Understanding meningitis Flashcards
what is meningitis
- inflammation of the meninges
- meninges are the 3 membranes which enclose the brain and spinal cord
- meningism is the signs and symptoms that accompany the inflammation
give examples of the agents that can cause meningitis
- microbial agents
- bacteria
- viruses
- fungi
who is particularly at risk of meningitis
- babies and young children
- teenagers and young adults
- elderly
- people with a weak immune system
how are the microbial agents of meningitis acquired
- usually caused by organisms which colonise the back of the nose and throat
- sometimes acquired from the mother during birth
- streptococci, e coli - through food- listeria, e coli
how can microbial agents of meningitis be spread
through kissing, coughing, sneezing
what is viral meningitis
- most common form
- relatively benign illness and usually doesn’t need medical attention
- usually presents as a mild flu like illness- headache, fever
- more severe cases- neck stiffness, joint pain, vomiting, diarrhoea
- usually make a full recovery but rarely can be left with residual side effects
give examples of viruses implicated in meningitis
- enteroviruses- echovirus, coxsackie virus
- mumps
- herpes viruses
- HIV
what are the causative fungi in fungal meningitis
- cryptococcus neoformans
- candida
- coccidioides immitis
- histoplasma
what is cryptococcus neoformans and what symptoms does it cause
- associated with immune deficiency- eg pre existing HIV infection
- symptoms appear more gradually over days or weeks
- symptoms: headache, fever, nausea, vomiting, stiff neck, changes in mental state and hallucinations
what is bacterial meningitis
- usually more severe than viral meningitis
- high fatality rate unless treated immediately
- even with antibiotic therapy, many left with disorders
- most commonly hearing loss, epilepsy - most commonly caused by streptococcus pneumoniae and niesseria meningitidis
outline the progression to bacterial meningitis
- nasopharyngeal colonisation
- invasion of the bloodstream
- bacteraemia
- meningeal invasion
- multiplication in subarachnoid space
- release of bacterial products and cytokines
what can neisseria meningitidis cause
can cause meningococcal meningitis and meningococcal septicaemia
describe what meningococcal disease is
- communicable
- gram - diplococci, various virulence factors
- meningococci colonise the oropharynx in some healthy people (carriers)
- in these people, transition from carrier state to invasive disease occurs due to unknown factors
- many serotypes- A, B, C, W, X , Y
- bacteria can enter the bloodstream and cross blood brain barrier to cause meningitis
describe how meningococcal septicaemia occurs
- results when bacteria enters the blood and multiply uncontrollably
- toxins damage lining of the blood vessels leading to leakage
- presents as non blanching rash - lower blood volumes is insufficient to carry oxygen to all parts of the body
- blood supply reduced - clots may form in skin/muscle tissue- may lead to amputation
what are the early warning signs of meningitis
- fever
- headache
- vomiting
- muscle pain
- fever with cold hands and feet
what are the specific symptoms of meningitis
- rash
- stiff neck
- dislike of bright light
- confusion
- seizures
what are the specific symptoms of meningococcal septicaemia
- aching limbs
- cold hands and feet
- rash which starts like pin prick spots and develops rapidly into purple bruising
- confusion
what is the tumbler test
- to identify meningococcal septicaemia rash, press a glass tumbler against it and if the rash doesn’t fade, it could be meningococcal septicaemia
- on dark skin, check for the rash on lighter parts of the body
- keep checking as rash may fade at first
how is meningitis diagnosed in the laboratory
- cerebrospinal fluid may be taken
- visually inspected (clear or turbid)
- cell count performed
- protein is analysed
- glucose levels are analysed
- a centrifuged deposit is gram stained and inoculated onto a range of media to support main pathogens
- further specific tests performed - blood cultures
what is cerebrospinal fluid
clear, colourless liquid that bathes the brain and spinal cord, providing shock absorption and support
how is a CSF specimen obtained
by doing a lumbar puncture
- long thin hollow needle is inserted between 2 bones in the lower spine and into the space where CSF circulates
what characteristics of CSF may be present in viral meningitis
- clear or turbid appearance
- leukocytes 50-500
- raised protein
- normal glucose
what characteristics of CSF may be present in bacterial meningitis
- turbid appearance
- leukocytes 100-10000
- very raised proteins
- reduced glucose
outline the treatment of fungal meningitis
- amphotericin B
- Flucytosine
- fluconazole
outline the treatment of viral meningitis
- no specific antiviral therapy but aciclovir for herpes simplex virus
outline the initial empirical therapy for bacterial meningitis
- transfer patient to hospital urgently
- if meningococcal disease suspected, benzylpenicillin given prior to transfer
- consider adjunctive treatment with dexamethasone
- unknown aetiology 3 months- 50 years: cefotaxime
- unknown aetiology 50+ years: cefotaxime and amoxicillin, possibly with vancomycin
why are the vaccines against meningitis so important
meningitis and septicaemia can kill in under 4 hours
- bacteria multiply in body with alarming speed, overwhelming immune system
- early symptoms can be flu like, making it difficult to diagnose
what vaccines exist which can prevent cases of bacterial or viral meningitis
- MMR vaccine
- DTaP/IPV/Hib (haemophilus influenza b)/Hep B 6 in 1 vaccine
- PCV (pneumococcal conjugate vaccine)
- Hib/Men C vaccine
- Meningitis ACWY vaccine
- Men B vaccine
