CNS Infections Flashcards
What are the causes of CNS infections
- bacteria
- viruses/aseptic
- aseptic/meds
- fungi
- parasites
- prion
define meningitis
inflammation of membranes surrounding the brain
define encephalitis
inflammation of brain parenchyma
define myelitis
inflammation of spinal cord
What determines the presentation of meningitis/encephalitis
the location of the infection, not the organism
Which organisms cause acute onset meningitis
viruses, aerobic bacteria
Which organisms cause subacute or chronic meningitis
anaerobic bacteria, tuberculosis, fungi
T. pallidum
Describe the pathophys of meningitis/encephalitis
organism enters body via GI, resp, skin nidus. Replication begins. Travels to CNS by blood, peripheral nerves, bone and penetrates the blood/CSF barrier, infects endothelial cells of cerebral blood vessels, or through infected emboli.
Describe the hallmarks of bacterial meningitis
- abrupt, acute inflammatory process
- acute onset of severe headache, fever, stiff neck
- multiple infectious causes
What are the 2 common organisms in bacterial meningitis
What is the most common cause of bacterial meningitis
staphylococcus pneumoniae among adults and newborns
neisseria meningitidis on college campuses
What are the goals of a work-up for bacterial meningitis
start IV, start abx, get lumbar puncture within 60 mins
Describe the big 3 symptoms for bacterial meningitis
- fever, stiff neck, altered mental status
- also HA, fever, N/V, pain
What signs on physical exam would potentially be seen in bacterial meningitis
- fever
- nuchal rigidity to neck flexion
- kernig sign
- brudzinksi sigh
- rash (n. meningitidis)
- do lumbar puncture
What might be on a DDx for bacterial meningitis
- non-infectious meningitis
- stroke
- encephalitis
- vasculitis
What labs are done for bacterial meningitis
- WBC & ESR high
- BMP to assess electrolytes and kidney
- blood cultures to ID organism
- CSF analysis through LP (ID organism, susceptibility testing)
Describe LP opening pressure
- rate of production and drainage of CSF
- measured over 1 min with manometer while obtaining LP sample
- increased indicates infection, inflammation, hemorrhage
How to interpret LP results
What are some AEs of a LP
- headache
- CSF leak
- pain
- iatrogenic menigitis
- nerve root injury
- uncal herniation
Who should get a CT prior to a LP
- immunocompromised
- hx CNS disease
- new onset seizure
- papilledema
Describe papilledema
- increased pressure in or around brain causing swelling of the optic nerve inside the eye, blurring of optic disc, enlarged retinal veins
What are some contraindications of an LP
- brain shift seen on CT
- clinical signs of impending herniation
- thrombocytopenia
- spinal epidural abscess
What is the order of operations in bacterial meningitis management
- blood cultures
- empiric abx therapy
- CT if needed
- LP if not contraindicated
Describe the empiric antimicrobial treatment for bacterial meningitis
Should steroids be used with treatment of bacterial meningitis
Recommended only in high income countries (dexamethasone)
- consider for adults and children especially with S. pneumo
Describe the mortality of bacterial meningitis
10% overall but varies by organism (higher for s. pneumo)
What are some complications of bacterial meningitis
- CN palsy
- focal deficits
- sensorineural
- seizures
- hydrocephalus
- memory/gait/etc.
