CNS Infections Flashcards
What is meningitis?
Inflammation of meninges (dura mater/arachnoid mater & pia mater) surrounding brain & spinal cord
Result in irritation of nerves that pass through meninges
What are the causes of meningitis?
Viral, bacterial and fungal
What is the early signs of meningitis?
Meninges are highly inflamed and red in colour
What is the late/chronic sign of meningitis?
White colour = fibrosis
*extensive meningitis = whole brainstem affected
What are the symptoms of meningitis?
- Fever
- Headache
- Irritability
- Delirium
- LOC
- Stiff neck (May feel pain when flexing neck + chin cannot touch sternum; *most common sign)
- Vomiting
- Joint pain
- Purpura (in some cases)
*meningococcal meningitis can cause ecchymoptic patches over skin
What are the 2 signs that confirms the diagnosis of meningitis?
- Kernig sign (hamstring muscle spam when trying to extend flexed knee when hip is flexed)
- Brudzinski sign (severe neck stiffness which causes hips and knees to flex when neck is flexed)
What are the causal bacteria for bacterial meningitis?
- Streptococcal pneumonias
- Haemophillus influenzae
- Meningococcus
What does bacterial meningitis show?
- Purulent exudate and thormbosed veins on surface and base of brain
- Haemorrhagic infarction of penetrating vessels
- Neutrophils in subarachnoid space and CSF
What can bacterial meningitis cause?
Septicaemia and haemorrhage over body = high mortality
What is bacterial meningitis associated with?
Adrenal haemorrhagic necrosis (Waterhouse-friderischen syndrome)
How is TB spread for TB meningitis
Haematogenous spread to CNS (primary site: lungs)
What can you see in TB meningitis?
Small yellow nodules (tubers) on brain surface
Histology shows langerhans giant cells, lymphocytes and vasculitis
What viruses are involved in viral meningitis?
- Mumps
- Measles
- Echovirus
What investigations are done for meningitis?
- CT scan (to exclude mass lesion in drowsy/unconscious pt)
- Lumbar puncture
- CSF contains
a) neutrophils (>5000 cells/mm3): bacterial meningitis
b) lymphocytes (viral and tb meningitis)
c) increased protein
d) decreased glucose (esp bacterial meningitis)
e) gram stain may show organisms (gram +ve/-ve)
- CSF contains
- Blood culture (TRO septicaemia)
What are the treatments available for meningitis?
- IV abx
- Supportive measures
- Rifampicin prophylactics for contacts of meningococcal meningitis
- Vaccination
- quadrivalent vaccine A, C, Y, W135
- HIB vaccine against H. Influenza B meningitis
What are the complications of meningitis?
- Cranial nerve palsies (due to fibrosis of meningitis - esp if it involves the base of brain)
- Hydrocephalus (due to blockage of aqueduct in subarachnoid space)
- Cortical atrophy
- vessel thrombosis and increase ICP
- can lead to mental retardation, blindness, deafness and paralysis
What are the indications for lumbar puncture?
- Diagnostic
a) CNS infections (meningitis)
b) thunderclap headache (TRO SAH when MRI/CT is normal/headache last beyond 3 days) - Therapeutic - evaluate for normal pressure encephalitis (with walk test)
What are the contraindications for lumbar puncture?
- Patient with infection in tissues near puncture site
- Patient with space-occupying lesions
- Patient with bleeding tendencies (platelet <80/INR > 1.4)
How much lignocaine should be given for lumbar puncture?
5-10ml
How long should you wait for lignocaine to take effect?
3mins
What is the normal opening pressure of lumbar puncture?
10-18cm H2O
What could the causes of elevated opening pressure for lumbar puncture?
- Infective causes: TB, fungal and bacterial
- Hydrocephalus: communicative type
- Benign intracranial hypertension
What could be the causes of low opening pressure for lumbar puncture?
- Blockage: spinal block but high ICP
- Intracranial hypotension
How many drops of CSF should one bottle hold?
15 drops/1ml (each drop = 0.06ml)
