--but, still, given that spot on the MRI, you may want to get that lumbar puncture to gain more evidence, or rule out, the possiblity of MS or other central nervous system demyelinating disease.

There are many things which can cause spots to show up on MRI, B12 deficiency and migraines among them, but the widespread presentation you describe is more common among those with central nervous system issues than it is with peripheral neuropathy. This is not to say that one cannot have an acute onset body wide neuropathy that is peripheral in nature--in fact, one reason to get the lumbar puncture is to also look for signs of acute onset Guillain Barre syndrome (a demyelinating peripheral nueorpathy) or sub-acute onset chronic deyelinating inflammatory polyneuroapthy (CIDP). I would think some more extensive testing, including some nerve conduction or possibly evoked potential tests--to try to isolate the SOURCE of the symptoms (central or peripheral) is in order.