L37 Bacterial infection of CNS Flashcards
Acute vs Chronic meningitis?
Acute: meningeal symptoms from few hours to few days;
Chronic: over weeks, CSF remains abnormal for >4 weeks
What is the dural venous sinus?
It is where the periosteal and meningeal layers separate
CSF is produced at the choroid plexus in the ventricles > flow?
- To the 3rd ventricle > 4th ventricle through cerebral aqueduct
- Flows into subarachnoid space by the lateral and medial apertures + spinal canal
- CSF removes waste and provide buoyancy from within the subarachnoid space
- Excess CSF will be absorbed by arachnoid villi > drained to superior sagittal sinus
Clinical presentations of acute bacterial meningitis can be non- specific, e.g. acute onset of fever and headache.
What are the signs of meningeal irritation? (4)
- Nuchal rigidity: neck stiffness, inability to flex the neck
- Kernig’s sign: when thigh is flexed and knee at 90 degrees, subsequent extension of knee is painful
- Brudzinski’s sign: when patient lies supine, lifting the patient’s head off the couch causes lifting of legs involuntarily
- Jolt accentuation of headache: increase headache when head is turned horizontally 2-3 times
List some examples of the below manifestations in acute bacterial meningitis
- Eye effects
- Mental alteration
- Hemorrhage
- Raised ICP
- Photophobia, diplopia
- Confusion, coma
- Petechiae, ecchymosis
- Early: headache, vomiting, papilloedema
- Late: CN3,6 palsies, hemiparesis
What are the signs of raised ICP in neonates? (3)
- Bulging fontanelle
- Enlarged cranium
- Seizures
What are the general risk factors for acute bacterial meningitis?
- Immunocompromised: complement deficiency, splenectomy, HIV
- NPC - post-radiotherapy may lead to deformities of the bone > prone to invasive strep pneumoniae infection
- Skull base fracture
- Otitis media
- Cranial trauma, CSF shunts (placement of CSF shunt systems to treat hydrocephalus before)
What are the most common organisms causing bacterial meningitis in neonates (infants <3m)? (3)
MC:
Group B strep >
E.coli >
Listeria monocytogenes
What are the specific risk factors for neonatal bacterial meningitis? (3)
- Maternal GBS colonisation
- Prematurity
- Prolonged rupture of membrane during labor
How can neonatal meningitis be prevented?
- Screening at 35-37 weeks for GBS
2. Intrapartum antibiotic prophylaxis (penicillin/ampicillin)
What are the MC organisms for bacterial meningitis in children >3m?
similar to adults (5)
+ Haemophilis influenzae
What are the MC organisms for bacterial meningitis in adults? (5)
- Strep pneumoniae
- N. meningitidis
- Strep suis
- Listeria monocytogenes
- M. tuberculosis
What are the specific risk factor(s) for bacterial meningitis in
a) children >3m
b) adults?
a) pre-existing acute otitis media
b) Debilitated (weak), Elderly, Diabetic
What can be done to prevent bacterial meningitis in children >3m? (4)
Vaccination x4
- PCV 13
- Pneumococcal conjugate vacine - Hib vaccine
- Meningococcal group C+ Y
- BCG (in children immunisation programme)
What can be done to prevent bacterial meningitis in adults? (3)
- PCV13 + booster PPSV23 (Pneumococcal polysaccharide vaccine)
- Meningococcal A/C/W/Y-135 (for travellers to endemic areas)
- Meningococcal group B (teenagers)
Procedure-related meningitis/ Intra-cranial shunts can be causes for meningitis.
What are the usual organisms? (2)
Prevention is by infection control
- S.aureus/ MRSA
2. GN rods
Prophylaxis for pneumococcal meningitis?
PCV13/
PPSV23
vaccine
Streptococcus pneumoniae can be commonly found in which organ?
It causes the highest morality of meningitis (20%), can causes cerebral edema, CN palsy etc.
What is the treatment ?
Nasopharynx
- IV Cefotaxime as empirical treatment until organisms sensitivity is available >
depending on resistance, IV penicillin G > IV cefotaxime > IV vancomycin + rifampicin
- Dexamethasone -.15mg/kg, IV Q6h x4/7 may reduce mortality and hearing loss
Neisseria meningitidis can be normally found at?
What are the commonest presentations in patients infected?
Nasopharynx
- Petechiae, purpura 50%
Neisseria meningitides can have a rapid progression , and may even cause Waterhouse-Friderichsen syndrome. What is that?
Treatment?
Waterhouse-Friderichsen syndrome - shock, DIC, bilateral adrenal hemorrhage
> adrenocortical insuffciency
Treatment: Cefotaxime
What are the preventive measures for meningococcal meningitis?
- Group A/C/Y/W-135 vaccine
- Group B vaccine
- Rifampicin for close contacts, not necessary for medical personnel
Which organism infect infants from 1 month to 3 years old most?
What serotype is the most virulent?
It causes cerebral oedema, hydrocephalus, CN palsy (e.g. deafness)
How to prevent?
Haemophilus influenzae; Type B
Hib vaccine, rifampicin for close contacts
*Cefotaxime is given for treatment, ampicillin if sensitive
Which organism causing meningitis is found in pigs thus butchers, and associated with high incidence of deafness?
