Lecture: Path of neuro syst (Farina) Flashcards
Encephalo-
Prefix for brain
Myelo-
Prefix for spinal cord
Leuko-
Prefix for white matter
Polio-
Previx for grey matter
Grey matter location
Where the neurons are
- peripherally in cerebral and cerebellum
- All the nuclei
- columns of spinal cord
White matter
Bundles of myelinated axons
- cortex of cerebrum and cerebellum
- peripherally in spinal cord
- mixed in some of gray matter
Neuropil
- all the matter in between glial cells and neurons
- only in grey matter
Nissl substance
- cytoplasmic basophilic granular material
- rER
- polysomes
Axons special stain
Silver stain
black lines are axons
Myelin
Special stain
- Surrounds some of the axons
- clear areas around little dots
*Special stain to look for demyelination: Luxol fast blue stain
Meninges
Layers of Meninges
- Covering of brain and spinal cord
- Outermost layer: dura mater (periosteum of skull)
- Middle layer: arachnoid
- Inner later: Pia mater (vascular layer)
Lepto meninges
arachnoid plus pia mater
Ependymal cells
- Ciliated cuboidal cells that line ventricles
- Helps the flow of CSF
Choroid plexus
- Papillary structure in ventricles
- Lined by epithelial cells
- Produces CSF
*Some inflammatory cells in Choroid plexus is ok
Glial cells
- Oligodendrocytes:
- form myelin that wraps around axons in CNS
- Same as Schwann cells in PNS
- Astrocytes:
- star-shaped cells with special stains
- have elaborate cell processes that form the BBB
- Microglia:
- phagocytic cells
- small nuclei, relatively little cytoplasm
- Glial cells are the tiny dense cells
- Astrocytes are a little larger nuclei and more open chromatin
- Oligadendracytes are smaller with denser nuclei
- Astrocyte
- wrap around blood vessels forming foot processes that make up the BBB
Gitter cells
- Phagocytic cells of the nervous system
- derived from microglia or monocytes
Central chromatolysis
- Degenerative change
- Swollen neuron
- eosinophilic
- dispersion of nissel substance
- nucleus pushed to side
Neuronal necrosis
- Red is dead
- Neurons usually have basophilic cytoplasm, eosinophilic is bad (dead)
- pyknosis, karyorexus, karyolysis
Neuronophagia
Characteristic of….
- Phagocytes (microglia) gather arond a necrotic neuron and phagocytose it to remove debris
- Characteristic of viral infections
Wallerian degeneration
Results in….
Characteristic of…..
- Focal damage to a myelinated axon
- Results in degeneration of the axon segment distal to site of damage
- Characteristic of compressive lesons (IVDD) (wobblers in a horse)
- Wallerian degeneration
- Swollen/empty myelin sheaths
Wallerian degeneration
The little caterpillars are…
- Digestion chambers
- Gitter cells come in and eat degenerate axons
Gitter cells in digestion chambers
Spheroids
- Degenerate axons
- foxal axonal swellings
- big eosinophilic swelling filled with degenerate organelles
Liquefactive necrosis
Typical injuries
End result…
- Lose cell outlines
- Ischemic lesions
- abcesses with lots of proteolytic enzymes
- first area looks squishy, end result is a hole
Coagulative necrosis
- Maintains cell outlines
Fibroblasts
- Can’t repair brain because there are no fibroblasts in the brain
- There are fibroblasts in meninges
Liquefactive necrosis
- Liquefactive necrosis are the holes (spots with no tissue)
Astrocytosis
- Inc in size and number of astrocytes in response to injury
- Repair after CNS injury is largely job of astrocytes
- swell and divide and cell processes proliferate
- Reactive astrocytes
- purple cells with swollen cytoplasm in middle
Gemistocytosis
- Plump, reactive astrocytes with eosinophilic cytoplasm
- Nuclei are NOT necrotic
Alzheimer’s type II astrocytes
- Typical of hyperammonnemia
- Enlarged, vesicular nuclei, typical of hepatic encephalopathy
- Large nuclei with open chromatin pattern
- Flank the neurons in the cerebral cortex
Hydrocephalus
3 types
Most common in….
Can be…
- Internal:
- Fluid in ventricles
- Most common type
- External:
- fluid in arachnoid space
- Communicating:
- fluid in ventricles and arachnoid space
*Most common in brachycephalic breeds
*Can be acquired: CSF flow blockage
- Hydrocephalus
- Brain should not look like a deflated party balloon
Microencephaly
- Abnormally small brain
- Usually cerebrum
Hydranencephaly
- Near complete or complete abscence of cerebral hemispheres
- Leaves fluid-filled sacs formed by meninges filled with CSF
Porencephaly
- Cystic cavitation of the brain
- Usually involving cerebral white matter
- thought to be in-utero infarcts
Lissencephaly
Normal Lissencephalic animals
Posterchild in dogs…
- No Gyri and Sulci in brain (flat brain)
- Species that don’t have gyri and sulci
- rodents
- rats
- bats
- Marmosets and tamarins
- non-mammals
*Lhaso Apso’s poster children
Dysraphia: definition
Types of defects…
- Neural tube closure defects
- Types of defects
- Anencephaly: abscence of the brain
- Prosencephalic hypoplasia: absence of cerebral hemispheres w/ preservation of brainstem
- Cranium bifidum/spina bifida: dorsal midline defect through which brain/spinal cord and meninges can protrude
- meningocele: herniation of meninges
- meningoencephalocele/meningomyelocele: herniation of meninges and brain/spinal cord
Prosencephalic hypoplasia
- cerebellum and brainstem
- Foal with Prosencephalic hypoplasia, almost anencephaly
- Cranium bifidum and meningoencephalocele
- Brain and meninges are up in the defect
- Cranium bifidum and meningocele with age match control
- Spina bifida
Viral causes of malformations
Classic culprits..
