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104 Cards in this Set
- Front
- Back
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What are the characteristics of acute bacterial meningitis?
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1) Acute infection of meninges
2) Pyrexia 3) Headache 4) Meinigism (neck stiffness, +Kernig's sign) MEDICAL EMERGENCY |
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What is encephalitis?
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Widespread infect within the brain and/or SC
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What pathogens are more common in 0 -3 months (neonatal) meningitis and where are these pathogens found?
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1) E. Coli
2) Listeria Monocytogenes 3) Group B strep (S. agalactiae) Birth canal |
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What pathogens are commonly the cause of 3 months -4 years (childhood) meningitis?
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1) HIB -pharynx
2) N. meningitis -oro/naso pharynx 3) S. pneumonia -pharynx all have polysaccharide capsule |
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What pathogens would you expect in adult meningitis? And in what age groups are they seen more commonly in?
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1) N. meningitides (15-25 years)
2) Strep. pneumonia (esp. elderly) |
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What populations are more likely to be affected by meningitis?
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Very young and old (>60 years)
Males slightly more affected |
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Overall, what are the most common bacterial strains to cause meningitis?
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1) N. meningitides
2) H. influenzae type B (HIB) 3) S. pneumoniae |
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In viral meningitis, what is the most common group of viruses?
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Enteroviruses
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When should Listeria monocytogenes be considered as a likely pathogen for meningitis?
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<1mo, >60yo, alcoholics, cancer patients, immunosuppressed
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When should S. aureus be considered as a likely pathogen for meningitis?
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After head trauma or neurosurgery
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What is the most important pathogen in neonates?
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HIB
"HI Baby!" -the way I remember it |
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What pathogens are likely to be responsible for chronic meningitis?
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TB
Cryptoccoccus |
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What is the most important non-bacterial, non-viral cause of meningitis in Australia? What population is it most commonly seen in and how is it spread?
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1) cryptococcus neoformans
2) immunocompromised patients 3) pigeon poop |
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What type of bacterias would a patient be at risk of getting meningitis from if the patient has hyposplenism?
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Encapsulated bacterias
Spleen protects from encapsulated bacteria |
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What are environmental factors that would increase the risk of meningitis?
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Over-crowding
Proverty Head injury LP immunisation geography |
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What is the more common entry to the meninges for bacteria?
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Haematogenous spread
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How does haematogenous spread occur?
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colonisation of nasopharynx -> invasion of nasal mucosa -> blood
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What does the presence of the polysaccharide capsule infer to the bacteria?
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Interferes with complement and phagocytosis
Common with most common meningeal pathogens |
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What is the main protective immune response against polysaccharide bacteria in the blood?
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antibodies + complement
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When do antibodies natural develop?
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From the age of 2
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How would a polysaccharide vaccine have to have in order for it to get an immune response in a child <2yo?
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polysaccharide has to be conjugated to protein (principle for HIB vaccine)
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What are the routes of entry into meninges across the BBB?
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1) paracellular route
2) transcellular route |
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The BBB is usually very selective in what it lets through. How might bacteria cross the BBB paracellularly?
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Bacteraemia causes inflammation -> release of cytokines (e.g. IL-1 and leukotrines) -> BBB endothelium contraction -> increase permeability
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What are the adjacent structures in which defects may occur such that normal bacterial flora can come into contact with CSF?
And what can these defects be caused by? |
facial sinuses
nasal cavity middle ear Trauma (e.g. skull fracture at these sites) Congential (e.g defect in oval or round window of middle ear) |
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What mediates tissue damage in bacterial meningitis?
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microbal factors
cytokines |
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Why should corticosteriods be given together with antibiotic therapy in bacterial meningitis?
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antibiotic therapy leads to microbal lysis and promotoes release of cell wall components that leads to cytokine stimulation hence tissue damage
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What would you expect the spinal tap results to look like with bacterial meningitis?
