I suppose that a docter’s recipe of plain kitchen salt (sodium chloride as an additive of course) could possibly activate the charged diffusion of the ion canals. Maybe chicken soap or steak as example. Assuming that the body splits the sodium to the left as example, while the chloride goes to the right. Those atoms aren’t the only compounds that bear a charge, but only the charge matters.
I would have no idea how much salt is necessary though.
I haven’t deepened myself that much into the subject, but if the cerebrospinal fluid is low too, than I would guess that it’s due to failure in ion transport itself. A process which they call facilitaded diffusion. Transporting the ions where they need to be. Assuming that the salt inside the cerebrospinal fluid is too low (like osmosis), so perhaps not the salt density. I assume that genetic modification of humans wouldn’t be necessary, because the disease didn’t express itself all that time.
It could also be important to determine the cause. What went wrong with the proteins.