CNS Infections Flashcards
normal values of WCC, red cells, protein and glucose in CSF
White cells: <5/mm3
Red cells: <5mm
Protein: 150-450 mg/L
Glucose: 60-70% of blood glucose
what are most aspectic meningitis cases caused by
viruses
pathology of bacterial meningitis
- subarachnoid space is congest with polymorphs, layer of pus forms over the brain
- can form adhesions - CN palsies and hydrocephalus
what is the most common cause of spread for bacterial meningitis
nasopharyngeal colonisation
aetiology of brain infection
- Nasopharyngeal colonisation
- Most common
- Direct extension of bacteria
- Parameningeal foci (sinusitis, mastoiditis, brain abscess)
- Across skull defects or fracture
- Post-trauma, post-surgery
- From remote foci of infection
- Endocarditis, pneumonia, UTI
what is the classic triad of meningitis
headache, neck stifness and feve
other CF
- photophobia
- vomiting
- altered mental state - GCS
- fever, rigors
- rash
- seizures
describe the classical meningococcal rash and its signifance
non blanching on tumbler test, may be only 1 or 2 spots
Neisseria meningitidis infection
Kernig’s sign
inability to extend the knee with the hip fuly flexed
what is a risk factor for infection with encapsulated bacteria
Hyposplenism is a risk factor for encapsulated bacteria: H influenzae, Strep pneumoniae
most common organism in children
H influenzae - uncommon now due to vaccination
vaccination schedule for HiB
in the 6 in 1 at 2,3,4 months
wtih MenC at 12-13 months
gram stain for HiB
aerobic gram negative bacilli
2 most common organisms for bacterial meningitis
Neisseria meningitidis and S pneumoniae
in which age groups are s pneumoniae and n meningitidis most common
NM from 1-0-21, SP > 21
neisseria meningitidis classification
gram negative encapsulated diplococci aerobic, is intracellular
strep pneumoniae classification
gram positive, alpha haemolytic streptococci
in which conditions does listeria multiply
poorly refridgerated temperatures
which pt are more liekly to be infected with listeria, and what precuation is taken for these individuals
IS, elderly, alcoholics, chemo, neonatal
amoxicillin is given until culture results returned in those >60 and IS as a precaution
how does Neisseria usually spread to the brain
found in the throats of health people, bacteria probs gain access through blood stream
what type of vaccine is the HiB vaccine
conjugated
which pt are more susceptible to strep p infection
patients with skull fractures, hospitalized pt, diabetics, alcohlics, youn children
which surgical procedure particularly increases the risk of s pneumoniae
cochlear implant
which other group of organisms are implicated eg in head trauma/surgery
skin commensals (Staph (epidermidis), gram neg bacilli)
how does TB meningitis present
- Develops over 1-3 weeks: fever, headache, vomiting, abdominal pain, drowsiness, meningism, delirium ± seizures
what is a typical feature of TB meningitis
cranial nerve palsies
management of TB meningitis
isoniazid and rifampicin are key for 12m (add pyrazinamide and ethambutol)
what is cryptococcus
a fungus that is found in soil and bird droppings
who tends to egt cryptococcal meningitis
seen mainly in HIV, those with a low CD4 count (<100)
presentation of crytopcoccal
subtle neurological presentation, aseptic picture on CSF
what are the likely organisms in neonatal meningitis
Group B Strep and Listeria
how does Group B strep get passed on to neonate
acquired from mother (vaginal colonisation), occurs within the first few days after birth
subtle presentation
management and prevention of Group B Strep for neonatal meningitis
- Management: benzylpenicillin and gentamicin
- Prevention: intrapartum ABx given if pre-term labour, prolonged rupture of membranes, fever, known past infection/colonisation
how does Listeria infect neonate in neonatal meningitis
- Found in various foods (poorly refrigerated temperatures)
- Transplacental infection, causes stillbirth as well as neonatal sepsis/meningitis
management of Listeria causing neonatal meningitis
amoxicillin and gentamicin
sequelae of meningitis
Fatal disease. 25% of those who survive suffer from limb loss deafness, blindness, cerebral palsy, quadriplegia and severe mental impairment.
