BRACHIAL PLEXUSAnatomy &

localisation of lesion

anatomy

• Formed by anterior primary rami of c5,c6, c7,c8 and t1

• 15 cms long ,spinal column to axilla• Divided into 5 major components-Roots, Trunks,

Divisions,Cords,and Branches(robert taylor drinks cold beer) from proximal to distal

• Pre fixed-c4 ,one level up• Post fixd-T2 ,one level down

Anatomy of brachial plexus

trunks

• C5,c6 roots pass down wards between scalenus medius and scalenus anterior muscles and unite to form upper trunk

• C7 root pass between scalenus muscles and at laeral border of scalenus anterior emeges as middle trunk

• C8, T1 roots unite behind a fascial sheet (sibson”s fascia) and beneath the subclavian artery form lower trunk

• The three trunks traverse supraclavicular fossa protected by cervical and scalene musculature

Divisions,cords

• Lateral to the 1st rib , where three trunks are located behind the axillary artery ,they separate into 3 anterior and 3 posterior divisions

• 3 posterior divisions unite to form posterior cord• Anterior divisions of upper and ,middle trunks (C5-C7)

unite to form lateral cord• Anterior division of lower trunk forms medial

cord(C8-T1) • Cords passes through the thoracic outlet and give off

major branches

Branches from roots

• Dorsal scapular nerve-(c4-c5)- levator scapulae, rhomboids

• Subclavian nerve(c5-c6)- subclavian muscle• Long thoracic nerve(c5-c7)- serratus anterior

muscle– isolated palsy may be a manifestation of neuralgic amyotrophy or familial nerve palsy

Branch from trunk

• Supra scapular nerve(c5-c6)- branch from upper trunk.

• Gives branches to supraspinatus ,capsule of shoulder joint and supplies infraspinatus

Pectoral nerves

• Lateral anterior thoracic nerve(c5-c7) arises from anterior divisions of upper, middle trunks

• Medial anterior thoracic nerve(c8-T1) branch of medial cord

• Anterior thoracic nerves(c5-T1) supplies pectoralis major, pectoralis minor

BRANCHES FROM CORDS• Lateral cord-1)musculocutaneous nerve(c5-c7) 2)lateral head of median nerve(c5-c7)• Medial cord-1)med.ant.thoracic nerve(c8-T1) 2)med. Cut. Nerve of arm(c8-T1) 3)med.cut. Nerve of forearm(c8-T1) 4)ulnar nerve(c7-T1) 5)med. Head of median nerve(c8-T1)• Posterior cord- 1)subscapular nerve(upper,lower)(c5-c7) 2)thoraco dorsal nerve(c5-c7) 3)axillary nerve(c5-c6) 4)radial nerve(c5-c8)

Lesions of brachial plexus

• Usually incomplete• Muscle paralysis• Muscle atrophy• Loss of tendon reflexes• Sensory changes• Clinical deficit involving >one

spinal/peripheral nerve

Total plexus palsy

• Usually due to severe trauma• Entire arm is paralysed• All arm”s musculature may undergo rapid

atrophy• Complete anesthesia of arm distal to a line

extending obliquely from tip of shoulder to medial arm half way to elbow

• Entire upper limb is areflexic

Upper plexus paralysis• Erb –duchenne palsy results from the damage to c5,c6 roots/upper trunk • Causes- forceful separation of head and shoulder,pressure on shoulder, fire arm

recoil, birth injury, and idiopathic plexitis • Paralysis of deltoid, biceps, brachioradialis, brachialis, and occasionally supra

spinatus,infraspinatus and sub scapularis• Iimb is internally rotated, adducted, fore arm is extended and pronated,palm

facing out and back ward-police man”s tip position• shoulder abduction(deltoid, supraspinatus);elbow flexion(biceps,

brachioradialis, brachialis);ext.rotation of arm(infraspinatus);fore arm supination (biceps) are impaired

• Very proximal lesions can cause weakness of rhomboids,levator scapulae, serratus anterior,and scalene muscles

• Sensation is usually intact, some sensory loss may occur over the outer surface of upper arm

• Biceps, brachioradialis reflexes are depressed or absent

Middle plexus paralysis

• C7 root of radial nerve is involved• Rare occurrence but occasionally with trauma• Extensors of fore arm, hand, and finger are

paretic(triceps, anconeus, ext. carpi radialis and ulnaris,ext. digitorum, ext. digiti minimi,ext.pollices longus and brevis,abductor pollicis longus,and ext.indices)

• Triceps reflex is absent• Sensory deficit is inconsistent and patchy, may occur over

the ext. surface of fore arm and radial aspect of dorsum of hand

Lower plexus paralysis

• Dejerine-klumpke -follows injury to c8,T1 roots• Results from trauma; arm traction in abducted position,surgical

procedures for lung tumour , mass lesion like aneurysm of aortic arch

• Weakness of wrist flexion, finger flexion, and intrinsic muscles of hand resulting in claw hand deformity

