Rituxan and x rays

After 2 treatments of Rituxan, my uncle could barely walk into the doctor's office. It progressively worsened even after he quit the treatments, and now he has absolutely no muscle strength in his legs and has to be carried or in a wheel chair to go from one side of the house to the other. It didn't affect anything but his legs oddly enough. He went through a series of tests, x-rays, PET, Spinal Tap, even chiropracter, etc., and can't find any sign of cancer or attributing problems. The doctors think that maybe it was a symptom of the chemo treatments, more particularly the Rituxan since it began after the first and worsened with the second until he was unable to walk at all.