CNS infections AR Flashcards
Name some CNS infections
Encephalitis Meningitis Epidural Abscess Cerebral Abscess VP shunt infection
Some non infectious conditions which mimic CNS infections are:
Neoplastic disease
Intracranial tumours and cysts
Medications
Collagen Vascular Disease
What is Meningitis?
Meningitis -> inflammation of the meninges
What is meningitis characterised by?
Fever and headaches
Meningismus and altered mental state
What is a clinical diagnostic sign?
Cerebrospinal leucocytosis (>6WCC)
- ASeptic
- Purulent
Common Pathogens in 18-50 yo’s for Meningitis??
Streptococcus pneumoniae
Neisseria meningitidis
Common Pathogens in immunocompromised for Meningitis??
Streptococcus pneumoniae
Neisseria meningitidis +
Listeria monocytogenes
What is the pathogenesis of BACTERIAL meningitis?
Initial colonisation of mucosal surfaces including nasopharynx by haematogenous or contiguous spread
- Specific antibody is an important defence
- After bacterial invasion of the meninges, REPLICATION WITHIN THE SUBARACHNOID SPACE LEADS TO AN INFLAMMATORY RESPONSE
- Levels of inflammatory cytokines are proportional to the severity of symptoms and risk of adverse outcome, suggesting role of adjunctive steroids
Meningitis Causal Organisms in Neonates
E.coli
Group B strep
In Pregnant women what are causal bacterial organisms?
L.monocytogenes
In unvaccinated children what can cause meningitis?
HAEMOPHYLUS INFLUENZAE TYPE B
What is the pathogenesis of VIRAL meningitis?
Virus infection of the mucosal surfaces of the RESPIRATORY OR GIT tract
Followed by viral multiplication in tonsillar or gut lymphatics
Viraemia with haematogenous dissemination to CNS leads to meningeal inflammation
Causal VIRAL organisms
HSV (aseptic meningitis)
Enteroviruses (80%)
Other: VZV, Mumps, HIV
What are some additional risk factors for bacterial meningitis?
Adults >60 Children <5 People with sickle cell anaemia People recieving chemo Immunosuppressed Diabetics Exposure to meningitis People living in close quarters (military barracks, dormitorys) IVDU People with shunts in place for hydrocephalus
Classic symptoms of meningitis:
Fever, headache, STIFF NECK
What are some SYMPTOMS of Bacterial meningitis
Onset often abrupt Vomiting PHOTOPHOBIA convulsions Irritability Apathy Drowsiness Unconsiousness
What are some SIGNS of Bacterial meningitis
NEck and spinal stiffness
Pain and resistance on extending the knee when thigh is flexed- KERNIG’s SIGN
What would you want to differentiate between?
Subarachnoid haemorrhage
Cerebral abscess
What are the SYMPTOMS of VIRAL meningitis?
Commonly consitutional
- Diarrhoea
- Fever
- Vomitting
- Anorexia
- Rash
- Cough
- Myalgia
HSV-2 associated with primary genital herpes
Enteroviral syndromes seasonal- include hand, foot and mouth disease
What is Brudzinski’s sign?
Severe neck stifness cause a patients hips and knees to flex wihen the neck is flexed
How do you diagnose Meningitis?
LUMBAR PUNCTURE:
For removal and analysis of CSF
what are some of the complications of Lumbar punctures?
Headache - 10-25%
Traumatic Tap 20%
Brain herniation : CAUTION IF: GCS <11, Brain stem signs, very recent seizure
When would you use a CT of the brain?
- immunosuppresed
- History of CNS disease
- New onset siezure
- Abnormal level of consciousness
- Papilloedema
- Focal neurological defect
What tests would you perform on the CSF fluid from the LP?
ROUTINE TESTS:
- WBC count with differential
- RBC count
- Glucose concentration
- Protein concentration
- Gram Stain
- Bacterial Culture
SPECIFIC TESTS
- Viral PCR/Culture
- AFB smears
- VDRL
- India ink and cryptococcus antigen
- Fungal Culture
- Antibody tests
- Cytology and flow cytometry
What are some CSF findings in patients with VIRAL MENINGITIS?
ie. what would WBCC be
- Cell type
- Glycose
- Protein
WBC: 50-1000
Cell Type: Increased LYMPHOCYTES
Glucose: NORMAL
Protein: NORMAL
What are some CSF findings in patients with BACTERIAL MENINGITIS?
ie. what would WBCC be
- Cell type
- Glycose
- Protein
WBC: 100->10000
Cell Type: Increased NEUTROPHILS
Glucose: 6g/l
What are some CSF findings in patients with TB associated MENINGITIS?
