CNS Infections Flashcards
Direct spread of intracerebral abscess pathogens
-Solitary head and neck infections
=Chronic otitis media
=Mastoiditis
=Frontal sinusitis
=Dental
=Trauma or surgery to scalp, penetrating head injury
-Oral streptococci
-Haemophilus spp
-Bacteroides spp
-Fusobacterium spp
-Prevotella spp
-Enterobacteriacae
-Pseudomonas aeurginosa
Haematogenous spread of intracerebral abscess conditions
-TRVAEL THROUGH LEFT SIDE OF BODY
-MCA territory, multiple abscess at grey-white matter junction (disruption of BBB)
-Endocarditis
-Chronic pulmonary infection
-Pulmonary arterio-venous
malformations
-Skin infection
-Pelvic infection
-Intra-abdominal infection
-Presence of prosthetic material
=Streptococci
=S. aureus
=Less common= fusobacterium
Pathogens in neurosurgical intervention for intracerebral abscess
-Staphylococcus spp
-Streptococcus spp
-Pseudomonas aeurginosa spp
-Enterobacter spp
-Remember pre-surgical colonisation (MRSA positive?)
Pathogens in intracerebral abscess via immunocompromise
-Toxoplasma
-Mycobacteria spp
-Listeria spp
-Nocardia spp
-Aspergillous spp
cryptococcal
coccidioides
-Candida spp
Pathogens leading to intracerebral abscess via travel
-Cysticercosis
-Entamoeba
-Schistosoma
-Paragonimus
Clinical presentation of intracerebral abscess
-Headache (often dull, persistent)
∙ Fever (usually not swinging, may be absent)
∙ Focal neurological signs (oculomotor nerve palsy, abducens, secondary to raised ICP)
-Nausea
-Papilledema
-Seizure
∙ Seizure activity
∙ Raised intracranial
pressure
=CN III and VI lesions, papilloedema
Examination in intracerebral abscess
→ Otoscopy / ENT exam
→ Heart sounds
→ Review of prosthetic
material
→ Recent Neurosurgery
=Intracerebral bleed
=Malignant process
=DIFFERENTIALS
Investigations in intracerebral abscess
-ASPIRATION AND CULTURE
∙ Routine bloods (inflammatory markers)
∙ Blood cultures
∙ CT head with contrast= lesions more differentiated
∙ MRI
∙ (CSF examination- may be necessary, raised ICP considered?)
∙ HIV test
∙ serology
Treatment for intracerebral abscess
- Neurosurgical input for drainage (craniotomy with abscess debridement)
– routine culture
– mycobacterial culture/mycology culture
– pathology
– molecular techniques - Empirical antibiotics
– IV ceftriaxone /ceftazidime and IV metronidazole (cover anaerobic infection)
-Intracranial pressure management: dexamethasone - Specialist advice following Neurosurgery
– IV ceftazidime, IV vancomycin and IV metronidazole
=4-8 weeks, radiological follow up (oedema, fibrotic capsule, scarring)
=Mortality 10%, seizure activity?
Pathogenesis of meningitis
-Colonisation= nose/ear
-Invasion
-Blood stream survival
-Infection= crossing BBB into CSF space
-Significant host response
-25% meningitis
Category and cause of meningitis
-Bacterial
-Viral
=Enterovirus
=Mumps
=Measles
=HSV
=VZV
=Influenza
-Fungal
=Cryptococcal
-Other organisms
=Rickettsia
=Protozoa
=Helminths
-Non-infectious presentation (meningism= inflammation not infection)
=Migraine
=SAH
=Vasculitis
Common organisms in 0-4 weeks
Group B streptococcus, E.coli, L.monocytogenes, K.pneumoniae,
Enterococcus spp., Salmonella spp.
