CNS Infections: Meningitis, Encephalitis Flashcards
Important history questions
Locate the source of infection
Skull infection => CNS spread
-Otitis media
-Sinusitis
-Mastoiditis
Internal
-heart, lung, skin, abdo, pelvic
Via bloodstream more likely in IC
-HIV
-chemo
-immunosuppressed
Head trauma
-fracture, wounds
Surgery
-dental
-head
-valve, implants
Travel, vaccinations
Key investigations
Blood culture
Head CT/MRI
CT body
Echo
Dental review
Management
Urgent neurosurgical review
-ABx
-aspiration, drainage
Surgery needed if mass effect/neuro deficit
General presentation of CNS infections
Headache - not relieved by simple analgesia
Fever
Seizure
N+V
Stiff neck
Visual changes
Mental state change
Focal neuro deficit
Encephalitis
-pathophysiology
-presentation
-cause
Brain inflammation
-fever, headache
-reduced consciousness => coma
-seizure
-agitation
-focal neuro
Direct infection - mainly viruses
-HSV, VZV
-MMR
-rabies
AI
Encephalitis
-investigations
GOLD STANDARD - CSF PCR
-identify cause
Blood, throat, stool, urine culture
Head CT - rule out other causes
EEG - lateralised periodic discharge in HSE
Encephalitis
-management
Treat the underlying cause
HSE - aciclovir
HIV - HAART
JC - reverse immunosuppression
HSE presentation
Typical encephalitis symptoms
-fever
-headache
-agitation
-seizures
-vomiting
Focal features - temporal lobe signs
-Wernicke’s aphasia
-prosopagnosia
-auditory agnosia
-sup hom quadrantopia
Cold sores
Meningitis
-causes, pathogenesis
Bacterial, viral, protozoal, Non-infectious, AI
Contact with infected people/travel to endemic areas
-bacteria enter meninges => SA inflammation
Increased CSF outflow resistance => hydrocephalus, increased ICP => cerebral ischemia
Meningitis
Most common causative organisms in
-U3 months - 3
-3months - 60 years - 2
-60+ - 3
-IC
-post surgery
In general
-in 20-40s
U3 months - Ecoli, GBS, listeria
3months - 60years - NMeningitidis, SPneumonia
60+ - +listeria
IC - listeria
Post surgery - S aureus, S epidermidis, G-ves
Most common causes in general - S pneumonia
20-40s => viral meningitis (ENTEROVIRUS)
Meningitis
-classic triad
-presentation
-signs
-drawback of identifying these symptoms
Fever, confusion, neck stiffness
Headache
N+V
Non blanching rash
Photophobia, phonophobia
Fatigue, irritability
Meningeal irritation
-Kernig - unable to extend knee when hip flexed
-Brudzinski - knees, hip flexed when neck flexed
Cannot distinguish between viral and bacterial meningitis
What are the CSF findings when healthy
- opening pressure
- appearance
- WCC
- differential count
- protein
- CSF/plasma glucose ratio
Opening pressure => 12-20
Appearance => clear
WCC CSF => <5
Differential count => N/A
CSF protein => < 0.4
CSF/plasma glucose => >0.66
What are the CSF findings if you have bacterial meningitis
- opening pressure
- appearance
- WCC
- differential count
- protein (indicator of the no of inflammatory cells)
- CSF/plasma glucose ratio
Opening pressure => high
Appearance => turbid
WCC => raised (may be normal in early infection)
Differential count => neutrophils
Protein => raised (protein leak into fluid)
CSF/plasma glucose => v low (bacteria using glucose)
ALWAYS INTERPRET FINDINGS IN CLINICAL CONTEXT
What are the CSF findings if you have viral meningitis
- opening pressure
- appearance
- WCC
- differential count
- protein
- CSF/plasma glucose ratio
Opening pressure => normal/high
Appearance => clear
WCC => raised
Differential count => lymphocytes
Protein => mildly raised
CSF/plasma glucose => normal
~~~
ALWAYS INTERPRET FINDINGS IN CLINICAL CONTEXT
What are the CSF findings if you have TB/fungal meningitis
- opening pressure
- appearance
- WCC
- differential count
- protein
- CSF/plasma glucose ratio
Opening pressure => high
Appearance => clear/cloudy
WCC => raised
Differential count => lymphocytes
Protein => markedly raised
CSF/plasma glucose => v low
ALWAYS INTERPRET FINDINGS IN CLINICAL CONTEXT
Meningitis
-diagnosis, investigations
Blood
-FBC, U&E, CRP, clotting, culture - organ function and sepsis
-meningococcal PCR
-glucose
-ABG
LP - GOLD STANDARD WITHNI 1 HR
MUST BE DELAYED IF
-sepsis/rapidly evolving rash
-resp/cardiac compromise
-significant bleed risk
-high ICP, focal neuro, papilledema, continuous/uncontrolled seizures, GCS U12
If not possible within 1hr, give ABx after cultures taken
-CSF analysed for cell count, gram stain, glucose, protein, lactate, culture, bacterial/viral PCR
-analysed alongside blood glucose
If LP not possible => whole blood PCR and blood cultures
CT - if focal neurological deficits/specific underlying cause suspected
-identify ICP
Acute bacterial meningitis
Management in
-primary care
-secondary care
-management of viral
-prophylaxis of close contacts
IV/IM benzylpenicillin => admit to A&E
Supportive - fluids, nutrition, analgesia, antipyretics, antiemetics
Treat causative organism - EMPIRICALLY AS BACTERIAL UNTIL PROVEN OTHERWISE
-U3 months or 50+ - IV amox+cefotaxime
-3 months+ - IV cefotaxime
IV dexmeth if pneumococcal
Don’t give if
-U3months - affects neurodevelopment
-septic shock
-meningococcal septicemia
-IC
-post-surgery
Viral - supportive only
-aciclovir if HSV encephalitis
Prophylaxis within 24hrs if close contact within 7 days before onset - cipro 1 dose or rifampicin
What is the difference between purpura/petichiae in septicaemia and vasodilation of blood vessels
What do you need to consider in a patient with purpura/petichiae?
Purpura/petichiae => bleeding into skin, no blanching
Not specific to meningits, not always found in early disease
Vasodilation => compression of vessels => blanching
Meningitis
What are the red flag signs and symptom in
-young children
Why is it important to identify these symptoms?
The younger the child, the less likely they are to present typically
-typical signs are often late due to greater physiological reserve
All ages => first specific clinical features = signs of sepsis
Cold, painful limbs
Pale, mottled skin
Rash (often a late sign)
Changes in HR, RR
Drowsy
Diarrhea
Thirst
Why does meningococcal septicaemia kill/permanently damage survivors?
-complications?
Endotoxins => inflammatory response
Septic shock
-widespread VD
-myocardial damage
- intravascular coagulation => distal areas blocked, gangrenous, needs amputation
- vessel damage => petichiae, purpura
DISRUPTION OF NORMAL CV FUNCTIONING
Complications
- hearing loss
- seizures
- cognitive, motor, visual impairment
- hydrocephalus
- amputations
What vaccines are currently being offered
MenB - part of baby vaccinations
ACWY - Year 9-10, advised for uni students
Contraindications to CSF LP
High ICP
- reduced/fluctuating consciousness
- bradycardia
- HTN
- focal neuro signs
- abnormal posture, pupil reflexes
- papilloedema
Shock
Extensive/spreading purpura
Seizures
Coagulation abnormalities
- AC use
- thrombocytopenia
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