- BVD: d. 100-170 of gestation
- usually cerebellar hypoplasia
- Feline panleukopenia
- Hog cholera (classical swine fever)
- Canine Parvovirus
- Border disease (sheep)
*Parvoviruses and Pestiviruses are classic culprits
Cyclopia (synopthalmus)
- Veratrum californicum ingestion on or about day 14
- Usually sheep
Storage Diseases
Most are….conditions
- Accumulation of substances in cells
- Usually due to defective catabolism: defect in lysosomal enzymes
- Tissues which accumulate the substance are those most active in turning over substrate
- Usually autosomal recessive conditions
- neuro signs early in life
- typically progressive and fatal
Storage diseases names according to:
Examples…
- Substrate that has defective degradation
- Examples
- Sphingolipidoses: molecules that form cell membranes
- Glycoproteinoses: carbohydrate component of N-linked glycoproteins
- Mucopolysaccharidoses: glycosaminoglycans
- Glycogenoses: glycogen
- Ceroid lipofuscinoses: lipofuscin
- Ceroid lipofuscinosis
- tan stuff is lipofuscin
- GM2 gangliosidosis (Tay Sachs disease)
Tissues most sensitive to Ischemic lesions….
Examples:
Vascular occlusions in domestic animals are…
- Tissues with high metabolic requirements
- Neurons and oligodendroglia most sensitive to ischemia
- Grey matter is more sensitive than white matter
- Vascular occlusive lesions are rare in domestic animals
Infarct (looks squishy and red)
Histologically: pale region is the necrotic region
Neonatal maladjustment syndrome of foals
(dummy foals)
Histologically:
- Presumed to be due to ischemia and reperfusion
- Lesions
- laminar neuronal necrosis
- multifocal small hemorrhages
- Histologically:
- laminar cortical necrosis
- most foals make it ok tho
Malacic diseases
Definition
Softening => usually means CNS necrosis
Polioencephalomalacia
Def
Associations
Often seen in…
- Def
- softening of the grey matter of the brain
- Associated with
- high sulfur intake
- deficiency in thiamine or disturbance in thiamine metabolism
- occasionally observed in cases of water deprivation
- Often seen in ruminants
- Polioencephalomalacia
- only normal grey matter is at the bottom
- fluoresces under UV light
- Polioencephalomalacia
- fragmented and necrotic
Thiamine deficiency
- Thiamine (Vitamin B1) is a dietary requirement in carnivores
- Some fish have a thiaminase
- Horses can consume plants (Bracken fern and horsetail) that have a thiaminase
Thiamine deficiency
CS
Lesion
- CS
- ataxia
- neck ventroflexion
- incoordination
- mydriasis
- convulsions
- Lesions
- hemorrhage
- necrosis
- neuropil vacuolation in periventricular grey matter
Salt poisoning
Direct
Animal commonly affected
CS
Lesion
- Direct
- too much salt ingestion (high salinity in drinking water)
- Mainly affects cattle
- CS
- vomiting
- diarrhea
- paresis
- blindness
- abdominal pain
- Lesions
- Congestion of abomasal mucosa
- dark water intestinal contents
- NO CNS LESIONS
Salt poisoning
Indirect
CS
Lesions
Usually affects…
- Ingestion of a high salt diet (>/= 2%) in addition to dec water intake
- CS
- blindness
- deafness
- head pressing
- convulsions
- Lesions
- Cerebral edema
- laminar cortical necrosis
- nonsuppurative and eosinophilic meningoencephalitis
- Usually affects pigs
Eosinophils usually….
parasite related
Salt poisoning
- gyri and sulci may look flattened from being squished up against the skull
- Cerebellar coning/herniation
- Salt poisoning
- red, eosinophilic, necrotic neurons
Non-supporative
No neutraphils
Nigropallidal encephalomalacia in horses
Cause
Toxin
Result
- Cause
- ingestion of yellow star thistle (Centaurea solstitialis) and Russian knapweed (Centaurea repens)
- Toxin
- repin-sesquiterpene lactone => causes glutathione depletion
- Result
- Malacia in the blobus pallidus and substantia nigra
- Nigropallidal encephalomalacia
- bilaterally symmetrical holes in the brain
Leukoencephalomalacia in horses
Cause
CS
Lesion
- Cause
- moldy corn consumption for >/= 1 month
- toxin: fumonisin produced by Fusarium moniliforme
- CS
- Circling
- Somnolence
- visual impairment
- weakness
- pharyngeal paralysis
- usually death 2-3 days after onset of clinical signs
- Lesion
- necrosis of cerebral white matter
- moldy corn consumption for >/= 1 month
- Leukoencephalomalacia
- Necrotic white matter
- Holes in the histologic section are bad
- Leukoencephalomalacia
- vacuolization, hemorrhage, necrosis
Lead poisoning
- Most common in Cattle
- also seen in sheep, dogs, and horses
- Cattle usually acquire lead from paint or batteries
- Dogs usually acquire lead from drinking leaded gasoline
Lead poisoning
CS in cattle
Lesions in cattle
Lesions in dogs
Clinically looks like…
- CS in cattle
- staggering
- muscle tremors
- convulsions
- head pressing
- blindness
- hypersalivation
- ruminal atony
- recumbency
- hyperesthesia (to touch and sound)
- death
- Lesions in cattle
- laminar cerebral cortical necrosis if disease course longer than several days
- Lesion in dogs
- White matter edema in brain and spinal cord
- demyelination
*Clinically looks like rabies
