A 24 year old man is brought into the emergency room reporting that his right arm is paralyzed. Heart rate and blood pressure are normal, but he appears to be pale and dehydrated. He reports that because of the lack of decent hockey on tv, he and his buddies resorted to watching Stanley Cup playoff games from the 1980s (go Oilers!) until approximately 2am when he fell asleep in a chair. When we awoke around 9am he realized he had no feeling in his right arm and could not move it properly. After thinking it was “pins and needles” and pacing back and forth for a while and tapping his right arm with his left hand, his condition did not improve. The patient’s history reveals no evidence of recent injuries or illness and he has not reported tingling or burning sensations in his feet or toes prior to this event. He reports some mild nausea and a headache. The cranial nerve exam was mostly normal. The only abnormality was a slower pupil dilation response and this occurred bilaterally. Upon further examination of his right arm, the patient reports numbness on the back of his forearm, back of the hand and his middle, ring and pinky fingers. He is capable of extending his arm, but his wrist flops down. Manipulating his arm further reveals a complete inability to extend the wrist.  Differential Diagnosis  What is most likely responsible for the symptoms?  What brain regions, or associated anatomical structures, are affected?  How do the symptoms relate to the function of the anatomical regions?  How would you determine that the brain region(s) in question is involved in the symptomology of the patient? What course of treatment is advised?