CNS Infections Flashcards by Martha Innes

What are the different CNS infections?

Meningitis

Encephalitis

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What is meningitis?

Inflammation of the brain meninges

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What is the pathology of acute bacterial meningitis?

Pia-arachnoid congested with neutrophils
Layer of pus forms
May organise to form adhesions, causing cranial nerve palsies and hydrocephalus

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What is the pathology of chronic meningitis?

Brain is covered in exudate with numerous meningeal tubercles (small abscesses)
Adhesions form
Cerebral oedema occurs

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What is the pathology of viral meningitis?

Predominantly lymphocytic

No pus formation, neutrophils or adhesions, little to no cerebral oedema

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What is an example of a cause of chronic meningitis?

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What is the most common cause of meningitis?

Viral

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When in the year does viral meningitis occur more often?

Late summer, early autumn

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What are the most common causative organisms of viral meningitis?

Enteroviruses - coxsackie or echo viruses

Herpes simplex

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How does the onset of viral meningitis differ from bacterial?

Viral has more insidious onset

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What are the three ways that bacteria can spread into the CNS?

Spread from nasopharynx
Direct extension due to skull fractures or para-meningeal foci in the mastoid or air sinuses
Spread from remote foci due to sepsis

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What are the most common causative bacteria in meningitis?

Strep pneumoniae
Neisseria meningitis
Haemophilus influenzae
Listeria monocytogenes
TB

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Who are more likely to get strep pneumoniae meningitis?

Hospitalised patients
CSF skull fractures
Diabetics
Alcoholics
Young children

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Who are more likely to get neisseria meningitis?

Young children

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How can neisseria meningitis be differentiated?

Rash doesn’t blanch

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What is the name for meningitis caused by neisseria meningitis?

Meningococcal meningitis

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Who are more likely to get haemophilia influenzae meningitis?

<40 year olds

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What is the most common cause of meningitis in children under 4?

Haemophilus type B

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Who are more likely to get listeria monocytogenes meningitis?

Over 55 year olds, or neonates
Soft cheese consumption
Immunocompromised

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What is important about listeria monocytogenes meningitis?

Resistant to ceftriaxone - ampicillin/amoxicillin used instead (co-trimoxazole if pen allergic)

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Who are more likely to get fungal meningitis?

Severely immunosuppressed (e.g. active HIV)

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How can fungal meningitis be differentiated?

More subtle presentation

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What are infective and non-infective causes of aseptic meningitis?

Infective: HIV, cryptococcal, TB

Non-infective: vasculitis, dural sinus thrombosis, drug-induced (NSAIDs, co-trimoxazole)

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What are the more likely causative organisms in neonates?

Listeria
Group B strep
E coli

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What are the more likely causative organisms in children <10?

Haemophilus influenza

What are the more likely causative organisms in people aged 10-21?

Meningococcal | Pneumococcal

What are the more likely causative organisms in people aged >21?

Pneumoccal | Neisseria meningitides

What are the more likely causative organisms in the elderly?

Pneumococcal | Listeria

What are the more likely causative organisms in immunocompromised patients?

All the conventional organisms TB Cryptococcal

What are the more likely causative organisms in patients with skull fractures?

Pneumococcal

What are the more likely causative organisms in patients who have had surgery or open head wound?

Staph aureus

What are the more likely causative organisms in patients with a CSF shunt?

Staph epidermidis

What is the main triad of symptoms in meningitis?

Fever Headache Neck stiffness

What are the visual symptoms of meningitis?

Photophobia

What are the dermatological symptoms of meningitis?

Non-blanching purpuric rash (meningococcal)

What are the neurological symptoms of meningitis?

Confusion Agitation Altered level of consciousness Seizures

What is Kernig's sign?

Pain and resistance on passive extension of the knee with a flexed hip

What is the clinical presentation of meningitis?

Fever, headache, neck stiffness Visual (photophobia) Dermatological (Non-blanching purpuric rash - meningococcal septicaemia) Neurological (Confusion, agitation, altered level of consciousness, seizures) Kernig's sign Vomiting, riggers, malaise

What are the patterns of onset in meningitis?