• Sensation may be lost in medial arm ,medial fore arm ,ulnar aspect of hand

• Finger flexor reflex is lost/depressed(c8-T1)• When T1 root is involved, sympathetic fibers destined for

superior cevical ganglion are inturrupted;ipsilatral horner syndrome develops(ptosis, miosis,anhydrosis)

Lesions of lateral cord

• Surgical/local trauma• Musculocutaneous nerve, lateral head of median nerve are

involved• Paralysis of biceps, brachialis and coraco brachialis,which

control elbow flexion and fore arm supination-musculocutaneous nerve

• Paresis of muscles supplied by median nerve except intrinsic hand muscles-pronator teres, flexo carpi radialis,flexor digitorum superficialis;(flexor nerve of wrist)

• Biceps reflex is absent• Sensory loss may occur lateral fore arm

Lesions of medial cord

• Weakness of muscles supplied by ulnar nerve and medial head of median nerve

• ulnar muscles involved are flexor carpi ulnaris, flexor digitorum lll and lV and ulnar intrinsic hand muscles

• Median muscles involved are abductor pollicis brevis, superficial head of flexor pollicis brevis, opponens pollicis, 1st and 2nd lumbricals

• With proximal lesions med. Ant. Tho. Nerve may be injured ,paresis of pectoralis

• Finger flexor reflex is depressed• Sensory loss over medial arm and fore arm

Lesions of posterior cord

• Subscapular, thoraco dorsal, axillary, and radial nerves are involved

• Sub scapular nerve- paresis of teres major,subscapularis(internal rotators of humerus)

• Thoraco dorsal nerve- lattismus dorsi paresis• Axillary injury manifest as deltoid(arm abduction) and teres

minor(lateral rotation of shoulder)paresis and sensory loss over lateral arm

• Radial injury results in paresis of elbow extension ,wrist extension ,fore arm supination and finger extension, sensory loss over entire extensor surface of arm and fore arm and on the back of the hand and dorsum of first four fingers

Electro diagnostic studies• NCS,EMG Confirming clinical diagnosis Character of lesion Prognosis for recovery• Axonal loss brachial plexopathy-SNAPs, CMAPs are attenuated /lost• Demyelinating lesions-CVs are slowed, motor evoked responses dispersed , distal latencies

prolonged• EMG is very sensitive for detecting even mild motor fiber loss, because fibrillations potentials

develop in affected muscles by 3 wks after onset of disease• Axonal loss plexopathy- 1)minimal lesion-SNAPs, CMAPs are unaffected, but needle ex. Shows fibrillation potentials 2)increase in severity in lesion –SNAPs become attenuated, while CMAPs are still spared 3)most severe lesions – compromise both sensory and motor responses• In post ganglionic plexopathy numbness, sensory loss are associated with reduced/absent

SNAPs because lesion is locatd distal to DRG• In pure radiculopathy sensory loss is found in presence of normal SNAPs

Radiological studies

• Plain films of neck & chest- cervical rib, long transverse process of C7, in thoracic out let syndrome ; lesion in pulmonary apex , erosion of head of 1st 2nd rib , or transverse process of c7 andT1 as in pancoast”s tumor

• High resolution CT and MRI scanning useful in detecting mass lesions of plexus and allow early diagnosis and specific therapy

• CT guided biopsy can be used to obtain cytological and histological material for precise diagnosis

Traumatic plexopathy

1)direct trauma2)secondary injury from damage to structures around the

shoulder and neck, such as fractures of clavicle and first rib3)iatrogenic injury as in nerve blocksEarly management-weakness and sensory loss depending on

part involved if portions of plexus have been sharply transected early

repair can be done in open injuries ,disrupted nerve elements can be tagged for

later repair , damage to vessels and lung require immediate intervention

Long term management• Sensory and motor function assessment made after the general

condition stabilization• Neuraprxia and minimal axontmesis- return to normal strength

and sensation is expected• Intra operative motor evoked potentials are helpful in assessing

functional state of anterior motor roots and motor fibers• Depending on the findings ,neurolysis, nerve grafting or

reneurotization is performed• Joint and tendon surgeries are best performed as secondary

operations after a period of physiotherapy• The chances of recovery are reduced if repair was delayed for

more than 6 months

Thoracic out let syndrome

• Compression of brachial plexus or subclavian vessels In the space between 1st rib and the clavicle

Compressive factors 1) cervical rib 2)enlarged c7 transverse process 3)hypertrophied anterior scalene muscle 4)clavicular abnormalities 5)fibrous band from c7 transverse process to 1st rib

or anterior scalene muscle

• Vascular signs-• recurrent coldness, cyanosis, pallor of hand; • frank gangrene or raynaud”s phenomenon is rare;• a bruit may be heard over supra clavicular or infra

clavicular areas, especially when arm is fully abducted

• radial pulse obliteration with arm abduction to 90 degrees, and ext. rotation ;

