Lecture 33: Nervous 2 Flashcards
What does dysraphia mean?
abnormal seam
= neural tube defect
List 4 typees of dysraphia that can occur?
anencephaly
meningocele
meningoencephalocele
meningomyelocele
What is anencephaly? What causes it?
no brain
- cerebral hemispheres dont develop but the brainstem does
- can live because brainstem is there
rostral neural tube defect (it doesn’t close)
What is a meningocele? What causes it?
meninges herniate out of the skull
due to dorsal midline defect with sac of meninges
What is a meningoencephalocele? What causes it?
it is a protruding sac of brain and meninges
due to dorsal midline defect
‘cranium bifidum’
What is a meningomyelocele? What causes it?
It is when the meninges and spinal cord protrude out in a sac
due to spina bifida (vertebrae don’t close)
can be related to an autosomal dominant condition (manx cats are prone)
What is lissencephaly? What causes it?
cerebrum develops without gyri and sulci = smooth brain
due to abnormal neuron migration
What species are prone to lissencephaly? Is it normal or abnormal?
abnormal in lhasa apso dogs/kittens/labs
normal in birds/rats/lagomorphs/mice
What causes cerebellar hypoplasia? Give 3 examples?
in utero viral infection
cat = panleukemia virus
cow = BVDV
pig = classical swine fever
What is the pathogenesis of cerbellar hypoplasia
viral infection in dividing cells
- impacts the cerebellum
causes neuronal necrosis resulting in hypoplasia
What is the most common congenital neurologic disease in animals
congenital hydrocephalus
What are 3 causes of congenital hydrocephalus?
in utero viral infection
developmental abnormalitis of the ependyma and/or ventricles
reduced brain tissue adjacent to the ventricles
What is the pathogenesis of congenital hydrocephalus
viral infection destroys ependymal cells
narrowing of the mesencephalic aquaduct that connects the 3rd and 4th ventricles
CSF accumulates and is forced into the adjacent white matter (the grey matter can remain normal)
edema and degeneration and atrophy of the myelin and axons in the white matter
reduced white matter resulting in expanded ventricles
Where in the brain does congenital hydrocephalus usually affect?
it depends on where the CSF is obstructed
it can affect the lateral/3rd/4th ventricles and the subarachnoid space
What are the gross lesions associated with congenital hydrocephalus
doming of cranium if it occurs before the skull sutures fuse
thin bones of the calvarium
fontanelles are prominant
enlarged ventricles
thin white matter and potentially normal grey matter
if it is rapid = herniation of the cerebellum into the foramen magnum (caudal displacement of the cerebral hemispheres)
What animals are commonly affected by congenital hydrocephalus?
< 3 months
brachycephalic and toy breeds
What are the clinical signs of congenital hydrocephalus
behaviour change
- slow learning
- dull
- periodic aggression
circling/seizures
slow motor development
What animals does acquired hydrocephalus usually affected?
mature animals
What are 3 causes of acquired hydrocephalus
compression from a space occupying mass
infection/inflammation
hydrocephalus ex vacuo
- it is secondary to neural tissue loss without an obstruction
What is porencephaly?
small CSF cysts in the cerebral cortex
What is hydraencephaly
large CSF cavities in the CNS tissue due to abnormal development
What causes porencephaly and hydraencephaly? Give 2 examples
in utero viral infection
resulting in necrosis of neuroblasts which forms a defect that is filled with CSF
ex. cow with BVDV or rift valley fever
