Due to the severe cold we had this year, hydrangeas (along with many other plants) were damaged and instead of being full of leaves right now have a mass of leaves at the very bottom with dead looking sticks at the top.
First impulse is to trim these sticks off because they look so bad but with patience, some of these will leaf out. To determine how much growth has been damaged, use your fingernail or a knife to scrape across the stems. Move down from the tip towards the base of the plant until you find a location where the stem underneath the bark is still green and living. Trim off the dead part and if the whole limb is brown underneath, trim at the base of the plant.
Here is a branch that has been scraped and you can see from the green