Cerebral disease: inflammatory/infectious diseases Flashcards
How frequent are intracranial inflammatory/infectious diseases
Inflammatory and infectious diseases are relatively common causes of cerebral signs in cats
How do inflammatory/infectious diseases express themselves
Often they produce multifocal neurological disease as well as concurrent systemic illness (especially FIP)
What would be your main differentials for infectious/inflammatory causes of cerebral disease in cats
Viral
- FIP
- FeLV/FIV
- Rabies
- Borna disease virus
- Unknown/uncharacterized viral causes
Protozoal
- Toxoplasmosis
Fungal
- cryptococcosis
- coccidioidomycosis
Bacterial
- meningitis
- brain abscess
Other infections
- Aberrant parasites
- Feline poliomyelitis
- progressive lymphohistiocytic meningoencephalomyelitis
What are the defenses of the brain against aggression/infection
The CNS has a basic immune system and, to protect itself, relies on physical mechanisms such as:
- skull
- meninges
- blood-brain barrier
The blood-brain barrier is a modified tight endothelium that lines the brain’s capillaries
What is the pathomechanism for intracranial infection
Inflammation of the CNS may involve the neural parenchyma, meninges or both
- during inflammation, the integrity of the BBB is compromised, enhancing access to the brain parenchyma by the organism, as well as inflammatory cells and edema fluid that may cause collateral damage to the neurons via the effects of inflammatory cytokines or ischemia
The majority of the infectious agents that cause CNS disease establish primary infection in the peripheral tissues first
- organisms may enter the CNS either via direct invasion of the endothelial cells or may infect peripheral white blood cells that then acquire access to the brain
- infectious emboli may also become lodged within the vessels of the brain and form local abscessation
- some microorganisms are directly cytopathic to neural tissue
How could you make a diagnosis of inflammatory disease of the brain
There may be systemic evidence of the presence of infectious organisms (e.g., positive LCAAT)
CSF analysis is the most direct way to establish the presence of inflammatory CNS disease
- CSF collection should not be performed if increased intracranial pressure is suspected (this is usually indicated by mental depression) because of a risk of brain herniation
What is the condition to observe inflammatory cells in the CSF analysis
The absence of inflammatory changes on CSF analysis does not rule out inflammatory CNS diseases because either meningeal or ventricular inflammation must be present for changes to be observed
- it would be unusual for these structures not to be involved in the inflammatoory process
Which causes are associated to a suppurative inflammation in the CSF analysis
Suppurative inflammation is seen most commonly with bacterial infections and FIP
- bacterial infections of the CNS are rare
- observation of degenerate neutrophils and intracellular bacteria make the diagnosis of a bacterial disease much more likely