Develops within hours or minutes in acute bacterial meningitis More insidious in viral or encephalitis

What investigations should be done in meningitis?

``` Bloods Throat swab CXR (if TB suspected) Lumbar puncture CT brain before LP if needed ```

What is the diagnostic investigation for meningitis?

Lumbar puncture

What bloods should be done in meningitis?

``` FBC U&Es Coagulation screen Glucose Cultures ```

What are the contraindications to a lumbar puncture?

``` Immunosuppressed Papilloedema Focal neurological signs Altered level of consciousness History of CNS disease ```

Why does a CT brain need to be done if any contraindications to LP are present?

To rule out raised ICP

What results from a LP would suggest viral meningitis?

``` Cell - lymphocytes Gram stain - negative Bacterial antigen - negative Protein - normal Glucose - normal ```

What results from a LP would suggest bacterial meningitis?

``` Cell - neutrophils Gram stain - positive Bacterial antigen - positive Protein - high Glucose - low <70% plasma ```

What results from a LP would suggest TB meningitis?

``` Cell - lymphocytes Gram stain - positive or negative Bacterial antigen - negative Protein - high or very high Glucose - low <60% plasma ```

What results from a LP would suggest aseptic meningitis?

``` Cell - low WCC Gram stain - negative Bacterial antigen - negative Protein - minimally increased Glucose - normal ```

What is the management for bacterial meningitis?

1st line - ceftriaxone Penicillin allergy - chloramphenicol + vancomycin >60 or immunosuppressed (listeria) - add amoxicillin (co-trimoxazole if penicillin allergy) Give dexamethasone with or just before first dose of antibiotics - if pneumococcal confirmed continue for 4 days, if ruled out stop dex

When should you not give dexamethosone with antibiotics?

Post-surgical meningitis Severe immunocompromise Meningococcal or septic shock Patient hypersensitive to steroids

What is the management for viral meningitis?

Treat as bacterial until viral confirmed | Then stop antibiotics and care switched to supportive

What contact tracing needs to be done in meningitis?

Notify public health | Contact prophylaxis - ciprofloxacin single dose

How many who survive meningitis are affected by after-effects?

25%

What are examples of after-effects that can occur in meningitis?

``` Lim loss Deafness Blindness Cerebral palsy Quadriplegia Severe mental impairment ```

What are complications of meningitis?

Purulence - exudate compressing cranial nerves (III and IV most vulnerable) Invasion causing abscesses Cerebral oedema Hydrocephalus

What is encephalitis?

Inflammation of the brain parenchyma (substance of the brain)

How is encephalitis different from encephalopathy?

Encephalopathy is not always an infection, but can be any condition that alters brain function or structure

What are the microbiological causes of encephalitis?

herpes simplex Varicella zoster CMV/HIV

What is the presentation of encephalitis?

Similar to meningitis | Seizures

How is encephalitis differentiated from meningitis?

``` Presence of: Psychosis Odd behaviours Speech and memory problems Confusion ```

What investigations are done for encephalitis?

Lumbar puncture EEG MRI

How can HSV encephalitis be determined?

Bilateral focal temporal lobe enhancement on MRI

What is the treatment of encephalitis?

Acyclovir

What is meningoencephalitis?

Headache, fever and neck stiffness PLUS features of encephalitis

What are the causes of a brain abscess?

Skull fractures Endocarditis Ear, sinus or dental infection

What is the presentation of a brain abscess?

Raised ICP (headache, drowsiness) Focal neurological signs Fever Epilepsy

What investigations are done for brain abscesses, and what do they show?

CT/MRI - shows ring-enhancing mass, usually with surrounding oedema Don't do LP - because of raised ICP

What is the management of brain abscess?

Neurosurgical referral for urgent drainage High dose antibiotics Mortality is high

What is progressive multifocal leukoencephalopathy?

Caused by infection with JC virus within multiple areas of infection Causes demyelinaion

What are the risk factors for progressive multifocal leukoencephalopathy?

Immunosuppression Autoimmune disease Use of MS drugs (tysabri)

How is progressive multifocal leukoencephalopathy diagnosed?

Symptoms of demyelination (similar to MS) LP - JC virus DNA MRI - enhancing lesions

What is the treatment for progressive multifocal leukoencephalopathy?

No effective treatment - treat underlying cause