If there are still viable leaves or green shoots showing, just keep the tree well watered. It is quite likely it will produce new growth still this season.

Something quite similar happened to one of my small, containerized maples -- got overlooked in its watering during a record breaking heat wave. The entire tree shriveled up. I thought it was a goner but it has sprouted fresh new growth on all but the outermost stems, which are indeed dead.

Thanks for the good news, Gardengal. :)

we have near 100 temp summers and my 4 potted JMs usually have crispy leaves around july-august each year. last year 2 of my smaller ones went into early hibernation and stayed leafless until this spring. one of the larger ones dropped its leaves in Sept and releafed later in Oct and then turned a nice fiery red in Jan.

your JMs should be fine. one sign of life would be to look at the joints/notches and look for full and firm buds.

heres the pic taken in mid Jan