Erb's palsy occurs due to involvement of____ of brachial plexus.

Ans. a (Upper trunk) (Ref. BDC vol. l/4th/53).The upper trunk or Erb's palsy is seen in newborn usually during forceps delivery when there may be forceful separation of neck and shoulder with resultant stretching of the upper trunk (the 'Erb's point'). Claw-hand deformity is due to lesion of lower trunk of brachial plexus (Klumpke's palsy).BRACHIAL PLEXUS# It is formed by anterior primary rami of spinal nerves C5 to T1 with contribution of C4 and T2 roots.- C5 and C6 join to form upper trunk9 (Erb's point).- Root C7 forms middle trunk and root C8 and T1 join to form lower trunk.# Each trunk has anterior and posterior divisions.- Posterior divisions of all the three cords unite to form posterior cord.- Anterior division of upper and middle trunks forms lateral cord.- Anterior division of lower trunk forms medial cord.# Erb's paralysis involves Cs and C6 while Klumpke's is involvement of C8 and T1 Banches of posterior cord(Mnemonic: ULNAR)Branches of Medial cord(mnemonic: M4U)Branches of Lateral cord(mnemonic: LML)1. Upper subscapular nerve (C5,C6)Medial cutaneous nerve of arm (C8/T1)Lateral pectoral nerve2. Lower subscapular nerve (C5,C6)Medial pectoral nerve (C8/T1)Lateral root of median3. Nerve to latissimus dorsi/ thoracodorsal nerve (C6,C7,C8)Medial cutaneous nerve of forearm (C8/T1)Musculocutaneous nerve4. Axillary/circumflex nerve (C5,C6)Medial root of median nerve (C8/T1)-5. Radial nerve (C5, C6, C7, Cg8 and T1)Ulnar (C7,C8, T1)-Branches of rootsBranches of trunk: Only upper trunk gives branches (middle and lower trunk has no branch).1. Long thoracic nerve of Bell (C5, C6, C7) = Supplies serratus anterior.Suprascapular nerve (C5,C6) = Supplies supraspinatus, infraspinatus.2. Dorsal scapular nerve (C5) = Supplies rhomboids and levator scapulae.Nerve to subclavius (C5,C6) = Supplies subclavius muscle.