you don't say which species it is? but they are quirte tender and sometimes die off in a cold or wet winter - never mind all the icy snow etc. But it may just kill off some of the top growth. In april/may snap a few twigs at the top and see if they are brown inside. If they are look further down, maybe prune a lower branch back and see if there is any green showing. Sometimes they sprout back from lower down. If so, wait until there is quite a bit of new growth, then prune out the dead stuff.