Bacterial CNS Infections Flashcards
Clinical features of an acute Bacterial meningitis
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
What is the most common organisms by age to cause a bacterial meningitis
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
Characteristics of a streptococcus pneumonia CNS infection
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
Characteristics of Neisseria meningitis causing meningitis
– 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
Characteristics of a haemophilus influenza meningitis
– 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
Typical CNS findings in a bacterial versus viral versus tuberculous meningitis
Normal: neutrophils 0, lymphs 0-6, glucose3.6–5.6, protein 0 .15–0 .45
Bacteria: neutrophils100–50,000, Glucose 1.1–1.6
When is a CT or MR I indicated in meningitis
– 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
When might a CSF sample show a neutrophil predominance without it being a bacterial meningitis
Early viral meningitis
Early tuberculosis meningitis
Causes of a recurrent meningitis
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
Complications of meningitis
– 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
Why Are third-generation cephalosporins preferred in the management of a bacterial meningitis
There is increasing emergence of resistance to penicillin in strains of streptococcus pneumonia
What prophylactic measures can be taken against bacterial meningitis
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
How can we prevent bacterial meningitis
Haemophilus Influenza B vaccine
Pneumococcal vaccine
What scoring system can be used to predict the prognosis of meningitis
Herson-Todd
What is the mechanism of damage in a bacterial meningitis
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
How do organisms causing the brain abscess gain access to the central nervous system
Via the bloodstream
Direct spread from a nearby focus e.g. sinuses or middle
Most common organisms causing the brain abscess
Streptococci Staphylococcus Pneumococcal Haemophilus influenza Bacteriodes Anaerobic organisms in 25% of cases
What is a major predisposing factor to developing a brain abscess
Cyanotic congenital heart disease with the right-to-left shunt especially under two years of age
Purulent otitis media
Mastoiditis
Sinusitis
How will a brain abscess show up on the CT
Ring enhancing lesion
Clinical manifestations of the brain abscess
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
