All of the following muscles undergo paralysis after injury to C5 and C6 spinal nerves EXCEPT

This is a controversial question, since a lesion of C-5,6 will paralyse all the given muscles. The most appropriate option (Coracobrachialis) has been taken as the answer. Coracobrachialis is innervated through the anterior division of C5, 6 and 7 segmental levels (Gray's Anatomy Ed 41). Hence, a lesion at C5 and 6 may not paralyse coracobrachialis completely, as C-7 is still intact. Brachioradialis is supplied by root value C-5 and 6, so compromised. Biceps brachii has the root value (C-5,6), hence paralysed. Brachialis: is supplied by C-5,6,7 (Dominant value is C-6), thence compromised.