CNS

• Reaction to injury


  • Central chromatolysis or the axonal reaction
  • Swelling of the neuronal cell body, dispersion of central Nissl substance and peripheral displacement of nucleus
• Wallerian degeneration


  • Evident within 24 hours of injury
  • Irregularity of axonal diameter that is followed after 48 to 72 hours by fragmentation of the axon and myelin along its length
• Satellitosis


  • Abnormal clustering of cells around another, different, one; especially a clustering of glial cells around damaged neurons
  • Perineuronal microenvironment is altered
  • Neuron cell bodies are injured
  • Oligodendrogliocytes proliferate and hypertrophy
• Astrocytes


  • Swelling and hypertrophy
  • Gemistocytes – degenerative condition
• Gitter cells


  • Microglia that are foamy lipid-laden macrophages; laden with degenerating myelin
  • Occurs in necrosis
  • Participation on immunoregulation, degeneration and inflammation
• Congenital anomalies


  • Anencephaly
  • Exencephaly
  • Hydranencephaly
  • Lissencephaly
  • Hydroencephalus
  • Cyclopia
  • Narcolepsy
  • Hepatic encephalopathy
• Viral infection of the fetus

  • Organogenesis – microencephaly and myeloschisis (influenza); myeloschisis in young chicken and embryos ( NCD)
  • Cerebellar hypoplasia-atrophy – BVD
  • Hog cholera hypomyelinogenesis, cerebellar hypoplasia
  • Border disease
  • Akabane
  • Blue tongue
• Inflammatory and infectious disease of spinal cord (Bacterial disease)


  • Diskospondylitis is inflammation of intervertebral disk and adjacent vertebral bodies; common in large dogs
  • Vertebral osteomyleitis – inflammation of vertebra without concurrent disk infection
  • Hematogenous spread of infection due to Brucella canis, Streptococcus, E. coli, Proteus spp, Corynebacterium spp., Nocardia spp. And Aspergillus spp
  • Spinal pain is the most consistent finding with fever, depression and weight loss
• Cerebral trauma


  • Concussion – temporary loss of consciousness with recovery; diffuse brain injury
  • Contusion - Focal brain injury; grossly detectable usually hemorrhage
• Cerebral trauma


  • Coup contusion – impact site
  • Contrecoup contusion – opposite side of the brain
  • Coup-contrecoup or contrecoup – coup : two lesions occur together; first term indicates the site of most severe injury
• Specific diseases


  • Salt poisoning
  • Thiamine deficiency
  • Copper deficiency
  • Vitamin E
  • Lead poisoning
  • Selenium
  • Arsenic
  • Organophosphates
  • Cryptococcus
• Inflammatory and infectious disease of spinal cord (Rickettsial disease)


  • Seen in dogs with Rocky mounted spotted fever often with thrombocytopenia, leukocytosis and increased CSF analysis
  • Diagnosis is based on 4 fold increase in serum antibody formation
  • Dogs with Erlichiosis
• Inflammatory and infectious diseases of spinal cord (viral disease)

  • Canine distemper - most common disorder in dogs worldwide; acute or slowly progressive; brain and spinal cord are the most commonly affected
  • Caprine arthritis encephalomyelitis – cause by lentivirus, also cause pneumonitis and arthritis; common in 2-4 mo goat; non suppurative inflammation with demyelination or necrosis in white matter of the spinal cord
• Inflammatory and infectious disease of spinal cord (viral disease)


  • Equine infectious anemia – occasionally produce encephalomyelitis
  • Equine herpesvirus 1 (EHV-1) encephalomyelopathy – affects horses worldwide; infects vascular endothelial cells particularly CNS
  • Feline infectious peritonitis (FIP) - Immune mediated response to coronavirus; Associated with dry than wet form; pyogranulomatous lesion in neural parenchyma, choroid plexus, ependyma and leptomeninges
• Inflammatory and infectious disease of spinal cord (viral disease)

  • Feline leukemia virus-associated myelopathy - ataxia, weakness of pelvic limbs and paraplegia within 1 year; pathologic findings: white matter degeneration, swollen axons and dilation of myelin sheath in spinal cord and brain
  • Rabies –caused by neurotropic virus; produces multifocal, non suppurative polioencephalomyelitis in all domestic animals
• Inflammatory and infectious disease of spinal cord (fungal disease)

  • Cryptococcus neoformans – most common to involve cns in all domestic animals; Common in dogs and cats ; occasional in horses
  • Blastomyces dermatitides, Histoplasma capsulatum, Coccidiodes immitis, Aspergillus – affected animals have other organs involvement such as lungs, skin, eyes, bones
• Inflammatory and infectious disease of spinal cord (protozoal disease)


  • Equine protozoal myeloencephalitis - Produce nonsuppurative, necrotizing meningoencephalomyelitis caused by Sarcocystis neurona
  • Neosporosis – caused by Neospora caninum; Nonsuppurative encephalomyelitis most common in dogs; In young puppies, can cause ascending paralysis with rigid contraction of the muscles of one or both pelvic limb
  • Toxoplasmosis - Nonsuppurative encephalomyelitis in dogs and cats
• Inflammatory and infectious disease of spinal cord (nutritional disorders)

  • Copper deficiency - CNS disease in sheep, goat and pigs; Swayback is the congenital form in lambs characterized by degeneration and necrosis of the cerebrum; Enzootic ataxia : the acquired form; normal at birth but develop progressive Para paresis with hyporeflexia and muscle atrophy within first few months of life; other signs of diarrhea and unthriftiness in lambs
  • Hypervitaminosis A - develops in cats fed with excess Vit A consisting mainly of liver; Extensive exostoses prominent in cervical and thoracic spine; Clinical signs of neck pain, rigidity of forelimb lameness
• Anencephaly


  Brain is absent at birth; occurs in calves; rare
• Exencephaly


  Brain is exposed through large defect in the skull; inherited in pigs
• Hydroencephalus


  Increase volume of csf; sporadic in large animals, common in calves and vitamin A deficiency implicated; in toy and brachycephalic dogs
• Cyclopia


  Single orbital fossa due to ingestion of plant alkaloid seen in lambs
• Narcolepsy


  Disorder of sleep wake control; excessive sleepiness seen in equine breeds
• Hepatic encephalopathy


  Congenital portosystemic shunt of blood within the liver
• Hydranencephaly


  Marked loss of cerebral cortical tissue within a cranial vault of normal conformation; epidemic in calves, lambs less in piglets; infection in utero with akabane virus, bluetongue, rift valley fever, wesselsborn disease, BVD; in kittens with panleukopenia
• Lissencephaly


  Absence or reduction of cerebral gyri seen in lassa apsos