Flashcards in CNS Infections Deck (77):
What can an untreated CNS infection cause?
Brain herniation and death
Cord compression and necrosis with subsequent permanent paralysis
What does the gross morphology of pyogenic (bacterial) meningitis show?
Thick layer of suppurative exudate covering the leptomeninges over the surface of the brain
Exudate in basal and convexity surface
What does pyogenic meningitis show microscopically?
Neutrophils in the SA space
What is the DDx for fever and altered mental status?
Severe sepsis syndrome due to infection elsewhere
When does viral meningitis usually present?
What causes viral meningitis?
Enteroviruses e.g. ECHO virus
Other microbes and non-infectious causes also
How is viral meningitis diagnosed?
Viral stool culture, throat swab and CSF PCR
What is the treatment for viral meningitis?
Supportive as self-limiting
What viruses can cause viral encephalitis?
What is the treatment of HSV encephalitis?
Aciclovir IV high doses- must be recognised, admitted and treated within 6 hours
What is the history and treatment of VZV encephalitis?
History of shingles
High dose acyclovir
What are the travel related causes of viral encephalitis?
West Nile, Japanese B encephalitis, Tick Borne encephalitis
What are the occupational related causes of viral encephalitis?
What are the non-infectious causes of viral encephalitis?
What are the clinical features of encephalitis?
Insidious onset-sometimes sudden
Seizures, partial paralysis
Speech, memory symptoms
What investigations are required in viral encephalitis?
If there is a delay in investigations in suspected viral encephalitis what should be done?
Start pre-emptive acyclovir as prompt therapy improves outcome
What are the MRI findings in encephalitis?
Inflamed portion of the temporal lobe, involving the uncus and adjacent parahippocampa I gyrus (brightest white on MR)
What are the common causes of bacterial meningitis related to age?
Neonates: listeria, group B streptococci, E. coli
Children: H. influenza
10 to 21: meningococcal
21 onward: pneumococcal >meningococcal
What are the common causes of bacterial meningitis related to RFs?
Decreased CMI: listeria
S/P neurosurgery or opened head trauma: Staphylococcus, Gram Negative Rods
Fracture of the cribiform plate: pneumococcal
What is the likely causative organism in bacterial meningitis due to an immunocompromised state?
aerobic GNR (including Ps.aeruginosa)
What is the likely causative organism in bacterial meningitis due to a basilar skull fracture?
beta-hemolytic strep group A.
What is the likely causative organism in bacterial meningitis due to head trauma or post-neurosurgery?
What is the likely causative organism in bacterial meningitis due to a CSF shunt?
What can be some long term effects of meningitis and septicaemia?
Severe mental impairment
What is the pathogenesis of bacterial meningitis?
1. Nasopharyngeal colonisation
2.Direct extension of bacteria: parameningeal foci (sinusitis, mastoiditis, or brain abscess), across skull defects
3. From remote foci of infection: (e.g. endocarditis, pneumonia, UTI etc)
What are some agents of meningitis in immunocompromised patients?
Conventional agents- s.pneumonia, s.aureus etc
Cryptococcus neoformans (AIDS)
What does Neisseria meningitides cause?
What are the symptoms in meningococcal meningitis due to?
Endotoxin from bacteria
In whom does Meningococcal meningitis most commonly occur?
What are military recruits vaccinated with to prevent outbreaks of meningococcal meningitis in training camps?
Purified capsular polysaccharide
What type of H. influenza is the most common cause of meningitis in children under 4yo?
Where is S. pneumoniae commonly found in the nasopharynx?
Who are most susceptible to S. pneumonia meningitis?
Hospitalised patients, patients with CSF skull fractures, diabetics, alcoholics and young children
What does the conjugate vaccine for pneumoccal pneumonia always provide protection against?
What is listeria monocytogenes?
Gram +ve bacilli
What cultures should be taken in suspected listeria monocytogenes meningitis?
Who are most likely to have listeria monocytogenes meningitis?
Immuno-suppressed esp. malignancy
What is the antibiotic of choice in listeria monocytogenes meningitis?
Ceftriaxone has no value as intrinsically resistant
Describe tuberculous meningitis
Can reactivate in elderly
Often non specific ill health
Previous TB on CXR
Poor yield from CSF
How is tuberculous meningitis treated?
Isoniazid + rifampicin (add pyrazinamide + ethambutol)
Describe cryptococcal meningitis?
How should cryptococcal meningitis be treated?
What are the clinical signs of bacterial meningitis?
Alteration in consciousness
What are some signs and symptoms in bacterial meningitis?
Who are signs of bacterial meningitis often absent or atypical in?
What DDx should be suspected in possible bacterial meningitis?
Severe sepsis from other source
What is the rule regarding LP's and bacterial meningitis?
LP is CSF pleocytosis, not symptoms of bacterial meningitis
What should be in each LP tube for interpretation?
Tube 1. Haematology: cell count, differential
Tube 2. Microbiology: gram stain, cultures
Tube 3. Chemistry: glucose, protein
Tube 4. Haematology: cell count, differential
How should meningitis be diagnosed?
