CNS infections Flashcards
what is meningitis inflammation of
all the meninges
why is time important in CNS infections
to save neural tissue
untreated infection may cause:
-brain herniation and death
-cord compression and necrosis (paralysis)
what is encephalitis
global infection of the brain parenchyma often caused by viruses
what is meningoencephalitis
inflammatory process (most often caused by viral infection), involving both the brain and meninges
what is encephalomyelitis
inflammation of the brain and spinal cord
what is neuritis
inflammation of one or more nerves
what are the types of menigitis
acute pyogenic (bacterial)
acute aseptic (viral)
acute focal suppurative infection (brain abscess, subdural and extradural empyema)
chronic bacterial infection (TB)
what is encephalopathy
any disease or disoder that affects the brain
what are the features of pyogenic meningitis
have a thich layer of suppurative exudate covering the leptomeninges over the surface of the brain
exudate in basal and convexity surface
what is seen microscopically in pyogenic meningitis
neutrophils in the subarachnoid space- lots of neutrophils in lumbar puncture= bacterial meningitis
do you get lots of neutrophils in CSF in a viral meningitis
no
what bacteria commonly cause bacterial meningitis
pneumococcus (strep pneumoniae)
meningococcus
haemophilus influenzae
listeria if >60 or immunocompressed
what is the treatment for bacterial meningitis
ceftriaxone IV
(if penicillin allergy chloramphenicol)
+
dexamethasone (IV) start with or just before abx
if listeria cover required add in amoxicillin IV (or co-trimoxazole if p allergic)
if recent travel ass in vancomycin IV for pneumococcal resistance
why should you make sure someone is allergic to penicillin before giving chloramphenicol
as v nasty drug - grey baby
what type of bacteria is strep pneumoniae
gram +ve cocci
what type of bacteria is listeria monocytogenes
gram +ve rod
what type of bacteria is haemophilis influenza
gram -ve bacillus
what causes viral meningitis
enteroviruses (echo virus) herpes simplex (will have coldsores) varicellar zoster virus
(in immunosuppressed EBV and CMV)
how is viral menigitis diagnosed
viral stool culture
throat swab
CSF PCR (will have only a few lymphocytes)
what is the treatment for viral meningitis
initially same as bacterial
supportive- e.g. vomiting give anti emetic
what should you not delay in suspected encephalitis
lumbar puncture (unless they have had seizures)
what Tx for viral encephalitis
IV aciclovir
LP after 14 days, HSV PCR weekly until negative
what are the clinical features of encephalitis
insidious onset
meningismus (features of meningitis without inflammation of the meninges)
cerebral cortex is diffusely involved: mental changes confusion stupor coma seizures partial paralysis speech and memory symptoms pychosis focal or diffuse neurological changes
what are the clinical features of meningoencephalitis
features of encephalitis but with alos:
- headache
- fever
- neck stiffness
what viruses commonly causes viral encephalitis
herpes simplex
what investigations for encephalitis
LP, EEG, MRI
what are the symptoms of meningitis
headache vomiting pyrexia neck stiffness photophobia lethargy confusion rash (non blanching) muscle pain
what causes bacterial meningitis in neonates
listerior, group B strep, e coli
what causes bacterial meningitis in children
h influenza (vaccinate against this)
what causes bacterial meningitis in ages 10-21
neisseria meningitidis
what causes bacterial meningitis in ages over 21
strep pneumoniae , neisseria meningitidis
what causes bacterial meningitis in overs 65s
streptococcus pneumoniae, listeria
what causes bacterial meningitis in the immunocompromised
S. pneumoniae, N. meningitidis, listeria, aerobic GNR
what causes bacterial meningitis in basilar skull fractures
s. pneumoniae, h. influenzae, beta hemolytic strep group A
what causes bacterial meningitis in head trauma/ post op
s. aureus, s epidermis, aerobic GNR
what causes bacterial meningitis in a CSF shunt
s. epidermis, S aureus, aerobic GNR, p. acnes
what are the possible complications of meningitis
as limb loss, deafness, blindness, cerebral palsy, quadriplegia and severe mental impairment
Purulence
Exudate around nerves (III, VI cranial nerves particularly vulnerable)
invasion and abscesses
cerebral oedema
ventriculitis/ hydrocephalus
what are the pathogeneses of bacterial meningitis
- nasopharyngeal colonisation (most common)
- direct (sinusitis, mastoiditis, brain abscess, skull defects/ fracture
- from remote foci of infection (endocarditis, pneumonia, UTI)
what do you analyse in CSF from a lumbar puncture
Tube 1. Hematology: cell count, differential
Tube 2. Microbiology: gram stain, cultures
Tube 3. Chemistry: glucose (will be low in meningitis as bacteria eating it), protein
Tube 4. Hematology: cell count, differential
opening pressure
lactate
what precautions must be made in lumbar punctures
be careful of raised ICP (dont do)
treat with antibiotics first in suspected bacterial infection
what CSF results are 99% predictive of bacterial meningitis
high WBC count higher neutrophils high protien low glucose low glucose (CSF/serum)
what are the typical CSF findings in viral meningitis
lymphocytes
protein normal/ slightly high
glucose usually normal
gram stain will be negative
what will the gram stain be in TB CSF analysis
may be pos or negative
what causes the symptoms in neisseria meningitis
endotoxin
who usually gets neisseria meningitis
young children
what does the rash look like in meningococcal infection
non blanching purpura that look like coalesced bruises
what does H influenza require for growth
blood factors
what is the most common cause of meningitis in children under 4
h influenzae
where is strep pneumoniae usually found- why is this important
nasopharynx
Hospitalized patients, patients with CSF skull fractures, diabetics/ alcoholics and young children are most susceptible to S. pneumoniae meningitis.