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1) cloudy or frankly purulent CSF under increased pressure
2) as many as 90,000 neutrophils/mm2 3) raised protein level 4) marked decrease in glucose |
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What would you expect the spinal tap results to look like with aseptic meningitis?
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1) lymphocytic pleocyptosis
2) moderate protein levelation 3) sugar content is nearly always normal |
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What would you expect the results of a spinal tap to look like in a patient with a brain abscess?
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1) CSF is under increased pressure
2) WCC raised 3) protein raised 4) sugar normal |
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What would you expect the result of a spinal tap to look like in a patient with subdural empyema?
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Similar to brain abscess because they're both parameningeal infectious processes
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What is the morphology of an acute bacterial meningitis?
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1) exudate evident within leptomeninges (pia and arachnoid)
2) meningeal vessels are engorged |
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The location of the exduate varies for HIB and pneumococcal meningitis. What are the locations?
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HIB: basal
pneumococcal: densest over cerebral convexities near the sagital sinus |
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What are the complications of acute inflammatory exudate in the subarachnoid space?
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Occulsion of BVs (veins and arteries)
Block of CSF pathway (hydrocephalus) Cranial nerve damage (esp CN6 + CN8 -> can lead to deafness) |
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How might hydrocephalus occur in acute bacterial meingitis?
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leptomeningeal fibrosis -> adhesive arachnoid layers -> hydrocephalus
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What are the ways in which bacteria can enter CNS?
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Direct implatation
Extension from a contigous focus of infection Haematogenous spread |
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How might a Otitis Media lead to meningitis?
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1) Colonisation of nasopharynx
2) goes eustacian tube 3) repeated infections and inadequate healing 4) invasion of mastoid cells 5a) petrous apex migration to trigeminal ganglion -> Gradenigo's syndrome OR 5b) bone breaks into posterior fossa -> extradural abscess -> cerebellum (epidural empyema) 6) focal invasion to leptomeningies (now meningitis |
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How might sinusitis lead to meninigitis?
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1) penetration of columnar epithelial cells by capsulated bacteria
2) drainage into nasal capillaries 3) intravascular space 4) bacteraemia -> haematogenous spread 5) intraventricular chorid plexus 6) infects plexus 7) penetrates BBB |
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Which clinical course is more fulminant?
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aseptic meningitis
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How are viral meningitis treated
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Symptomatically
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True or false
Viral meningitis are self limiting |
True
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What are the most common pathogens causing viral meningitis?
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Commonly: enterovirus
up to 80% of cases are due to the following: echovirus coxsackievirus nonparalytic poliomyelitis |
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What are the macroscopic characteristics of aseptic meningitis?
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nothing distinctive except for brain swelling
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What does the microscopic examination look like in aspetic meningitis?
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no abnormality
at most: mild-moderate infiltration of leptomeninges with lymphocytes |
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For brain abscesses, where are the most likely local extension foci of infection from?
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mastoiditis
paranasal sinuses |
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What are the usual primary sites of infection such that haematogenous spread causes brain abscesses
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heart
lungs distal bones tooth extraction |
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What are the predisposing conditions that can lead to brain abscesses?
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cyanotic heat disease (L->R shunt) = loss of pulmonary filtration
acute bacterial endocarditis chronic pulmonary sepsis e.g. bronchiectasis |
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What is the most common offending organisms in nonimmunosuppressed popluation when it comes to brain abscesses?
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Staph
Strep |
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What would a macroscopic examination of a brain abscess look like?
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discrete lesions
central liqufactive necrosis fibrous capsule oedema |
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What are the most common brain regions affected by brain abcesses?
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in decending order of frequency
1) frontal lobe 2) parietal lobe 3) cerebellum |
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What would a microscopic examination of a brain abscess look like?
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exuberant granulation tissue
neovascularisation around neurosis (responsible for oedema) fibroblast -> collagen -> fibrous capsule Zone (outside capsule) of reactive gliosis with numerous gemistocytic astrocytes |
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What can a ruptured abscess lead to?