Throat swab (meningococci)
Blood EDTA for PCR (meningococci)
Microscopy, biochemistry, culture, antigen detection
What bacteria will be found in the ddx of meningitis in normal patients?
What bacteria will be found in the ddx of meningitis in immunocompromised patients?
What are the CSF findings in viral acute adult meningitis?
10^1-10^3 cells (lymphocytes)
Negative gram stain
Negative bacterial antigen detection
Normal or slightly high protein
Usually normal glucose
What are the CSF findings in bacterial acute adult meningitis?
10^1-10^4 cells (predominantly polymorphs)
Positive gram stain
Positive bacterial antigen detection
Less than 70% glucose
What are the CSF findings in tuberculous acute adult meningitis?
10^1-10^3 cells (predominantly lymphocytes)
Positive or negative gram stain
Negative bacterial antigen detection
High or very high protein
Less than 60% glucose
What test results are predictive of bacterial meningitis with 99% accuracy?
If not bacterial meningitis, what infectious conditions may cause neutrophilic pleocytosis and low csf glucose?
Viral meningitis (early phase only)
Some parameningeal foci/ cerebritis
Leakage of brain abscess into ventricle
TB meningitis (rarely, & usu. only early)
If not bacterial meningitis, what non-infectious conditions may cause neutrophilic pleocytosis and low csf glucose?
Drug –induced ( NSAIDs, Sulfa, INH, IVIG, OKT3…)
What is aseptic meningitis?
A term used to mean non-pyogenic bacterial meningitis
It describes a spinal fluid formula that has:
low number of WBC
minimally elevated protein
What are some infectious treatable causes of aseptic meningitis/encephalitis syndrome?
HSV 1 and 2
African tick typhus
What are some non-infectious treatable causes of aseptic meningitis/encephalitis syndrome?
Dural venous sinus thrombosis
What are the adult bacterial meningitis guidelines?
Early inpatient management
Antimicrobial adjunctive treatment
Prevention of secondary cases of meningitis
Screening for predisposing factors to meningitis
What management occurs in pre-hospital acute adult bacterial meningitis?
Look for indications for hospital admission
What are some indications for hospital admission of acute adult bacterial meningitis?
Signs of meningeal irritation
An impaired conscious level
A petechial rash
Who are febrile or unwell and have had a recent fit
Any illness, especially headache, and are close contacts of patients with meningococcal infection, even if they have received a prophylactic antibiotic
What should happen immediately on hospital admission in acute adult bacterial meningitis, provided ABC is fine?
Bloods for culture and coag screen
Antibiotic treatment before pathogens are identified, and immediately after
Throat swab which should be plated soon as practical
Disrupt and swab/aspirate any petechial or purpuric skin lesion for microscopy and culture
CT/MRI for patients with papilloedema or focal neuro signs
Who should undergo CT prior to LP?
History of CNS disease
New onset seizure (within 1 wk of presentation)
Abnormal level of consciousness
Focal neurologic deficit
What are some key warning signs in acute adult bacterial meningitis?
Marked depressive conscious level (GCS 2)
Seizure before/at presentation
Bradycardia and HT
Who should undergo an LP in acute adult bacterial meningitis?
All adults with suspected meningitis except when a clear contraindication exists, or if there is a confident clinical diagnosis of meningococcal infection with a typical rash
What is the empiric antibiotic therapy for acute adult bacterial meningitis?
IV Ceftriaxone 2g bd
Add IV Ampicillin/amoxicillin 2g qds if listeria suspected
(If pen allergic Chloramphenicol IV 25mg/kg 6-hourly with vancomycin IV 500mg 6-hourly or 1g 12 hourly
What treatment should be given in acute adult bacterial meningitis if listeria is suspected and patient is pen. allergic?
What additional drug therapy other than antibiotics should be given to all patients with suspected bacterial meningitis?
Steroids 10mg IV 15-20 min before or with first antibiotic dose, then every 6hrs for 4 days
When should steroids not be given in bacterial meningitis?
Post surgical meningitis, severe immunocompromised, meningococcal or septic shock or those hypersensitive to steroids
What indicates a poor prognosis on admission in meningococcal disease?
Rapidly developing rash
What are key interventions in management of bacterial meningitis with low GCS (2)?
Admit to highly supervised area- baseline investigations
Secure airway and high flow O2
IV 2G Ceftriazone stat (+- amoxicillin if >55 to cover listeria)
Do not wait for CT/LP
What is the standard contact prophylaxis regimen in bacterial meningitis?
600 mg rifampicin orally 12-hourly for four doses (adults and children over 12 years), 10 mg/kg orally 12-hourly for four doses (aged 3-11 months) (IV).
What vaccines against organisms which can cause meningitis exist?
Neisseria meningitidis: serogroups A and C (W135 & Y)- travel. Group C conjugate vaccine
H. influenza (HiB vaccine)
Strep. pneumoniae- pneumocccal vaccines-polysaccharide and conjugate