Neuropath and infectious dz

What is the term for a brain without gyri?

Lissencephaly

What is in gray matter?

Neurons and neuropil

What is in white matter?

Myelin and axons

Layers of the cerebellar cortex

External granular layer (not present on this image)

Molecular layer - light pink

Purkinje cell layer - large cells on border of pink and purple

Internal granular layer - purple layer

**Inner pink layer is white matter!!!**

Where is the lesion located and is it a polioencephalopathy or a leukoencephalopathy?

Cerebral cortex

Polioencephalopathy

Where is the lesion located and is it a polioencephalopathy or a leukoencephalopathy?

Corona radiata

Leukoencephalopathy

What is malacia?

Softening and liquefactive necrosis of neuroparenchyma

Morphologic diagnosis

Leukoencephalomalacia

Morphologic diagnosis

Poliomyelomalacia

Name the meninges

Dura mater - attached to bone in cranium, not attached to bone in SC

Arachnoid mater - avascular

Pia mater - where vessels are located

What are the leptomeninges

Arachnoid mater and pia mater

What is this

Dura mater

Morphologic diagnosis

Focal symmetrical encephalomalacia

Inflammation of the dura mater

Pachymeningitis

Where is the lesion

Cerebellopontine angle

What is this, what does it do, and what is inflammation here called

Choroid plexus

Produces CSF

Choroid plexitis

Normal CNS neurons

Chromatolysis - cell body swollen with loss of Nissl substance

Degenerative change associated with axonal injury

Ischemic neuronal necrosis

Can be seen with toxins, seizures, degenerative disease

What is the structure separating the lateral ventricles?

Septum pellucidum

What happened here?

Hydrocephalus happened

Neuronophagia

Piecemeal phagocytosis of dead neurons

Can be seen with neuronal infection

What is this inclusion called

Negri body

From a cow with rabies

Spongiform encephalopathy

due to Prion disease

What cells produce myelin in CNS?

Oligodendrocytes

What cells produce myelin in the PNS?

Schwann cells

Spheroid (swollen axon)

What is a hydrocephalus lesion in the spinal cord called?

Hydromelia

Wallerian degeneration

Axons die and shrink distal to damage

Remnants of myelin sheathes form vacuoles and “digestion chambers”

Functions of astrocytes

“Brain glue”

Structural support - fibrous tissue

Repair

Blood-brain barrier

Increase in number of astrocytes

Astrocytosis

Increase in astrocytic cell processes

Astrogliosis

Gemistocyte - reactive astrocyte with visible eosinophiolic cytoplasm

Alzheimer type II cell

Astrocyte with clear, swollen nuclei

Seen in hepatic and renal encephalopathies

Role of oligodendrocytes

Myelin formation in CNS

Demyelination

Function of microglia

Macrophages in brain

Phagocytic

Immune defense

What is the single layer of epithelium lining the ventricles and central canal?

Ependyma

Ependymitis - inflammation and necrosis of ependyma

Causes obstructive hydrocephalus

Arrow is pointing to irregular surface in cerebral aqueduct

Microgliosis - proliferation of microglia

Focal proliferation = glial nodule → viral encephalitis

What are gitter cells?

Foamy, lipid-laden macrophages in brain

Have ingested a lot of stuff

Sources of gitter cells

Circulating macrophages

Resident microglia

Where are these hematomas

Epidural

Where are these hematomas

Subdural

Where is this hematoma

Subarachnoid

Term for hemorrhage in the spinal cord

Hematomyelia

What type of lesion is associated with an in-utero BVD infection in a calf?

Hypomyelinogenesis

What is hypomyelinogenesis

Deficient myelin formation

What is leukodystrophy

Abnormal myelin formation or maintenance

Ex) Globoid cell leukodystrophy (Krabbe’s disease)

What is demyelination

Removal of normal myelin

Primary: removal of myelin only, no axon damage - often inflammatory

Secondary: removal of myelin following axonal damage (Wallerian degeneration)

Examples of primary demyelinating diseases?

Coonhound paralysis

Distemper

CAE

Causes of purulent/neutrophilic inflammation

Bacterial infection

Bad viral infection (EEE, WNV)

Causes of lymphoplasmacytic inflammation

Viral

Immune mediated

Causes of granulomatous inflammation

Protozoa

Mycobacteria

Fungi

Causes of eosinophilic inflammation

Parasites

Causes of pyogranulomatous inflammation

Fungi

FIP

Routes of bacterial infection in the brain

Hematogenous spread

Spread from nearby structure (bone, middle ear)

Spread via peripheral nerves (Listeria encephalitis)

Penetrating wound (deer fights)

How does Listeria encephalitis invade the brain?

Enters peripheral nerve fibers via abrasion orally or nasally

V (trigeminal), VII (facial)

Travels to brain stem

General and specific features of viral infections

General features: mononuclear cells, perivacular cuffing, glia, mild meningeal inflammation

Specific features: neuronal degeneration (neuronophagia), viral inclusion bodies, demyelination

What is this and what might it indicate?

