 Shares of NeuroMetrix Inc. rocketed 241 toward a two-year high on record volume, after the Massachusetts-based medical device company said its Quell transcutaneous electric nerve stimulator received Breakthrough Designation from the Food and Drug Administration to treat fibromyalgia symptoms in adults. Trading volume ballooned to 228.3 million shares, compared with the full-day average over the past 30 days of about 125,600 shares, to make the stock the biggest gainer and most actively traded on major U.S. exchanges. 