<prompt> Erbs palsy occurs due to involvement ofUpper trunk of brachial plexusMiddle trunk of brachial plexusMedial cord of brachial plexusLateral trunk of brachial plexus  <response>: ERBS PARALYSIS:- upper plexus injury.Caused by forceful widening of the angle between the head and shoulder which may occur by traction of arm during the bih of a child or by fall on the shoulder.Involves upper trunk - C5, C6 roots. Leads to typical deformity in the limb- policemans tip hand poers tip hand. The arm hangs by the side,adducted and medially rotated, forearm is extended and pronated. 1. Adduction of arm due to deltoid paralysis.2. Medial rotation of arm-paralysis of supraspinatus, infraspinatus and teres minor.3. Extension of elbow- paralysis of biceps brachii4. Pronation of forearm- paralysis of biceps brachi5. Loss of sensation over outer aspect of arm due to C6 spinal nerve involvement.Reference: vishram singh, page no. 62 