Neuro path: study guide (farina) Flashcards
Function of oligodendrocytes
Form myelin in the CNS
Function of astrocytes
They form the BBB
Function of microglia
- Phagocytic cells of the CNS
- They have a small nuclei and little cytoplasm
What is central chromatolysis
- Response of the nervous sytem to injury - neuronal change
- Cells swollen with central clearing due to dispersio of Nissl substance
- Nucleus is peripherally displace
What is neuronophagia
Phagocytes (microglia) gather around necrotic nucle and phagocytose it to remove debris
histologic characterisctics of neuronal degeneration
- Empty, dilated axon sheaths
- Gitter cells in digestive chambers
- Vacuolization of axons
- Spheroids
Spheroid
- Focal axonal swellings filled wtih degenerative organelles
Type of necrosis typically seen in CNS, and characteristics of this type of necrosis
- Liquifactive necrosis
- Seen with ischemic injury to CNS like infarcts
- Cells digested by liquefaction and all cell outlines are absent
Astrocytosis
Increase in number and size of astrocytes in response to injury
Gemistiocytic astrocytes
- Plump, reactive astrocytes with eosinophilic (red) cytosplasm
Appearance of Alzheimers type II astrocytes
What disease process are these typically seen in
- Swollen with large nuclei and chromatin clearing
- Occurs with hyperammonemia
- often due to hepatic encephalopathy
Hydroencephalus
Abnormal accumulation of fluid in crania cavity
Types of hydroencephalus
- Internal: fluid in ventricles
- External: fluid in arachnoid space
- Communicating: fluid in ventricles and arachnoid space
Breed commonly affected by hydroencephalus
Brachycephalic breeds
Microencephaly
Abnormally small brain
Hydranencephaly
- Near complete or complete absence of cerebral hemispheres, leaving fluid filled sacs formed by minges filled with CSF
Porencephaly
- Cystic cavitation of the brain, usually involving cerebral white matter
Lissencephaly
lack of normal gyri and sulci on brain
anencephaly
absence of brain
Prosencephalic hypoplasia
- absence of cerebral hemisphere but has brainstem
Cranium bifidum/spina bifida
- defect in dorsal midline through which meninges and brain can extrude
- Meningocele: herniation of meninges
- Meningoencephalocele: herniation of meninges and brain
Most common brain malformation seen with BVD
cerebellar hypoplasia
What is the underlying cause of storage disease
- Defects in lysosomal enzymes within the catabolism stage
What happens to cells that accumulate substrate in lysosomal storage diseases?
- Tissues that accumulate substrate first are those that are most active, they cannot clear material so their normal cellular functions get disrupted and the cell will eventually die
How are storage diseases inherited?
When do they present with neuro signs?
- Autosomal recessive
- Present early in life with neuro signs
- Progressive and fatal dsease
How are the storage diseases named
- Named according to class of molecule whose degeneration is defective
What cells in the CNS are most sensitive to ischemia?
- Neurons and oligodentocytes
- Grey matter is more sensitive than white matter
Causes of polioencephalomalacia?
Where are the lesions located?
- Causes
- high sulfur intake
- deficiency of thiamine
- disturbance of thiamine metabolism
- Lesions
- laminar softening of grey matter in cerebral cortex
Cause of leukoencephalomalacia?
Where are the lesions located?
- Cause
- consumption of moldy corn for > 1 month
- causes a mycotoxicosis due to fumonisin
- Lesions
- cerebral white matter necrosis
Lesions of indirect salt poisoning?
What are the causes
- Cause
- high salt diet with restricted water access
- occurs in swine
- Lesions
- cerebral edema
- laminar cortical necrosis
- eosinophilic meningoencephalitis
Ways in which bacterial infections get into CNS
- Heatongenous
- Direct invasion
- through the cribiform plate
- through the middle ear
In what species do we see listeriosis?
What is the causative agent?
