Charles Louis Davis and Samuel Wesley Thompson DVM Foundation

For the Advancement of Veterinary and Comparative Pathology

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Image: F30221

Pathology Image
  • SPECIES:
    • EQUINE
  • SYSTEM:
    • NERVOUS
  • ORGAN:
    • BRAIN
  • DIAGNOSIS:
    • FOCALLY EXTENSIVE HEMORHAGE AND NECROSIS OF THE GLOBUS PALLIDUS
  • CONTRIBUTOR:
    • O'TOOLE
  • INSTITUTION:
    • WYOMING STATE VETERINARY LABORATORY
  • GENPATH:
    • TOXICOLOGIC
  • COMMENTS:
    • This is nigropallidal encephalomalacia (NPEM; ‘chewing disease’), for which three toxic plants are now recognized as causative. Two occur in the United States, primarily western states. A third is Rhaponticum repens (creeping knapweed), which is native to central Russia, Turkey, Afghanistan and Mongolia, has been documented as a problem in a nice paper from Australia (below). The major sign in the Wyoming filly was purposeless chewing with inability to swallow. The alert veterinarians had NPEM on her differential list. It was a pleasant surprise to find characteristic lesions at gross-in. Additional information: Chang HT et al. 2012, Toxic equine parkinsonism: an immunohistochemical study of 10 horses with nigropallidal encephalomalacia. Vet Pathol. 49(2):398-402. JF Zachary and MD McGavin, 2012: Pathologic Basis of Veterinary Disease, 5th edition,, p. 844. Sanders SG, Tucker RL, Bagley RS, Gavin PR.: 2001, Magnetic resonance imaging features of nigropallidal encephalomalacia. Vet Radiol Ultrasound 42:4:291– 296. Elliott and McCowan: 2012, Nigropallidal encephalomalacia in horses grazing Rhaponticum repens (creeping knapweed). Aust Vet J. 90(4):151-154]