Meningitis Flashcards
What is meningitis?
Inflammation of the meninges, the membranes that surround the brain.
What causes bacterial meningitis?
These are the commonest causes of bacterial meningitis according to age-
- group b strep in those aged less than 3 months
- neisseria meningitidis in those aged 3 months to 45 years
- strep pneumoniae in those aged over 45 years
Other causes- staph aureus, e.coli, TB and haemophilus influenzae (now rare due to vaccine)
Listeria monosytogenes can cause meningitis in pregnancy, neonates, the elderly or alcohol misusers.
What causes viral meningitis?
slightly commoner than bacterial meningitis, is often mild and mistaken for flu.
- enteroviruses
- herpes simplex (HSV2 more than HSV1)
- Mumps
- Measles
What causes fungal meningitis?
- usually cryptococcus neoformans
- it has an insidious onset
Name some non-infectious causes of meningitis.
- cancer
- drugs- co-amoxiclav, NSAIDs, IVIg, axathioprine
- inflammatory or auto-immune- sarcoidosis, SLE, Behcets
What percentage of cases of bacterial meningitis occur in children under the age of 15?
40 percent. Commonest in the first few months of life.
Why are 90 percent of cases of meningococcal disease caused by serogroup B?
C is prevented by vaccine. The MenB vaccine may change how many cases are due to serogroup B.
How is meningococcal disease transmitted?
droplets from upper respiratory tract. Incubation period is 3-7 days. Is most infectious before symptom onset.
What are the symptoms of meningitis?
- the classic triad- neck stiffness, fever and headache/altered mental status. Will be present in 50%.
- other features include vomiting, photophobia, mottled skin, confusion, seizures, rigors, cold hands and feet.
- headache, stiff neck and photophobia are actually signs of meningeal irritation (meningism) which is also seen in subarachnoid haemorrhage.
Viral meningitis-
prominent headache
flu like symptoms
other features minimal or absent.
What are the signs of meningism?
- kernig’s sign- with hip and knee flexed, pain limits passive extension of the knee.
- brudzinski’s sign- neck flexion leads to involuntary hip and knee flexion.
Both tests are 10% sensitive and 90% specific for meningitis. Meaning that if present, they point towards meningitis as the very likely diagnosis. However many people with meningitis will not have these signs.
Name some complications of meninigitis.
-cerebral oedema
may lead to reduced level of consciousness, papilloedema or focal CNS signs.
-meniingococcaemia
petechiae and purpura- look carefully all over body for rashes.
septic shock- low blood pressure and increased cap refill time.
DIC
Pneumonia can be present in pneumococcal meningitis.
What are the risk factors for meningitis?
- immunosuppression, including complement deficiencies and asplenia.
- skull fractures/anatomical defects
- crowding- university halls, military barracks, Hajj (mass gatherings).
Which investigations should be performed in suspected meningitis?
INITIAL ANTIBIOTICS SHOULD PRECEDE ANY INVESTIGATIONS!
Bloods-
- FBC- high white cells and CRP
- U&Es and LFTs
- Blood culture +/- PCR for neisseria meningitidis
- Coag- DIC
Lumbar puncture-
- CT and opthalmoscopy first if raised intracranial pressure suspected.
- Bacterial CSF- high polymorphs, high protein, low glucose, bacteria on culture. Listeria can be mixed polymorphs and lymphocytes.
- TB CSF- high lymphocytes, high protein, low glucose, ZN stain positive.
- Viral csf- high lymphocytes, viral PCR positive
Other investigations-
- throat swab for n. meningitidis
- CXR- pneumococcal pneumonia, TB
How should management of meningitis be approached?
ACUTE
- resuscitate, including oxygen and fluids
- broad-spectrum IV antibiotics stat eg. cefotaxime. Add amoxicillin if aged over 50 years or under 3 months to cover listeria. Benzyllpenicillin IM if pre-hospital can be given by the GP.
- dexamethasone IV if less than 3 months old- reduces neurological complications- does not affect mortality.
PUBLIC HEALTH MEASURES
- notify public health authorities about any case of meningitis or meningococcaemia.
- isolate the patient
- prophylactic antibiotics - single dose of ciprofloxacin or 2 days of rifampicin. Give to all close contacts from the last 7 days regardless of vaccination status. This includes household contacts or healthcare workers with high exposure.
- further cases are likely to present in the 7 days after the first.
Infective clusters-
- defined as more than 2 cases in the same setting in 4 weeks.
- prophylactic antibiotics to those at risk or the whole iinstitution.
- Vaccinate all except those with vaccine in the past year.
What complications can occur in meningitis?
SHORT TERM- increased intracranial pressure, shock, DIC, subdural effusions, SIADH, seizures, venous sinus thrombosis.
LONG TERM- cranial nerve palsies, deafness, limb amputation (in meningococcal septicaemia), memory or cognitive problems (25%)
Mortality 5% in meningococcal, 25% in pneumococcal and 35% for listeria.