ie. what would WBCC be
- Cell type
- Glycose
- Protein
WBC: 50-300
Cell Type: Increased LYMPHOCYTES
Glucose: <60% blood level
Protein: elevated
PRogressive steps in MANAGEMENT OF MENINGITIS
Severe headache & fever ->
1. Blood Culture + IV penicillin
2. CT - check intracranial pressure
& LP if no evidence of raised ICP
If LP shows LYMPHOCYTES predominate->
(a) & photophobia- viral meningitis -> PCR and CSF (for enterovirus)
(b) If consciousness or cognitive state impaired but NO meningism -> ENCEPHALITIS likely -> measure glucose, sodium and calcium - give IC aciclovir
If LP shows NEUTROPHILS predominate->
Bacterial meningitis likely
->
Causative organism identified on gram stain of CSF -> specific therapy is necessary
if not identified - give CEFTRIAXONE
What are common SEQUELAE of meningitis? (5)
- NOTE - the strongest risk factors for an unfavourable outcome are those indicative of systemic compromise:
- Impaired consciousness
- Low white-cell count in the cerebrospinal fluid
- Infection with S. pneumoniae
- Encephalopathy (altered cerebral function and convulsion)
- Cranial nerve palsies
- Cerebral infarction or abscess
- Obstructive hydrocephalus (from basal obstruction of CSF)
- Subdural effusion of sterile or infected fluid
- Transtentorial herniation - caused by swelling of brain
What is the empirical treatment for Bacterial meningitis?
Benzylpenicillin dosage **
10 : 1.2 g
PLUS
Dexamethasone (10mg IV) (not Use VANCOMYCIN
What is meningococcus?
Neisseria meningitidis, a bacteria that causes meningitis - ie.meningococcal
Neisseria meningitidis- who does it affect?
Affects all ages- most common in children and young adults
Serotypes A,B, C associated with most morbidity and mortality
Neisseria meningitidis- Incubation period? Source? Spread? Carriage rate? Route of INFECTION? Defence mechanisms?
Incubation period: Short , 3 days
Source: Nasopharynx
Spread: via infected respiratory secretions
Carraige rate: 1/10 people
Route of infection: nasopharynx-> blood stream -> meninges
*during meningococcaemia a characteristic petechial rash is a common finding
Defence mechanism: possession of antibodies bactericidal to the invasive strain -
What is the microbiology of Neisseria meningitidis?
GRAM ->?
Gram NEGATIVE
Have Pili- attachment- undergo phsic and antigenic variation
Smooth moist colonies , glistening surfaces
What is the CULTURE of Neisseria meningitidis?
GRAM ->?
Oxidase +/-
Strict aerobe
Fastidious
Complex growth requirements
Identify: biochemical testing- oxidase +
When would you use multiplex PCR?
When patietns have already recieved ABX
What prophylaxis would you give household members/close contacts to a person who has meningitis?
RIFAMPICIN
or
CEFTRIAXONE
What vaccine do you get at 12 months?
Meningococcal C conjugate vaccine
92% effective in protecting toddlers
97% effective in teenagers.
Meningococcal quadrivalent Polysacharide vacines are 85% protective in adults, and usually for people at higher risks
What is a common cause of Meningococcal in Infants and pre school children?
Which type?
Is there a vaccination
HAEMOPHILUS INFLUENZAE
type B
Vaccination at 2,4,6 months!
What can you get post penumococcal infection?
S. pneumoniae meningitidis
- often sequel f pneumococcal infection of lungs, sinus or middle ear (40% of cases)
- Aggressive
what are the virulence factors of S.pneumoniae
Adherance Invasion Tissue Damage Phagocytic survival >90 serotypes
What are the fatalaty rates for pneumococcal meningitis?
Long term sequelae?
What treatment?
19-37% fatality rate
In up to 30% of survivors, long term neurologic sequelae develop (heairng loss and other focal neurological deficits)
MIC to penicillin and ceftriaxone required
21 days of treatment
What are the 2 types of pneumoccocal vaccination?
POLYSACCARIDE VACCINE
- + mature B lymphocytes- not T lymphocytes)
- polysaccharides form the capsules of 23 of the most virulent, invasive disease.
- ADULTS should get given.
Given to aboriginal children 18-24m onths and patients at risk at 15-65 years + all people >65
CONJUGATE VACCINE
- A t helper cell response
- 13 strains
- Good response in infants (95% efficacy)
- Given at 2 months, 4 months and 6 months
-
What adjunctive therapy would you give in pneumococcal meningitis?
STEROIDS- DEXAMETHASONE (reduces risk of unfavourable outcome)
Rare causes of Meningitis
Listeria monocytogenes aerobic non spore forming Gram positive rod enters peyers patches of LIVER
Presentation of Listeria meningitis
Healthy adults: bacteremia with or without high grade fever, or mild flu like illness
Pregnancy: fever/back pain- > can result in SPONTANEOUS ABORTION
Neonates: granulomatosis infantiseptica
- Late onset death
Lab investigations of Listeria meningitis
Lab investigation
- Get vaginal swab, CSF, blood culture
CSF microscopy
Culture- BETA HEMOLYTIC, tumbling motility
Summary for MENINGITIS:
Presentation
Headache vomiting fever irritability drowsiness rash
Summary for Meningitis
Diagnosis
CSF
Blood culture
PCR
Serology
Management
IV ABX
RIFAMPICIN to close contact
Steroids
Vaccination
