CNS Infections

Question 1

Pathogenesis of bacterial infection?

Answer 1

1. bacterial invasion
2. Production of cytokines ( e.g TNF, IL-1
3. Increased Blood Brain Barrier Permeability (BBBP)
4. Hypercoagulability
5. Raised intracranial pressure (vasogenic, cytotoxic and interstitial oedema)
6. Reduced Cerebral Blood Flow

Question 2

Clinical features of acute bacterial infection in neonates?

Answer 2

1. Irritability
2. Poor feeding
3. A bulging fontanelle
4. Hypo/hyperthermia

Question 3

Clinical features of ABI in older children?

Answer 3

1. Fever
2. Signs of raised intracranial
3. pressure (headache, nausea and vomiting
4. signs of meningeal irritation (neck stiffness, Kernig’s sign and Brudzinski’s sign)
5. Signs of cortical involvement (encephalopathy, coma)

Question 4

Risk factors of ABI in neonates?

Answer 4

1. Premature rupture of membranes
2. Low birth weight
3. Male babies
4. Difficulty delivery with extensive manipulations

Question 5

Causative organisms for ABI in neonates?

Answer 5

E. Coli
Group B Streptococcus
L. monocytogenes
Klebsiella
Enterobacter

Question 6

Causative organisms in infants (1 month - 2 years)?

Answer 6

Group B Streptococcus
S. Pneumoniae
H. Influenzae
N. meningitidis
Salmonella species

Question 7

Causative organisms in childhood and adolescence?

Answer 7

S. Pneumoniae
N. Meningitidis
H. Influenzae type B

Question 8

What is strep. pneumoniae?

Answer 8

Gram-positive diplococcus

Question 9

When should you suspect strep. pneumoniae?

Answer 9

Should be suspected in meningitis associated with:
1. Skull fracture
2. Paranasal sinuses
3. Frontal bone CSF leak
4. Otorrhoea

Question 10

Medical conditions to suspect strep. pneumoniae?

Answer 10

1. Sickle cell patients (functional asplenia)
2. Immunodeficiency e.g HIV infection

Question 11

What is neisseria meninigitidis?

Answer 11

Gram negative intracellular organism
Epidemic forms are A and C
Other groups are A. B, C, D, X, Y, Z and W135

Question 12

Clinical features of N. meningitides?

Answer 12

Very rapid onset (a few hours)
Petechial and purpuric rash can rapidly progress to purpura fulminans
Petechial rash contains organisms
Endotoxin can induce shock, bilateral adrenal haemorrhage and DIC

Question 13

What is hemophilus influenzae?

Answer 13

Gram-negative pleomorphic bacillus
Onset of meningitis is moderately slow

Question 14

Epidemiology of H. influenzae?

Answer 14

Found in situations of overcrowding and splenoctemized patients
Common in infants and pre-school children less than 2 years old

Question 15

Sequelae associated with H. influenzae?

Answer 15

Subdural effusions
Hearing loss
Epileptic fits
Mental retardation
Cerebral infarctions

Question 16

CSF analysis of bacterial meningitis?

Answer 16

white cells - 100 – 50,000
Neutrophil predominant
glucose - 1.1 – 1.6
<0.5 = severe infection
protein - Mild to moderately increased

Question 17

CSF analysis for viral meningitis?

Answer 17

white cells - 25 – 500
Lymphocytes predominant
glucose - normal
protein - mildly increased

Question 18

CSF analysis of TBM?

Answer 18

white cells - 25 – 100 (can go up to 500)
Lymphocyte predominant but neutrophils predominate early
glucose - Less than 2.2 – 2.7
Usually less than 0.5
protein - moderately increased

Question 19

Complications of acute bacterial meningitis?

Answer 19

Subdural effusions – mainly HiB (to a lesser extent - N. meningitidis and S. Pneumoniae)
Epileptic fits – focal or generalized.
Cerebral oedema – vasogenic and cytotoxic
Hydrocephalus – esp in neonatal meningitis - TBM, S. pneumonia (Arachnoditis and occlusion of CSF flow)
Syndrome of inappropriate ADH secretion (SIADH) – 15 – 20%; (water intoxication: irritability and convulsions)
Cranial palsies – most commonly sensorineural hearing loss;
Hemiplegias – vasculitis and infarction
Brain abscess

Question 20

Treatment for acute bacterial meningitis?

Answer 20

Antibiotics
Prevent/treat complications
General care of unconscious child
Steroids ( Dexamethasone 10-15 minutes before initiation of antibiotics in children more than 2 months)

Question 21

What is the Herson-Todd scoring?

Answer 21

prediction of morbidity in acute bacterial meningitis

Question 22

Scoring of Herson-Todd?

Question 23

Prevention of N.meningitidis?

Answer 23

Rifampicin 10mg/kg twice a day for 2 days
Ceftriaxone 250mg imi sta (adults); 125mg imi stat children

Question 24

Prevention of H. influenzae?

Answer 24

Rifampicin 20mg/kg twice a day for 4 days; < 1month 10mg/kg twice a day for 4 days.