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Ventriculitis
Meningitis Venous sinus thromosis |
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What are the basic clinical features of bacterial meningitis?
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1) headache
2) neck stiffness 3) fever 4) photophobia 5) vomiting |
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True of false:
A patient with bacterial meningitis will prefer to lie still |
True
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What are the first few symptoms of bacterial meningitis that can develop between minutes -hours?
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intense malaise
fever rigors severe headache photophobia vomitting |
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What are the symptoms of bacterial meningitis that develop winthnig hours?
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Neck stiffness
Positive Kernig's sing |
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How would you look for Kernig's sign?
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attempt to straigten the knee while the hip is flex
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What is a positive Kernig's sign and why does it happen?
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Positive sign = pain
Cause: movement is limited by spam of hamstring -> pain due to inflammatory exduates around the roots of the lumbar theca |
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What might chronic meningitis be confused for?
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Intracranial mass lesion
epilepsy focal signs |
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What is Cushing's triad?
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HT
bradycardia cheyne stroke's respiration |
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Wha are the classical signs of raised ICP
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Cushing's triad
headache papilledema vomiting |
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Explain the mechanism of how a patient with raised ICP would get cushing's triad
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increased ICP -> decrease brain perfusion -> hypothalamic ischemia -> SNS activation -> increase HR and peripheral vasoconstriction -> increase BP -> baroreceptors -> vagal slowing of heart in response -> bradycardia
BUT SNS maintains HT BS function is imparied by poor perfusion -> irregular breathing |
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What causes headaches in raised ICP?
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distortion of intracranial blood vessels and stretching of dura
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Why is headaches caused by raised ICP worse in the morning?
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Poor venous drainage during sleep and probably a rise in PCO2 due to diminished resp. efforts which naturally lead to an increase ICP therefore excerbating any raised ICP already present
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Explain the mechanims of papilledema in raised ICP
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not fully understood
factors that may be involved: 1) interference with axoplasmic transport in the retina 2) vascular congestion transmission of the raised CSF pressure along optic nerve -> compression of central retinal vein -> oedema |
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Explain the mechanism of vomiting in raised ICP
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Particularly common in children, esp with lesions involving floor of 4th ventricle and direct irritation of the vagus nucleus
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What time of the day is vomitting more common in raised ICP?
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morning
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What is the main clinical feature of meningococcal meningitis
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Petechial rash
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What clinical features when present would point you towards pneumococcal meninigitis?
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Skull fracture,
Ear disease, Congenital CNS lesion |
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What type of patient would you expect to see with HIV meningitis?
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immunocompromise
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What clinical features would present with enterovirus meningitis?
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Rash
Pleuritic pain |
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What patient history would point you towards poliomyelitis meningitis?
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International travel
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What clinical cues would point to you towards leptospirosis meningitis?
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Occupational hx: working in drains, polluted water, recreation swimming
Rostration Myalgia Conjunctivitis Jaundice |
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A patient presents with fever and signs of nerve root compression on a background of backpain and headache. Blood test shows elevated peripheral WCC
What is the likely diagnosis? How would you confirm it? How would you treat it? |
Epidural abscess in the spinal canal (common site)
Confirmation by emergency MRI Treatment: surgical drainage and antibiotics (early cases without progression can treat with antibiotics alone) |
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What are the common organisms of epidrual abscesses?
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S. aureus
Strep gram -ve bacilli anaerobes |
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What are the antiobotic options for treatming epidural abscesses?
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nafcilin
ceftriaxone |
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A patient presents with confusion, nausea and vomtting, drowisness, hemiparesis and focal seziures, on a background of fever, headache (started focally and later generalised), blurred vision and speech difficulty.
The patient also has a recent (<2week) history of pulmonary infection What the likely diagonsis? How would you confirm it? How would you treat it? |
Subdural emphyema
Confirm: MRI, elevated ESR, blood culture Treatment: surgical drainage and antibiotics |
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What would a recent history of a patient with subdural empyma sound like?
