It is not a painful condition, does not cause muscular weakness, and does not affect the mind of the dog. (oldenglishsheepdogclubofamerica.org)
This is defined as muscular weakness of a neural (brain) origin which involves partial or incomplete paralysis, resulting from lesions at any level of the descending pathway from the brain. (homevet.com)
It is characterized by the wasting of skeletal muscles and caused by progressive degeneration of nerve cells in the spinal cord; the disease leads to increasing muscular weakness, atrophy and premature death due to respiratory problems. (smafoundation.org)