Serratus Anterior which abducts the scapula
3.Suprascapular nerve (C5). It supplies the Supraspinatus which abducts the shoulder and the Infraspinatus which externally rotates the shoulder.
4. Medial (C8) and Lateral Pectoral (C7) nerves. Both nerves supply the Pectoralis Major which adducts and medially rotates the upper limb. The Pectoralis Minor is supplied by the Medial Pectoral nerve and it stabilizes the scapula.
5.Subscapular nerve (C5). It supplies the Subscapularis and the Teres Major which produce internal rotation of the shoulder.
6.Thoracodorsal nerve (C7). It supplies the Latissimus Dorsi which adducts the shoulder.
7.Musculocutaneous nerve (C5). It supplies the Biceps brachii and the Brachialis which flex the elbow.
8.Ulnar nerve (C8,T1) . It supplies the Flexor carpi ulnaris and Intrinsic muscles of hand which helps in wrist flexion and flexion of ring and little fingers as well as abduction of all fingers.
9. Median nerve (C6-T1). It supplies the pronatus and the flexors of the wrist and fingers (index and middle).
10. Radial nerve (C6-C8). It supplies the supinator, triceps and extensors of the wrist and fingers.
11. Axillary  nerve (C5). It supplies the Deltoid and the Teres minor which abduct the shoulder.

Sensory testing

The C5 root supplies the skin over the deltoid, the C6 provides sensation to the thumb and index finger. The middle finger sensation is provided by the C7 and the little and part of ring finger sensation is provided by the C8 root. The T1 root provides sensation to the medial side of the forearm while the T2 root provides sensation to the inner side of the arm.

Electrodiagnostic Tests

Electrodiagnostic tests are useful in confirming the diagnosis, localization of the lesion, determining the severity of axial discontinuity, and eliminating other causes for the clinical findings. Electrodiagnostic tests are always used in conjunction with a meticulous physical examination in the management of patients with suspected brachial plexus injuries.
Electromyography (EMG) and nerve conduction velocity studies (NCSs) are usually performed 3 to 4 weeks after the injury by when Wallerian degeneration has completed in postganglionic lesions and the conduction of potentials along the nerves have stopped. Serial testing will provide information about reinnervation or continued denervation.

Electromyography

Electromyography evaluates and records electrical activity produced by muscles. A needle electrode is inserted through the skin into the muscle that is being studied. The nerve supplying the muscle is stimulated and electromyogram detects the tiny amount of electricity generated by muscle cells. The EMG tests muscles at rest and during activity. The denervation fibrillation potentials can be seen as early as 10 to 14 days after injury in proximal muscles and as late as 3 to 6 weeks in distal muscles. When voluntary motor unit potentials with limited fibrillation potentials are present it signifies better prognosis than the cases where there is a complete absence of motor unit potentials and many fibrillation potentials.
Abnormalities of EMG can be seen in any condition which damages the anterior horn cell body, axon, Schwann cells, the neuromuscular junction, or the muscle cell itself. The size, shape, and morphology of the action potential can help determine the state of myelination, the number of functioning muscle fibers, and the function of the neuromuscular junction. Since the cell body of motor nerves is located in the anterior horn cell within the spinal cord the motor nerve conduction is abnormal in both preganglionic and postganglionic lesions.

Sensory nerve conduction studies

Sensory nerve conduction studies are performed by stimulation of a peripheral nerve (sufficient to produce an action potential) at one point while the action potential is measured at another point along the course of the nerve. The latency, conduction velocity, and amplitude of the action potential are analysed. The information obtained can localise the level of the lesion and help differentiate between preganglionic disorders (eg, radiculopathies, cauda equina lesions, posterior column disease) from postganglionic disorders (eg, neuropathies, plexopathies). In patients with  preganglionic lesion, the sensory nerve action potential is normal (although clinically abnormal) because axonal transport from the cell body to the peripheral axon remains intact and in patients with postganglionic lesions sensory nerve action potential will be abnormal [5].

Radiological investigations

In patients with traumatic brachial plexus injuries, plain xrays of the neck and shoulder may be useful to look for associated injuries to cervical spine and to look for fractures of the clavicle and the surrounding region. A transverse process fracture of the cervical vertebrae is likely to indicate a root avulsion. A scapulothoracic dissociation is also associated with root avulsion. The X Rays will also show the presences of any shrapnel in patients with gunshot injuries. An inspirational and expirational chest X Ray film would be useful to exclude hemidiaphragm paralysis due to a phrenic nerve palsy.
In the past CT-myelography was considered as the "gold standard" for studying root lesions, but now with recent advances in magnetic resonance imaging (MRI), MRIs of the cervical spine can the diagnostic accuracy of CT-myelography [6]. Cervical MRIs provide a non-invasive means of detecting nerve root avulsions and the scans can also show the presences of pseudomeningoceles (sign of root avulsion) and spinal cord edema (an indirect sign of nerve root avulsion) [7]. MR neurography is very useful in imaging the brachial plexus for injuries.

