Figure 14-103.

Granulomatous Meningoencephalitis, Transverse Section of Midbrain Just Rostral to the Pons, Dog.

A, The mesencephalon is swollen, discolored, markedly distorted, and soft as the result of extensive granulomatous inflammation (arrows), which has displaced the midline to the right. The mesencephalic aqueduct is also compressed and distorted. B, Note the accumulation of granulomatous inflammatory cells in the perivascular space. Such layers of cells expand over time and compress adjacent neural tissue, resulting in Wallerian-like degeneration of affected myelinated axons and atrophy of affected neuron cell bodies. H&E.

(A courtesy Dr. J. Edwards, College of Veterinary Medicine, Texas A&M University; and Dr. J. King, College of Veterinary Medicine, Cornell University. B courtesy Dr. J.F. Zachary, College of Veterinary Medicine, University of Illinois.)