CNS infection Flashcards
What are the anatomical categories of CNS infection?
- Meningitis
- Encephalitis
- Mass lesion
- Myelitis
What CNS infections can be caused by bacteria?
- Meningitis
- Meningo-encephalitis
- Abscess
What CNS infections can be caused by viruses?
- Encephalitis
* Meningitis
What CNS infections can be caused by fungi?
- Meningo-encephalitis
* Mass lesions
What CNS infections can be caused by protozoa?
- Mass lesion
* Eosinophilic-meningitis
What are the common bacterial causes of meningitis?
- Meningococcus
- Pneumococcus
- Haemophilus influenza
What are the common bacterial causes of meningoencephalitis?
- Listeria
- Lyme
- Syphilis
What are the common bacterial causes of abscess
- Strep species
- Anaerobes
- Nocardia
What are the common viral causes of encephalitis?
- Herpes simplex virus
- Varicella zoster virus
- Enterovirus
- HIV
What are the common viral causes of meningitis?
- Mumps
- cytomegalovirus
- West nile
- JBE
- JCV
What are the common fungal causes of meningoencephalitis?
Cryptococcosis
What is meningitis?
- Inflammation of the meninges +/- cerebrum (meningoencephalitis)
- Inflammatory CSF
- Can be acute (bacterial or viral) or sub-acute (bacterial)
What are the signs and symptoms of meningitis?
•95% have two of:
- headache
- neck stiffness/rigidity
- reduced GCS
- fever
•Confusion indicative of cerebritis/encephalitis
•Rash - purpuric or petechial but macular early on
Describe the appearance of streptococcus pneumoniae
Gram positive diplococcus
Describe the appearance of neisseria meningitidis
Gram negative diplococcus (pink stained)
What is the appearance of listeria monocytogenes?
Gram positive rods
What are the risk factors of meningitis?
- Travel abroad -non endemic disease
- IVDU - Staph aureus and streptococci
- South east Asia - strep suis spread by pigs
- cochlear implant
Describe the risk factors of pneumococcal meningitis
70% have an underlying disorder: •Middle ear disease •Head injury •Neurosurgery •Alcohol •Immunosuppression
What are the risk factors of listeria meningitis
- Immunosuppression
- Pregnancy
- Age >60
What are the signs of pneumococcal meningitis?
•Much more likely to have neurological effects:
- focal signs
- seizures
- VIII palsy
•Community acquired infection, ENT infection, endocarditis
What are the poor prognostic indicators?
- Pneumococcus
- Reduced GCS
- CNS signs
- Older age
- CN palsy
- Bleeding
Describe the investigations for suspected meningitis
•History and exam: examine throat and examine for cervial lymph nodes •Blood cultures (PCR) •Throat culture, viral gargle •FBC, UEs, LFTs, CRP •Lumbar puncture: - cell count, gram stain, culture, PCR - protein and glucose - viral PCR
When should you do a CT in a suspected meningitis case?
•To exclude mass lesion/mass effect or gross cerebral oedema
•Doesn’t exclude raised intracranial pressure
•You should CT before a lumbar puncture if:
- GCS<12
- CNS signs
- papilloedema
- immunocompromised
- seizure
What should you give before CT scan in suspected meningitis?
Antibiotics
When is a lumbar puncture contraindicated?
- Brain shift
- Rapid GCS reduction
- Respiratory or cardiac compromise
- Severe sepsis
- Rapidly evolving rash
- Infection at LP site
- Coagulopathy (INR>/1.5, platelets<40, DOAC, therapeutic LMWH)
Describe bacterial meningitis CSF
- Neutrophils (and lymphocytes with listeria)
- Raised protein
- Glucose reduced <50%
Describe viral meningitis CSF
- Lymphocytes (neutrophils early on)
- Raised protein
- Normal glucose
Describe TB meningitis CSF
- Lymphocytes
- Raised protein
- Reduced glucose <50%
Describe fungal meningitis CSF
- Lymphocytes
- Raised protein
- Reduced glucose <50%
