What makes you say that? Can you give a description of what you see and what's been happening out of the ordinary? This will help in assessing the problem.

the photo is upside down and blurred so it is difficult to tell. what is happening is it dropping leaves?

If the leaves are turning yellow then falling off this dieback could be a soil problem but I can't give you specifics because I am unfamiliar with climbing hydrangias. Perhaps there will be other GOY members to give you some answers.

The photo I can see might be sideways on - looking at it left to right, there's the bottom of what could be a window frame (white) on the left, or possibly french doors, can't tell, and then there's the top of some trellis with bare twiggy bits sticking up with a little bit of growth just showing - the rest of the picture (moving right) shows a bushy, healthy plant, with what might be a fuchsia flower in the top right quadrant.

If you're concerned about the area sticking up above the trellis which is largely bare of foliage, it might be that the growth there is crammed or squeezed inbetween the trellis and the wall , and is unable to grow properly? Otherwise, can't see much wrong with what's green and bushy there.

I'd say it's old wood on the trellis by the window that needs pruning out. And a good prune after flowering has finished to leave strong shoots with room to grow.