Meningoencephalomyelitis associated with foreign plant material in a dog: case report and brief literature review

Abstract

Neurologic disease associated with migration of plant material is reported infrequently in dogs. Here we describe meningoencephalomyelitis associated with foreign plant material in a 2-y-old castrated male West Highland White Terrier dog with acute neck pain. Magnetic resonance imaging revealed spinal meningeal contrast enhancement. Although clinical signs improved after treatment with steroids, the dog was readmitted for further evaluation 3-mo later and was euthanized after generalized epileptic seizures. Autopsy findings consisted of coalescing, pus-filled, neuroparenchymal cavitations surrounded by hemorrhage in the left caudal colliculus and rostral left cerebellar hemisphere. Histologically, lesions consisted of necrosis and suppuration, which surrounded a 1 × 2-mm foreign body morphologically consistent with plant material and clusters of gram-positive bacterial cocci. Affected areas were surrounded by reactive astrocytes, fibrous connective tissue, and mixed inflammatory infiltrates. Areas of hemorrhage and infiltration by neutrophils and foamy macrophages with fibrinoid change of small capillaries were observed in the adjacent neuroparenchyma. The inflammation extended to the perivascular spaces in the leptomeninges (mesencephalon, cerebellum, and brainstem, and spinal cord) and spinal central canal. Anaerobic bacterial culture of frozen samples of cerebellum yielded heavy growth of Bacteroides pyogenes.

Keywords: dogs; foreign body; meningoencephalitis; myelitis; neuropathology.

Figure 1.

Meningoencephalitis associated with foreign plant material in a dog. Coalescing pus-filled cavitations rimmed by hemorrhage expand the left caudal colliculus and shift the midline to the right.

Figures 2–8.

Meningoencephalomyelitis associated with foreign plant material in a dog. Figure 2. The left caudal colliculus is effaced by coalescing areas of necrosis and suppuration (arrow) surrounding foreign plant material (arrowhead). There is abundant fibrosis (black asterisk) and hemorrhage (white asterisk) surrounding the central lesion. H&E. Figure 3. The plant material has an outer multicellular wall (arrow) containing pointed barbs (arrowhead) and is surrounded by sheets of neutrophils. Figure 4. Closer view of the plant material wall with clusters of bacterial cocci (asterisk). H&E. Inset: gram-positive bacterial cocci. Gram stain. Figure 5. Thick bands of fibrous connective tissue (arrow) admixed with clusters of mixed inflammatory cells (arrowhead) surround the necrotic areas. H&E. Figure 6. The adjacent neuroparenchyma is effaced by hemorrhage (arrow), neutrophils, and foamy macrophages (arrowhead), with small vessels that have undergone fibrinoid change (asterisk). H&E. Figure 7. Spinal leptomeninges are expanded by neutrophils, lymphocytes, and plasma cells. H&E. Figure 8. The central spinal canal is filled with neutrophils. H&E.