Neuropath Lecture 3 Flashcards
describe hypomelinogenesis
- not enough myelin forms
- described in many dog breeds; puppies develop tremors between 10 days and 8 weeks of age
- due to in utero viral infections
-border disease: sheep
-hog cholera: pigs
-BVD: calves
describe leukodystrophies
- disorders of myelin synthesis and maintenance
- also called demyelinating diseases
- typically heritable, early onset, lack of inflammation, symmetrical lesions, qualitative defect in myelin
example is globoid cell leukodystrophy
describe globoid cell leukodystrophy (Krabbe’s disease)
- lysosomal storage disease
- deficiency of galactocerebroside beta-galactosidase
- globoid cells (like gitter cells but bigger because can’t break anything down) accumulate in CNS and PNS
- diagnose via nerve biopsy
describe demyelination
- removal of structurally normal myelin
- primary/true demyelination:
-removal of myelin is the primary lesion, axon sparing, may see status spongiosus on report
-often in inflammatory setting
-causes:
–coonhound paralysis
–viral diseases: canine distemper, CAE - secondary:
-removal of myelin following axonal damage (wallerian degeneration)
-subsequent degeneration and removal of myelin
-will see: spheroids, swollen myelin sheaths (clear vacuoles), and digestion chambers from macrophages coming in to clean up
what are the 6 types of inflammation we see in neural tissue?
- suppurative/purulent/neutrophilic: bacterial, eastern equine encephalitis virus, or west nile virus
- lymphoplasmacytic: viral or immune-mediated
- granulomatous:
-protozoa and metazoan parasites
-mycobacterial
-fungal - eosinophilic (+/- granulomatous): helminths and other metazoan parasites
- pyogranulomatous (neutrophils + granulomatous):
-fungal
-FIP - idiopathic:
-granulomatous, lymphoplasmacytic, necrotizing
what are the 4 routes of bacterial disease in neural tissue?
- hematogenous
- direct extension from adjacent structure: erosion of bone or along nerves
- via peripheral nerves (listeria encephalitis)
- implantation via penetrating wound
describe listeria encephalitis
organism: gram + rods
pathogenesis:
enter peripheral nerve fibers (V and VII) via oral/nasal abrasion, travels to caudal brain stem to V/VII nuclei, causes inflammation via perivascular cuffs, microabscesses, neuronopahagia)
- moves via actin polymerization
diagnostic confirmation: microscopic plus fluoroscopic antibody, IHC, culture, PCR
clinical signs:
1. unilateral cranial nerve signs: circling, head tilt
2. bilateral lesions in the CAUDAL brainstem!!
3. primarily a winter-spring disease of feedlot or houses ruminants
4. less acidic pH of spoiled silage enhances multiplication of L. monocytogenes
what are the two routes of origin of viral infections?
- via blood: most common
-EEE
-WNV
-canine distemper - via nerves:
-lyssaviruses
-herpesviruses
what are 4 general and 3 specific features of viral infections?
general features:
1. mononuclear cells (primarily lymphocytes)
2. MNCs form perivascular cuff
3. glial response (primarily microglia)
4. milk meningeal inflammation
specific features:
1. neuronal degeneration (neuronophagia): WNV, BVD, listeria
2. viral inclusion bodies: rabies, canine distemper
3. demyelination: canine distemper
describe rabies (3)
- enters/spreads via nerves
- salient/most important feature: Negri bodies (intracellular inclusions in neurons)
- confirmatory testing: FA is gold
standard but need correct area of fresh brain tissue
describe canine distemper (5)
- immune response:
-prompt: subclinical disease
-none: fatal encephalomyelitis
-delayed: chronic inflammatory white matter disease - age:
-young/juvenile: primary GRAY matter disease
-mature: primarily WHITE matter disease - viral strain: some strains primarily cause gray matter disease, some primarily cause white matter disease
- salient features:
-lymphoplasmacytic meningoencephalitis
-intranuclear and inctracellular inclusions: mostly in astrocytes
-demyelination - ancillary testing:
-FA: fresh tissue
-IHC: formalin fixed
-PCR: fresh tissue/CSF
describe Feline Infectious Peritonitis (FIP)
- salient features:
-surface oriented leptomeninges, choroid plexus, ependyma (ratty edges)
-pyogranulomatous, lymphoplasmacytic, fibrinous - ancillary testing:
-FA: fresh
-PCR: typically fresh
-IHC: formalin fixed - immune-complexed mediated disease, where pre-existing antibodies accelerate the disease and virus infected macrophages disseminate the disease
- cell mediated immunity determines outcome:
-effusive FIP: produce antibodies but fail to generate effective cell-mediated immunity response
-noneffusive FIP: partially protective cell-mediated immunity response that is unable to contain the virus
describe EEE and West Nile Virus (5)
- seasonal, mosquito borne virus
- hyperexcitability and restlessness, developing to lethargy and depression and cortical blindness
- may be primarily neutrophilic response that progresses to lymphoplasmacytic
- infects neurons resulting in neuronophagia
- diagnostic confirmation: IHC, serology (IgM), VI PCR
describe CAE
- lentivirus transmitted by colostrum and milk, +/- direct contact
- immune-mediated, virus replicates in macrophages
- encephalitis occurs in younger animals, unlike other lentiviral infections
- in kids, lesions are most severe in the brainstem and spinal cord and asymmetrical
- will see leukoencephalomyelitis with demyelination
describe 3 yeast fungal diseases
- blastomycosis:
-surface related
-broad based budding - cryptococcosis:
-surface related
-narrow-base budding - coccidioidomycosis:
-out west mostly
-endosporulation
generally describe 2 types of hyphal fungal disease
- phaeohyphomycosis:
-cladosporium/cladophialophora
-large discolored areas of necrosis
-cats - apsergillosis:
-angiophilic, necrotizing
-secondary to gastroenteritis
describe 2 metazoan parasite diseases
- parelaphostringylosis:
-P. tenius: meningeal worm of deer
-affects small ruminants and camelids
-spinal cord: necrosis and hemorrhage
–larvae tunnel in spinal cords and form tracks
-will see eosinophilic inflammation but need to localize lesion to make diagnosis! - halicephalobus gingivalus: horses
-encephalomyelitis, nephritis, posthitis, osteomyelitis
-granulomatous, multinodular
-larvae and female adults parthenogenic
describe equine protozoal myelitis
- sarcocystis neurona
- variable signs; often asymmetric
- usually no gross lesions, but if present: multifocal necrosis and hemorrhage anywhere, more commonly spinal cord
- ancillary testing: IHC, PLEASE localize lesion locally
what are 3 types of protozoal encephalitis
- toxoplasmosis: many species
- neosporosis: affect dogs, cattle, horses
- sarcocystis: horses and dogs
ancillary testing: IHC, PCR
describe transmissible spongiform encephalopathies
- prion diseases; NOT viruses, are devoid of nucleic acids
- disorders of protein conformation
- result in neuronal and neuropil (axons and dendrites) vacuolation
- examples include: scrapie, BSE, chronic wasting disease
