expanding tingling and numbness

[Gary-H]

  In October I noticed tingling on the bottom of my right foot.  Within a couple of weeks it spread up the foot through the ankle area and up the back ot the calf.  It then started on the left leg.  Next the tingling started to turn into numbness in the areas where the tingling had first started.  Since that time the numbness has spread up the legs through the buttocks and into the right chest and right back area.  Within the last few days the tricep area of my right arm has started to feel numb.
      I have had blood tests, MRI's of the spine and brain, nerve conductivity tests, a spinal tap, and  Methylprednisolone.  The only thing to show up from all these tests was a slight scarring inside the spine in the neck which can be explained by past medical history.  (Radiation therapy from Hodgkins disease 30 years ago.)
      My doctors do not seem to know what could be causing the problem.  Could toxicity be an issue?  I take vitamin and mineral supplements and drink quite a lot of Diet Coke with Aspartame.
      What other possible causes might there be?  Can you tell me of any other tests I should undergo?
      Help!                Thank you.
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Dear Gary:
It is difficult for me to make an accurate assessment without having the opportunity of interviewing you in an office visit and examining you. With the avalable information, the problem you have could either be in the cervical spinal cord or in the peripheral sensory nerves. In this context, the "scarring" that you mention may be relevant, and may be the actual lesion causing your symptoms. Arguing against a spinal cord localization is the fact that you mention sensory symptoms, but not gait troubles, weakness, difficulty voiding, or other symptoms that are often seen with spinal cord lesions. If the cervical cord lesion on MRI is a new and active one (unrelated to Hodgkin's disease radiation), it my represent inflammatory myelitis. Inflammatory myelitis can occur in isolation (such as after a viral infection), or as part of the picture of multiple sclerosis. Vitamin B12 deficiency is another cause of spinal cord disease.
If the problem is in the peripheral nerves (sensory with/without motor), a long list of other possibilities opens up. Included are disorders such as Guillain Barre syndrome, remote effects of cancer, some drug toxicities (such as some cancer drugs, megadoses of Vitamin B6), Lyme disease, connective tissue diseases, and several other uncommon conditions.
Aspartame does not cause such symptoms.
In case a visit to Cleveland is practical, any of the neuromuscular specialists at the Cleveland Clinic would be most happy to address your problem. Appointments can be made by calling [phone], or [phone] locally.