What are the types of neuronal injuries?
-accumulations
-vacuolation
-necrosis
What are the characteristics of neuronal accumulations?
-genetic diseases
-storage diseases
-example is canine mucopolysaccharidosis
What are the characteristics of neuronal vacuolation diseases?
-occur with prion diseases
-no inflammation, just vacuoles
What are the signs of neuronal necrosis?
-hypereosinophilic
-loss of nissle substance
-increased nuclear pigmentation
What are the causes of neuronal necrosis?
-hypoxia*
-hypoglycemia*
-seizures
-excitotoxicity
-chemical intoxications
What are the possible causes of axonal degeneration?
*dying back
-secondary to neuronal necrosis
*trauma
-compression or transection
*spheroids
-bottleneck of axoplasmic flow
What are the steps of axonal degeneration?
-fragmentation of the axon and myelin
-phagocytosis of debris by infiltrating macrophages
What are the possible gross lesions seen with neuronal injury?
-no gross lesions (common)
-hemorrhage
-gray to yellow discoloration
-softening/flattening of tissues
What are possible causes of increased intracranial pressure?
-inflammation with associated edema
-edema without associated inflammation; intracellular or extracellular
-hemorrhage/hematoma
-mass
What is the end result of any cause of increased intracranial pressure?
cerebellar herniation
What is the significance of a “key hole” foramen magnum?
can make it difficult to identify cerebellar herniation vs normal cerebellum with key hole allowing greater visibility
What is subtentorial herniation?
when the cerebellar lobes herniate under the tentorium cerebelli that normally separates the cerebrum and cerebelli
What is the main sign of subtentorial herniation?
abnormal dents on the cerebellar lobes
What are the possible signs of trauma to the nervous system?
-fractures
-hemorrhage
What nervous system trauma can be seen in rabbits that kick too hard?
comminuted vertebral fracture
What is the pathogenesis behind IVDD in chondrodystrophic dogs?
-loss of elasticity of the nucleus pulposa
-extra stress on the annulus fibrosus
-herniation
What is the difference between disc herniation in chondrodystrophic and non-chondrodystrophic dogs?
-chondrodystrophic dogs experience type 1; herniation of nucleus pulposus through the annulus fibrosis
-non-chondrodystrophic dogs experience type 2; herniation/buldging of nucleus pulposus and annulus fibrosis
What microscopic change will be seen at the site of disc extrusion?
axonal degeneration
What are the characteristics of fibrocartilagenous embolus?
-comes from nucleus pulposus
-more common than stroke in animals
-can be identified with special alcian blue stain for fibrocartilage
What are the gross lesions seen with necrosis?
-often none
-may see soft, tan to gray/yellow areas
What can cause laminar cortical necrosis/polioencephalomalacia?
-thiamine deficiency
-sulfur compounds
-salt toxicity or water deprivation
What are the characteristics of nigropallidal encephalomalacia?
-associated with yellow star thistle
-globus pallidus and substantia nigra are affected
What are the characteristics of leukoencephalomalacia?
-white matter turns yellow and necrotic
-can see hemorrhage in gray matter
-associated with moldy corn poisoning
What are the gross changes seen in the meninges with bacterial infection?
-cloudy
-possible pus
-possible redness
-possible herniation
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