what tx for cryptococcus meningitis
will have very high ICP so give serial LPs and anti fungals (IV amphotericin A/ flucytosine, fluconazole)
who gets cryptococcus
HIV patients
what is the most common meningitis in immunocompromised
listeria
what are the features of cryptococcal meningitis
fungal mainly in HIV disease low CD4 disseminated infection aseptic CSF
who gets listeria meningitis infections
neonates
>55s
immunosuprpessed (esp malignancy)
what antibiotic for listeria
IV amoxicillin (or ampicillin)
what are the features of tuberculous meningitis
reactivation, elderly
often non specific illness
previous TB on CXR
hard to diagnose- poor yield on culture
tx for TB meningitis
Isoniazid + rifampicin key (add pyrazinamide + ethambutol)
why can bacterial meningitis be culture negative
10-15% are anyway
pre LB use of oral antibiotics can lower culture
what other than bacterial meningitis can a neutrophilic & low glucose CSF mena
early viral
leakage of abscess into ventricle
TB
chemical meningitis
behcet syndrome
drug induced
what is aspetic meningitis
non pyogenic bacterial meningitis: spinal fluid that contains -low WBC -minimally elevated protein -normal glucose
can be lots of things other than viral meningitis
what are the (treatable) causes of aseptic meningitis/ encephalitis
Infectious: HSV 1 and 2 Syphilis Listeria (occasionally) Tuberculosis Cryptococcus Leptospirosis Cerebral malaria African tick typhus Lyme disease
Non-Infectious: Carcinomatous Sarcoidosis Vasculitis Dural venous sinus thrombosis Migraine Drug Co-trimoxazole IVIG NSAIDS
what are the contact prophylaxis regimes for meningitis
500 mg ciprofloxacin orally as a single dose for adults and children aged more than 12 years
600 mg rifampicin orally 12-hourly for four doses (adults and children over 12 years)
should you involve public health about meningitis
yes- all suspected cases
what vaccines protect against meningitis
travel vaccinations (neisseria)
HiB vaccine
pneumococcal vaccines
which space are samples obtained from in an LP
subarachnoid space
what are normal CSF WBC and RBC counts
white 0-5
red 0
what are the expected ratios for protein and glucose in CSF
glucose 0.6 (should be 2/3rds of blood glucose)
protein 150-450:1
proportionally more neutrophils (aka polymorphs) in CSF= ?
bacterial infection
proportionally more lymphocytes in CSF= ?
viral/ fungal infection
what is petechea
non blanching rash, meningitis
what are the rules for CTs and LPs
NEVER DO LP WITHOUT DOING CT AS MIGHT HAVE RAISED ICP- cause brain to herniate = coning (when cerebellum goes through foramen magnum)
unless
in suspected meningitis if patient has no focal deficit, is not immunocompromised, no skull #, has had no seizures,no Hx of CNS disease, no papilloedema, normal conscious level then do LP ASAP and start antibiotics
gram -ve cocci meningitis= ?
meningococcus meningitis (caused by neisseria)
what drug for chemoprophylaxis for bacterial meningitis
ciprofloxacin
what is the abx treatment for a brain abscess
IV ceftriaxone
IV metronidazole
add flucloxacillin in staph suspected
IV vancomycin if pen allergic/ MRSA suspected
for 4 weeks minimum
what other tests should be done in viral meningitisi
throat swap
stool sample
HIV test
what CNS infection causes oedema in the temporal loves
herpes simplex encephalitis
what test to confirm herpes simplex encephalitis
PCR from LP
what 3 tests do you prioritise in meningitis
LP
CT
blood culture
gram +ve diplococci meningitis= ?
pneumococcus
where can an brain abscess originate from
mastoiditis
sinusitis
orbital cellulitis
what organisms can cause brain abscesses
streptococci, bacteriodes, staphylococci, anaerobes, colliforms
why do you give ceftriaxone and not penicillin for meninigitis
as lasts longer in CSF
when do you delay an LP in meningitis
signs of severe sepsis cardiac/ resp compromise rapidly evolving rash significant bleeding risk signs suggesting shift of brain compartments (do CT) - focal neuro signs - papilloedema - seizures that are continuous/ uncontrolled - GCS = 12
buzzworrds: summer/ autumn time, GI symptoms
enterovirus viral meningitis
what is the key symptom in encephalitis
confusion
