Motor Neuron Disease

  : My father was recently diagnosed with Motor Neuron Disease by the Neurology Dept at the University of Michigan in Ann Arbor.  The neurologist explained that his condition was distinct from "ALS".  He also stated that the form of MND he has, which has been slowly progressing from his feet to legs, is the slowest progressing form.  I have done extensive reading on the internet about Motor Neuron Disease but none of what I read distinguishes it from ALS.  Can you inform me of the significant differences between MDN of this sort and ALS.  I am also interested in the prognosis.
  :Typo in original message should be "MND" not "MDN"
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Motor neuron disease refers to selective loss of neurons which are either in the primary motor area of the cerebral cortex (so-called "upper motor neurons") or the alpha motor neurons located at each segment of the spinal cord, whose fibers make up nerves which go to muscles (so-called "lower motor neuron"). There is no loss of sensory neurons, and many parts of the brain and spinal cord which are not strictly "motor" are unaffected.
ALS (amyotrophic lateral sclerosis) is a combination of upper and lower motor neuron degeneration.
PLS (primary lateral sclerosis) is predominantly upper motor neuron, typically progressing more slowly.
PMA (progressive muscular atrophy) is predominantly lower motor neuron.
There are variations and other diseases included in the category of motor neuron disease. For example, polio is an infectious (viral) disease which affects primarily lower motor neurons. Some hereditary diseases such as spinomuscular atrophy or spinobulbar muscular atrophy are in this group.
I hope this information helps direct your search for more about motor neuron disease, and enhances your understanding of your father's diagnosis. CCF MD mdf.