The 30-share BSE Sensex slumped 477 points or 0.73 per cent to trade at 64,846, while the broader NSE Nifty was down 156 points or 0.80 per cent to trade at 19,272. Mid- and small-cap shares were down as Nifty Midcap 100 fell 1.32 per cent and small-cap dived 1.80 per cent. On the global front, Asian markets struggled today.