Case History: Case Y

A 51-year-old man with a history of chronic alcoholism and binge drinking disappeared for over a week. When he was found, he was confused and appeared malnourished. He could carry on a conversation, but seemed confused and talked about being on a cruise on a yacht with fabulous meals. On examination, he showed ataxia, nystagmus, and impairment of medial gaze. The image shows one brain section that would correspond with his condition. What is the diagnosis and what structure shows pathology?