2 - Nervous System II Flashcards
Malformations of the CNS
- Meningoencephalocele and Cranium bifidum
- Meningomyelocele and Spina Bifida
- Lissencephaly
- Hydracephaly
- Cerebellar hypoplasia
- Hydrocephaly
- Hydromyelia
- Syringomyelia
Meningoencephalocele and Crainium Bifidium
- When meninges and brain go OUTSIDE
Meningomyelocele and Spina Bifida
- Failure of ‘bone’ to fuse
Lissencephaly
- NO gyri
- More common in Lhasa Apso
- *prone to seizures
Hydraencephaly
- Fluid filled brain cavities
- *fluid replacing brain parenchyma
- *if small cavity=porencephaly
What are the 3 reasons why hydraencephaly might occur?
- Congenital malformation
- In utero infections
- Copper deficiency in ruminants
What causes cerebellar hypoplasia? Calves, kittens, puppies, piglets
- Calves: pestivirus (BVD)
- Kittens: panleukopenia virus
- Puppies: canine parvovirus
- Piglets: classic swine fever virus
- *or CONGENITAL MALFORMATION
Hydrocephalus
- Accumulation of CSF in ventricular system and/or subarachnoid space
- *dilation which causes pressure ATROPHY of the brain
- *2 types: internal and external AND communicating and non-communicating
- *communicating is MOST common and MOST important
Internal hydrocephalus
- If fluid accumulates in ventricular system
External hydrocephalus
- If fluid accumulates in the sub-arachnoid system
Non-communicating hydrocephalus
- Fluid accumulations is SECONDARY to obstruction (ex. mass)
Congenital hydrocephalus causes and type
- Hereditary: brachycephalic dog breeds
- In utero viral infections
- *communicating hydrocephalus
Acquired hydrocephalus causes
- MAIN: Obstruction (non-communicating hydrocephalus)
a. Ex. cholesterol granuloma in horses - Loss of brain tissue (less common and less pronounced)
a. Ex. polioencephalomalacia
*usually older animals
Hydromyelia
- Abnormal dilation of central canal of SC that leads to formation of a cavity in which CSF may accumulate
Syringomyelia
- Fluid filled cyst within the SC separate from the central canal and NOT lined by ependymal cells
- *outside central canal
Encephalitis
- Inflammation of brain
Meningitis
- Inflammation of meninges
Myelitis
- Inflammation of spinal cord and meninges
Ganglioneuritis
- Inflammation of the ganglia
- Ex. certain viral diseases
Choroditis
- Inflammation of choroid plexus
What are the portals of entry into the CNS?
- Direct extension
o Inner ear
o Nasal sinuses through cribriform plate or bones - Hematogenous
- Retrograde axonal transport (ex. rabies and listeria)
Brain abscesses
- Uncommon
- Caused by bacteria
o Usually secondary to septicemia - Direction extension OR from the brain
- Streptococcus, E. coli, Staphylococcus, Cornyebacterium, Klebsiella
2 differentials for a calf with meningitis: causes
- Streptococcus
- E. coli
- *secondary to septicemia from an umbilical cord infection
What will you see if an animal has septicemia?
- Petechial hemorrhages
- Polyserositis (fibrin in multiple cavities)
- Polyarthritis
- *enlarged SPLEEN (CULTURE)
- Pus in eye
- *meningitis
Meningitis and neonatal septicemia
- Common, especially in neonates
- Blood born infection OR caused by direct extension
What do blood born infections in neonates cause?
- Blood born infection
*meningitis +/- encephalitis and lesions of septicaemia
What does meningitis look like groosly?
- *meninges appear cloudy and congested
- may see PUS=accumulates below the cerebellum (VENTRAL ACCUMULATION)
What are the bacteria that can cause meningitis?
- E. coli
- Streptococcus spp.
- Salmonella spp.
- Pasteurella spp.
- Haemophilus spp.
(neurotropic) Herpesvirus
- Mainly enter CNS by RETROGRADE axonal transport
o Can enter by hematogenous spread via viremia - Hide in neurons (ganglia) and lie their dormantly (viral latency)
- *ganglioneuritis is ALWAYS present
What causes ganlioneuritis?
- Equine herpes virus 1
- Bovine herepesvirus 1
- Pseudorabies in pigs
Rabies
- Caused: lyssavirus
- Zoonotic
- Infection through biting
- *reach brain via retrograde axoplasmic transport system
- *NO GROSS LESIONS
- GANGLIONEURITIS
Rabies histologically
- Ganglioneuritis
- Non suppurative encephalitis +/- eosinophilic intracytoplasmic inclusion bodies (Negri bodies)
Cryptococcus neoformans (ex. in cats)
- Particular affinity for CNS
- Enter leptomeninges and subarachnoid space by DIRECT extension through CRIBIFROM PLATE after a nasal or sinus infection OR hematogenously
- Has a think mucinous capsule=protects organism from host defenses
o *’soap bubble’ like lesions due to MUCIONOUS CAPSULE
Other fungi infections
- Coccidioides immitis
- Blastomyces dermatitidis
- Histoplasma capsulatum
- *reach brain by hematologic spread (usually from LUNG)
- **produce granulomatous lesions everywhere
Neospora and brain
- Affinity for CNS
o *CNS in utero: abortion
o CNS after birth - DH=dog
Equine protozoal encephalomyelitis
- Sarcocysis neurona
- Affects SC and brain stem: inflammation
Toxoplasma
- DH=cat
- *multisysteminc infection +/- nervous system
- Abortions
What causes Feline Ischemic Encephalopathy (transient ischemic attacks)?
- Aberrant cerebrospinal migration of Cuterebra larva after entry into the brain via nasal cavity
What does feline ischemic encephalopathy look like grossly?
- Unilateral NECROSIS of white and grey matter
What does feline ischemic encephalopathy look like on histo?
- Vasculitis
- Thrombosis
- ischemia
- INFARCTION
Coenurus cerebralis (cestode) in brain
- Larval form of dog tapeworm (multiceps multiceps)
- *most commonly infests sheep (occasionally other ruminants)
- **form cyst in brain
What causes transmissible spongiform encephalopathies?
- PRIONS (proteinaceous infectious organism)
o Miss folded protein and becomes resistant to degradation
o Present in neurons and is infectious - *disease transmission has only been achieved by inoculation of brain extracts from infected animals NOT just misfolded-PrP
TSE in sheep
- Scrapie
TSE in bovine
- BSE
TSE in feline
- FSE
TSE in deer (mule, elk, black-tailed, white-tailed)
- Chronic wasting disease
Hepatic encephalopathy: steps
- Acute and chronic liver failure and hepatic atrophy associated with congenital or acquired vascular shunts
- Veery high blood AMMONIA (toxic to brain!)
- Hepatic encephalopathy
What are the 2 types of hepatic encephalopathy seen histologically (except in horse, only one)
- Alzheimer’s type II astrocytes
- Spongy change (vacuolation at grey and white matter junction): NOT IN HORSES
Radiculoneuritis
- Inflammation of nerve roots of SC
- Ex. cauda equina