Layer of pus can form adhesions - CN palsies (III and IV) and hydrocephalus
should you admit someone to hospita with just eg a headache if they have had contact with meningococcal infection
yes
even if they have received prophylactic ABx
pt presents with suspicion of bacterial meningitis
- bloods and LP
- treatment
- throat swab, swab any lesions
contra indications/reasons to delay lumbar puncture
- ANY sign of raised ICP
- IC
- history of CNS disease
- new onset seizure
- altered consciousness
- focal neurological deficit
- GCS ≤12
- signs of severe sepsis or rapidly evolving rash
- bleeding risk
- severe resp/cardio compromise
suspected meningitis, w/ raised ICP, w/ severe sepsis/rapidly evolving rash:
perform CT first
what would happen if you did a LP in someone with inc ICP
forms a low pressure shunt - CSF and brain mass shift towards low pressure outlet - herniation
why is LP normally performed before ABx given
use of ABx first would lower gram stain and culture positivity
ABx
ceftriaxone and dexamethasone IV
ABx penicillin allergy
chloramphenicol and vancomycin
Listeria coverage
Amoxicillin (Co-t if penicillin allergic)
when should Listeria coverage be given first instance
if there is a risk eg old age, IS, alcoholic, chemo
which organism do steroids have the best benefit for
pneumococcal meningitis
who should not receive steroid therapy
post surgical, severe IC, septic shock, hypersenitive to steroids
LP results for viral, bacterial and TB infection
contact prophylaxis
rifampicin, ciprofloxacin, ceftriaxone
women on rifampicin
reduces the effiacy of oral contraceptive
must you inform public health about meningitis ?
yes
vaccination schedule: meningitis
Men C at 3 months
Men B at 2m, 4m, 12-13m
MenC/HiB 12-13 m
Men ACWY at 13-14y
what is a brain abscess
inflammation and collection of infected material
how do brain abscesses arise
either local spread of infection or 2y to remote infective process
clinical features of brain abscess
classic triad of fever, headache and focal neurological signs
seizures
microbiology of brain abscess
Streptococci (S milleri), coliforms (e.g. Proteus), anaerobes, S aureus, Actinomyces
diagnosis of brain abscess
ring enhancing lesion on CT
strep pneumoniae
management of brain abscess
drainage, ceftriaxone (gram neg and pos) and metronidazole (anaerobes) for 6 weeks
modify in light of culture
when is viral meningitis more common
late summer/autumn (freshers)
describe the course of viral meningitis
bengin and self limiting (4-10 days)
headache may follow on for some months after, no serious sequelae normally
is there pus, polymorphs, adhesions etc in viral meningitis?
no it is a predominantly lymphocytic inflammatory reaction
- no adhesions etc form
- little or no cerebral oedema
key features of viral meningitis history
GI symptoms and travel history
what is the main cause of viral meningitis
enteroviruses
diagnosis of viral meningitis
LP - lymphocytes
viral stool culture, throat PCR and CSF PCR
treatment of viral meningitis
supportive as it is self limiting
clinical features of encephalitis
- personality and behavioural change - reduced level of consciousness - coma
- seizures
- focal neurological deficits
what is the onset of encephalitis like
insidious
what is encephalitis caued by, and treatment
HSV, IV acyclovir
investigations of encephalitis
LP
EEG
CT
MRI
viral PCR
what is a CT/MRI of encephalitis likely to show
focal oedema in temporal lobes
inflammation and swelling
which lobe does HSV encephalitis tend to affect
temporal
management of encephalitis
As shown below: ABCDE and glucose - LP (if ok) - MRI/CT - ACYCLOVIR - PCR Results
(pre-emptive acyclovir is beneficial)
what are 2 positive movement signs in bacterial meningitis
