<prompt> Erbs palsy occurs due to involvement of___ of brachial plexus.Upper trunkMiddle trunkMedial cordLateral trunk  <response>: Ans. a Upper trunk Ref. BDC vol. l4th53.The upper trunk or Erbs 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 Erbs point. Claw-hand deformity is due to lesion of lower trunk of brachial plexus Klumpkes 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 Erbs 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. Erbs paralysis involves Cs and C6 while Klumpkes is involvement of C8 and T1 Banches of posterior cordMnemonic: ULNARBranches of Medial cordmnemonic: M4UBranches of Lateral cordmnemonic: LML1. Upper subscapular nerve C5,C6Medial cutaneous nerve of arm C8T1Lateral pectoral nerve2. Lower subscapular nerve C5,C6Medial pectoral nerve C8T1Lateral root of median3. Nerve to latissimus dorsi thoracodorsal nerve C6,C7,C8Medial cutaneous nerve of forearm C8T1Musculocutaneous nerve4. Axillarycircumflex nerve C5,C6Medial root of median nerve C8T1-5. Radial nerve C5, C6, C7, Cg8 and T1Ulnar 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. 