These kinds of situations are so very difficult, because the facts are, it's rare that a person would have such long term effects
from a medication, or from a med w/d. It's not impossible, just not likely.
I guess my advice to you would be for you to ask the doctors (probably the Neurologist) what your options are. If you are going on the assumption that this is related to the Valium, what are his recommendations? Is there something he could try, to see if you notice any improvements?