• vein compression results in arm edema , cyanosis, and prominence of veins of arm and chest

• Neuropathic signs-• lower trunk of plexus is involved;• intermittent pain referred to ulnar border of hand and

medial fore arm and arm;• paresthesias and sensory loss in same distribution;• motor and reflex findings are those of lower plexus

palsy;• when only c8 is involved thenar wasting and paresis

may be prominent sparing ulnar supplied muscles• Treatment is surgical division of compression factor

Metastatic plexopathy

• Lung and breast carcinoma most common• Lymphoma ,sarcoma, melanoma less common• Tumor metastasis spread through lymphatics , most

commonly involved is adjacent to lateral group of axillary lymph nodes,which are close to lower plexus

• Severe pain is hallmark of disease• Signs referable to lower plexus and its divisions• > ½ patients have horner”s syndrome• Few may have lymphedema of hands• Pancoast syndrome in non small cell bronchogenic

carcinoma

Pancoast syndrome• Superior pulmonary sulcus tumor• Arises from the pleural surface of apex of lung• Grows into para vertebral space and posterior chest wall • Invades C8 ,T1 spinal nerves , sympathetic chain, stellate

ganglion, necks of 1st 3 ribs, transverse processes and borders of the vertebral bodies of C7 through T3

• Eventually invade spinal canal and compress the spinal cord• Severe shoulder pain radiating to head and neck ,axilla, chest,

and arm• Pain and paresthesias of the medial aspect of arm and 4th 5th

digits, • Weakness with atrophy of intrinsic hand muscles

Metastatic plexopathy

• DD radiation plexopathyTreatment-1)Radiotherapy 2)chemotherapy 3)opioids , NSAIDs , AEDs , transcutaneous

stimulation, para sympathetic blockade, and dorsal rhijotomy

4) Surgical resection if possible

Radiation –induced plexopathy

• > 6000 c GY • Interval 3 months – 26 years , mean -6 yrs• Limb paresthesias, and swelling.• Pain is less severe• Usually affects upper trunk or entire plexus• Lower trunk relatively protected by clavicle, shorter course• Pathogenesis- 1)endo neural and peri neural fibrosis with obliteration of

blood vessels. 2) direct damage to myelin sheaths and axons

Metastatic plexopathy Radiation plexopahy

Trunks involved Lower trunk Upper trunk or entire plexus

Duration of symptoms Short long

Onset symptoms Pain Paresthesia, weakness

EMG Myokemic discharges

Horner syndrome Common Less common

Lymphedema Less common Common

Idiopathic brachial plexopathy

• Arm pain , weakness• All age groups ,3rd- 7th decades• Men involved in vigorous activities• Precipitating event in > ½ URI ,flu like illness ,

immunisation , surgery, stress or post partum • Familial form-AD, chr. 17q 25, episodes of pain,

paresthesias, paralysis with good prognosis for recovery with each attack children

Clinical features• Abrupt onset of pain in shoulder, scapular area, trepezius ridge, upper

arm, fore arm ,hand;pain lasts for hours to wks and abates gradually• Weakness develops simultaneously progress for 2-3 wks• O/E weakness of shoulder girdle muscles both upper &lower plexus

involved• Arm kept in position of adduction at shoulder and flexion at elbow• Discrete lesions of individual nerves can occur• Can also involve cranial nerves VII and X , phrenic nerves• Sensory loss is less common ,outer surface of upper arm , fore arm• 1/3 rd are bilateral• In small no. of patients diaphragm paralysis can occur

diagnosis

• DD – cervical radiculopathy- persistent pain , neck stiffness, pain persists as weakness develops, EMG increased insertional activity and fibrillation potentials

neoplastic plexopathy- unremittingly painful, lower plexus mostly involved

motor neuron disease- sensation is usually spared

Diagnostic tests

• Confirm diagnosis and r/o other conditions• Reduced amplitudes of SNAPs , CMAPs• EMG absence of fibrillations because distal to DRG• MRI of plexus – to exclude structural lesions , high T2 signal

intensity , fatty atrophy of involved muscles• Elevated liver enjymes in patients with b/l disease and

phrenic nerve involvement• Anti ganglioside anti bodies in some • CSF priein elevation, and oligoclonal bands in few• Pathogenesis- ischemic /auto immune mechanism

suggested

Treatment

• Opioid analgesics for pain• 2 wks course of oral prednisone is tried• Immobilisation of arm in sling• With onset of paralysis , exercises can prevent

contractures• Natural course of disease is benign • 36% recovered by one year• 76% by the end of 2 yrs• 89% b y the end of 3 yrs