CNS Infections Flashcards
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?
Encephalitis Meningitis Meningoencephalitis Encephalomyelitis Severe sepsis syndrome due to infection elsewhere
When does viral meningitis usually present?
Late summer/autumn
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?
HSV (serious) VZV CMV HIV Measles
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?
Rabies
What are the non-infectious causes of viral encephalitis?
Autoimmune etc
What are the clinical features of encephalitis?
Insidious onset-sometimes sudden Meningismus Stupor, coma Seizures, partial paralysis Confusion, psychosis Speech, memory symptoms
What investigations are required in viral encephalitis?
LP
EEG
MRI
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 Elderly: pneumococcal>listeria
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?
S. pneumoniae
N. meningitidis
Listeria
aerobic GNR (including Ps.aeruginosa)
What is the likely causative organism in bacterial meningitis due to a basilar skull fracture?
S. pneumonia
H. influenzae
beta-hemolytic strep group A.
What is the likely causative organism in bacterial meningitis due to head trauma or post-neurosurgery?
S.aureus
S.epidermidis
aerobic GNR
What is the likely causative organism in bacterial meningitis due to a CSF shunt?
S. epidermidis
S. aureus
aerobic GNR
Propionibacterium acnes
What can be some long term effects of meningitis and septicaemia?
Limb loss Deafness Blindness Cerebral palsy Quadriplegia Severe mental impairment
What is the pathogenesis of bacterial meningitis?
- Nasopharyngeal colonisation
- Direct extension of bacteria: parameningeal foci (sinusitis, mastoiditis, or brain abscess), across skull defects
- 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 Listerio monocytogenes Mycobacterium tuberculosis Nocardia asteroides Cryptococcus neoformans (AIDS)
What does Neisseria meningitides cause?
Meningococcal meningitis
What are the symptoms in meningococcal meningitis due to?
Endotoxin from bacteria
In whom does Meningococcal meningitis most commonly occur?
Young children
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?
Type B
Where is S. pneumoniae commonly found in the nasopharynx?
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?
Pneumococcal meningitis
What is listeria monocytogenes?
Gram +ve bacilli
What cultures should be taken in suspected listeria monocytogenes meningitis?
Blood cultures
Who are most likely to have listeria monocytogenes meningitis?
Neonates
>55yo
Immuno-suppressed esp. malignancy
What is the antibiotic of choice in listeria monocytogenes meningitis?
IV Ampicillin/Amoxicillin
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?
Fungal
Mainly HIV
CD4
How should cryptococcal meningitis be treated?
IV Amphotericin
B/Flucytosine
Fluconazole
What are the clinical signs of bacterial meningitis?
Fever
Stiff neck
Alteration in consciousness
What are some signs and symptoms in bacterial meningitis?
Headache Vomiting Pyrexia Neck stiffness Photophobia Lethargy Confusion Rash
Who are signs of bacterial meningitis often absent or atypical in?
Very young/old
Immunocompromised
What DDx should be suspected in possible bacterial meningitis?
Meningitis Encephalitis Cerebral abscess Severe sepsis from other source SA haemorrhage Cerebral tumour
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?
Blood cultures Throat swab (meningococci) Blood EDTA for PCR (meningococci) CSF (LP) Microscopy, biochemistry, culture, antigen detection
What bacteria will be found in the ddx of meningitis in normal patients?
Enteroviruses HSV1, HSV2 VZV M. tuberculosis B. burgdorferi Pneumococci Meningococci H. influenza
What bacteria will be found in the ddx of meningitis in immunocompromised patients?
EBV CMV HHV-6/7 T. gondii JC virus
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 High protein 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?
WBC >2000
Neutrophils >1180
Protein >220mg/dl
Glucose
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 Amebic meningoencephalitis TB meningitis (rarely, & usu. only early)
If not bacterial meningitis, what non-infectious conditions may cause neutrophilic pleocytosis and low csf glucose?
Chemical-meningitis (contrast…)
Behcet syndrome
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
normal glucose
What are some infectious treatable causes of aseptic meningitis/encephalitis syndrome?
HSV 1 and 2 Syphilis Listeria (occasionally) Tuberculosis Cryptococcus Leptospirosis Cerebral malaria African tick typhus Lyme disease
What are some non-infectious treatable causes of aseptic meningitis/encephalitis syndrome?
Carcinomatous Sarcoidosis Vasculitis Dural venous sinus thrombosis Migraine Drug: Co-trimoxazole IVIG NSAIDS
What are the adult bacterial meningitis guidelines?
Pre-hospital management
Early inpatient management
Antimicrobial adjunctive treatment
Supportive therapy
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
Pre-hospital antibiotics
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?
Immunocompromised History of CNS disease New onset seizure (within 1 wk of presentation) Papilloedema Abnormal level of consciousness Focal neurologic deficit
What are some key warning signs in acute adult bacterial meningitis?
Marked depressive conscious level (GCS 2) Focal neurology Seizure before/at presentation Shock Bradycardia and HT Papilloedema
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?
Co-trimoxazole
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?
Haemorrhagic Diatheses Deteriorating consciousness Multi-organ failure Rapidly developing rash Age >60
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)
IV corticosteroids
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
What indicates a poor prognosis on admission in all types of meningitis?
Tachycardia GCS <12 on admission Low GCS, cranial nerve palsy Seizures within 24hr Hypotension on admission Age >60
