2-3. neuro sys path 2-3

leukodystrophy vs. demyelination

• leukodystrophy: formation of abnormal myelin or lack of myelination during development

  • rare

  • genetic or infectious

• demyelination: myelin forms normally, then is lost due to a disease process

  • more common

causes of demyelination

• virus-induced

  • canine distemper virus

• immune-mediated (type II or type IV hypersensitivity)

pathogenesis of lysosomal storage diseases

genetic defects in lysosomal enzymes that would usually break down specific substrates → material accumulates in lysosomes → lysosomes swell, causing cells to swell → loss of cellular function

• neurons & oligodendrocytes are particularly sensitive (can affect other cell types too)

• clinical signs usually appear early in life

breeds associated with globoid cell leukodystrophy

• west highland white terriers

• cairn terriers

what cells are involved in globoid cell leukodystrophy?

• oligodendrocytes affected → demyelination

• gitter cells help phagocytose degraded myelin

general routes of entry into the CNS

• hematogenous

• leukocyte trafficking

• retrograde axonal transport

• direct extension (ex. through ear canal, trauma)

causative agents of pyogenic infections

• streptococcus spp.

• staphylococcus spp.

• e. coli

• trueperella pyogenes

• klebsiella spp.

• corynebacterium spp.

histophilus somni lesions in the brain

infarction → thrombotic meningoencephalitis (TME)

what is the typical distribution of listeriosis lesions in the brain? (how does it get to the brain?)

• retrograde axonal transport via cranial nerves to enter the pons/medulla (often most severe in brainstem)

• asymmetric inflammation → unilateral clinical signs

histological findings of listeriosis

• gram stain: gram positive, short chains of bacilli

• inflammation rich in neutrophils

general histological findings of viral diseases

• non-suppurative encephalitis (perivascular cuff)

• glial nodule (gliosis)

• intranuclear/intracytoplasmic inclusion bodies