Formed by anterior(ventral) rami of C5 to C8, and most of the anterior ramus of T1.
Originates from neck, passes laterally and inferiorly over rib I, and enters axilla.
The part of brachial plexus from medial to laterally are roots, trunks, divisions, and cords.
Proximal part is posterior to subclavian artery
Distal part is surrounds by axilliary artery.
ROOTS Originates froms C5-C8 and most of T1 Receives grays rami communicates from the symphatetic trunk. Carry postganglionic symphatetic fibers onto root for distribution of periphery. Root and trunk enter posterior triangle of neck by passing between anterior scalene and middle scalene muscles and lies between superior and posterior to subclavian artery.
TRUNKS C5,c6 roots pass down wards between scalenusmedius and scalenus anterior muscles and unite to form SUPERIOR 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
DIVISION Lateral to the 1st rib , where three trunks are located behind the axillary artery ,they separate into 3 anterior and 3 posterior divisions The 3 anterior division form parts of brachial plexus that ultimately give rise to peripheral nerves associated with the anterior compartment of arm or forearm. The 3 posterior division combine to form parts of the brachial plexus that give rise to nerves associated with the posterior compartments.
CORDS 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
Long thoracic nerve(c5-c7)- serratus anterior muscle
PECTORAL NERVE 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 CORD Lateral cord-1)musculocutaneous nerve(c5-c7) FUNCTION:sensory for skin on lateral side of forearm 2)lateral head of median nerve(c5-c7) FUNCTION: motor nerve for ,Pectoralis major
MEDIAL CORD. Medial cord-1)med.ant.thoracic nerve(c8-T1) FUNCTION: Pectoralos major and minor 2)med. Cut. Nerve of arm(c8-T1) FUNCTION: Skin on medial side of distal one-third of arm 3)med.cut. Nerve of forearm(c8-T1) FUNCTION: Skin of medial side of forearm 4)ulnar nerve(c7-T1) FUNCTION: supply all intrinsic muscle of hand(except thenar muscles and 2 lateral lembricals),also carpiulnaris and median half of flexor digitorumprofundus in forearm. 5)med. Head of median nerve(c8-T1)
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, serratusanterior,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
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;ipsilatralhorner syndrome develops(ptosis, miosis,anhydrosis)
Lesions of posterior cord Subscapular, thoraco dorsal, axillary, and radial nerves are involved Sub scapular nerve- paresis of teresmajor,subscapularis(internal rotators of humerus) Thoraco dorsal nerve- lattismusdorsi 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
Lesions of lateral cord Surgical/local trauma Musculocutaneous nerve, lateral head of median nerve are involved Paralysis of biceps, brachialis and coracobrachialis,which control elbow flexion and fore arm supination-musculocutaneous nerve Paresis of muscles supplied by median nerve except intrinsic hand muscles-pronatorteres, flexocarpiradialis,flexordigitorumsuperficialis;(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 carpiulnaris, flexor digitorumlll and lV and ulnar intrinsic hand muscles Median muscles involved are abductor pollicisbrevis, superficial head of flexor pollicisbrevis, opponenspollicis, 1st and 2ndlumbricals 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
Traumatic plexopathy 1)direct trauma 2)secondary injury from damage to structures around the shoulder and neck, such as fractures of clavicle and first rib 3)iatrogenic injury as in nerve blocks Early 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
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 Treatment- 1)Radiotherapy 2)chemotherapy 3)opioids , NSAIDs , AEDs , transcutaneous stimulation, para sympathetic blockade, and dorsal rhijotomy 4) Surgical resection if possible
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
Erb’sparalysis •C5 -C6 •Birth injury •Arm hangs by the side+Rotatemedially •Forearm pronated+ extended •Flexed wrist + fingers •deltoid –supraspinatus–infraspinatus–biceps -brachialis
Klumpke’sparalysis •C8 –T1 •Intrinsic muscles of the hand + long flexors of the hand ------paralysis •Claw hand = extension at MPJ + flexion at IPJ •Cervical rib can cause paralysis similar to Klumpke’sparalysis with post-fixed T2 contribution
Winging of the scapula •Injury to the long thoracic nerve •Paralysis of serratusanterior muscle
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
DIAGONOSTIC cervical radiculopathy- persistent pain , neck stiffness, pain persists as weakness develops, EMG increased insertional activity and fibrillation potentials neoplasticplexopathy- 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 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