highlight of my day

This really did just happen to me, and it really was quite exciting. (pitiful). So, for all the other medical students out there studying for boards, here's a question for you:

While flipping through flashcards on a rainy afternoon, I fell asleep curled up on an arm chair, with my right arm, held in flexion, between the chair and my body. When I woke up and stretched, I realized that part of my right hand felt tingly and my 4th and 5th digits did not extend with all the rest. Name that brachial plexus lesion!