Meningitis Flashcards
What was mortality rate for meningitis caused by S pneumoniae, 90yrs ago / today?
90 yrs ago = 98-100%
Today = 40%
What was mortality rate for meningitis caused by N meningitidis, 90yrs ago / today?
90 yrs ago = 77%
Today = 10%
What was mortality rate for meningitis caused by H influenzae, 90yrs ago / today?
90 yrs ago = 98-100%
Today = 5-10%
When was penicillin discovered / on the market?
Discovered - 1928
On the market - 1942
What is mortality rate for meningitis now?
S pneumoniae - 40%
N meningitidis - 10%
H influenzae - 5-10%
What morbidity is associated with meningitis?
deafness paralysis speech issues epilepsy neuro-psychiatric issues
Who gets meningitis?
neonates
- poorly developed capillaries (not closely knit)
- from flora from mother’s birth canal
young & old
- weaker BBB
Why do neonates get meningitis?
- poorly developed capillaries (not closely knit)
- from flora from mother’s birth canal
What are three meninges layers?
dura mater
arachnoid mater
pia mater
where is CSF?
subarachnoid space
between arachnoid and pia mater
What is in subarachnoid space?
CSF (cerebrospinal fluid)
Blood vessels
Define meningitis
inflammation of lepto-meningeal membranes
ie dura / arachnoid / pia mater
What are 4 main causes of meningitis?
- inflammation
- infection
- parameningeal foci (max sinus, venous plexus)
- neo-plastic / para-neoplastic (ie a consequence of cancer, eg lymphoma)
What parameningeal foci can cause meningitis?
- infection in maxillary sinus / venous plexus
What is a neoplastic / paraneoplastic cause of meningitis?
a consequence of cancer, eg lymphoma
What infectious agents cause meningitis?
Virus - most common
- enterovirus, mumps, herpes
Bacteria - 2nd most common
- meningococci, Pneumococci, H. influenzae
Fungal
- Cryptococus neoformans, Coccidioidomycosis
- NOT usually candida
Parasitic
- Naegleria fowleri, Acanthamoeba spp. (ie amoeba)
What viruses cause meningitis?
- enterovirus
- mumps
- herpes
What bacteria cause meningitis?
- meningococci
- pneumococci
- H influenzae
What fungus causes meningitis?
- Crytococcus neoformans
- Coccidioidomycosis
- NOT candida
What parasites cause meningitis?
- Naegleria fowleri
- Acanthamoeba spp
How does the blood brain barrier (BBB) work?
closely knit capillaries
Where is the likely entry point into the BBB?
choroid plexus - weaker emissary veins (connect the extracranial venous system with the intracranial venous sinuses)
What three ways can organisms reach the CSF?
BBB
- bacteraemia / viraemia / parasitaemia
- can enter anywhere, but most likely at choroid plexus
Direct
- chronic infections in cranial bones, ears, sinuses, oral cavity, upper respiratory tract
Neuronal
- infection in peripheral neurons, axonal transport, replication, cell-to-cell spread of infection to connection neurons in CNS
- eg rabies
How do organisms causing meningitis DIRECTLY access the CSF?
chronic infections in:
- cranial bones
- ears
- sinuses
- oral cavity
- upper respiratory tract
What type of blood infections can cause meningitis?
bacteraemia
viraemia
parasitaemia
How does a neuronal infection reach the CSF to cause meningitis?
- infection in peripheral neuron
- axonal transport
- replication
- cell-to-cell spread
- infection passed to connecting neurons in CSF
What is the pathogenesis of meningitis?
- mucosal colonisation - eg in sinus / oropharyngeal fossa
- intravascular survival (ie pathogen gets from origin into blood)
- meningeal invasion (through dura and arachnoid mater)
- survival in subarachnoid space
- inflammatory response / increase BBB permeability / cerebral vasculitis
- vessels leaky and blocked, therefore cerebal oedema
- CSF flow disturbances
- increased intercranial pressure
- decreased cerebral blood flow
- loss of cerebro-vascular autoregulation
- coma / death
What are the 4 main risk factors for meningitis?
Age
- neonates - close knit capillaries not well dev
- young / old (75+) - weaker BBB
Geography
- overcrowding
- tropical climates - increased organisms, meningitis ‘belt ‘ in Africa
Immunity
- steroids, chemotherapy, HIV
Trauma / post-neurosurgical
- esp base of skull trauma
- Neurosurgery (cerebral shunt, external vascular drain)
What are the GEOGRAPHICAL risk factors for meningitis?
- overcrowding
- tropical climates - increased organisms, meningitis ‘belt ‘ in Africa
What are the IMMUNITY risk factors for meningitis?
- steroids, chemotherapy, HIV
What NUEROLOGICAL SURGERY could cause meningitis?
- cerebral shunts
- external vascular drain
Where is worst place to have skull fracture?
Base of skull (base of occipital / temporal bones)
- rare
What bacteria commonly cause meningitis in neonates?
