Infection: Meningitis Flashcards by Kirsty Sutherland

What is meningitis?

Inflammation of meninges covering the brain

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How can meningitis be confirmed?

Finding WBCs in CSF

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What are the most common causes of meningitis?

Viral infections - and most are self resolving

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Can bacterial meningitis have serious consequences?

Yes

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Tuberculous meningitis is rare in..

Countries with low TB prevalence

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TB meningitis mainly affects children under what age?

5 years

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Are fungal and parasitic meningitis rare in children?

Yes, predominantly affect immunocompromised

Fungi typically cause chronic meningitis (unlike bacterial and viral that cause acute)

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What causes of non infectious meningitis are there?

Malignancy
Autoimmune diseases e.g SLE
Adverse reaction to medication e.g intrathecal therapy

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Over 80% of patients with bacterial meningitis are under what age?

16 years

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What is the mortality level in children for bacterial meningitis?

5-10%

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Over 10% of survivors of bacterial meningitis are left with what?

Long term neurological impairment

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What bacteria most commonly cause meningitis in neonates to 3 months?

Group b streptococcus
E. coli and other coli forms
Listeria monocytogenes

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What bacteria most commonly cause meningitis in the 1 month to 6 years group?

Neisseria meningitidis
Streptococcus pneumoniae
Haemophilius influenza

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What bacteria most commonly produce meningitis in over 6 year olds?

Neisseria meningitidis

Streptococcus pneumoniae

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Bacterial infection of the meninges usually follows..

Bacteraemia

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Does most of the damage to meninges come from the bacteria itself or the host’s response ?

Host’s response to infection

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What does the release of inflammatory mediators, activated leukocytes and endothelial damage lead to?

Cerebral oedema
Raised ICP
Decreased cerebral blood flow

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Why can hydrocephalus occur with bacterial meningitis?

Fibrin deposits block the resorption of CSF

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Are the early signs and symptoms of bacterial meningitis nonspecific ?

Yes especially in infants and young children

Only children able to talk are able to describe the classical: photophobia, neck stiffness, headache

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What signs are associated with neck stiffness?

Brudzinski sign - flexion of the neck with the child supine causes flexion of the knees and hips
Kernig sign - with the child laying supine and with hips and knees flexed, there is back pain on extension of knee

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What contraindications for LP are there?

Cardiorespiratory instability
Focal neurological signs
Signs of raised ICP - high BP, coma, low HR or papilloedema, fontanelle bulging
DIC, coagulation abnormalities or on anticoagulation therapy, thrombocytopenia
Signs of cerebral herniation - odd posture or breathing, GCS<13, dilated pupils, doll’s eye reflex’s, increased BP, low HR, papilloedema)
Local infection at site of LP
Concerns of meningococcal sepsis
If it causes delay in starting antibiotics

= risks of coning of cerebellum through foramen magnum

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What symptoms are associated with bacterial meningitis?

Headache
Photophobia
Fever
Lethargy
Irritability, abnormal cry 
LOC seizures
Poor feeding/vomiting 
Hypotonia 
Drowsiness

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What examination findings are associated with bacterial meningitis?

Fever
Purpuric rash (meningococcal disease)
Neck stiffness
Bulging fontanelle 
Opisthotonus (arching back)
Positive Brudzinski/Kernig sign 
Signs of shock - tachycardia, tachypnoea, hypotension, prolonged cap refill
Focal neurological signs 
Altered conscious level 
Papilloedema (rare)

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What investigations should be done?

FBC, U&E, LFT, CRP, coagulation test
Blood glucose and blood gas
Blood culture, throat swab, urine and stool for bacteria
Rapid antigen test for meningitis organisms (can be done on blood, urine, CSF)
Samples for viral PCRs (throat swab, nasopharyngeal aspirate, conjunctival swab, stool)
LP
If TB suspected: CXR, Mantoux test/ interferon
Consider CT/MRI brain scan and EEG

Describe group B streptococcus

Also called S. agalactiae Lancefield group B of the beta haemolytic streptococci (complete RBC lysis) Causes meningitis and pneumonia in newborns and elderly with occasional systemic bacteremia

When is group B streptococcus usually acquired?

From mother at birth | More common in: low birth weights, following prolonged rupture of the membranes

Do septic signs commonly present before or after meningeal signs?

Before E.g : fever, cold hands/feet, limb/joint pain, abnormal skin colour, odd behaviour, rash, DIC, tachycardia, hypotension, tachypnoea

What other causes of stiff neck are there?

Tonsillitis Lymphadenitis Subarachnoid bleed

Should antimicrobial therapy be started before LP results reported?

Yes - do not delay antibiotics (follow sepsis 6 pathway) Review results as soon as available and amend the antimicrobial regime if necessary

Between what meningeal layer is the CSF found?

