Cut off one of the dead branches as close to a main stem as possible and take into your county extension office for a diagnosis. Take these photos in as well. It could well be your tree is suffering from Verticillium wilt, a fatal soil borne pathogen. Unfortunately, Japanese maples are highly susceptible.

It is important to get an accurate diagnosis (which we cannot provide from this distance) as if it IS VW, it will impact on what you can replace the tree with.

Your tree is entirely too close to the house. When is the last time branches were removed? If branches have been pruned incorrectly, or at the wrong time of year when parasite spores are on the move, that would open up the tree immediately to fast decline from a pathogen. Or,if you've had honey mushrooms (Armillaria species) in your yard in the last few years, you can pretty much guarantee Armillaria is at work here. I do not think you will ever get that tree back to the way you like it. If any (or a lot) of bark is loose around the main trunk, or if it has holes in it that look spongy, japanese maples are also susceptible to Stereum parasitism (a shelf fungus). They last quite a while and can put up a fight for most stuff except the Verticillium and the Armillaria murheooms, which start at the roots and eat their way upwards until the tree dies. And, because none of the top branches bear foliage whatsoever, those branches are dead. Your tree has limited time in my opinion. Yank it out of there and find one of it's seedlings in your yard, and plant away from the house..

Minimum 100 feet away if possible. Our Japanese Maple is just about dead from the Stereum parasite. It has been in decline for several years.

Michael, Please, please refrain from making comments which are so inaccurate!! I have planted, grown and sold hundreds of JM's over the years and as a consulting horticulturist, I am extremely familiar with Verticillium wilt. I have encountered it dozens of times. It can appear at any time of year and often, a failure to leaf out fully in spring is a clear sign. It also has almost nothing to do with excess water. It is a soil pathogen virtually omnipresent in soils, often staying dormant for decades before becoming activated by some sort of stressor - drought, root disturbance, late spring freezes, mechanical damage, etc. It can be slow, developing over a period of months limb by limb, or very fast, taking down an entire tree in a matter of days. It destroys the vascular system and an affected branch will NOT releaf the next spring! You will be very lucky if the tree is even alive next spring!!! it is virtually assured 100% fatality.

So far your record here on GardenWeb is very poor. First day, 3 comments, ALL with inaccurate information you insist is correct. Please get your facts straight before commenting again!!

ETA: Michael in all his numerous personas and aliases over the last few days has disappeared/closed his account(s) and deleted most of his comments. Considering that most were highly inaccurate and filled with misinformation, maybe that is not a bad thing. Apparently he/she/it was just trolling.

This type of question, when asked, always reminds me of my noted, horticulturist father. Often, from a young age, he would let me tag along if I was quiet, when he did garden consultations. Very clearly I remember him standing beside Japanese maples and slowly making a very a strong statement which informed the garden customer that this beautiful tree...."must be treated like a Queen! Once planted, never allow your gardener or yourself to dig or plant beneath/around this tree. Remember! No activity that involves cutting through the roots of this maple. There is a lethal wilt that lives naturally in our soils and enters maples usually through cut/damaged roots. Once infected the tree slowly dies.")

It was a true statement then...and still is. Over the years I have noted that the simple act of

digging or refreshing garden edging near Japanese maples is enough disturbance to cut surface hair roots and allow entrance of Verticillium wilt into a maple. Remember this please!

Here is a comprehensive, science-based fact sheet on Verticillium wilt: Verticillium Wilt of Ornamental Trees and Shrubs. (Michael's initial quote is from HomeGuides - SFGate, which is a cut and paste, quick and dirty, hobby gardener resource and is not considered a scientific or reliable horticultural, reference source.)

Pay close attention to the Management Strategies portion which clearly states a) no fungicides are effective against this pathogen; b) infected plants cannot be cured or recover fully; and c) verticillium fungi exists in all soils but can remain dormant or inactive for many years.