Probably winter cold injury. It often doesn't really show the full effect until it turns hot. Then the damaged trunk can't move enough water to the leaves.

What he said..that is at least what it looks like. No matter the case, that doesn't look like anything that can be fixed and might be need to A...be chopped and replaced or B....pruned back hard to get new branching lower. I'm pretty sure (i've never had that severe of damage) those branches willl not fill in...meaning you'll have vast expanses of dead areas with lush growth up in the treetop...