Group B streptocuccus
E coli
Listeria
K pneumoniae (NOT S pneumoniae)
What bacteria commonly cause meningitis in
S pneumoniae
N meningitidis
What bacteria commonly cause meningitis in >50yrs?
S pneumoniae
N meningitidis
Listeria
aerobic gram -ve bacilli
What bacteria commonly cause meningitis in immunocompromised?
S pneumoniae N meningitidis Listeria gram -ve bacilli Pseudomonas aeruginosa
What bacteria commonly cause meningitis in basilar skull fracture (base of skull)?
S pneumoniae
H influenzae
Group A beta-haemolytic streptococci
ie oral organisms
What bacteria commonly cause meningitis in head injuries / post-neurosurgery?
A aureus
S epidermidis
aerobic gram -ve bacilli
P aeruginosa
ie skin flora
What oral organisms can cause meningitis and what type of person is at risk?
S pneumoniae
H influenzae
Group A beta-haemolytic streptococci
Base of skull fracture
What skin flora organisms can cause meningitis and what type of person is at risk?
A aureus
S epidermidis
aerobic gram -ve bacilli
P aeruginosa
Head injury / post-neurosurgery
Who is at risk of S pneumoniae and N meningitidis meningitis?
50yrs
immunocompromised
Who is at risk of S pneumoniae meningitis?
50yrs
immunocompromised
base of skull fracture
Who is at risk of N meningitidis meningitis?
50yrs
immunocompromised
Who is at risk of H influenzae meningitis?
basilar skull fracture (base of skull)
Who is at risk of Listeria meningitis?
neonates
>50yrs
immunocompromised
Who is at risk of gram -ve bacilli meningitis?
> 50ys
immunocompromised
head injury
post-neurosurgery
What are four clinical signs of meningitis?
- fever
- neck stiffness
- altered mental state
- headache / photophobia
What % get 3 of 4 signs of meningitis?
44%
What % get 2 of 4 symptoms of meningitis?
95%
What could fever and headache be a symptom of?
meningitis!
What positional tests are there to diagnose meningitis?
Kernig’s sign
- lie flat, lift head, if meningitis - knees will bend too
Brudzinski’s sign
- lie flat, lift one left 90 degrees in air, if can’t straighten leg = meningitis (stiff hamstring)
What is Kernig’s sign?
- lie flat, lift head, if meningitis - knees will bend too
What is Brudzinski’s sign?
- lie flat, lift one left 90 degrees in air, if can’t straighten leg = meningitis (stiff hamstring)
What is sensitivity of Kernig’s and Brudzinski’s sign?
5% !
What is gold std to diagnose meningitis?
Lumber puncture
How do you do lumber puncture?
foetal position
insert needle between L3 and L4
collect CSF
What are normal CSF values?
- clear appearance
- opening pressure 5-20cm
- cell count
What is the opening pressure during a lumber puncture?
The pressure measured in CSF when needle first inserted
Normal = 5-20cm
What is - cell count - cell type - glucose CSF : blood ratio - Protein levels in CSF in viral meningitis?
- cell count = 50-1000
- cell type = lymphocytes
- glucose CSF : blood ratio >0.45 (ie >45% of blood glucose)
- Protein
What is - cell count - cell type - glucose CSF : blood ratio - Protein levels in CSF in bacterial meningitis?
- cell count = 1000-10,000
- cell type = neutrophils
- glucose CSF : blood ratio
What is - cell count - cell type - glucose CSF : blood ratio - Protein levels in CSF in fungal meningitis?
- cell count = 20-500
- cell type = lymphocytes
- glucose CSF : blood ratio 45mg/dL
What is - cell count - cell type - glucose CSF : blood ratio - Protein levels in CSF in TB meningitis?
- cell count = 50-300
- cell type = lymphocytes
- glucose CSF : blood ratio
What is - cell count - cell type - glucose CSF : blood ratio - Protein levels in CSF in partially treated meningitis? (ie with antibiotics)
unknown!
When should lumber puncture be done?
ASAP
- antibiotics will affect results of CSF
What type of meningitis has CSF with:
cell count 750?
Viral
What type of meningitis has CSF with:
cell count 300?
viral, TB, fungal
What type of meningitis has CSF with:
cell count 9000?
bacterial
What type of meningitis has CSF with:
lymphocytes as main cell type?
viral, fungal, TB
What type of meningitis has CSF with:
neutrophils as main cell type?
bacterial
What type of meningitis has CSF with:
bacterial, TB, fungal
What type of meningitis has CSF with:
>0.45 CSF : blood glucose ratio?
viral
What type of meningitis has CSF with:
0.5 CSF : blood glucose ratio?
viral
What type of meningitis has CSF with:
0.6 CSF : blood glucose ratio?
This is the normal level!
What type of meningitis has CSF with:
protein 150mg/dL?
viral (45mg/dL)
What type of meningitis has CSF with:
The highest protein?
bacterial (100-500mg/dL)
What type of meningitis has CSF which is sterile?
viral
What type of meningitis has CSF with:
the highest glucose CSF : blood ratio?
viral (>0.45)
What extra tests can be done on CSF?