Arachnoid and pia (within the subarachnoid space)

What are the leptomeninges?

The inner 2 meningeal layers around the brain and spinal cord (arachnoid and pia) - meningitis = inflammation of the leptomeninges

How can infection reach the CSF?

1) Direct spread - pathogen gets inside skull or spinal column and then penetrates the meninges - via overlying skin/nose - anatomical defect e.g congenital: spina bifida or acquired: skull fracture 2) haematogenous spread - pathogen moved through endothelial cells in blood vessels that make up BBB and get into CSF

More than how many WBCs in a micro litre typically define meningitis?

More than 5

Describe a normal CSF sample

``` Appearance = clear WBCs = 0-5/mm3 Protein = 0.15-0.4g/L Glucose = >or equal to 50% of blood ```

What are polymorphs ?

Also called granulocytes Varying shape of nucleus - usually lobed Often refers to neutrophils (the other types= eosinophils, basophils, mast cells) Neutrophils = most abundant type of phagocyte

Describe a bacterial meningitis CSF sample

``` Appearance = turbid WBCs = predominance of polymorphs, >100 WBCs/microlitre Protein = raised Glucose = reduced ```

Describe a viral meningitis CSF sample

``` Appearance = clear WBCs = lymphocytes raised, initially may be polymorphs, 10-1000 WBCs/microlitre Protein = normal/slightly raised Glucose = normal/slightly reduced ```

Describe a tuberculoid meningitis CSF sample

``` Appearance = turbid/clear/viscous WBCs = raised lymphocytes Protein = raised Glucose = lower ```

Describe a CSF sample associated with encephalitis

``` Appearance = clear WBCs = normal or raised, lymphocytes Protein = normal or raised Glucose = normal or reduced ```

What does the CSF pressure typically rise above?

200mmH20 | Due to more immune cells attracting additional water

What bacteria causes tick borne meningitis?

Borrelia burgdorferi (cause of Lyme disease)

How is bacterial meningitis managed?

Empirical antibiotics IV Steroids in children older than 3 months Fluids

What empirical antibiotics are used in children younger than 28 days?

``` Cefotaxime 50mg/kg/dose IV AND Amoxicillin 50mg/kg/dose IV (consider double dose if Listeria) AND Gentamicin IV ``` In this age group ceftriaxone may be used as an alternative to cefotaxime once clinical recovery evident, but not in premature babies or those with jaundice, hypoalbuminaemia or acidosis

What empirical antibiotics are used in 1-3 months?

Ceftriaxone IV 80mg/kg (max 2g) OD AND Amoxicillin IV 50mg/kg (max 2g) IV 8 hourly

In children older than 3 months old, what empirical antibiotics should be given?

Ceftriaxone IV 80mg/kg (max 2g) OD | If considering listeria add amoxicillin IV 50mg/kg (max 2g) 6 hourly

When should IV dexamethasone be considered?

``` Older than 3 months Less than 12 hours from first dose of antibiotic If LP reveals: Frank purulent CSF CSF protein greater than 1g/L Bacteria on gram stain ```

What is given for all household contacts from meningococcal meningitis and Hib infection?

Ciprofloxacin - eradicate nasopharyngeal carriage

If antibiotics have been given before LP takes place what can happen?

False negative readings | Rapid antigen test and PCR can aid diagnosis in these situations

In partially treated bacterial meningitis e.g children given oral antibiotics for a non specific febrile illness, what with CSF and cultures usually show?

CSF high WCC count | Blood culture - negative

What class of antibiotics are ceftriaxone and cefotaxime?

Third generation cephalosporins

What complications can occur?

Hearing impairment - inflammatory damage to the cochleae hair cells Local vasculitis - can cause CN lesions Local cerebral infarction - can cause focal seizures and may cause long term epilepsy Subdural effusion - associated with infective agents e.g haemophilius influenzae, pneumococcal strains Hydrocephalus- if there is reduced CSF reabsorption Cerebral abscess - condition deteriorates with/without signs of SOL

What assessment should be done after meningitis infection?

Audiological assessment | The earlier an implant is placed, the greater the chance of success (cochlear can calcify if no treatment given)

How can a subdural effusion be confirmed?

Cranial CT or MRI | Most resolve spontaneously, but some require neurosurgical intervention

How is a cerebral abscess confirmed?

Cranial CT or MRI | Drainage required

What common viral causes of meningitis are there?

Enteroviruses EBV Adenoviruses Mumps (rare due to the MMR vaccine)

Is viral meningitis more or less severe than bacterial?

Much less usually | Most cases make a full recovery

How can viral meningitis be diagnosed?

Culture or PCR of CSF Stool, urine, nasopharyngeal aspirate, throat swabs Serology

Is meningitis a notifiable disease?

Yes even suspected meningitis should be notified to public health England

Is a LP contraindicated in meningococcal sepsis?

Yes