meningitis - microbiology Flashcards
Encaphelitis
Encephalitis – inflammation of the brain parenchyma
Present clinically as: altered brain function
myelitis
Myelitis – inflammation of the spinal cord
Present clinically as paralysis to parts of body and incontinence
meningitis
meningitis - inflammation of the meninges. Presents as: headache, neck stiffness, photophobia, and nausea and vomiting
Encephalomyelitis
Encephalomyelitis – both the brain and spinal cord are affected
4 acute neurological syndromes caused by viruses
Aseptic meningitis
Encephalitis
Acute Flaccid Paralysis (AFP)
Post-infectious encephalomyelitis
How is CNS injury caused by viruses?
cytolytic viral replication
immunopathology
How do viruses reach the CNS?
Spread from adjacent structures Along peripheral nerves (e.g. Rabies) Crossing the BBB Trojan horsing (HIV, EBV, CMV)
What are the symptoms and signs of aseptic meningitis?
General meningitis signs.
CSF findings of
- pleocytosis of both polymorphs and lymphocytes, with a lymphocyte dominance; Normal glucose; no bacterial growth (aseptic meningitis). Viral presence in the CSF can be confirmed by CPR.
Aseptic meningitis
clinical/lab evidence of meningeal inflammation with negative routine bacterial culture
Post-infectious encephalomyelitis
aka Acute dessiminated encaphalomylitis.
Following a viral infection in some individuals, T- cell confuse the myelin in the brain with viral antigen epitope - molecular mimicry - and then attack it. This is the cause for the delay in onset of neurological symptoms.
When this happens in PNS, it is called Guillain Barre syndrome
With Post-infectious encephalomyelitis, would the virus be cultured in the CSF?
NO. The syndrome occurs in the convalescent phase following some viral infection (or vaccination). What causes the neurological signs is not the virus but the antibodies to the virus.
Post-infectious encephalomyelitis histological features
lymphocytic infiltration and perivascular cuffing of adjacent blood vessels
Guillain Barre syndrome
The inflammation of several peripheral nerves occuring in the recovery phase of certain bacterial and viral infections.
This is a demylenating disease of peripheral nerves.
How do patients with Guillain Barre syndrome preasent
ascending paralysis, associated with pins and needles (paraesthaesia) . Spontaneous recovery
Rabies (Bullet shaped, ssRNA) - causes encaphelitis
It is a zoonosis usually transmitted by bites from dogs and bats
Virus first replicates in the bite site tissue such as muscles and nerve endings - this incubation period may take weeks (9-90 days depending on the bite site)
Then the virus is able to travel up the axons of motor neuron to the brain and cause encephalitis
Virus is shed in saliva
