CNS infections (cabs and clin med) Flashcards
what is the leptomeninges
the pia and arachnoid mater together
What is the dense outer layer
dura mater
what is the middle - web like layer
arachnoid mater
lies over the subarachnoid space which houses CSF
what is the Falx cerebri
folds into the longitudinal cerrebral fissue seperating the hemistpheres
what is the inner layer that is adhered to the brain parenchyma
pia matter
supports vasculature and creates the choroid plexus
Where is CSF made
within the choroid plexus of the ventricles in the pia matter
what is an inflammatory disease affecting the leptomeninges
Bacterial meningitis
MEDICAL EMERGENCY - DO NOT MISS
what prevents free flow of ions, cells and molecules from getting into the NS
BBB
what is the flow of CSF
secreted by choroid plexus within lateral ventricles
flows to third ventricle -> fourth ventricles -> flows outside of the brainstem into subarachnoid space (btwn pia and arachnoid), exits via arachnoid villi within the superior sagital sinus
What is rapidly fatal with mortality rate of 20-25% even with appropriate treatment
bacterial meningitis
what condition is fatal 70-100% of the time without treatment
bacterial meningitis
what are the predisposing factors of bacterial meningitis
prior viral infection
household crowding (college kids)
active and passive smoking
occupation risk (use and microbioligists)
what are the most common bacteria causing bacterial meningitis
S. pneumoniae
N. meningitidis
L. monocytogenese
what population is group B strep the cause of bacterial meningitis
Newborns
how can bacterial meningitis be spread
via droplet or secretions from colonized persons
bacterial entry into blood stream and enter CNS through BBB
where does bacteria cross the blood brain barrier
choroid plexus
what occurs when there is an inflammatory response with bacteria crossing the BBB
vasculitis and cerebral edema and increased ICP
what type of bacteria is Neisseria meningitidis
aerobic and gram negative diplococcus
outer membrane covered in polysaccharide which helps to resist phagocytosis
What is important about blood cultures
need to be extremely sterile and from two bodily sites
what is the drug of choice for N. meningitides
ceftriaxone
what type of bacteria is Streptococcus pneumoniae
lancet-shaped, gram positive, facultative anaerobic bacteria. typically diplococci.
what is the drug of choice against S. pneumoniae
Vancomycin plus ceftriaxone
what type of bacteria is listeria monocytogenes
gram positive facultative anaerobic bacilli
what are the likely presentation of listeria monocytogenesis in bacterial meningitis
seizures, focal deficits early in disease and ataxia
what is the drug of choice for listeria monocytogenes
ampicillin or penicillin (if allergic, Bactrim)
what type of bacteria is Haemorphilus influenzae
pleomorphic gram negative rods
where is haemorphilus influenze located
respiratory tract
what population is usually affected by haemorphilus influenzae
affects children most commonly
what is the drug of choice for Haemophilus influenzae
ceftriaxone
what is neucal regidity
neck stiffness
what is the presentation of bacterial meningitis
typically present < 24 hours after onset of symptoms
classic triad: fever, stiff neck, AMS
fever
severe headache
N/V
possible seizure, coma, CN palsy
petechiae and palable purpura
what are specific baby presentations of bacterial meninititis
poor feeding
irritable particularly when handles
high pitched or moaning cry
abnormal tone
vacant staring
poorly responsive or lethargic
tense fontanelle
cyanosis
what is the difference between sepsis and meninigitis
sepsis = death from cardiovascular failure
meningitis = death from raised ICP
what test has spontaneous flexion of hips with passive flexion or neck
Brudzinski sign
what test is when there is an inability for full extension of the knee with hip flexion
Kernig
what is the workup for bacterial meningitis
CBC
Coagulation studies
CMP
2 sets of blood cultures
head CT
LP
MRI
what is a left shift of leukocytosis
immature WBCs
what is seen on CBC for bacterial meningitis
leukocytosis with left shift and may have. thrombocytopenia
what is the lumbar cistern
the pool of CSF in the lumbar spine
when are LP contraindicated
anti-coagulated patients
if concern for herniation - elevated ICP (mass?)
