This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neuroanatomy, Subject name: Anatomy
All of the following are affected in Erb's palsy EXCEPT 
Select and explain. 
A. Upper trunk of brachial plexus, B. Lower trunk of brachial plexus, C. Dorsal scapular nerve, D. Suprascapular nerve
B: Lower trunk of brachial plexus
Answer: B: Lower trunk of brachial plexus 
Explanation: (B) Lower trunk of brachial plexus # Erb's palsy: Most common type when the 5th and 6th cervical nerve roots are involved as in the upper trunk of brachial plexus.> Resulting paralysis causes the arm to lie on the side with extension of the elbow, pronation of the forearm and flexion of the wrist (waiter's tip).> Moro reflex & biceps jerks are absent on the affected side> Treatment consists of use of a splint so as to hold the arm abducted to a right angle and externally rotated> Forearm is flexed at right angle and supinated and the hand is dorisflexed.> Massage and passive movements are advocated.> Fully recovery takes weeks or even months.> Severe injury may produce permanent disability.# Upper root lesions (Erb's palsy): Due to injury of C5, C6 and (sometimes) C7. Abductors and external rotators of the shoulder and the supinators are paralysed. Arm is held to the side, internally rotated and pronated. There may also be loss of finger extension, Sensation is intact.