10.3.2 Meningitis Flashcards
What are the categories of infection of the CNS?
Parenchyma- encephalitis
Meninges- meningitis (leptomeninges)
What are the typical causative organisms of meningitis in neonates?
E. Coli
Group B streptococcus
Listeria monocytogenes
What are the typical causative organisms of meningitis in children?
Haemophilus influenzae type B (HiB vaccine given, ‘meningococcus’)
Neisseria meningitidis
What are the typical causative organisms of meningitis in the elderly?
Streptococcus pneumoniae (vaccines now given)
Listeria monocytogenes
What are the risk factors for developing meningitis?
CSF defects e.g. spina bifida
Spinal procedures e.g. surgery, LP
Endocarditis
Diabetes (immunosuppression)
Alcoholism
Splenectomy (immunosuppression)
Crowded housing (students)
What is the triad of meningism?
Headache
Neck stiffness (nuchal rigidity)
Photophobia
(with fever)
When does the triad of meningism occur in bacterial vs viral?
Bacterial- hours
Viral- days
What are the associated symptoms of meningitis?
Flu-like symptoms
Joint pains and stiffness
Seizure
Meningococcal rash (non-blanching)
Drowsiness
Patient may be in shock
Outline the features of meningococcal rash
Often occurs in younger patients rather than old
Small- petechial
Larger >2mm- pupuric
Affects:
- Trunk
- Legs
- Mucous membranes
- Conjuctivae
- Rare, palms and soles
What are the symptoms of meningitis in babies?
Inconsolable crying
Off-feeds
Rigidity / floppiness
Bulging fontanelle (late sign)
What is the pathophysiology of meningitis?
Pathogens in the nose gain entry to circulation causing bacteraemia
Bacteraemia causes vessel wall damage in brain and meninges, allowing pathogens to enter subarachnoid space
Pathogens multiply causing purulent CSF and severe meningeal inflammation
Vasospasm of cerebral vessels can cause cerebral infarction
Oedema of brain parenchyma causes raised intracranial pressure
How can bactiera reach the CNS?
Ascent of bacteria through eustachian tube to middle ear- otitis media
Prolonged infection can lead bacteria to spread directly into CSF through mastoid sinuses
Or
Seeding to lower respiratory tract (pneumonia)
Lung inflammation allows bacteria to enter blood, invasion of CSF via capillaries that traverse choroid plexus or subarachnoid space
Neonates can get pathogens from maternal source
What causes the macuopapular rash in meningococcal septicaemia?
Microvascular thrombosis due to:
- Sluggish circulation
- Impaired fibrinolysis
- Increased tissue factor expression in endothelial cells
Can meningococcal sepsis occur without meningitis?
Yes
What are the investigations for meningitis?
Bloods- including sepsis screen and PCR
CXR
Mid-stream urine
LP
Compare how CSF looks in bacterial vs viral meningitis
Bacterial- cloudy
Viral-may be clear, can be cloudy (due to immune cells and proteins)
Protein in CSF, bacterial vs viral meningitis
Bacterial- high protein (immune proteins)
Viral- protein may be normal or raised
White cell count in CSF, bacterial vs viral meningitis
Bacterial- high white cells, primarily neutrophils (phagocytose bacteria)
Viral- high white cells, primarily lymphocytes to mount adaptive response
Glucose levels, bacterial vs viral meningitis
Bacterial- low glucose as bacteria and white cells metabolise it
Viral- normal glucose >60% plasma
What is the supportive treatment of meningitis?
Analgesia
Antipyretics
Fluid, if shocked
What is the medical treatment of meningitis?
IV ceftriaxone
Dexamethasone to prevent hearing loss (due to swelling of CNVIII on cochclea)
What is given for viral meningitis?
Acicolvir for Herpes
Ganciclovir for CMV
What are the two signs used to determine meningitis in children?
Kernig sign
- Supine patient with thigh flexed to 90 degrees
- Extension of knee met with resistance
- 53% of children
Brudzinski sign
- When neck is flexed there is an involuntary flexion of knees and hips
- 66% of children
What are the complications of meningitis?
Septic shock- due to bacteraemia
Disseminated intravascular coagulation- due to bacteraemia
Coma- due to raised ICP
Cerebral oedema- due to cerebral inflammation
Raised ICP
Death
SIADH- effect on hypothalamus/pituitary
Seizures- irritation of brain parenchyma
Hearing loss- swelling of CNVIII on cochlea, perilymph continuous with subarachnoid space
Intellectual deficits- due to brain damage
Hydrocephalus- interruption of CSF drainage pathways and effect on arachnoid granulations
Focal paralysis- due to cerebral abscess