Negri body in neuron

Rabies

Characteristic features of canine distemper

Lymphoplasmacytic meningoencephalitis

Intranuclear and intracytoplasmic inclusions

Demyelination

What is happening here

Hydrocephalus due to cerebral aqueduct obstruction from FIP

High protein exudate clots the CSF

What type of hypersensitivity is FIP

Type III

What kind of virus is CAE and how is it transmitted

Lentivirus, through colostrum and milk

Causes asymmetrical lesions in brain stem/spinal cord with demyelination

Difference between phaeohyphomycosis and aspergillosis

Phaeo: usually starts in the cerebellum, large areas of discolored necrosis

Asper: likes vessels, often secondary to gastroenteritis

Difference between blastomycosis and cryptococcosis

Blasto: broad-based budding

Crypto: narrow-base budding, snotty capsule

What is parelaphostrongylosis

Parasitic disease in small ruminants and camelids

Causes spinal cord necrosis and hemorrhage

What is cuterebriasis

Parasitic larvae of botfly that enters through nose in cats

Often in cats

Eosinophilic meningoencephalitis

Wah eh

Blastomycosis

Wat

Phaeohyphomycosis

wah eh

Cryptococcosis

What

Aspergillosis

Potential agents of protozoal encephalitis

Toxoplasma

Neospora

Sarcocystis

Common bacterial causes of otitis media/interna

Staphylococcus

Streptococcus

E. coli

Pseudomonas

Proteus

Mycoplasma bovis (calves)

What is discospondylitis and how is it caused

Inflammation of vertebral disc and adjacent vertebral bodies

Caused by hematogenous spread

Common bacteria involved in discospondylitis

Staphylococcus

Streptococcus

E. coli

Brucella canis

Common bacteria involved in ulcerative keratitis (corneal ulcer)

Staphylococcus

Streptococcus

Pseudomonas

E. coli

Gram staining characteristics of Listeria monocytogenes and where it is found?

Gram-positive rod

Everywhere in nature, often in spoiled food

Pathogenic features of Listeria monocytogenes

Facultatively intracellular; can invade many cells

Hemolysin enzyme

Can spread to adjacent cells without exiting them

Polymerizes cell actin to form pseudopods

Transmission of Listeria

Primary route = ingestion (spoiled silage)

Disease is rare, more common in immunocompromised hosts and in winter

Inhalation also possible but less common

Pathogenesis of CNS Listeria infection

Ingesion/inhalation → entry through damaged mucosa → access to peripheral nerve endings → ascend nerve sheaths → CNS disease

Often infects trigeminal n. (CN V)

Primarily seen in ruminants

Clinical presentation of Listeriosis CNS disease

“Circling disease”/meningoencephalitis

Fever, CN deficit, circling, head tilt, nystagmus, head pressing

Fatal if left untreated

ZOONOTIC

Diagnosis of Listeriosis

Histopathology showing multifocal microabcesses in brain

Immunohistochemistry → Ab present for listeria

Culture/PCR from blood, infected brain, or abortive tissues

Treatment for Listeriosis

Antibiotics

No vaccine; avoid spoiled silage, lunch meats, dairy

Characteristics of Clostridium spp.

Gram-positive anaerobic rods

Produce spores and neurotoxins

Where is Clostridium botulinum found

Soil, decaying organic matter & surrounding plant material

Transmission of C. botulinum

Ingestion of pre-formed neurotoxin

Wound contamination also possible

Pathogenesis of Botulism

Toxin absorbed from GI tract → enters bloodstream → reaches peripheral nerves → taken up by presynaptic nerves at synapse → inhibits ACh release → flaccid paralysis

Clinical signs of Botulism in horses/ruminants

Dysphagia, slow to eat

Muscle weakness, altered gait, recumbency

Mydriasis (dilated pupils)

Decreased gut motility

Bladder distension

“Shaker Foal syndrome” in foals (similar presentation + muscle tremor)

Diagnosis of Botulism

Normal CBC/chem/UA

Toxin needs ID by laboratory (i.e. ELISA)

Treatment of Botulism

Antitoxin → restricts circulating toxin but does not help already ruined nerves

Recovery via rest & new nerve growth

5 types of edema in CNS

Vasogenic edema

Cytotoxic edema

Intramyelinic edema

Interstitial edema

Osmotic edema

What type of edema is associated with trauma, inflammatory lesions, and hemorrhagic lesions?

Vasogenic edema

Disruption of the BBB, buildup of extracellular fluid

What type of edema is associated with hypoxia, metabolic disturbance, and some toxins?

Cytotoxic edema

No BBB disruption, intracellular fluid buildup

What kind of edema is associated with bromethalin toxicity and hepatic/renal encephalopathy?

Intramyelinic edema (type of cytotoxic edema)

What type of edema is associated with hydrocephalus?

Interstitial edema (increased interstitial fluid)

Increased ventricular pressure → disruption of ependyma → CSF enters white matter interstitium → myelin is dissolved + atrophy