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<2wk: recent sinusitis/otitis media/ mastoiditis/ meningitis/ cranial surgery/ trauma/ sinus surgery/ pulmonary infection
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True or false
A patient with subdrual empyema can have generalised seizures |
True
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True of false
Subdural empyema only causes hemiplegia |
False
Can cause hemiparesis too |
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What antibotics are used to treat subdural empyema?
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ceftriaxone
metronidazole |
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What is subdural emphyema?
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collection of pus in the subdural space usually resulting as a direct infection of the nasal sinuses or inner ear
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Define encephalitis
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Inflammation of the brain parenchyma, usually viral. Brain inflammation also develops in bacterial and fungal meningitis
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What are the common organisms for actue viral encephalitis?
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HSV
ECHO coxsacki mumps EBV |
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Which virus accounts for the serve cases of viral encephailitis?
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HSV
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How servere are the symptoms and what is the progonsis of the patient?
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Most infections = symptoms are mild and recovery occurs
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How would you diagnose viral encephalitis? And what would the expected results be?
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CT, MRI, EEG and LP
Viral serology of blood and CSF CT and MRI: diffuse areas of oedema EEG: slow waves(characteristic) CSF: raised cell count |
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What is the treatment of viral encephalitis?
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IV aciclovir (active form)
inhibits DNA synthesis |
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What is the only way to get a rapid and specific diagnosis?
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LP
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What are the contraindications to LP?
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1) shock and/or coagulopathy such that there is an increase bleeding
2) signs of raised ICP or focal neurologic signs -> risk of herniation |
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What are the signs of a dangerously raised ICP?
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rapidly deteriorating conscious state
retinal changes of papilloedema altered pupillary response increase in BP with slow pulse rate |
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How do you reduce raised ICP?
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reduction of arterial CO2 by intubation or hyperventilation
inducing osmotic diuresis |
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What is the effect of CO2 on ICP?
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CO2 causes vasodilation hence increases ICP
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What is the recommended antibotic therapy given to in a previously well patient with meningitis that is under the age of 3 months after obtaining blood for blood culture?
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3rd G cephalosporin AND ampicillin
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What is the recommended antibotic therapy in a previsouly well patient with meningitis that is over the age of 3 and does not have pneumococcal meningitis after obtaining blood for blood culture?
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Ampicillin alone in fine
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When would you give vancomycin along with ampicillin?
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1) When gram stain suggests pneumococcal meningitis and the sensitivity to pencillin is unknown
2) in high level resistant strep pneumoniae |
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Why is ampicillin given to a patient with meningitis who is under the age of 3 months while waiting for blood culture results?
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Under the age 3 months you have to cover infections from Listeria as it is not sensitive to 3rd G cephalosporin
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Why can 3rd G cehalosporin be used alone in a patient with meninigitis who is over the age of 3months while waiting for blood cultures results?
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Will be effective with most strains of Streptococcus pneumoniae (resistant to ampillcin)
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What antibotic would you give if meningococcal is suspected?
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Penicillin
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What are the main factors that contribute to adverse neurological outcomes of meningitis?
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Raised ICP
reduced CPP |
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In a patient that's being treated for meningitis, when should you see a steady improvement in responsiveness and alertness?
And if that doesn't occur, what could be causing the delay? |
within the first 24 hours
If not: causative organism might be resistant to antibiotic therapy or complications such as concomitant focus of infection or focal cerebral pathology present |
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True or false
Meningococcal infection can either cause meningitis or septicasemia |
False
Can cause both too |
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What are the typical features of meningococcal speticaemia?
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Septic shock: fever, myalgia, hypotension
May be accompanied by petechial or haemorrhagic rash |
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In meningococcal infection, why can some patients deteriorate rapidly?
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shock
DIC mutiorgan failure |
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If a patient suspected to have bacterial meningitis needs to be transfered to another hospital, what do you give them for the trip?
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IV pencillin (might save their life!)
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