Infection: Meningitis Flashcards
What is meningitis?
Inflammation of meninges covering the brain
How can meningitis be confirmed?
Finding WBCs in CSF
What are the most common causes of meningitis?
Viral infections - and most are self resolving
Can bacterial meningitis have serious consequences?
Yes
Tuberculous meningitis is rare in..
Countries with low TB prevalence
TB meningitis mainly affects children under what age?
5 years
Are fungal and parasitic meningitis rare in children?
Yes, predominantly affect immunocompromised
Fungi typically cause chronic meningitis (unlike bacterial and viral that cause acute)
What causes of non infectious meningitis are there?
Malignancy
Autoimmune diseases e.g SLE
Adverse reaction to medication e.g intrathecal therapy
Over 80% of patients with bacterial meningitis are under what age?
16 years
What is the mortality level in children for bacterial meningitis?
5-10%
Over 10% of survivors of bacterial meningitis are left with what?
Long term neurological impairment
What bacteria most commonly cause meningitis in neonates to 3 months?
Group b streptococcus
E. coli and other coli forms
Listeria monocytogenes
What bacteria most commonly cause meningitis in the 1 month to 6 years group?
Neisseria meningitidis
Streptococcus pneumoniae
Haemophilius influenza
What bacteria most commonly produce meningitis in over 6 year olds?
Neisseria meningitidis
Streptococcus pneumoniae
Bacterial infection of the meninges usually follows..
Bacteraemia
Does most of the damage to meninges come from the bacteria itself or the host’s response ?
Host’s response to infection
What does the release of inflammatory mediators, activated leukocytes and endothelial damage lead to?
Cerebral oedema
Raised ICP
Decreased cerebral blood flow
Why can hydrocephalus occur with bacterial meningitis?
Fibrin deposits block the resorption of CSF
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
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
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
What symptoms are associated with bacterial meningitis?
Headache Photophobia Fever Lethargy Irritability, abnormal cry LOC seizures Poor feeding/vomiting Hypotonia Drowsiness
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)
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
