Brachial Plexus Injury


Original Editor Aarti Sareen

Top Contributors - Aarti Sareen, Lucinda hampton, Kapil Narale, Garima Gedamkar, Kim Jackson, Vidya Acharya, Naomi O'Reilly, Mande Jooste, Admin, Laura Ritchie, WikiSysop, Wendy Walker, Evan Thomas and Meaghan Rieke

Introduction

Brachial plexus is the network of nerves which runs through the cervical spine, neck,axilla and then into arm or it is a network of nerves passing through the cervico-axillary canal to reach axilla and innervates brachium (upper arm), antebrachium (forearm) and hand.It is a somatic nerve plexus formed by intercommunications among the ventral rami (roots) of the lower 4 cervical nerves (C5-C8) and the first thoracic nerve (T1).

                                

Function

The brachial plexus is responsible for cutaneous and muscular innervation of the entire upper limb, with two exceptions: the trapezius muscle innervated by the spinal accessory nerve (CN XI) and an area of skin near the axilla innervated by the intercostobrachial nerve.

Clinical Anatomy

The plexus consists of roots, trunks, divisions,cords and branches.

1. ROOTS: These are consititued by the anterior primary rami of spinal nerves C5,6,7,8 and T1 with contributions from the anterior primary rami of C4 and T2. The origin of the plexus may shift one segment either upward or downward resulting in a PRE FIXED PLEUS or POST FIXED PLEXUS respectively. Ina prefixed plexus, the contribution by C4 is large and in that from T2 is often absent. In a post fixed plexus, the contribution by T1 is large, T2 is always present, C4 is absent, and C5 is reduced in size. The roots join to form trunks as follows:

                    

2.TRUNKS: Upper trunk is formed by C5 & C6

                   Middle trunk is formed by C7

                   Lower trunk is formed by C8 & T1

3. DIVISIONS OF THE TRUNKS: Each trunk divides into ventral and dorsal divisions (which ultimately supply the anterior and posterior aspects of the limb). These divisions join to form cords.

4. CORDS:  it forms 3 cords

• The Posterior Cord is formed from the three posterior divisions of the trunks (C5-C8,T1)
• The Lateral Cord is the anterior divisions from the upper and middle trunks (C5-C7)
• The Medial Cord is simply a continuation of the anterior division of the lower trunk (C8,T1)

5. BRANCHES: The specific branches of each cord can be seen at this page

Mechanism of injury

Injury to brachial plexus can occur in many ways. These include the contact sports, road traffic accident, motorvehicle accident or during birth. Grossly, it can be divided into

• Traumatic e.g motorvehicle accident, contact sports
• Non traumatic e.g.obstretic palsy and Parsonage-Turner Syndrome
  

The network of nerves is fragile and can be damaged by pressure,stretching, or cutting. Stretching can occur when the head and neck are forced away from the shoulder, such as might happen in a fall off a motorcycle. If severe enough, the nerves can actually avulse, or tear out of, their roots in the neck. Pressure could occur from crushing of the brachial plexus between the collarbone and first rib, or swelling in this area from injured muscles or other structures.Although these are but a common few events, there is one of two mechanisms of injury that remain constant during the point of injury.. The two mechanisms that can occur are traction and heavy impact. These two methods disturb the nerves of the brachial plexus and cause the injury.

TRACTION: Traction, also known as stretch injury, is one of the mechanisms that cause brachial plexus injury. The nerves of the brachial plexus are damaged due to the forced pull by the widening of the shoulder and neck.Traction occurs from severe movement and causes a pull or tension among the nerves. There are two types of traction: downward traction and upward traction. In downward traction there is tension of the arm which forces the angle of the neck and shoulder to become broader. This tension is forced and can cause lesions of the upper roots and trunk of the nerves of the brachial plexus. Upward traction also results in the broadening of the neck and shoulder angle but this time the nerves of T1 and C8 are torn away.

IMPACT: Heavy impact to the shoulder is the second common mechanism to causing injury to the brachial plexus. Depending on the severity of the impact, lesions can occur at all nerves in the brachial plexus. The location of impact also affects the severity of the injury and depending on the location the nerves of the brachial plexus may be ruptured or avulsed. Some forms of impact that affect the injury to the brachial plexus are shoulder dislocation, clavicle fractures, hyperextension of the arm and sometimes delivery at birth. During the delivery of a baby, the shoulder of the baby may graze against the pelvic bone of the mother. During this process, the brachial plexus can receive damage resulting in injury.This is very low compared to the other identified brachial plexus injuries.

