Meningitis Flashcards
List some DDx for a presentation of:
- 22yo female soldier
- fever
- headache
- neck stiffness
- rash
PDx. meningitis (viral most common)
DDx.
• Infective- meningitis, cerebral abscess, encephalitis, dengue, tetanus, malaria, influenza
- Meningitis (viral, bacterial, fungal, spirochetal, iatrogenic, malignant infiltration, multisystem disease)
• AI disease- vasculitis, dermamyositis, SLE
• Neoplastic- brain tumour
• Vascular- SAH
• Migraine- with aura
List some possible causative organisms of meningitis?
• Bacterial- strep pneumonia, Neisseria meningitis, H influenza, Listeria monocytogenes (elderly/immunocompromised), GS or E coli (neonates)
o Hospital- staph aureus, pseudomonas
• Viral- Enterovirus (coxsackie virus, echovirus, poliovirus), HSV. HIV, EBV, Influenza, VZV, CMV, mumps
• Fungal- Cryptococcus neoforms, candida albicans, Coccidiodes, Histoplasma
• Protazoa- treponema pallidum, toxoplasma
What are signs of raised ICP?
Raised ICP signs- headache, irritability, drowsiness, decreased LOC, vomiting, papilloedmea, decreased RR, bradycardia, Cushing’s reflex (response to raised ICP with triad of HTN, bradycardia and irregular breathing)
What are some signs of sepsis?
Sepsis signs- rash, fever, malaise, arthralgia, DIC, decreased cap refill, tachycardia, hypotension
What are Kernig’s and Brudzinski’s signs?
Both test meningism:
o Kernig’s test- pt supine, flex hip and knee at 90 degrees each, immobilize hip and attempt to extend knee -> resisted, hamstring pain (meningeal irritation)
o Brudzinski sign (nuchal rigidity) - pt supine, hold down thorax, attempt neck flexion -> involuntary hip flexion (meningeal irritation)
What investigations would you order for meningitis?
• LP CSF MCS and PCR - pressure, appearance, protein, glucose, gram stain, WCC - CI: raised ICP, coagulopathy, localised lumbar infection Bloods: - FBC (neutrophilia) - ESR/CRP - EUC - LFT - blood culture - ABG- lactate (sepsis) - Coag profile- intracranial haemorrhage risk, DIC - BSL Imaging: - CT head
What would you see in the CSF if it were bacteria, viral or fungal?
Bacterial meningitis: o High pressure (>20cmH2O) o Turbid o High protein (>0.45g/L) o Low glucose (<2.5mmol/L) o Gram positive (60%) o High WCC- predominantly neutrophils Viral meningitis: o Normal/mild increased pressure o Clear o Normal protein o Normal glucose o Normal gram stain o Higher WCC- mostly lymphocytic • Fungal o Decreased glucose o Higher WCC- mostly lymphocytic
What organisms are most likely to cause meningitis in which age groups?
• Neonates o Group B streptococcus o Listeria monocytogenes o E coli • Children/teens o Neisseria menigitidis o Strep pneumonia • Adults/elderly o Neisseria menigitidis o Step pneumonia • Immunocompromised- S aureus, Step pneumonia, gram neg bacilli • Not immunized- H influenza
What is meningitis and what are some clinical features observed?
Def: inflammation of the leptomeninges (pia, arachnoid and dura mater) surrounding the brain and spinal cord
- fever, headache, confusion, N/V, neck stiffness, petechial, non-blanching rash (N meningidites), raised ICP
Explain the mechanism of these clinical signs:
- fever
- headache
- confusion
- N/V
- neck stiffness
- Fever: pyrogenic cytokines (IL-1) -> alters hypothalamic thermostat
- Headache: inflammaed meninges -> raised ICP -> activate stretch nerve fibers
- Confusion: inflamed meninges -> raised ICP -> decreased blood flow -> neuronal ischaemia -> neuro deficits (general)
- N/V: inflamed meninges -> raised ICP -> compress medullary vomit centres
- Neck stiffness: meningeal irritation with movement -> reflex muscles spasm to limit movement
How is a lumbar puncture performed?
Method:
• Position- pt lying on side or sitting up, max flexion of spine (foetal position), avoid neck flexion (resp compromise)
• Location- L3-4 or L4-5 intervertebral space (line between top of iliac crests)
• Preparation: aseptic technique, chlorhexidine, drapes, local anaesthetic (1% lignocaine)
• Lumbar puncture: bevel up, aim slightly up, advance into spinous ligament (increased resistance), advance into subarachnoid space (decreased resistance), observe CSF flow, collect in 2 tubes (5-10 drops each)
• Post: CSF MCS and PCR, cover puncture site
List some complications of an LP?
Complications: • Failure to obtain CSF, need repeat • Traumatic tap (common) • Post-dural puncture headache (5%) • Paraesthesia transient/persistent • Spinal haematoma • Spinal infection/abscess • Tonsillar herniation (rare)
How would you treat this patient and why?
• Empiric abx
o Ceftriaxone (4g IV)- good gram neg coverage (e.g. N menigitidis)
• Tailor abx to suit causative organism (w CSF stain and culture)
o N meningidites- Benzypenicillin
o Streponeumoniae- Benzypenicillin
o Haem influenzae (B)- Ceftriaxone
o Listeria monocytogenes- Benzypenicillin
• Dexamethasone (10mg IV)- reduced ICP, mortality benefit
• Supportive therapy: O2, positioning
Describe the MA of Ceftriaxone?
Ceftriaxone
o Class: 3rd generation cephalosporin, B lactam, crosses BBB
o MA: inhibits peptidoglycal cross linking -> inhibiting cell wall synthesis -> accumulating cell wall precursors -> autolysis -> cell death
Describe the MA of Benzypenicillin?
Benzypenicillin
o Class: penicillin, beta lactam
o MA: binds to penicillin binding protein (PBP), inhibits peptidoglycan cross linking -> inhibits cell wall synthesis -> accumulating cell wall precursors -> autolysis -> cell death
