Bacterial CNS Infections

Question 1

Clinical features of an acute Bacterial meningitis

Answer 1

Varies with the causal organism and the age of the child
Neonatal period:
– Less specific: irritability poor feeding, bulging fontanelle , and hypo or hyper thermia
– High index of suspicion needed
Rest of children:
–fever
– Signs of raised intracranial pressure e.g. headache vomiting and nausea
– Menigeal irritation: neck stiffness, kernig’s +Brudzinski’s
– Cortical involvement: encephalopathy and coma

Question 2

What is the most common organisms by age to cause a bacterial meningitis

Answer 2

Neonates(0-28days) : E. coli, group B Streptococcus, listeria monocytogenes, klebsiella, Enterobacter
Infants: Group B Streptococcus, H influenza type B, Streptococcus pneumoniae, Neisseria meningitis, salmonella
Childhood and adolescence: streptococcus pneumonia, Neisseria meningitis, H influenza type B

Question 3

Characteristics of a streptococcus pneumonia CNS infection

Answer 3

Associated with
- meningitis caused by fractures of the Skull, sinuses or frontal bones leading to a CNS leak and otorrhoea
-functional asplenia: sickle-cell disease
– Very high mobility and maternity
–multi-resistant to penicillin
– Vaccine available

Question 4

Characteristics of Neisseria meningitis causing meningitis

Answer 4

– Gram negative interest cellular organism
– Causes meningeal cockle meningitis
– Very rapid onset with petechial or purpuric rash
– Scrape of a rash may yield organism
– Can produce an endotoxin which can cause shock, adrenal haemorrhage, DIC uncommonly pericarditis arthritis and Eye involvement

Question 5

Characteristics of a haemophilus influenza meningitis

Answer 5

– Gram negative pleomorphic Bacillus
– Moderately slow onset
– Found and conditions of overcrowding and in children with splenectomies
Primarily affects children below two years of age
– Complications include: subdural effusions, hearing loss, epileptic fits, mental retardation, Cerebral infractions
– Prevented by H I B vaccine

Question 6

Typical CNS findings in a bacterial versus viral versus tuberculous meningitis

Answer 6

Normal: neutrophils 0, lymphs 0-6, glucose3.6–5.6, protein 0 .15–0 .45
Bacteria: neutrophils100–50,000, Glucose 1.1–1.6

Question 7

When is a CT or MR I indicated in meningitis

Answer 7

– Prolonge of persistent of tundish and decreased level of consciousness or coma
– Persistent focal neurological signs
– Relapsed after an initial response
–increasing head circumference
– Deteriorating level of consciousness
– Suspicion of the subdural effusion(focal neurological signs, re-emergence of a fever on day 3 to 6)
– Change in mental status
– Associated purulent otitis media with the fear of a brain abscess

Question 8

When might a CSF sample show a neutrophil predominance without it being a bacterial meningitis

Answer 8

Early viral meningitis

Early tuberculosis meningitis

Question 9

Causes of a recurrent meningitis

Answer 9

Organism: unresponsive 2 antibiotic /unusual organisms e.g. listeria cryptococcus TB and Staphylococcus aureus
Brain abscess, subdural empyema
Anatomical defect:
-fractured skull, sinuses, orbits, cribriform plate
-Meningomyelocoele , congenital Dermal sinus, neuroenteric cyst
Defects of the middle ear,:
Immune deficiency:
– Congenital hypogammaglobulinaemia
– Compliment deficiency
– Splenectomy
– Sickle-cell anaemia

Question 10

Complications of meningitis

Answer 10

– Vasculitis with resultant thrombosis
– Subdural effusion usually from haemophilus
– Epileptic fits
– Cerebral oedema
– Hydrocephalus: More common in neonatal meningitis
– S I a DH
– Cranial nerve palsy: most common is a sensorineural hearing loss
– Hemiplegia
– Brain abscess: extremely uncommon

Question 11

Why Are third-generation cephalosporins preferred in the management of a bacterial meningitis

Answer 11

There is increasing emergence of resistance to penicillin in strains of streptococcus pneumonia

Question 12

What prophylactic measures can be taken against bacterial meningitis

Answer 12

Neisseria m meningitis: close contacts i.e. immediate family members and nursery school friends
– Rifampicin for two days
– ceftriaxone
– Ciprofloxacin
Haemophilus: only children younger than five need prophylaxis
–rifampicin for four days

Question 13

How can we prevent bacterial meningitis

Answer 13

Haemophilus Influenza B vaccine

Pneumococcal vaccine

Question 14

What scoring system can be used to predict the prognosis of meningitis

Answer 14

Herson-Todd

Question 15

What is the mechanism of damage in a bacterial meningitis

Answer 15

Most often damage is as a result of host factors rather than direct
– Host response to bacterial invasion includes:
– – Cytokines E.g. TNF interleukin-1 other mediators inflammatory sponsors
There is responses lead to increase blood brain barrier permeability, hypercoaguability, raised intercranial pressure, vasogenic, cytotoxic and interstitial oedeama and reduced cerebral blood flow

Question 16

How do organisms causing the brain abscess gain access to the central nervous system

Answer 16

Via the bloodstream

Direct spread from a nearby focus e.g. sinuses or middle

Question 17

Most common organisms causing the brain abscess

Answer 17

Streptococci
Staphylococcus
Pneumococcal
Haemophilus influenza
Bacteriodes
Anaerobic organisms in 25% of cases

Question 18

What is a major predisposing factor to developing a brain abscess

Answer 18

Cyanotic congenital heart disease with the right-to-left shunt especially under two years of age
Purulent otitis media
Mastoiditis
Sinusitis

Question 19

How will a brain abscess show up on the CT

Answer 19

Ring enhancing lesion

Question 20

Clinical manifestations of the brain abscess

Answer 20

Signs of raised intracranial pressure
Sepsis and fever
Focal neurological signs with or without seizures seizures
If the abscess breaks through to the ventricular cavity signs of Meningitis may occur