What is the etiology of aseptic meningitis
- viral
- TB, mycoplasma, lyme, fungal
- meds
- CNS lymphoma
- autoimmune
What differentiates aseptic from bacterial meningitis
- more benign and self limited
- lymphocytic cellular response
- routine bacterial cultures are negative
Describe the presentation of viral meningitis
- fever, HA, irritation of meninges, photophobia
- malaise, muscle aches, N/V, diarrhea
- mild lethargy
What is the etiology of viral meningitis
- enteroviroses (coxsackieviruses)
- varicella zoster
- HSV2
- EBV
- arbovirus
- HIV
- influenza or mumps
What diagnostic testing is done with viral meningitis
- LP
- bacterial cultures: negative
- PCR testing on CSF
- can culture other sites and do serology
define lymphocytic pleocytosis
increase in WBCs in the CSF
How to treat viral meningitis
- treat symptoms
- begin as if treating bacterial meningitis if severely ill (acyclovir for HSV, EBV, VZV)
Prognosis of viral meningitis
super great
- 1-2 weeks, sometimes develop chronic headaches
Who gets admitted with viral meningitis
- elderly
- immunocompromised
- uncertain diagnosis
Who may be susceptible to TB/fungal meningitis
- malnourished, debilitated, immunosuppressed
- chronic, weeks/months of feeling unwell
What might labs show for TB/fungal meningitis
elevated protein and low glucose found in CSF
Mortality for TB/fungal meningitis
- 20-50%
- consult infectious disease
What can cause spirochete aseptic meningitis (chronic)
- syphilis
- lyme
What is the etiology of encephalitis
- virus reaching brain by hematogenous route
- associated with meningitis
- same organisms involved as viral meningitis
- neuronal necrosis and lysis of glial cells causing cerebral edema
What organisms are common in encephalitis
- epidemic west nile arbovirus
- HSV1 is most common
- measles virus
describe the presentation of encephalitis
abrupt onset of symptoms
- HA
- AMS (obtunded/unresponsive)
- seizures
- hyperreflexia
- +babinski
- focal neuro findings
- no nuchal rigidity, normal kernigs and brudzinski
What might be on the DDx for encephalitis
- vascular disease
- abscess
- other infection
- tumor
- SLE, autoimmune
Describe the work up for encephalitis
- EEG: abnormal, shows diffuse bilateral slowing, seizure
- CSF looks similar to viral meningitis
- opening pressure: normal or elevated
- WBC: lymphocyte predominance
- protein: elevated
- **CT/MRI normal early on but then may show edema, necrosis, hemorrhage
- PCR or serologic testing
Management of encephalitis
Symptomatic care
- ASMs
- hyperventilation and mannitol for increased ICP
- steroids = controversial
- early acyclovir for HSV
- rehab cognitive impairment
Prognosis for encephalitis
Depends on infectious agent
- Mumps = excellent
- arbovirus = reasonable (15% mortality, up to 25% dementia, seizures, focal deficits)
- HSV, others = poor (20-40% mortality)
- rabies = fatal
Describe primary amebic meningoencephalitis (PAM)
- rare, extremely fatal
- Naegleria fowleri (brain eating amoeba)
- presents as HA, fever, N/V, meningoencephalitis symptoms
- death due to brain swelling
How can someone get PAM (brain amoeba)
- lives in soil, washes into pond/lakes
- enters the nose
- get a good social/travel history
- swimming, diving, body of water, neti pot, religious nasal cleaning
How to treat PAM
- consult ID
- multi drug, like bacterial meningitis until ruled out
Describe a the pathophys of a brain abscess
What causes brain abscesses
- direct extension after surgery, infections from trauma, hematogenous spread
What is the most common organism in brain abscess
- bacteriodes fragilis
- staph aureus post trauma
- fungi and parasites in immunocompromised
Describe the presentation of brain abscesses
- subacute onset of symptoms from localized brain infection
- symptoms result from increased intracranial pressure
- symptoms depend on location in the brain
- headache, lethargy, intermittent fever, focal/generalized seizure
- classic triad of headache, fever, focal neuro deficit
What is on the DDx for brain abscesses
- bacterial meningitis
- brain cancer
- epidural abscess
- focal encephalitis
What is this
brain abscess
Work up for a brain abscess
- neurosurgical needle aspiration with gram stain and culture
- EEG often abnormal, localized slowing
- LP: potentially dangerous
- blood culture + in 10%
Management of a brain abscess
- abx therapy, surgical drainage thru aspiration/excision
- broad spectrum abx for aerobic and anaerobic coverage (4-8 weeks)
- mannitol for cerebral edema
- ASMs
What is a prion
protein normally made by neurons that is misfolded into abnormal infectious particle that is hard to kill
- can be transmitted thru inoculation or hereditary
What are the common forms of prion disease
- CJD (creutzfeldt-Jakob)
- GSS
- fatal familial insomnia
- Kuru
- bovine spongiform (mad cow)
Presentation of prion disease
subacute to chronic progressive dementia, fatal of 6 mos - 2 years
- memory loss, impaired judgement, intellectual decline
- myoclonis
workup for prion disease
Prion present in CSF, brain, pituitary, peripheral nerves
- hard to diagnose
- labs mostly normal
Steps of diagnosing and treating CNS infections
Brain abscess prognosis
- mortality significantly better now = 15%
Neuro sequelae of brain abscess
in 50%
- seizures
- focal deficits