- Ruminants who eat a lot of silage
- Listeria monocytogenes
What are the characteristic lesions of listeriosis?
Where are they located?
- Lesions
- micro abscesses in the brainstem
- Often in focus of microgliosis
Pathogenesis of the encephalitis of listeriosis?
- Bacteria spread up the motor and sensory branches of the trigeminal nerve
What is the causative agent of thrombotic meningoencephalitis?
What species does it affect?
- Histophilus somni
- Affects cattle and sheep, especially young feedlot cattle
Pathogenesis of development of CNS lesions of thrombotic meningoencephalitis?
What are the lesions?
- Pathogenesis
- Septicemia leads to cerebral vasculitis with hemorrhage, necrosis, and thrombosis
- Gross lesions
- multifocal hemorrhage and necrosis
- Histologic lesions
- vasculitis, thrombosis, infarction, neutrophilic meningoencephalitis
General histologic features of viral infections
- Non-suppurative meningoencephalitis
- +/- myelitis
- Perivascular cuffing
- Gliosis: infiltration of glial cells
- +/- viral inclusions
- +/- neuronal degeneration/necrosis
Principal reservoirs for rabies in the US
- Skunks
- Raccoons
- Foxes
- Bats
What tissues is the rabies virus trophic for?
- CNS
- Salivary gland
Pathogenesis of rabies from inoculation to spread to CNS
- Virus inoculated into wound from bite - virus replicates in muscle cells near inoculation site - spreads to sensory paravertebral ganglia - virus travels along peripheral nerves to CNS
What do lesions in rabies look like?
- Non-suppurative encephalomyelitis
- ganglioneuritis
- parotid adenitis
- amount of inflammation and neuronal degeration varies
- Negri bodies (cytoplasmic inclusions) present most often in hippocampus in carnivores and Purkinje cells in herbivores
What is the cause of pseudorabies
Porcine herpes virus 1
Species affected by pseudorabies disease
can affect all common domestic species
CS pseudorabies in pigs
- Young
- prostration
- convlusions
- twitching
- high mortality rate
- Sows
- SMEDI
CS of seudorabies in other species
- Intense pruritis
- fever
- neuro signs (high mortality)
CS of caprine arthritis encephalitis virus
- Goat:
- kids 2-4 months
- Hind Limb ataxia
- paresis
- paralysis
- death
- Adults
- mastitis
- pneumonia
- arthritis
CS of Visna-Maedi virus
- Sheep > 2 yrs old
- Hind limb ataxia
- lip trembling
- Hind limb paresis
- death due to secondary infection and starving
- Adults
- mastitis
- pneumonia
- arthritis
Lesions associated with caprine arthritis encephalitis virus
- Non suppurative leukoencephalomyelitis
- demyelination
Species typically affected by Cryptococcus neoformans
- Cats
- Dogs
- Horses
How do Visna-Maedi viruses get to the brain
- Starts in nasal or sinus infection, enters through direct invasion through cribiform plate
What are the histologic lesions of the cryptococcus
- Thick, non-staining mucopolysaccharide capsule, makes it look like soap bubbles on tissue sections
Infectious agent of equine protozoal myelopathy
- Sarcocystic neurona
Why are organisms not usually seen in most cases of EPM
Most animals have been treated for EPM before they were euthanized
Cause of transmissible spongiform encephalopathies
- Prions
- Normal is PrPC and changed into abnormal form PrPSc
How do animals typically acquire TSEs
- Horizontal transmission
- Due to consumption of infected feed material
What are the lesions of TSE
- Intracytoplasmic neuronal vacuolation
- astrocytosis
Difference between static and dynamic stenosis in wobblers
- Dynamic
- compression of spinal cord only when horse bends or extends neck
- usually occurs in young animals
- C3-C4 and C4-C5 usually affected
- Static
- Occurs regardless of position of neck
- usually older animals
- C5-C6 and C6-C7 usually affected
