Neuro Flashcards
What is the function of oligodendrocytes?
Form myelin that wraps around axons (same function as Schwann cells in PNS)
What is the function of astrocytes?
Star shaped cells whose processes form blood brain barrier
What is the function of microglia?
Phagocytic cells, fixed macrophages of CNS
What is central chromatolysis?
Degenerative change, dispersal of Nissl substance
What is neuronophagia?
Microglia gather around necrotic neuron and phagocytose it to remove the debris
What are the histological characteristics of axonal degeneration?
Empty, dilated
What is a spheroid?
Focal axonal swellings filled with degenerate organelles
What kind of necrosis is typically seen in the CNS, and what are the characteristics of this type of necrosis?
Liquifactive necrosis
Empty looking brain
What is astrocytosis?
Increase in size and number of astrocytes in response to injury
Repair of CNS after injury (not very good at their job though)
What are gemistocytic astrocytes?
Plump, reactive astrocytes with eosinophilic cytoplasm
What is the appearance of Alzheimer’s type II astrocytes, and what disease process are these cells typically seen in?
Enlarged, vesicular nuclei
Classic of hepatic encephalopathy (lots of ammonia)
What is hydrocephalus?
Excess fluid in the brain
What are the different types of hydrocephalus?
Internal: fluid in ventricles (most common in veterinary medicine: in mesocephalic aquaduct)
External: fluid in arachnoid space
Communicating: fluid in both
In which breeds of dog is hydrocephalus most common?
Brachycephalic breeds and some toys breeds (chihuahuas)
Microencephaly
Abnormally small brain, seen in BVD in cattle and Border Disease in sheep
Hydranencephaly
Near complete or complete absence of cerebral hemispheres, leaving fluid filled sacs formed by meninges lined by CSF
Porencephaly
Cystic cavitation of brain (less severe manifestation of hydranencephaly)
Lissencephaly
Brain lacks normal gyri and sulci
Not normal for any domestic animals, but normal for some exotics
Anencephaly
Absence of brain
Prosencephalic hypoplasia
Absence of cerebral hemispheres with preservation of some portion of brain stem
Cranium bifidum/spina bifida
Defect through which brain/spinal cord and meninges can protrude; almost always on dorsal midline
What is the most common brain malformation seen with BVD infection?
Cerebellar hypoplasia
What is the underlying cause of storage diseases?
Accumulation of substance in cells
What happens to cells which accumulate substrate in lysosomal storage diseases?
Loss of function, distended cells, don’t normally die
How are storage disease inherited, and when do they typically present with neurologic signs?
Autosomal recessive; present early in life, progressive, die
How are storage diseases named (in general, you do not need to know specific names)?
Named according to substance that doesn’t degrade
Which cells in the CNS are most sensitive to ischemia?
Neurons and oligodendroglia most susceptible (gray matter)
What are the causes of polioencephalomalacia? Where are the lesions located?
Thiamine deficiency, high sulfur intake (which inactivates thiamine), some cases of water deprivation
Necrosis of gray matter of brain
What is the cause of leukoencephalomalacia? Where are the lesions located?
Eating moldy corn for longer than 1 month
Necrosis of white matter of brain
What is the cause of indirect salt poisoning?
Ingestion of high salt diet WITH restricted water intake for several days
Think pigs
What are the ways in which bacterial infections get to the CNS?
- Most are secondary to septicemia
- Septic emboli from endocarditis
- Abscesses from hematogenous spread or direct invastion – usually through cribiform plate or middle ear
In what species do we most often seen listeriosis?
Sheep (and other ruminants)
What is the causative agent of listeriosis?
Listeria monocytogenes
Outbreaks associated with heavy feeding of silage
What are the characteristic lesions of listeriosis, and where are the lesions typically located?
No gross lesions, but microabscesses histologically
Lesions located in brainstem
What is the pathogenesis of the listeriosis encephalitis?
Bacteria invade oral mucosa and then spreads up branches of trigeminal nerve
What is the causative agent of thrombotic meningoencephalitis? Which species does it affect?
Histophilus somni
Affects cattle (and sheep)
What is the pathogenesis of development of CNS lesions for thrombotic meningoencephalitis, and what are the lesions?
Septicemia causes vasculitis with hemorrhage, necrosis, and thrombosis
Lesions include hemorrhage, vasculitis, thrombosis, infarction, neutrophilic meningoencephalitis
What are the general histologic features of viral infections?
- Non-supperative meningoencephalitis
- Perivascular cuffing
- Gliosis
- +/- viral inclusions
- +/- neuronal necrosis
What are the principal reservoirs for rabies in the US?
skunks, foxes, racoons, bats
What tissues is the rabies virus tropic for?
CNS and salivary gland
What is the pathogenesis of rabies viral infection from inoculation to spread to the CNS?
Virus inoculated into wound –> replicates in muscles cells –> spreads to sensory paravertebral ganglia –> travels along peripheral nerves to CNS
What are the lesions for rabies?
Non-supperative encephalomyelitis, ganglioneuritis, and parotid adenitis
Negri bodies in hippocampus of carnivores
Negri bodies in Purkinje cells of herbivores
What is the cause of pseudorabies? What species are affected by this disease? What are the clinical signs?
Caused by suid herpesvirus 1
Can affect ALL common domestic species
Clinical signs in pigs: NO pruritis, mild fever, prostrate, convulsions, SMEDI in sows
Clinical signs in non pigs: INTENSE pruritis, high fever, neurologic signs, ALWAYS fatal
What are the clinical signs of caprine arthritis-encephalitis virus and visna-maedi virus?
CAE: hind limb ataxia, paresis, paralysis, death in GOATS
VM: hind limb ataxia, paralysis, death due to starvation in SHEEP
In both: pneumonia, arthritis, mastitis
In what age animals is neurologic disease typically observed with CAE and VM?
CAE: young kids 2-4 months of age
VM: sheep > 2 years of age
What are the lesions of CAE and VM?
CAE: non-supperative leukoencephalomyelitis, demyelination
VM: non-supperative meningoencephalitis most severely affecting white matter, demyelination
What species are typically affected by fungal infections with Cryptococcus neoformans?
Cats (but also dogs and horses)
Immunocompromised animals
How do Cryptococcus neoformans infections get into the brain?
Starts as nasal or sinus infection –> directly enters brain through cribiform plate
May spread hematogenously from pulmonary lesions
What are the histologic lesions of Cryptococcus neoformans?
Mucopolysaccharide capsule, non-staining
What is the cause of equine protozoal myelitis? Why are organisms not seen in most cases?
Cause is Sarcocystis neurona
Not seen because animal has been treated prior to euthanasia
What is the cause of transmissible spongiform encephalopathies (TSEs)?
Cause by prions, abnormal isoforms of a normal cellular protein called prion protein
How do animals typically acquire TSEs?
Transmitted horizontally through consumption of infected feed material
What are the lesions of TSEs?
Intracytoplasmic neuronal vacuolation, astrocytosis
What are the histologic lesions of FIP?
Loss of ependymal cells
Reactive astrocytes
Periventricularitis
