A 68 year old male, chronic smoker and alcoholic presented to medicine OP with complaint of persistent vomiting of one month duration. He had a bad headache during these days. Clinical examination was essentially normal except for clubbing. Lab parameters were within normal limits except an elevated ESR. During detailed evaluation he gave history of dry cough of two month duration. Chest X-ray was taken and showed a peripheral opacity. CECT chest showed evidence of carcinoma lung. What could be the cause for his persistent vomiting?