As stated above, the main cause of a Wrist Drop is overuse of the wrist whether it be with occupation or sports. Wrist drop may also be caused due to a trauma to the radial nerve by way of a cut or stab wound, or if a person suffers a gunshot wound to the wrist affecting directly the radial nerve. Another cause for a Wrist Drop is some sort of injury to the joint in the wrist or elbow resulting in persistent swelling of the elbow.
With cream cubes, you're likely to have a block of frozen water on the bottom and a crumbly layer of butterfat/milk solids on top. Jumble them around in a freezer bag and you'll wind up with a mess that's not very easy to use.
So what happens is the water that is just slightly above the freezing point rises to the top so the freezing process starts there. This is the same reason why ice is at the top of a lake in the winter and not at the bottom.