PCR - Meningococci, Pneumococci
Virology PCR
Antigen test - Cryptococcal Ag, Pneumo latex
India ink - Cryptococci
Fungal cultures - Crytococcus neoformans, Coccidioidomycosis
ZN stain
AFB culture - acid fast bacilli smear and culture - test for TB
Cytology
Oligoclonal bands - bands of Ig seen in CSF after electrophoresis
Xanthochromia - yellow discolouration = bilirubin present (likely subarachnoid haemorrhage)
What is a Xanthochromia test?
tests CSF for yellow discolouration = bilirubin present (likely subarachnoid haemorrhage)
What is a Oligoclonal bands test?
tests CSF for bands of Ig seen in CSF after electrophoresis
What is a AFB culture?
acid fast bacilli smear and culture - test for TB in CSF
What can india ink test for?
Cryptococci
Is an MRI / CT needed before lumbar puncture?
most people have normal MRI / CT with meningitis
but should do MRI / CT
- exclude other diagnoses
(intracranial haemorrhage, migraine, cerebral tumour)
- all get headaches and neck stiffness
Apart from meningitis, what other diagnoses for headaches and neck stiffness?
- intracranial haemhorrhage
- migraine
- cerebral tumour
How you do determine if it’s meningitis or a haemorrhage?
MRI / CT
When should you do neuro-imaging in meningitis?
Before lumbar puncture If history of unconsciousness history of seizures focal neurology (specific area of body affected) low GCS
What is GCS?
Glasgow Coma Scale
Where is the inflammation in meningitis?
subarachnoid space mainly
Why do you do neuro-imaging (MRI / CT) in meningitis?
if cerebral abcess, then can’t do lumbar puncture
- it may rupture and cause hernia
Symptoms of cerebral abcess
- seizures
- focal neurology (specific area of body affected)
- Low GCS (Glasgow Coma Scale
What are 4 main complications of meningitis?
Seizures
- scar tissue from infection / inflam = scar epilepsy
Hydrocephalus
- increase in CSF in ventricles, therefore compression of brain
- CSF is thicker (increase cell count), therefore reduced flow, therefore increased risk blockage
- pressure released down and out via foramen magnum (pons compressed = cardiorespiratory arrest)
- rare
Transtentorial herniation
- brain expands inwards, towards pons/brain stem (motor / respiratory centre)
- can cause coma, death
Infarcts
- caused by vasculitis and vascular compression
What is Seizure complication in meningitis?
- scar tissue from infection / inflam = scar epilepsy
What is hydrocephalus complication in meningitis?
- increase in CSF in ventricles, therefore compression of brain
- CSF is thicker (increase cell count), therefore reduced flow, therefore increased risk blockage
- pressure released down and out via foramen magnum (pons compressed = cardiorespiratory arrest)
- rare
What is transtentorial herniation complication in meningitis?
- downward brain hernia
- brain expands inwards, towards pons/brain stem (motor / respiratory centre)
- can cause coma, death
What is infarct complication in meningitis?
- caused by vasculitis and vascular compression
How do you manage meningitis?
Supportive care
- specialist input
- if lacking, most common reason meningitis gets worse
Specific antimicrobial therapy
- give ASAP
- via IV (not all AB can cross BBB), IT (intrathecal - into spinal cord), IM, PO
- duration of treatment
- consider allergies / renal function
Steroids (?)
- views keep changing on use
- evidence shows in developed world - steroids beneficial if used before or with first dose AB.
- if given after 1st dose AB - effects unknown
Surgical intervention
Prophylaxis
- vaccinations - universal
- antibiotics - for ppl close to others with meningitis - prevents secondary infection
What is most common cause of meningitis getting worse?
Lack of supportive care / specialist input
What is early meningitis treatment?
ABCDE
What is late meningitis treatment?
Nutrition
Physiotherapy
Rehabilitation
What is issue with IV antibiotics?
Some drugs cannot cross BBB
What is alternative to IV is drug cannot cross BBB to treat meningitis?
Intrathecal injection (IT)
Which AB can cross BBB?
Penicillin
Ceftriaxone
Meropenem
Choramphenicol
Which AB cannot cross BBB?
Vancomycin
Gentamicin
What should your chose of AB depend on in treating meningitis?
- cause of meningitis
- route of administration
What other medication can be used with AB in meningitis treatment?
Steroids
- views keep changing on use
- evidence shows in developed world - steroids beneficial if used before or with first dose AB.
- if given after 1st dose AB - effects unknown
What types of supportive methods can be used with neurosurgery in meningitis?
- EVD - external ventricular drain (needed for hydocephalus)
- IT of AB (intrathecal injection of AB) - port needs to be added by surgeon
What surgery can be done in hydrocephalus?
EVD - external ventricular drain
What types of prophylaxis is available for meningitis?
- vaccinations - universal
- antibiotics - for ppl close to others with meningitis - prevents secondary infection
Who should you tell about pt with meningitis?
BACTERIAL meningitis is a notifiable disease
- public health issue
- legal requirement to tell public health authorities