Meningitis Flashcards
What is meningitis?
Inflammation of the leptomeninges and underlying subarachnoid CSF
What ages are more predisposed to meningitis?
Infants, young children and the elderly
What is the underlying cause of most cases of meningitis?
An infectious agent that has colonised or established a localised infection elsewhere in the host and spread to the CNS
What sites of infections are commonly associated with meningitis?
- Skin
- Nasopharynx
- Respiratory tract
- GI tract
- GU tract
How can an infectious organism at a distant site cause meningitis?
By circumventing the hosts defense and gaining access to the CNS
How might bacteria gain access to the CNS to cause meningeal disease?
- Invasion of blood stream and haematogenous seeding
- Retrograde neuronal pathway e.g. olfactory or peripheral nerves
- Direct contiguous spread
In what conditions might organisms directly spread to cause meningeal disease?
- Sinusitis
- Otitis media
- Congenital malformations
- Trauma
What can often worsen the problem in meningitis?
The immune response
How can the immune response worsen meningitis?
Creates leaky blood vessels, allowing fluid and WBC to enter meninges and cause swelling
What is the result of swelling in meningitis?
Decreased blood flow to the brain
What can cause inflammation of the meninges?
- Viruses
- Bacteria
- Other micro-organisms
- Non-infective causes
What is the more common form of meningitis?
Viral
What is the more serious form of meningitis?
Bacterial
Due to the severity of bacterial meningitis, what should happen to all patients?
Treat as bacterial meningitis until proven otherwise
What viruses can cause meningitis?
- Enterovirus
- HSV (generally type 2)
- VZV
- Mumps
- HIV
What are the most common bacterial causes of meningitis in neonates?
- GBS
- Listeria monocytogenes
- E. coli
What are the most common bacterial causes of meningitis in infants?
- H. Influenzae type B
- Nisseria meningitides
- Strep. pneumonia
What group of infants are at risk of H. influenza B meningitis?
Those who are unvaccinated
What are the most common bacterial causes of meningitis in adults?
- Strep. pneumoniae
- H. influenza B
- N. meningitidis
- Gram -ve bacilli
- Staphylococci
- Streptococci
- L. monocytogenes
What are the most common bacterial causes of meningitis in the elderly and immunocompromised?
- Klebsiella pneumoniae
- E. coli
- Pseudomonas aeruginosa
- Staph aureus
What are the non-infective causes of meningitis?
- Malignant cells e.g. leukamia and lymphoma
- Chemicals e.g. intrathecal drugs
- Drugs e.g. NSAIDs, trimethoprim
- Sarcoidosis
- SLE
What are the risk factors for meningitis?
- CSF shunts
- Dural defects
- Spinal procedures
- DM
- Alcoholism
- Bacterial endocarditis
- IV drug use
- Adrenal insufficiency
- Malignancy
- CF
- Crowding e.g. students
What are the possible presenting features of meningitis?
- Fever
- Headaches
- Neck stiffness
- Photophobia
- Signs of shock
- Kernig’s sign
- Brudzinksi’s sign
- Paresis and focal neurological defecits
- Seizures
What are the signs of shock?
- Tachycardia
- Respiratory distress
- Poor urine output
What is Kernig’s sign?
Pain and resistance on passive knee extension with hips fully flexed
What is Brudzinksi’s sign?
Hips flex on bending the head forward
How may viral meningitis be distinguished from bacterial meningitis?
Often indistinguishable but can be more mild
In what age groups are the classical symptoms of meningitis often not seen?
Infants and the elderly
Are investigations used in meningitis?
Yes but should not delay treatment
What investigations may be useful in meningitis?
- LP
- Renal function testing
- Coagulation
- MRI
- CT
- CXR
When should an LP be performed in suspected meningitis?
Immediately if no signs of raised ICP or focal neurology