Before I can diagnose what might be affecting your big leaf maple, I would like more information. The first picture shows the openings in the bark, is there any signs of oozing, fine sawdust, or do you see any insects? The second picture is a bit blurry and it is hard to tell if this is a picture with the bark still attached to the tree or is this under the bark showing insect galleries. Can you confirm which it is? The last picture shows the canopy of the tree. It is hard to distinguish what is happening with the leaves. Are all the leaves affected, or just a portion? If only a portion, are the affected leaves only on one side of the tree or the entire tree? Or are the affected leaves only on one or two branches? Are they mainly on the outside of the canopy in the sun? Can you send a picture of the leaves and clearer pictures of the bark and the entire tree?

Other information that might help with the diagnosis would include, the approximate age of the tree, hours in the sun, any fertilization, watering practices, any standing water, has the damage spread, any other parts of the tree affected, and anything else of note that is happening in the area.

If this tree is of any importance to you, you may want to consult with a certified arborist. They are able to come out and take a look at the tree. They will let you know what they think is going on with your tree and what might need to be done to save it.