This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Regional Anesthesia, Subject name: Anaesthesia
Interscalene approach to brachial plexus block does not provide optimal analgesia in the area of distribution of which of the following nerves? 
Select and explain. 
A. Musculocutanoeus nerve, B. Ulnar nerve, C. Radial nerve, D. Median nerve
B: Ulnar nerve
Answer: B: Ulnar nerve 
Explanation: The interscalene block allows for coverage of the lateral two-thirds of the clavicle, shoulder, and proximalhumerus. When attempting a blockade of areas in the arm and forearm, it is impoant to keep in mindthat the inferior trunk (C8-T1) is often inadequately blocked and additional blockade of the ulnardistribution may be required. It traditionally has not been reliable for surgery on the hand. Theinterscalene nerve block is commonly used alone or in conjunction with other forms of anesthesia for paincontrol during surgery or in the perioperative period.