Treatment of Brachial plexus injuries

Open injuries 

Open injuries of the brachial plexus, though uncommon, require exploration at the earliest opportunity available. Injuries with associated vascular injuries also require emergency operation. In cases of sharp laceration of the neural structures an end to end repair of the structures is carried out. In cases of blunt laceration, the nerve is fixed to adjacent tissues to reduce  retraction and secondary repair is carried out two to three weeks later. This delay allows demarcation of the damaged neural tissue. If direct repair is not possible than nerve grafting is carried out.
Open high-velocity gunshot wounds are usually associated with significant soft-tissue damage and such wounds require early surgical exploration. On the other hand low energy civilian gunshot wounds do not have to be explored immediately because such injuries are usually associated with neuropraxia of neural structures where spontaneous recovery is possible [8]. Such injuries are usually explored after 3-4 months if no recovery occurs.

Close injuries

Close injuries of the brachial plexus are initially managed conservatively. The treatment includes pain management as well as therapy to mobilise the joints to prevent contractures and maintenance of strength of the uninvolved muscles. EMG can be considered after one month for more accurate evaluation of the brachial plexus lesion. Surgery is usually considered if there is no recovery after 3 to 6 months.
Management of pain can be difficult. Pain is most severe in patients who have complete lesions and when the lesions are preganglionic. The pain is often excruciating and exhausting. In the initially stages NSAIDs and opioids can used but antiepileptic drugs (gabapentin and carbamazepine) or antidepressants such as amitriptyline may be needed for neuropathic pain. Other modes of treatment such as biofeedback, punctuation, hypnosis, and percutaneous nerve stimulation have been used with some success [9].

Surgical treatment

Surgery is always performed under general anesthesia without the use of any muscle-blocking agents and the plexus is exposed through an anterior supraclavicular, infraclavicular, or a combined approach. Various operative techniques are used depending on the findings at the time of surgical exposure of the plexus.

Neurolysis

The presence, location and the extent of neuroma is noted and a direct bipolar electrical stimulation is carried out. A visual evaluation of muscle contraction is observed. When there is doubt about visual contraction of the muscles, than concentric needle electrodes are used for intraoperative electromyography evaluation of the motor response. If there is sufficient muscle response to electrical stimulation proximal to the neuroma then neurolysis is carried out [10]. All attempts are made to maintain the interfascicular structure and the nerve sheath during neurolysis. Interfascicular neurolysis is avoided so as to prevent vascular damage. An anterior epineurotomy is usually performed and the fibrous tissue is excised.
In the absence of any useful response to electrical stimulation the neuroma is exicised a little at a time till the neural ends are identified. The neural ends are then suture together. However if the gap is too wide for end to end suture, then a nerve graft is used to to fill the gap. The usual source of nerve graft is one or both sural nerves. Sural nerve is usually used as a graft material because removal of the sural nerve does not produce any significant deficit. The other nerves often used as graft material include the sensory branch of ulnar nerve, and the medial cutaneous nerve of the forearm. A success rate of 79% with a direct repair has been reported with evidence of reinnervation as measured by EMG at 12 months follow up [11].

Nerve transfer (neurotization)

Nerve transfer or neurotization involves the transfer of a functional but less important nerve to a non functional but more important recipient nerve. It is usually done for root avulsions and intractable proximal brachial plexus injuries. The choice of donor nerves for neurotization remains controversial [10]. There are two categories donor nerves for neurotization namely the extraplexal and intraplexal nerves.
For complete avulsion of the cervical roots forming the brachial plexus, only extraplexal nerves such as the accessory nerve, motor branches of the cervical plexus, intercostal nerves and the phrenic nerve are available for neurotization. Intraplexal nerves as donors for motor fibres can be derived from thoracodorsal nerve, the long thoracic nerve, and the pectoral nerves. The use of intraplexal nerves provides more favourable results as compared to that obtained with extraplexal nerves [11].

Fascicular transfer

More recently neurotization is being performed using only a part of the donor nerve. It involves the transfer of fascicles of a functional nerve to a non functional nerve. To restore deltoid function fascicles of the radial nerve to the triceps are transferred to the axillary nerve. With this transfer the effect on the triceps is negligible [12]. Oberlin introduced a neurotization technique where an ulnar nerve fascicle is transferred to the branch of the musculocutaneous nerve for biceps function thereby restoring flexion of elbow in patients with upper brachial plexus injuries without significant motor or sensory deficits of the ulnar nerve [13]. For this technique of restoration of elbow function the lower brachial plexus has to be intact since the ulnar nerve is formed from the C8 and T1 roots.
 Songcharoen in 2001,described a technique where a median nerve fascicle is used to repair the musculocutaneous nerve and restore biceps muscle function [14].