Treatment?
Streptococcus suis
(Group D strep)
High dose benzylpenicillin 14-21 days
List the 4 routes of entry of bacterial meningitis.
- Hematogenous spread (MC)
e. g. nasopharyngeal epithelium - Direct contiguous spread
- e.g AOM, sinusitis - Direct inoculation
- e.g. open skull fracture - Vertical transmission
Causative organisms invade the meninges via various BBB receptors, and replicate in the ________________due to local immunodeficiency. Then there is immune system activation and cytokine production.
What are the effects? (3)
subarachnoid space
- Increase BBB permeability > vasogenic edema > increase CSF outflow resistance > hydrocephalus > interstitial edema
- Increase ROS by bacterial toxin > cytotoxic edema
- Altered cerebral blood flow (CBF), reduced perfusion pressure, ischemia
ALL = Increase intracranial pressure - cerebral ischemia, brain herniation
What initial investigations to be done in suspected meningitis? (5)
- CT to rule out any mass lesion before LP
- if mass is present in brain/ elevated ICP, LP may lead to brain herniation - CSF for microbiological investigations; by lumbar puncture
- Plasma glucose
- Blood culture
- Serology for viral studies: throat swab, stool culture
If there is increased opening pressure (normal 10-20cm H2O) in CSF puncture, it suggested?
increased ICP from cerebral edema
What microbiological tests to be done in CSF sample?
- Gram stain (H.influenzae)
- ZN stain and rapid DNA detection for TB
- India ink for Cryptococcus
- Bacterial culture
- Latex agglutination for bacterial + Cryptococcus antigens
What is the typical CSF interpretation in bacterial meningitis? (5)
- Cloudy appearance
- Increase in WBC per ul
- Polymorphs as predominant cells (>80%) compared to lymphocytes
- Reduced glucose, <2.2 (due to increase consumption + reduced glucose transport to brain)
- Increased Protein (g/L) >0.5, plasma protein leakage due to inflammation
What is the typical CSF interpretation in TB meningitis? (5)
- Opalescent appearance
- Increase in WBC per ul
- Predominant cells: L**>P
- Very high protein
- Low glucose <2.2
What is the typical CSF interpretation in viral meningitis? (5)
- Clear appearance
- Increase in WBC per ul
- Predominant cells: P early, L late
- > 0.5 protein (elevated)
- Normal glucose
CSF interpretation:
1. Clear appearance
- Increase in WBC per ul
- Predominant cells: L>P
- > 0.5 protein (elevated)
- <2.2 glucose
Ddx?
Cryptococcal meningitis
~TB but TB has opalescent appearance
CSF interpretation in subarachnoid hemorrhage?
- Xanthochromic appearance (yellowish)
- Greatly elevated WBCs
- Crenated RBC as predominant cells
- Very high protein
- Normal glucose
What is the normal WBC count per ul in CSF?
What is the predominant cell L/P in CSF?
<4
- Lymphocytes
Others:
Protein: 0.15-0.45 g/L
Glucose: 2.8-4.2 mmol/L
What is defined as significant reduced CSF glucose when compared to plasma glucose?
CSF glucose <50% plasma glucose
Name 5 causative agents for chronic meningitis?
- Mycobacterium tuberculosis
- Cryptococcus neoformans
- Treponema pallidum (syphilis)
- Amoeba (Naegleria fowleri)
- HIV
Both TB and Cryptococcus neoformans can cause granulomatous meningitis.
For TB meningitis, L>P in CSF, and patient has insidious onset of headache, confusion, fever.
How to diagnose TB meningitis? (2)
- BAL for PCR (sputum is not sensitive enough)
2. CSF for antigen detection
What are the risk factors for Cryptococcal meningitis?
- Immunocompromised: AIDS, malignancy, steroid therapy, DM
- SLE
- Alcoholism
Pathogenesis of Cryptococcal meningitis: Inhalation of yeast > harmless airway colonisation > ______?
Pathology: SOL with granuloma and mucinous exudate
What to expect in CSF investigations?
Neurotropic;
- Increased opening pressure
- India ink +ve
- Culture: Sabouraud agar
- Serology: Latex agglutination test for antigen - for monitoring treatment response
Cryptoccocal meningitis: what test to do other than CSF investigation? (2)
- Blood culture
2. Latex agglutination test - for monitoring treatment response
What is the treatment for Cryptococcal meningitis? (2)
- IV amphotericin B + flucystosine
2. Life-long fluconazole prophylaxis in AIDS patients
What are the risk factors for brain abscess formation? (7)
- Hematogenous
- MC infective endocarditis - Contiguous spread:
- Bronchiectasis, sinusitis, AOM, dental caries - Direct inoculation
- Open fracture, post-neurosurgical patient
What can be observed in CT brain if brain abscess? (2)
Ring-enhancing lesion (1) with surrounding vasogenic edema (1)
Treatment for brain abscess? (3)
- Drainage
2. Antibiotics: 3rd generation cephalosporin (cefotaxime/ ceftriaxone) + metronidazole
