Thanks for the idea! I searched for code to do that.
Should this code work?
.custom #menu-item-AAA a {
display:block; height:24px; width:24px; padding:0px; margin-left:6px; outline:none; text-indent:-9999px;
background-image:url(‘images/my-nav-sprite.png’); background-position:0 0;
}
.custom #menu-item-AAA a:hover { background-position:0 -24px; }