CNS Infections and Meningitis Flashcards by Kat Qiao

What are the 4 modes to entry for CNS infections?

Haematogenous spread
Direct implantation - via instrumentation
Local extension - secondary to established infections
PNS into CNS

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What is meningitis?

Region: Meninges

Signs and symptoms: Fever, headache, stiff neck, usually some disturbance of brain function.

Causative agents: Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae, TB, Various viruses, Cryptococcus neoformans

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What is encephalitis?

Region: Brain

Signs and symptoms: Disturbance of brain function

Causative agents: Rabies virus, arboviruses, Trypanosoma species, Prions, Amoeba.

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What is myelitis?

Region: Spinal cord

Signs and symptoms: Disturbance of nerve transmission

Causative agents: Poliovirus

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What is neurotoxin?

Region: CNS and PNS

Signs and symptoms: Paralysis, rigid (tetanus) or flaccid (botulism)

Causative agents: Clostridium tetani, Clostridium botulinum

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What is meningoencephalitis?

Inflammation of meninges and brain parenchyma

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How does meningitis cause neurological damage?

Direct bacterial toxicity.
Indirect inflammatory process and cytokine release and oedema.
Shock, seizures, and cerebral hypoperfusion.

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What is the prognosis of meningitis?

Mortality ~ 10%

Morbidity ~ 5%

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What are the three classifications of meningitis?

Acute
Chronic
Aseptic

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What are signs and symptoms of meningitis?

Vomiting
Fever
Headache
Stiff neck
Light aversion
Drowsiness
Joint pain
Fitting

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What are causes of acute meningitis?

Mostly bacterial causes

Neisseria meningitidis
Streptococcus pneumoniae
Haemophilus influenzae
Listeria monocytogenes
Group B Streptococcus
Escherichia coli
Staphylococcus aureus
Mycobacterium tuberculosis
Treponema pallidum
Cryptococcus neoformans
Candida
Coccidioides immitis
Histoplasma capsulatum
Blastomyces dermatitidis

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What are features of infection with N. Meningitidis?

Infectious cause of childhood death in all countries.

Transmission is person-to-person, from asymptomatic carriers.

Pathogenic strains are found in only 1% of carriers.

Cause infections in less than 10 days.

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What is a classical feature of meningococcal meningitis?

A nonblanching rash (petechial or purpuric) develops in 80% of children.

A maculopapular rash remains in 13% of children, and no rash occurs in 7%.

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What are links between meningitis and septicaemia?

50% of cases have meningitis
7-10% have septicemia
40% have septicemia AND meningitis

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Why is the clinical difference between meningitis and septicaemia important?

The clinical difference between septicemia and meningitis is important because patients who present with shock are treated differently than patients who present primarily with increased intracranial pressure (ICP).

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Which 4 processes produce the clinical spectrum of septicaemia?

Capillary leak: Albumin and other plasma proteins leads to hypovolemia.

Coagulopathy: Leads to bleeding and thrombosis.

Endothelial injury results in platelet-release reactions
The protein C pathway.
Plasma anticoagulants.

Metabolic derangement: Particularly acidosis

Myocardial failue: And multi-organ failure.

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What is present on the CT scan of a patient with TB meningitis?

Enhancement in the basal cistern and meninges, with dilatation of the ventricles.

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What is chronic tuberculosis meningitis?

Incidence: 544 per 100,000 population in Africa.

More common in patients who are immunosuppressed.

Mortality was 5.5 deaths per 100,000 persons.

Involves the meninges and basal cisterns of the brain and spinal cord.

Can result in tuberculous granulomas, tuberculous abscesses, or cerebritis.

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What does a tuberculosis abscess look like on a CT head?

Enhancing thick-walled abscess.

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What are features of aseptic meningitis?

Aseptic meningitis is the most common infection of the CNS. Patients with aseptic meningitis have headache, stiff neck, and photophobia.

A nonspecific rash can accompany these symptoms.

Enteroviruses (e.g. Coxsackievirus group B and echoviruses) are responsible for 80-90% cases in which a causative organism of aseptic meningitis is identified. It most frequently occurs in children younger than 1 year.

The clinical course of aseptic meningitis is self-limited and resolves in 1-2 weeks.

How is encephalitis transmitted?

Transmission is commonly either person to person, or through vectors:

Mosquitoes
Lice
Ticks

What are some causative organisms of encephalitis?

Various viridae from Togavirus, Flavivirus, and Bunyavirus families.

But, West Nile Virus is becoming a leading cause of encephalitis internationally.

What are some non viral causes of encephalitis?

Bacterial encephalitis:

Listeria monocytogenes

Amoebic encephalitis:

Naegleria fowleri: Habitat – warm water
Acanthamoeba species, and Balamuthia mandrillaris: Brain abscess, aseptic or chronic meningitis.

What is a parasitic cause of encephalitis?

