The Sensex today tumbled by 162 points to close at 18,631.10 on across-the-board selling.After resuming over 100 points lower, the BSE benchmark index failed to stage a recovery amid fresh concerns over the sluggish global economic growth and Eurozone debt crisis.The rupee also wilted under pressure and fell below the 53-mark against the US dollar in early trade.Likewise, NSE Nifty fell below 5,700 level by losing 52.45 points, or 0.92 per cent, to 5,652.15.