Neuropathy Flashcards
What are the layers of the meninges from deep to superficial?
- Pia
- Thin
- Arachnoid
- Spider-like
- Thin
- Dura
- Thick
Where are the astrocytes found and what is their function?
- Found in the central nervous system
- Functions
- Structural- create blood-brain barrier and supportive framework for neurons
- Insulates synapses
- Mildly phagocytic
- Metabolic functions
- Monitor and regulate interstitial fluid surrounding neurons
- Transmit information to each other
- Stimulate the formation of scar tissue
Where are the microglia found and what is their function?
- Phagocytes of the CNS- similar to macrophages
- Brain will recruit if infection present
- Smallest of the glial cells
- Cigar-shaped when reactive
Where are the oligodendrocytes found? What are their functions?
- Produce myelin in the CNS
- Surround few axonal processes
- Injury will cause demyelination
Where are the ependymal cells found? What is their function?
- Found in the CNS
- Cuboidal cells
- Line cavities and ventricals of CNS
- CSF production
- Barrier functions
- Give rise to epithelial layer that surrounds the choroid plexu
Where are the Schwann cells found and what is their function?
- Myelinate axons in the PNS
- Surround all axons of neurons in the PNS
- One schwann cell can myelinate many axons
- Wraps around a cell and squeeze out the cytoplasm so that all that is left is the myelin sheath
Where are the satelite cells found and what is their function?
- Support cells in the PNS, mainly in ganglia
- PNS equivalent of astrocytes
Why are neurons vulnerable to injury?
- They have a high metabolic rate
- They have little energy storage
- They have to take care of their axon
- The axon has no nissl substance
- Cannot make protein
- Cannot dispose of own waste
- The axon has no nissl substance
What is being pictured here? In what condition will this be seen?
- Chromatolysis of neuronal cells
- Cells get bigger
- Adaptive response to injury
- Does not usually resolve
- Seen in equine grass sickness
What is being depicted here? What can cause this condition?
- Neuronal wallarian degeneration
- Cells fall apart
- Breakdown of a nerve fibre distal to the point of injury (downstream to where the insult took place)
- Can occur with compression or stretching injury
- Creates axonal debris which has to be cleared by the myelo-macrophages to create a platform for healing
- Some regeneration can occur and may form a neuroma (mass of neurons- can be painful)
What is being depicted here? What may cause this condition?
- Neuronal vacuolation
- Cells become vacuolated
- Rare form of injury
- Common artefact in histology
- Seen with
- Transmissible spongiform encephalopathies
- Lysosomal storage diseases
- Early cell injury
- Some toxins
- Order of susceptibility (from most to least susceptible)
- Nerons, oligodendrocytes, astrocytes, microglia, blood vessels
What is being depicted here? What causes this disorder?
- Acute neuronal necrosis
- Usually a result of ischaema
- Non-ischaemic causes of neuronal necrosis
- Hypoxia
- Hypoglycaemia
- Nutritional deficiency
- Toxins
What are some causes of laminar cortical necrosis?
- Salt poisoning
- Water deprivation
- Lead and mercury toxicity
- Polioencephalomalacia in ruminants (cerebrocortical necrosis (CCN))Pathology unclear but is thought to be a thiamine deficiency or sulfide toxicity
- Thiamine is required for glucose metabolism
Describe neural cytoxic oedema.
- ATP deficit and failure of sodium pump where sodium and water build up within the cell (similar to hydropic degeneration)
- Intracellular
- Can occur as a result of hypoxia, ischaemia, and toxins
Describe the types of demyelination.
- Primary
- Myelin forms normally and then is selectively destroyed
- Caused by: toxicity, circulatory oedema, immune mediated, infectious cases, idiopathic, and hereditary, impaired maintenance, nutritional (copper, vitamin B12), toxins (cyanide)
- Secondary
- Loss of myelin following axonal damage (Wallerian degeneration, for example)
- The myelin is not able to be formed properly
What is Fibrocartilaginous embolic myelopathy (FCEM)?
- Results from the blockage of blood vessels
- Key features
- Large breed dogs commonly affected
- Acute onset
- Non-progressive course
- Non-painful dramatic asymmetric paresis or paralysis without involvement of the head (animals are quite bright otherwise)
- 60% of cases have history of trauma
- Marrow Embolism following fracture
Describe different characteristics of viral entry into the central nervous system.
- Neurotropic
- Are able to bypass into the nervous system
- Viruses which can overcome innate immunity of brain- Rabies (Rhambdovirus), for examplee
- Lesions are microscopic
- Endothelioptropic
- Endothelial cell damage leads to vascular injury and secondary parenchymal necrosis and haemorrhage
- Pantropic
- affecting various tissues without showing special affinity for one of them
- Infectious Bovine Rhinotracheitis (IBR), for example
- Virus can be latent in nerve ganglia
Desribe the sequelae, symptoms, and forms of listeriosis.
- Sequelae
- Infection of oral mucosa caused by consuming basic silage
- Infections of trigeminal nerve
- Infection of trigeminal ganglion in brain
- Forms
- CNS
- Abortion
- Sepsis
- Symptoms
- Circling
- Facial nerve paralysis
- Drooling
- Pharyngeal paralysis
- Recumbency, paddling, death
What is a contusion?
A region of injured tissue or skin in which blood capillaries have been ruptured
Describe the different types of intervertebral Disk Disease (IVDD).
- Chondrodystrophic
- Nucleus pulposus replaced by chondroid tissue
- Degeneration of annulus fibrosis is secondary
- Common in young dogs
- Non-condrodystrophic
- Degeneration begins in annulus fibrosis
- Nucleus pulposus undergoes fibrsosis
- Common in middle-aged dogs
- Age-related and not breed dependent
What is cervical vertebral stenotic myelopathy?
- “Wobbler” horse syndrome
- Due to malformation and malalignment of the cervical vertebrae
- Found in fast-growing and young horses
- Can lead to cord compression and hindlimb ataxia
What is hydrocephalus? Describe the types of hydrocephalus.
- Increased amount of fluid within the cranial cavity as a whole
- Internal (Common)
- Within ventricles
- Congenital
- Obstruction not found
- Common in brachycephalic dogs- mesencephalic aqueduct may be stenotic
- Sporadic in cattle
- Acquired form
- Causes: obstruction due to inflammation or space-occupying lesion (SOL) compression
- External
- Within arachnoid space
- Communicating
- Within both locations
- Hyrocephalus ex vacuo
- Ventricles dilate to replace lost tissue
- Generally caused by blockage of flow through the ducts
What are the different types of cerebellar hypoplasia?
- Inherited
- Acquired
- Usually due to environmental teratogens which attack germinal cells in external granular layer of cerebellum (source of neurons)
- Can be caused by parvo and pestiviruses
- Feline panleukopaenia, canine parvovirus, schmallenberg virus, for example
What is cerebellar abiotrophy?
Premature degeneration of nervous tissue elements after they have formed
Describe the potential neuropathy of guttural pouch mycosis.
Can spread to the recurrent laryngeal nerve and lead to vocal cord hemiplegia (paralysis of one side)
Describe neural lysosomal storage diseases.
- A group of rare diseases, mostly inherited, which often affect the CNS
- Lack of enzymes in lysosomes leads to a build-up of waste substrate in the cell
- Globoid cell leukodystrophy (Krabbe’s disease)
- Myelin is not broken down properly to galactocerebroside and psychosine
