Figure 14-116.

Polyradiculoneuritis, Coonhound Paralysis, Peripheral Nerve, Dog.

This disease results from an autoimmune response leading to primary demyelination of cranial and spinal rootlets and nerves. Myelin sheaths in this peripheral nerve are distended and fragmented along their length (arrowheads) and have been infiltrated by a mixed population of inflammatory cells consisting of lymphocytes, macrophages (1), and plasma cells (2). Enlarged spaces in the myelin sheath, termed digestion chambers (arrows), which form in response to inflammatory and degradative processes, contain myelin debris and macrophages (not shown in this example). Axonal degeneration can occur secondary to primary demyelination. H&E stain.

(Courtesy Drs. R.A. Doty, J.J. Andrews, and J.F. Zachary, College of Veterinary Medicine, University of Illinois.)