Central Nervous Systems Infections Flashcards by Srishti D

What are the different types of central nervous system (CNS) infections?

Meningitis
Encephalitis
Brain abscess
Subdural empyema
Spinal epidural abscess
Vertebral osteomyelitis

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What differential diagnoses need to be considered when the patient reports that the headache is their “worst headache ever”?

Meningitis

Subarachnoid haemorrhage

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Does having no nuchal rigidity rule out meningitis?

Nuchal rigidity classically in paediatrics

In adults, presence is worrying, but not having it is common

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What are the common causes of acute headache?

Tension-type headache
Migraine
Infections around head
- Sinusitis
- Systemic infections

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What are the serious causes of acute headache?

Intracranial infections
- Meningitis
- Encephalitis
- Intracerebral abscess
Intracrainall haemorrhage/mass lesion
Giant cell arteritis
Glaucoma

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How can meningitis be categorised?

Purulent/acute bacterial meningitis

Aseptic meningitis

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What are the causes of aseptic meningitis?

Viral - most common
TB, other bacteria
Fungal
Parameningeal infections
Malignancy
Inflammatory

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What are the likely causes of meningitis if the timeline is acute?

Acute bacterial

Viral

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What are the likely causes of meningitis if the timeline is sub-acute or chronic?

TB
Fungal
Malignancy
Inflammatory

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What are the clinical features of acute bacterial meningitis?

Headache = primary symptom
- Rapid onset - but not thunderclap
- Patient presents fast - within 24 hours
- Severe
- May be absent in
   - Neonates
   - Elderly
   - Immunosuppressed
Classic triad of additional features
- Fever
- Neck stiffness
- Altered mental state
- Present in <1/2
- Most will have one
Altered mental state usually not primary feature at onset but can be prominent at presentation
Focal neurological signs
- Seizures can occur
Nuchal rigidity can be present on examination

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What is the clinical presentation of viral meningitis?

Acute, severe headache
\+/- fever
No
- Hypotension
- Decreased conscious state
- Focal neurological signs

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What is the clinical course of viral meningitis?

Self-limiting
Improvements within few days
Resolution within 1-2 weeks

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What are the investigations for suspected meningitis?

Brain CT
- Start empirical treatment before
Lumbar puncture
- To do this safely, need to know they don’t have space occupying lesion

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How long can CRP take to raise after sepsis?

12-24 hours

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What are the parameters for a normal lumbar puncture?

Opening pressure = 20 mmHg
- Any higher = raised intracranial pressure
White cell count = 5 cells/um
RBC:WBC ratio - if 1000:1, put your needle through and into peripheral blood (capillaries)
Polymorphs = 0, maybe 1
Glucose = 60-100% of peripheral glucose

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What does elevated protein the CSF mean?

Inflammation

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What does decreased glucose in the CSF mean?

Bacteria
Possibly cancer
Fungi
Mycobacteria

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What are the parameters of CSF in acute bacterial meningitis?

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Appearance = cloudy
WCC >1000 cells/uL
Differential: >95% polymorphs
Protein >1 g/L
Glucose: decreased

What are the parameters of CSF in viral meningitis?

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Appearance = clear
WCC <500 cells/uL
Differential: lymphocytes
Protein = 0.4-1 g/L
Glucose: normal

What are the common causes of bacterial meningitis in neonates?

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Group B Streptococcus
E coli
Listeria

What are the common causes of bacterial meningitis in infants and children?

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Streptococcus pneumoniae
Nesseria meningitidis
Haemophilus influenzae type b
- Decreased because of vaccine

What are the common causes of bacterial meningitis in adolescents and young adults?

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N meningitidis

S pneumoniae

What are the common causes of bacterial meningitis in older adults?

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S pneumoniae
N meningitidis
Listeria

What are the common causes of viral meningitis?

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Enteroviruses = most common
HSV
VZV
HIV

Who is antibiotic prophylaxis important for in bacterial meningitis?

Close contacts of cases of N meningitidis and H influenzae, but not S pneumoniae

What is the empirical therapy for acute bacterial meningitis?

``` Dexamethasone + ceftriaxone/cefotaxime + benzylpencillin to cover Listeria if - Immunocompromised - Age 50+ - History of hazardous alcohol consumption - Pregnant - Debilitated + vancomycin if - Gram positive diplococci seen on Gram stain of CSF - Pneumococcal Ag assay positive - Suspected otitis media/sinusitis - Recent treatment with beta lactam ```

What are the possible causes of altered mentation and fever?

``` Delirium with non-CNS condition Encephalitis Meningitis - later in course Brain abscess Intracranial tumour/haemorrhage Seizures ```

What is the treatment for presumed HSV encephalitis?

IV acyclovir

What is the clinical presentation of encephalitis?

``` Confusion Agitation Decreased conscious state Focal neurological signs Seizure Headache - not primary symptom Fever - common but not universal ```

What is the most common cause of encephalitis?

HSV-1

What are the investigation results for encephalitis?

``` CSF - Mild-moderate increase in lymphocytes - Mild increase protein - Normal glucose - HSV PCR sensitive but can be early false negatives MRI - Pattern of inflammation ```

What is the presentation of a brain abscess?

``` Classic triad - Focal neurological signs - Fever - Headache Often just - Confusion - Seizures - Nausea More prolonged presentation - weeks ```

What are the possible sources of a brain abscess?

Contiguous; eg: sinusitis | Haematogenous; eg: lung abscess

What are the possible organisms causing a brain abscess?

Oral Strep Anaerobes Staphylococcus aureus

What is the management of a brain abscess?

Drainage + prolonged antibiotics | - Antibiotics only go where there's blood - centre of abscess doesn't have blood flow

What does S aureus in the urine mean?

Result of S aureus bacteraemia until proven otherwise

What is the source of vertebral osteomyelitis?

Haematogenous seeding

What is the source of a spinal epidural abscess?

``` Contiguous spread; eg: vertebral osteomyelitis Haematogenous seeding; eg: - Skin - Soft tissue - Urinary - GI Iatrogenic - Surgery - Paraspinal injections ```

What are the risk factors for spinal infections?

``` IV drug use Endocarditis Bacteraemia Degenerative spinal disease/prior spinal surgery Diabetes Immunosuppression ```

What are the clinical features of spinal infections?

Primary symptom = back/neck pain Fever variable Back tenderness/percussion tenderness Nuchal rigidity variable

What are the four clinical stages of a spinal epidural abscess?

1. Back pain and fever 2. Radicular pain, nuchal rigidity/neck stiffness, and reflex changes 3. Sensory abnormalities, motor weakness, and bowel and bladder dysfunction 4. Paralysis

What are the causes of spinal infections?

``` S aureus = most common Enteric Gram negative bacilli Pseudomonas aeruginosa Candida Groups B and G haemolytic streptococci Uncommonly - TB - Brucellosis ```

What are the investigations for spinal investigations?

``` MRI for diagnosis and assessment of severity Attempt at ID of organism - Blood cultures - CT guided biopsy - Open biopsy ```

Central Nervous Systems Infections Flashcards

(43 cards)