"Occasional congenital deafness is associated with white or white-patterned, blue-eyed animals. This includes dogs and cats. It is important to note that most splashed white horses are not deaf. Hearing loss is due to the death of the necessary hair cells in the ear. This is caused by the absence of melanocytes in the inner ear. Although the majority of splash horses have pigment around the outside of the ear, the pigment must occur in the inner ear to prevent hearing loss."
The location of splash white has nothing to do with hearing. It's the embryonic stage of development. Splash White is an inherited mutation that affects normal pigment cell function and can also affect hearing. -Click-
The pigmentation in the skin is used by the fetus as a map of where to put the organs & nerves Thats why certain white patterns cause partial or minor things like blindness or deafness where as things that are completely white don't have any map Lethal white foals when born often don't live because their organs are either wrong and or incomplete