This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anaesthesia
Interscalene approach to brachial plexus block does not provide optimal surgical anaesthesia in the area of distribution of which of the following nerve – 
Select and explain. 
A. Musculo cutaneous, B. Ulnar, C. Radial, D. Median
B: Ulnar
Answer: B: Ulnar 
Explanation: Ulnar nerve is usually spared by interscalene approach because injection is given in close proximity of upper nerve roots and inferior nerve roots (C8-T1) may be spared.