A PTA is seeing a patient who reports numbness and tingling…

A PTA is seeing a patient who reports numbness and tingling in the right hand after falling asleep with his arm hanging over the arm rest of a chair.  The patient exhibits an inability to extend the wrist, extend the fingers or thumb, and hyperesthesia of the dorsum of his hand.   The assistant would report to the PT that the patient was demonstrating diminished sensation in the distribution of which peripheral nerve?