CNS Infections Flashcards
In what ways can the CNS become infected?
Direct invasion by neurotropic micro-organisms
Iatrogenic
Latent viral infection
Toxin mediated disease
Immune mediated disease
What does neurotropic mean?
Micro-organism has a tendency to attack the CNS
Give an example of a CNS infection caused by direct invasion by neurotropic micro-organisms?
Encephalitis
Meningitis
Meningoencephalitis
Give some examples of iatrogenic causes of CNS infection?
Neurosurgery
Shunts: to drain excess fluid on the brain in hydrocephalus
Give an example of a latent viral infection that causes CNS infection?
Shingles: Herpes Zoster
Give some examples of toxin mediated CNS infections?
What does ‘toxin mediated’ mean?
Botulism
Tetanus
The pathogen releases a toxin that causes the damage to the body
Give an example of some immune mediated diseases that are linked with CNS infections?
Guillain Barre
Post-infection inflammation
ADEM + AHLE
(diseases to do with demyelination)
What is Guillain Barre syndrome briefly?
When the body’s immune system attacks the peripheral nervous system
It occurs shortly after an infection, this triggers the immune system to go into overdrive
What is meningitis?
Inflammation of the meninges
Often caused by infection, but not always
What are the clinical features of meningitis?
Fever
Severe headache
Meningismus:
- photophobia
- neck stiffness
Altered mental state, not always
What is meningismus?
Symptoms that meningitis causes:
- photophobia
- neck stiffness
Only meningitis causes meningismus.
True or false?
False!
Can be caused by encephalitis and para-meningeal infections too
What is a para-meningeal infection?
Just another type of infection, such as tonsillitis
They can cause meningismus
What can cause meningitis?
Infection:
- bacteria
- virus
- fungal
- tuberculous
Non-infectious:
- tumours + cysts
- drugs
- autoimmune: SLE
- post-neurosurgery
When you see a patient with meningitis-like symptoms what should you do?
Always err on the side of caution and check for bacterial meningitis
It is very severe and if missed can be fatal
Which are common bacteria that cause meningitis in adults and children?
Neisseria meningitidis
Strep. pneumoniae
Listeria monocytogenes
Which are common bacteria that cause meningitis in neonates?
E. coli
Group B strep
Which pathogen is screened for in pregnant women? Why?
Group B streptococci
It can be picked up by neonates in the birth canal and can cause meningitis
Which viruses cause meningitis?
Mumps
Enteroviruses (like polio)
Investigations of meningitis?
Lumbar puncture promptly!
Analyse:
- cell count
- protein level
- glucose level
Blood cultures
CT: check for raised inter-cranial pressure
What is meningococcal septicaemia?
Septicaemia: infection in the bloodstream
Caused by a meningococcal pathogen
What’s the difference between meningococcal septicaemia and meningitis?
Meningitis is just inflammation of the meninges
Meningococcal septicaemia occurs as a result of meningitis and is infection of the bloodstream
Clinical features of meningococcal septicaemia?
Purpural, non-blanching rash
If you see a Purpural rash that doesn’t blanch, what have they likely got?
Meningococcal septicaemia
What is chronic meningitis and what causes it?
When symptoms last over weeks
- Mycobacterium tuberculosis
- Syphilis
- Lyme disease
- Fungal
- Parasitic
- Non-infectious, drugs
Why should you check inter-cranial pressure using a CT scan before you do a lumbar puncture?
Lumbar puncture is contraindicated if they have raised inter-cranial pressure
Doing a lumbar puncture will lower pressure in spinal cord, and since brain is at higher pressure than it wants to be it could herniate downwards: coning
Management of meningitis?
Start antibiotics immediately in all cases of suspected bacterial meningitis
You can always stop them if tests prove otherwise later
Supportive, ITU care
What drugs do you use to treat meningitis?
Cefotaxime
Amoxicillin
Dexamethasone, a steroid if suspected pneumococcal meningitis
How do you select antibiotics to use to treat meningitis?
Ones that are appropriate for the pathogen
Ones that can cross blood-brain barrier
Ones that are safe at high doses
When are steroids indicated in meningitis treatment?
If suspected pneumococcal meningitis
When analysing the CSF, what would you suspect the pathogen was if protein was raised?
Bacteria
Or TB
When analysing the CSF, what would you suspect the pathogen was if there were an excess of polymorphs?
Bacterial
What is encephalitis?
Inflammation of actual brain parenchyma
Often caused by infection
What causes encephalitis?
Viral infection most often
Immunosupression: AIDS
IV drug use
Auto-immune
Liver failure
Which viruses often cause encephalitis?
Herpes simplex
Other herpes
Enteroviruses, like mumps
Clinical features of encephalitis?
Fever Headache Decreased consciousness Confusion Coma Seizures Focal weakness Meningismus
Investigation of encephalitis?
CT and MRI show oedema often in the temporal lobes
CSF fluid analysis shows a moderate increase of WBCs
Blood:
Viral serology could indicate cause
Management of encephalitis?
Anti-virals
Supportive care
What is a cerebral abscess?
An abscess (an accumulation of pus) in the brain
Can you get abscesses in the spinal column?
Yes
In the epidural or subdural space, though they are rare
What causes cerebral abscesses?
Local spread from a local infection, i.e. ear or sinus
Haematological spread
What pathogens often cause cerebral abscesses?
Staph. aureus
Strep. pyogenes
Gram -ves
Anaerobes
Parasites, fungal etc.
Clinical features of cerebral abscess?
Fever
Headache
Seizures
Focal neurological signs: like a stroke, signs depend on where the abscess is in the brain
Investigation of cerebral abscess?
CT scan
NOT lumbar puncture, due to risk of coning
What is ‘coning’ of the brain?
Herniation of the cerebellum down through the foramen magnum
Causes compression of the brainstem, causing death/damage
Management of cerebral abscess?
Anti-microbials
Drainage/aspiration (rarely)
What is shingles?
A painful acute inflammation of the nerve ganglia
Caused by a virus that lies dormant for years and gets reactivated
What virus causes shingles?
Herpes Zoster
How does herpes zoster cause shingles?
After an infection, often in childhood (chickenpox) the virus lies dormant in the dorsal root ganglia
It gets reactivated for unknown reasons, and causes shingles
Clinical features of shingles?
Dermatomal distribution:
Pain and tingling precede a rash
Chicken-pox like rash
Very painful
This develops on the dermatome of the nerve that the virus is affecting
Often affects lower thorax
Or ophthalmic division of trigeminal nerve, affecting face
What is the shingles rash like?
Papules and vesicles
Weeping
Management of shingles?
Anti-virals
What is a complication that occurs from shingles?
Post-herpetic neuralgia
Pain that persists after shingles
Very disabling
How can you prevent shingles?
Vaccination of all adults over age 60
