I am 40 with unexplained lower extremity parapasesis. i cant move anything waist down. how much muscle loss/ nerve loss to expect.

Know the cause first: Have you seen a neurologist for your unexplained lower extremity paraparesis? Unless the cause is known, the extent of nerve/muscle compromise cannot be known. The many possibilities include spinal cord injury, multiple sclerosis, AIDS, skull fracture, HTLV, genetic condition, etc. See a neurologist to be evaluated. http://www.ncbi.nlm.nih.gov/pubmed/1802259

Insufficient data: First of all, "paraparesis" MEANS lower extremity weakness. What does "unexplained" mean? That you can't explain it, or your doctors can't? Are you absolutely sure they didn't find a cause? Some patients just don't get it the first time around. - If the weakness is from the CNS (spinal cord), you'll get disuse atrophy. If PNS (lumbosacral plexus), you'll get neurogenic atrophy - much worse.

Very Concerning: There is always a reason for Paraplegia, and your severe disability should be evaluated again. A spinal cord injury or stroke, Neuromyelitis Optica, spinal cord tumors, and motor neuron disease should all be considered. Would suggest a second opinion in Baltimore at Johns Hopkins or Univ of Maryland.