if platelets < 50,000
what is normal glucose levels on LP
45-85
what is a LP for bacterial meninigitis positive for
> 200 mm H20 opening pressure
1,000 WBCs
Neutrophils present
200 protein
<40 glucose
positive gram stain and culture
what is a LP for viral meningitis positive for
normal or slightly high opening pressure
100-1,000 WBCs
lymphocytes present
protein normal
normal glucose
negative gran stain and culture
what is the plan for patient with concern for meningitis
ABC
VS hx, exam
2 large bore IV
LABS: CBC, CMP, PT/PTT, culture, lactate
fluids
treat shock
dexamethasone
antibiotics
antivirals
head CT
LP
exposure prophylaxis
what is the treatment of bacterial meningitis
dexamethasone (prior to ABX)
Broad spectrum ABX
REAASSESS FREQUENTLY
what is the classic antibiotic regimen for bacterial meningitis
cetriaxone, vancoymcin, ampicillin
if penicillin allergy: vancomycin and Bactrim
what is used for prevention in people in close contact to known meningitis person
Chemoprophylaxis- ceftriaxone, rifampin or ciprofloxacin
what is aseptic meningitis
negative bacterial cultures - but otherwise suggestive of bacterial meningitis
usually associated with enteroviruses
what is the epidemoplogy of viral meningitis
infants <1yo or >5yo
most commonly in summer and fall
what is the pathophysioloyg of viral meningitis
virus invades respiratory or GI track
typically 3-6 days after exposure
Enterovirus - peak in summer and fall
Herpes virus - HSV-1
what is the presentation of viral meningitis
febrile
no neurologic dysfunction
headache
stiff neck
maculopapular rash
muscle aches
N/V
pharyngitis
fatigue
what is the workup of viral meningitis
same as bacterial
negative gram stain and cultures for CSF
CSF shows lymphocytes
Send out CSF for viral detection assay
imaging: may see enhancement of the meninges on MRI
what is the treatment of viral meningitis
typically supportive
depends on virus: acylovir IV
dark and quiet room
Tylenol for HA, fever, pain
what is the difference between meningitis and encephalitis
mental status with menigitis is baseline but lethargic or distracted
mental status with encephalitis will be altered
ALWAYS ASSUME THE WROSE - IF QUESTION - START ABX
what is encephalitis
inflammation of the brain parenchyma
what are the common causes of encephalitis
unknown in half of the cases
20-50% viral etiology: HSV or VZV)
Genetic predisposition
what is damaged with encephalitis
damage neurons can produce hemorrhagic necrosis
what is the pathophysiology of encephalitis
viral
other infectious source
drug induced
autoimmune
what are the 6 V’s of encephalitis
Vacation
Vaccination
Vectors
Viruses
Veterinary source
Vital statistics (people around you that have it)
what is the presentation of encephalitis
AMS
fever
HA
N/V
Seizures
focal neurologic abnormalities
meningeal irritation if meningoencephalitis
disease specific findings
what is the diagnostic criteria of encephalitis
Major: AMS lasting longer than or equal to 24 hours
Minor (2+): documented fever wtihin 72 hours
seizure
new onset focal neuro findings
CSF pleocytosis
abnormality of parenchyma on imaging
EEG abnormality consistent with encephalitis
what is the workup of encephlitis
LP with same testing as before plus PCR and RT- PCR
include HSV1,2, VZV, enteroviruses, parechoviruses
can consider influenca, mumps, rabies
fresh water ameba
Imaging: MRI or CT
what is a fresh water ameba that can cause encephalitis
naegleria fowleri
what is the treatment of encephalitis
ABCs
Acyclovir for HSV and VZV encephalitis
what is a focal collection of infection in the brain parenchyma
brain abscess
who are brain abscesses more common in?
men
what is the cause of brain abscess
direct spread from infection - otitis media, mastoiditis, dental infection
foreign body
post op infection
what is the typical presentation of Brain abscess
headache
fever
neck stiffness
focal neurologic deficit
seizures
and CN VI palsy secondary to elevated ICP
what is the presentation triad of brain abscess
headache, fever and focal neurologic deficit
what type of imaging is necessary with concern for brain abscess
MRI WITH CONTRAST
what is the initial treatment of brain abscesses
broad IV coverage abx (vanco, metronidazole, ceftriaxone) for 4-8 weeks with repeat imaging to guide and ensure clearance
what is used if mass effect in brain abscesses is noted
steroids
where is the most common sites of brain abscesses
frontal or temporal lobes
when is excision considered for brain abscesses
if secondary to TBI and material in the abscess
fungal abscess
loculated
no improvement >1week of treatment
elevated ICP
increased size
AMS after initial drainage and treatment
