* CNS Infections Flashcards
What are the 3 common CNS infections?
1) Meningitis (bacterial)
2) Encephalitis (viral)
3) Brain abscess
What is meningitis?
- Inflammation of the meninges surrounding the brain and spinal cord
- Can be caused by bacteria, viruses or fungi
What does the brain look like in early and late meningitis?
Early: Meninges are highly inflamed and red
Late: Fibrosis present (white areas) , brain stem may be affected
S/s of meningitis?
- Fever
- Headache
- Irritability
- LOC
- Delirium
- Vomiting
- Light aversion
- Purpura (skin rash)
Signs of nerve irritation
- Neck stiffness (chin cannot touch sternum)
- Kernig’s sign (cannot straighten leg when being lifted up)
- Brudzinski sign (bending of knees when neck is raised)
Types of meningitis?
1) Meningococcal meningitis
2) Bacterial meningitis
3) Tuberculous meningitis
4) Viral meningitis
What is the most prominent symptom of meningococcal meningitis?
Ecchymotic patches
What are the bacteria that commonly causes bacterial meningitis?
- Streptococcus pneumoniae
- Hemophilus influenzae
- Meningococcus
What are the common signs of bacterial meningitis?
- Purulent exudate + thrombosed veins on brain
- Hemorrhagic infarction on vessels
- Neutrophils in subarachnoid space
- May progress to adrenal hemorrhagic necrosis (Waterhouse-Friderischen syndrome)
What are the s/s of tuberculosis meningitis?
-Small yellow nodules on brain surface
- Brain histology shows
~ Lymphocytes
~ Vasculitis
~ Langhan’s giant cells
How is tuberculosis meningitis acquired?
Primary site through lungs -> Hematogenous spread into CNS
What viruses mostly cause viral meningitis?
- Mumps
- Measles
- Echoviruses
What findings are indicative of viral meningitis?
- Dense lymphocytic infiltration on microscopy
- CSF shows lymphocytes
How to diagnose meningitis?
1) CT scan
- To exclude mass lesions in unconscious px
2) Lumbar puncture
- ^ Protein
- Dec glucose
- Neutrophils >5000 cells/mm^3
3) Blood culture
- To rule out septicemia
Treatment for meningitis?
1) IV Abx
2) Vaccination
- Quadrivalent vaccine A,C,Y, W135
- HIB against H. influenza B
3) Supportive measures
4) Rifampicin prophylaxis for close contacts
- Of meningococcal meningitis
What are the complications of meningitis?
1) Cranial nerve palsies
- Due to fibrosis
- Damage on cranial nerves
2) Hydrocephalus
- Due to blockage of aqueduct in subarachnoid space
3) Cortical atrophy
- Due to vessel thrombosis + ^ ICP
- Leading to mental retardation, blindness, deafness and paralysis in children
What is encephalitis?
Inflammation of the parenchyma (tissue) of the brain by viruses
- Herpes simplex
- VZ
- CMV
Causes focal dysfunction
What are the types of encephalitis?
1) Herpes simplex encephalitis
2) Japanese encephalitis
What is the pathology and symptoms of Herpes simplex encephalitis?
Pathology:
- Edema -> hemorrhage of brain tissue which causes necrosis of temporal lobes
- Usually occurs in the temporal lobes first
S/s:
- Fever, chills, signs of ^ICP
- Behaviour and personality changes
- Seizures
- Drowsiness, coma
- Aphasia, hemiplegia
- 3 signs of meningism
What are the signs of meningism?
1) Neck stiffness
2) Photophobia
3) Headache
Who are those at risk of Japanese encephalitis?
- Regions with culex mosquito endemic
- Rural areas
How to diagnose encephalitis?
1) CT scan
- To exclude mass lesions
- To localise the site of lesion
2) Lumbar puncture
- ^ Protein
- Normal glucose
- ^ lymphocytes
3) EEG
- Will show slow waves in temporal lobes in herpes simplex encephalitis
What is a brain abscess?
- Localised collection of pus within the brain parenchyma
- Usually caused by pus forming/pyogenic bacteria
- Presents as a space-occupying lesion (SOL)
How to treat encephalitis?
1) Anticonvulsants
- To prevent and treat epilepsy
2) DEXAMETHASONE + MANNITOL
- To treat ^ ICP
3) Antivirals
- IV ACYCLOVIR
- For herpes simplex encephalitis
Treatment for brain abscess?
1) Drainage/excision of abscess
2) IV Abx
What are the indications for lumbar puncture?
1) for Diagnosis
- Rule out CNS infections/meningitis
- Thunderclap headache to rule out SAH
~ When CT/MRI is normal but headache is >3days
2) Therapy
- To evaluate for normal pressure hydrocephalus with walk test
What are the contra-indications for lumbar puncture?
- Infx near puncture site
- Presence of space-occupying lesions
- Bleeding tendencies
~ Plt <80 or INR >1.4
What is the procedure for lumbar puncture?
Drape -> Lignocaine (5-10mls) -> Tap -> Measure opening pressure -> Collect a few bottles of 15 drops/1ml -> Measure closing pressure
What does an abnormal opening pressure mean in a lumbar puncture?
Opening (Normal 10-18cm H20):
- ^ pressure
~ Infection, hydrocephalus or benign intracranial hypertension
- Low pressure
~ Spinal block with ^ ICP, intracranial hypotension
What are the investigations done on the CSF from a lumbar puncture?
- Cell count
- Gram stain
- Culture
- Glucose (compared with fingerprick BSL)
~ Low glucose indicates bacterial infx
Note: 1st bottle is never sent for cell count and microscopy due to high RBC
What are the meanings of the colours of CSF?
Clear
- Normal
Yellow
- Hyperbilirubinemia, ^ protein, ^ blood breakdown products
Orange
- ^ Blood breakdown products,^ carotenoid digestion
Pink
- ^ Blood breakdown products
Green
- Hyperbilirubinemia
- Purulent CSF
Brown
- Meningeal melanomastosis
Slide 38 typical CSF findings in different types of meningitis?