Toxoplasmosis

An obligate intracellular protozoal parasite, Toxoplasma gondii. Via the oral, transplacental route or organ transplantation.

Severe infection in immunocompromised patients.

Affected organs include the gray and white matter of the brain, retinas, alveolar lining of the lungs, heart, and skeletal muscle.

Which conditions can result in brain abscesses?

* Otitis media * Mastoiditis * Paranasal sinuses * Endocarditis * Haematogenously

What are some causative organisms of a brain abscess?

* Streptococci (both aerobic and anaerobic) * Staphylococci * Gram-negative organisms (particularly in neonates) * Mycobacterium tuberculosis * Fungi * Parasites * Actinomyces and Nocardia species

What can cause spinal infections?

Pyogenic vertebral osteomyelitis common form of vertebral infection. Direct open spinal trauma, from infections in adjacent structures, from hematogenous spread of bacteria to a vertebra. Left untreated, it can lead to permanent neurologic deficits, significant spinal deformity, or death.

What are risk factors of spinal infections?

* Advanced age * Intravenous drug use * Long-term systemic steroids * Diabetes mellitus * Organ transplantation * Malnutrition * Cancer

What are investigations for CNS infections?

MRI is superior to CT scanning in detecting parenchymal abnormalities such as abscesses and infarctions. Central nervous system infections: * CSF sample * Brain tissue

What does this CSF study represent? **Appearance:** Clear **Cells x 106/l:** 0-5 leukocytes **Gram stain:** Negative **Protein g/l:** 0.15-0.4 **Glucose mmol/l:** \>60% blood glucose level

Normal

What does this CSF study represent? **Appearance:** Turbid **Cells x 106/l:** 100-10,000 polymorphs **Gram stain:** Positive results **Protein g/l:** 0.5-4.0 **Glucose mmol/l:** \<60% blood glucose level

Purulent meningitis **DDx:** * Bacterial meningitis * ?Meningococcus * ?Pneumococcus * ?Listeria

What does this CSF study represent? **Appearance:** Clear or slightly turbid **Cells x 106/l:** 15-1000 lymphocytes **Gram stain:** Negative **Protein g/l:** 0.5-1.0 **Glucose mmol/l:** \>60% blood glucose level

Aseptic meningitis **DDx:** * Viral meningitis * Partially antibiotic treated bacterial meningitis * Encephalitis * Brain abscess * TB/fungal meningitis

What does this CSF study represent? **Appearance:** Clear or slightly turbid **Cells x 106/l:** 30-1000 lymphocytes or some polymorphs **Gram stain:** Negative **Protein g/l:** 1.0-6.0 **Glucose mmol/l:** \<60% blood glucose level

Tuberculosis meningitis **DDx:** * TB meningitis * Brain abscess * Cryptococcal meningitis

A 20 year old woman presents with headache and neck stiffness. What is the causative pathogen?

Gram positive cocci Pneumococcus

A 18 year old man present with headache and neck stiffness. What is the causative pathogen?

Gram negative cocci Meningococcus

A 65 year old presents with headache and neck stiffness. What is the causative pathogen?

Gram positive rod Listeria

A 45 year old presents with headache and neck stiffness. What is the causative pathogen?

Ziehl-Neelsen stain TB

A 35 year old presents with headache and neck stiffness. What is the causative pathogen?

Indian ink stains Cryptococcus

What are the limitations of diagnostics in CNS infections?

MRI oedema pattern and moderate mass effect cannot be differentiated from tumor or stroke or vasculitis in some patients. Infections in early stages and serological tests. Amount of CSF. PCR techniques. Methods to detect amoebic infections. Availability of good laboratory technique.

What is the management of meningitis?

**Ceftriaxone 2g IV bd** If \>50yrs or immunocompromised add: Amoxicillin 2g IV 4hourly

What is the management of meningoencephalitis?

**Aciclovir 10mg/kg IV tds** **Ceftriaxone 2g IV bd** If \>50yrs or immunocompromised add: Amoxicillin 2g IV 4hourly

What is the recommended therapy for S. Pneumoniae or N. Meningitidis?

Pen G 18-24 mu/d Amoxicillin 12 g/d Ceftriaxone 4 g/d Chloro 75-100 mg/kg/d

What is the recommended therapy for H. Influenzae?

Cefotaxime 12 g/d Ceftriaxone 4 g/d

What is the recommended therapy for Group B Strep?

Pen G Amoxicillin [plus aminoglycoside]

What is the recommended therapy for Listeria?

Amoxicillin 12 g/d [plus aminoglycoside]

What is the recommended therapy for Gram negative bacilli?

Cefotaxime 12 g/d Ceftriaxone 4g/d

What is the recommended therapy for Pseudomonas?

Meropenem 6g/d Ceftazidime 6g/d

What is the most common cause of encephalitis in the UK?

HSV-2