Distal symmetrical polyneuropathy in a dog.

A 1.3-year-old Great Dane dog had a chronic progressive neurologic disease clinically expressed as a distal symmetrical polyneuropathy characterized by weakness and bilateral atrophy of bulbar and distal appendicular musculature. Qualitative and quantitative studies showed neurogenic atrophy of muscles below the elbow and stifle. There was Wallerian-type degeneration, Schwann cell proliferation and cell bands of Büngner, and marked depletion of medium (5 to 8 microns) to large (9 to 15 microns) diameter myelinated fibers in the distal parts of appendicular and laryngeal nerves. Sensory (saphenous and superficial radial) and autonomic (sympathetic and dorsal vagal trunk) nerves were affected to a lesser degree. A distribution of distal axonal degeneration suggested a dying back process. The disease differed from classical dying back disorders by absence of axonal degeneration in selected pathways of the central nervous system.