End-to-side neurorrhaphy

In patients with combined supra- and infraclavicular brachial plexus injuries the proximal stump of an injured nerve is often unavailable or the nerve gap is too long to be bridged by a nerve graft. In such injuries the commonly used donor nerves are not available for nerve repair. To overcome the problem in such cases the distal stump of the transected nerve is coapted to adjacent donor by end-to-side neurorrhaphy. There is evidence to suggest that end-to-side neurorrhaphy can provide satisfactory functional outcome for the recipient nerve without affecting the function of the donor nerve. With this technique of end-to-side neurorrhaphy there is no need need to sacrifice the surrounding nerves or their fascicles.

Secondary Operations

In the event that no recovery occurs either spontaneously or following  surgical procedures involving the nerves, then secondary procedures may be required to improve the limb function. Some of the options include arthrodesis, tendon transfers and functional free muscle transplantation.

Arthrodesis

In patients with upper brachial plexus paralysis where the shoulder is unstable and painful an arthrodesis of the shoulder (glenohumeral arthrodesis) can improve function of the limb. The prerequisite for shoulder arthrodesis is good thoracic-shoulder functionality and intact acromioclavicular joint, sternoclavicular joint, and scapulothoracic joints. The shoulder is usually fused in 30 degrees of abduction, 30 degrees flexion, and 30 degrees of internal rotation (33-30-30 positioning). This allows about 60 degrees abduction and flexion with the scapulothoracic movements[15].
Wrist arthrodesis is sometimes done when there is flexion deformity of the wrist due to wrist extensor paralysis. Occasionally carpometacarpal arthrodesis of the thumb is done to improve hand function.

Osteotomy

Derotation osteotomies of the humerus and the forearm are sometimes done to correct internal rotation deformity of the arm and forearm.

Tendon Transfers

Tendon transfers are carried out for partial upper or lower plexus paralysis. For restoration of shoulder abduction a trapezius transfer to the deltoid or an anterior transfer of the posterior deltoid can be carried out. A latissimus dorsi transfer can be carried out to improve external rotation of the shoulder.
Restoration of elbow flexion is very important for a good clinical and functional outcome. The commonly used transfers for restoration of elbow flexion include Steindler’s proximal transfer of common origin of forearm flexors, transfer of triceps to the biceps, latissimus dorsi transfer to the tendon of the biceps brachialis and the Clark’s transfer of pectoralis major brachial branch tendon to brachial bicep [9].

Functioning Free Muscle Transplantation

The gracilis muscle transplantation with microvascular anastomosis and microneural coaptation to the recipient motor nerve has been used in many patients to restore elbow and finger flexion and extension. The accessory nerve and or the intercostal nerves are used as donor nerves. Both the gracilis muscles can be sacrificed with any significant functional loss.

Prognosis of brachial plexus injuries

Injuries in young individuals below 30 years generally have better prognosis. The more distal the injury better the prognosis. Patients with incomplete lesions do better than those with complete lesions. Patients with preganglionic lesions and those with vascular injury have poorer prognosis.

References

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2. Kaiser R, Mencl L, Haninec P. Injuries associated with serious brachial plexus involvement in polytrauma among patients requiring surgical repair. Injury. 2014; 45(1):223–226.
3. Jason McKean. Brachial Plexus Injuries at https://www.orthobullets.com/trauma/1008/brachial-plexus-injuries. Accessed on 8/12/2017.
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8. D. G. Kline, “Civilian gunshot wounds to the brachial plexus,” Journal of Neurosurgery, vol. 70, no. 2, pp. 166–174, 1989.
9. Vasileios I. Sakellariou, Nikolaos K. Badilas, Nikolaos A. Stavropoulos, et al., “Treatment Options for Brachial Plexus Injuries,” ISRN Orthopedics, vol. 2014, Article ID 314137, 10 pages, 2014. doi:10.1155/2014/314137.
10. Pavel Haninec and Libor Mencl. Surgical Treatment of Brachial Plexus Injury at http://dx.doi.org/10.5772/intechopen.68442. Accessed on 16/12/17.
11. Haninec P, et al. Direct repair (nerve grafting), neurotization, and end-to-side neurorrhaphy in the treatment of brachial plexus injury. Journal of Neurosurgery. 2007;106 (3):391–399.
12. Leechavengvongs S, et al. Nerve transfer to deltoid muscle using the nerve to the long head of the triceps, part II: A report of 7 cases. The Journal of Hand Surgery. 2003;28(4):633–638.
13. Oberlin C, et al. Nerve transfer to biceps muscle using a part of ulnar nerve for C5–C6 avulsion of the brachial plexus: Anatomical study and report of four cases. The Journal of Hand Surgery. 1994;19(2):232–237.
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