Common organisms in 4-12 weeks
(Group B streptococcus, E.coli, L.monocytogenes, K.pneumoniae,)
H.influenzae, S.pneumoniae, N.meningitidis
Common organisms in 3 months-18 years
H.influenzae, S.pneumoniae, N.meningitidis
Common organisms in 18-60 years
S.pneumoniae, N.meningitidis
Common organisms in >60 years
S.pneumoniae, N.meningitidis, L.monocytogenes, gram negative
bacilli, (Mycobacterium tuberculosis)
Common organisms in Immunocompromised
S.pneumoniae, N.meningitidis, L.monocytogenes, gram negative
bacilli, Mycobacterium tuberculosis
Common organisms in CSF shunt
S.aureus, coagulase negative staphylococci, gram negative bacilli
Clinical presentation in meningitis
- Fever
- Headache
- Neck stiffness
-Vomiting - Rash
-Seizure
-Altered consciousness
-Focal neurological deficit
Investigations in meningitis
- ABCDE and senior clinical assessment
- Routine bloods including coag
- Blood cultures
- Bacterial and viral throat swabs
- HIV test
- Blood PCR
– S.pneumoniae, H.infuenzae, N.meningitidis
-Lumbar puncture
-(CT scan)
Clinical indications for CT in meningitis
-Focal neurological signs
=Papilledema
=Continuous or uncontrolled seizures
=GCS 12
(Decompression in LP if raised ICP)
- Delays antibiotics
- Delays LP
– Prior to abx CSF diagnostic in 70-85%
– CSF can be sterile 2-4 hrs after the first dose of abx
– Prior abx can cause
lymphocyte predominance
Indications for lumbar puncture samples in meningitis
∙ microscopy
∙ gram stain
∙ routine culture
∙ PCR
∙ S.pneumoniae, H.infuenzae, N.meningitidis
∙ biochemistry
∙ glucose / protein / lactate
∙ pathology
∙ mycobacterial stain/culture
∙ other
Bacterial lumbar puncture interpretation
-Increased opening pressure (increased inflammatory response)
-Turbid appearance
-Severely increased WCC, predominantly NEUTROPHILS
-<50% plasma glucose (high metabolic requirement of bacteria)
-Moderately increased protein
Viral lumbar puncture interpretation
-Normal or increased opening pressure
-Clear appearance
-Raised WCC, predominantly lymphocytes
-Normal glucose
-Normal protein
Fungal/ TB lumbar puncture interpretation
Moderately increased opening pressure
-Turbid/fibrin web appearance
-Moderately increased WCC, predominantly LYMPHOCYTES
-<50% plasma glucose
-Moderately/ severely increased protein
Treatment for Meningitis
- Ceftriaxone 2g 12hr
– Meropenem/chloramphenicol alternative (penicillin allergy) - Add IV amoxicillin 2g 4hr for Listeria spp if
– >60y
– Immunocompromise
– Co-trimoxazole alternative - Add IV vancomycin 15-20mg/kg BD
– 6m travel to country with penicillin resistant pneumococci - 10mg IV dexamethasone 6hr pre abx
– Empirical treatment for all, if pneumococcal meningitis continue for 4d
-Reduce mortality, hearing loss - Aciclovir 10mg/kg TDS
Treatment duration for Neisseria meningitidis
5d ceftriaxone
Treatment duration for Streptococcus pneumoniae
10-14d benzylpenicillin/ ceftriaxone
Treatment duration for Listeria monocytogenes
21d high dose amoxicillin
Treatment duration for Haemophilus influenzae
10d ceftriaxone
Management of viral meningitis
-Viral PCR= enterovirus (other)
-Stop antibiotics and antivirals
-Supportive treatment
-Discuss with specialist team if concerns
HSV1 encephalitis pathophysiology
-Primary infection (enters skin through mucosa to infect nerve endings)
-Latent phase (replicates in root ganglia, trigeminal and maxillary branch)
-Reactivation phase (stress/ illness/ immunocompromise/ idiopathic- meningeal branches into temporal lobe)
-VIRAL AETIOLOGY MOST COMMON: HSV1 (5%)- temporal and inferior lobes
Clinical presentation of encephalitis
∙ Altered mental status / behaviour / personality (psychiatric symptoms)
∙ Seizure activity (temporal and inferior frontal lobe involvement): aphasia
∙ Fever – low grade
-Headache
-Vomiting
∙ Focal neurology – subtle, aphasia
∙ (meningeal irritation)
∙ Rash – vesicular (GU exam, HSV latency), cold sores often no relation
∙ Recent immunocompromise
∙ Travel history
∙ Vector exposure
Clinical investigation of encephalitis
∙ CT head with contrast: medial temporal and inferior frontal changes (petechial haemorrhages) can be normal
∙ LP:
=PCR for HSV1 (95%), HSV2, VZV, enterovirus
=Lymphocytosis, elevated protein
∙ Routine culture
∙ Biochemistry
∙ Blood cultures
∙ Baseline serology
∙ HIV test
∙ MRI! - temporal lobe changes, oedema, petechial haemorrhages
∙ EEG (lateralised periodic discharges at 2 Hz)
∙ Brain biopsy
Differential diagnosis of encephalitis
∙ Tumour
∙ Medication / substance misuse
-Delirium
∙ Autoimmune
∙ Vasculitis
∙ Paraneoplastic
Treatment of encephalitis
∙ High dose IV acyclovir 10mg/kg TDS
=May need to consider repeat lumbar puncture
∙ Continue for 14days then repeat LP
=If HSV PCR negative stop treatment
=If HSV PCR positive then further 7 days and repeat LP
∙ Assess cognitive function
