Parkinson's symptoms include progressive loss of muscle control, trembling, stiffness, slowness and impaired balance. (sciencedaily.com)
Between May when he went to the vet and September when he died he seemed to age rapidly, showing some of the signs you mentioned, such as loss of muscle control, fur losing shine, confusion. (consciouscat.net)
Degeneration of motor neurons in ALS leads to progressive loss of muscle control, paralysis and untimely death. (health.ucsd.edu)