2.14 - Cerebral inflammation Flashcards
What is meningitis?
- inflammation of the meninges caused by viral or bacterial infection
- usually subarachnoid - milky white exudate on autopsy over surface of brain
What is encephalitis?
Inflammation of the brain caused by infection or autoimmune mechanisms
What is cerebral vasculitis?
Inflammation of blood vessel walls (sometimes called angiitis) - can cause small blockages/haemorrhages
What is myelitis?
Inflammation of the spinal cord
How was the blood-brain barrier (BBB) found?
If you inject dye intravenously into organs removed from an animal, it will accumulate in most tissues except the brain (unless brain is compromised)
What is the vascularisation like of the brain?
- very densely vascularised (20% of cardiac output is to brain)
- no neuron is >100um from a capillary
What is the BBB formed from?
BBB capillaries have extensive tight junctions at the endothelial cell-cell contacts, massively reducing solute and fluid leak across the capillary wall
What is the function of the BBB?
- because of the ‘tightness’ of the BBB capillaries, solutes that can exchange across peripheral capillaries cannot cross the BBB
- allows BBB to control the exchange of these substances using specific membrane transporters to transport into and out of the CNS (influx and efflux transporters)
- blood-borne infectious agents have reduced entry into brain tissue
What defines the vasculature?
Astrocyte endfeet
What happens when the BBB gets compromised?
- BBB compromised through stroke / physical trauma etc
- blood components including fibrinogen leak into brain
- over time, the astrocytes react to the fibrinogen leakage by withdrawing their endfeet from the walls of the vessel, compromising BBB even more
- BBB compromise also leads to build up of collagen in basement membrane which hardens the vessel leading to small vessel disease in brain
What are the symptoms of encephalitis?
- initially flu-like with pyrexia and headaches
- subsequently within hours, days or weeks:
- confusion or disorientation
- seizures or fits
- changes in personality and behaviour (frontal lobe)
- difficulty speaking (left hemisphere)
- weakness or loss of movement (motor cortices)
- loss of consciousness (brainstem)
What are the causes of encephalitis?
- in most cases, encephalitis is caused by viral infection
- mosquito, tick and other insect bites
- bacterial and fungal infections
- trauma
- autoimmune
What are the commonest viruses which cause encephalitis?
- Herpes simplex virus
- measles
- varicella (chickenpox)
- rubella (German measles)
What are the treatments for encephalitis?
- depends on underlying cause but may include:
- antivirals e.g. acyclovir
- steroids
- antibiotics/antifungals
- analgesics
- anti-convulsants (prophylactic)
- ventilation
What is multiple sclerosis?
An autoimmune demyelinating disease of the CNS