Classification of injuries

The various classifications of brachial plexus injury are as follows:

1. Leffert classification of brachial plexus injury
   
2. Millesi classification of brachial plexus injury
   
3. Classification on anatomical location of injury
   

1. Leffert classification of brachial plexus injury: It is based on etiology and level of injury and is as follows

• I Open (usually from stabbing)
• II Closed (usually from motorcycle accident)
• IIa Supraclavicular
  
  • preganglionic:
    • avulsion of nerve roots, usually from high speed injuries with other injuries and LOC;
    • no proximal stump, no neuroma formation (neg Tinel's)
    • pseudomeningocele, denervation of neck muscles are common
    • horner's sign (ptosis, miosis, anhydrosis)
  • postgangionic:
    • roots remain intact;
    • usually from traction injuries;
    • there are proximal stump and neuroma formation (pos Tinel's)
    • deep dorsal neck muscles are intact, and pseudomeningoceles will not develop;
  • Infraclavicular Lesion:
    • usually involves branches from the trunks (supraclavicular);
    • function is affected based on trunk involved;
• III Radiation induced
• IV Obstetric
• IVa Erb's (upper root) - waiter's tip hand;
• IVb Klumpke (lower root)
  

2. Millesi classification of brachial plexus injury:  It is mainly divided into 4

I: supraganglionic/preganglionic.

II: infraganglionic/postganglionic

III: trunk.

IV: cord.

3. Classification on anatomical location of injury:

• Upper plexus palsy (Erb’s palsy in the OBPI cases) involves C5-C6+/-C7roots.
• Lower plexus palsy (Klumpke’s palsy) involves C8-T1 roots (and sometimes also C7)
• Total plexus lesions involve all nerve roots C5-T1
• Some authors have included a fourth type,an intermediate type that primarily involves the C7 root.
  

Injuries

Injuries to roots, trunks and cords of the brachial plexus produce characteristic defects which are as follow

ERB'S PARALYSIS:

Site of injury: The region of the upper trunk of the brachial plexus is called Erb's point. Six nerves meet here. Injury to the upper trunk causes Erb's Paralysis.

Causes of injury: Undue separation of the head from the shoulder, which is commanly encountered in 1)birth injury 2) fall on shoulder, and 3)during anaesthesia

Nerve roots involved: Mainly C5 and partly C6.

Muscles paralysed: Mainly biceps, deltoid,brachilais and brachioradialis.Partly supraspinatus, infraspinatus and supinator

Deformity

Arm: Hangs by the side, it is adducted and medially rotated

Forearm: Extended and pronated

The deformity is known as "Policeman's tip hand" or "Porter's tip hand".

Disability:

• Abduction and lateral rotation of the arm (shoulder).
• Flexion and supination of forearm.
• Biceps and supinator jerks are lost.
• Sensations are lost over a small area over the lower part of the deltoid.

For more information on Erb's paralysis see this page

KLUMPKE'S PARALYSIS:

Site of injury: Lower trunk of the brachial plexus.

Cause of injury: Undue abduction of the arm, as in clutching something with the hand after a fall from a height, or sometimes in birth injury.

Nerve roots involved: Mainly T1 and partly C8.

Muscles paralysed:

• Intrinsic muscles of the hand (T1)
• Ulnar flexors of the wrist and fingers (C8).

Deformity: (position of the hand): claw hand due to the unopposed action of the long flexors and extensors of the fingers. in a claw hand there is hyperextension at the metacarphalangeal joints and flexion at the interphalangeal joints.

Disability:

• Claw hand
• Cutaneous anaesthesia and analgesia in a narrow zone along the ulnar border of the forearm and hand.
• Horner's syndrome: ptosis, miosis, anhydrosis, enophthalmos and loss of ciliospinal reflex- may be associated. This  is because of injury to sympathetic fibres to the head and neck that leave the spinal cord through nerve T1.
• Vasomotor changes: The skin areas with sensory loss is warner due to arteriolar dilation. it is also drier due to the absence of sweating as there is loss of sympathetic activity.
• Tropic changes: Long standing case of paralysis leads to dry and scaly skin.The nails crack easily with atrophy of the pulp of fingers.

For more information on Klupmke's paralysis see this pgae

INJURY TO LATERAL CORD:

Cause: Dislocation of humerus associated with others

Nerve involved: musculocutaneous, lateral root of median.

Muscles paralysed:

• Biceps and coracobrachialis
• All muscles supplied by the median nerve,except those of hand.

Deformity and disability:

• Midprone forearm
• Loss of flexion of forearm
• Loss of flexion of the wrist
• Sensory loss on the radial side of the forearm
• Vasomotor and trophic changes.

INJURY TO MEDIAL CORD:

Cause: Subcoracoid dislocation of humerus

Nerves involved: Ulnar, Medial root of median

Muscles paralysed:

• Muscles supplied bye ulnar nerve
• Five muscles of the hand supplied bye the median nerve.

Deformity and disability

• Claw hand
• Sensory loss on the ulnar side of the forearm and hand
• Vasomotor and tropic changes as a bone.

Resources

http://www.ubpn.org/

http://brachialplexussurgery.com/

Recent Related Research (from Pubmed)

Failed to load RSS feed from http://www.ncbi.nlm.nih.gov/entrez/eutils/erss.cgi?rss_guid=1DWoAttMz857mYTkXFHgGndF5gpGpSEKuHEVYFYPDbAw1Gl9dt: Error parsing XML for RSS