The plant is not dead at all, but the leafless shoots and branches are. Cut the dead branches off about an inch or two from ground level (or as low as you can without damaging the live shoots). The plant will grow back to it's original size in no time. You may want to keep the number of trunks limited to three or four, or, let it grow as it is now. The trunks will grow larger and will be easier to manage (weed around, remove dead trunks, etc) if there are fewer. Air flow will also be better and any pest problems might even be slightly reduced. But, you don't have to limit the trunks if you don't feel like doing the upkeep necessary to maintain that form.