CNS Infections Flashcards
What does pyogenic meningitis mean?
Thick layer of suppurative exudate covers the leptomeninges over the surface of the brain and there are neutrophils in the subarachnoid space
Name four common pathogens that cause meningitis
Strep pneumonia/pneumococcal
Neisseria Meningitis
Haemophilus influenza
Listeria monocytogenes
Describe strep pneumonia
Gram positive coccus found in the nasopharynx
Often in neonates, elderly, patients with cribiform plate fractures or diabetes/alcoholics
May be linked to cochlear implants
Describe Neisseria Meningitis
Gram negative diplococcus found in the throat
Gains access to meninges through the blood stream
Often in young people particularly crowded areas leading to outbreaks
Endotoxin produces symptoms
What does haemophilus influenza require to grow?
Blood factors
Why is h.influenza meningitis rare?
Vaccination
Describe listeria monocytogenes
Gram positive bacilli, bacteraemia illness most commin in immunocompromised, diabetics, alcoholics or elderly patients
How does bacterial meningitis present?
Fever, stiff neck, headache, vomiting, photophobia, rash, confusion, lethergy
State three ways of which bacteria can spread to the meninges
Nasopharyngeal colonisation
Direct extension of bacteria (sinusitis, brain abscess)
From remote foci of infection (endocarditis, pneumonia)
What is the treatment for bacterial meningitis?
Ceftriaxone
Dexamethasone
Amoxicillin if >60 or immunocompromised
If a patient has been to a penicillin resistant country in last 6 months what is given instead of amoxicillin?
Vancomycin
If a patient is penicillin allergic what can be used?
Chloramphenicol
State the complications of bacterial meningitis
Purulence - clusters at base of the brain, convexities of sulci and exudate around nerves
Invasion - pia mater prevents abscess formation
Cerebral oedema
Ventriculitis/hydrocephalus
What is aseptic meningitis?
Meningitis not caused by bacteria - can be infectious or non-infectious
In aseptic meningitis what are the features of CSF
Low WBC
Minimal protein
Normal glucose
Describe viral meningitis
Common in late summer/autumn often due to enteroviruses. Associated with travel and can be diagnosed by stool sample , throat swab or CSF PCR
How is viral meningitis treated?
Supportive and self limiting
Define encephalitis
Infection of the brain parenchyma often due to a virus
How does encephalitis present?
Insidious onset, stupor, coma, seizures, paralysis, confusion, psychosis, behavioural/mental changes
How is encephalitis investigated?
Lumbar puncture
EEG
MRI
Ask specific questions to identify virus
What will an MRI of encephalitis look like?
Pus and oedema in gyrus and sulci
What treatment is given initially in encephalitis?
Aciclovir
When must a lumbar puncture not be performed?
If there is a possibility of increased ICP
Describe the CSF findings in viral meningitis
10^1 - 10^3 lymphocytes
Gram stain will be negative
No antigen
Normal protein and glucose
Describe CSF findings in bacterial meningitis
10^1 - 10^4 polymorphs Gram stain will be positive Antigen test will be positive High protein Low glucose, <70% blood glucose
What are warning signs in a patient with suspected meningitis?
Low/fluctuating GCS Focal neurology Seizure Shock Bradycardia/hypertension Papilloedema
