A 52-year-old man with cirrhosis presents with confusion and asterixis. His EEG shows generalized periodic discharges with a characteristic morphology: initial small positive deflection followed by a large negative wave and then a small positive deflection, occurring at 1.5–2 Hz and frontally predominant. The pattern marked **D** in the diagram suggests metabolic encephalopathy, often hepatic in origin. Which of the following clinical scenarios would make hepatic encephalopathy the LEAST likely diagnosis for this EEG finding?