Meningitis Flashcards
What is meningitis
inflammation of the meninges
how does bacteria reach the meninges
through bloodstream
direct contact between the meninges and either nasal cavity or the skin
how does meningitis lead to cerebral oedema?
blood brain barrier becomes more permeable - vasogenic cerebral oedema (fluid leaks from blood vessels)
white blood cells enter CSF leading to interstitial oedema (fluid between cells)
walls of blood vessels become inflamed, leads to decreased blood flow and cytotoxic oedema
what are the 5 types of meningitis
acute pyogenic (bacterial) meningitis acute aseptic (viral) meningitis acute focal suppurative infection (brain abscess, subdural and extradural empyema) Chronic bacterial infection (TB) acute encephalitis
What pathological features are seen in pyogenic meningitis
suppurative exudate covers leptomeninges
exudate in basal and convexity surfaces
what are the complications of meningitis
arachnoiditis - impacts on CSF absorption
Hydrocephalus and ventriculitis - communicating + non communicating
death
abscess formation
cerebral oedema
exudate can form around nerves (3+6)
what are the common causative organisms of pyogenic meningitis
neisseria meningitidis - gram negative bacterium
haemophilus influenzae - gram negative cornebacterium
streptococcus pneumoniae - gram posistive bacilli
listeria monocytogenes
what are the most likely causative organisms based on age group? (pyogenic meningitis)
neonates - listeria, streptococcus agalachie
children - h.influenzae
ages 10-21 - neisseria meningitidis
age over 21 - strep pneumoniae > neisseria meningitidis
over 65 - strep pneumoniae > listeria
which bacteria commonly affects students?
neisseria meningitidis
who are the three risk groups of listeria monocytogenes?
elderly, neonates, pregnancy
what are some common risk factors and their associated causative organisms? (pyogenic meningitis)
DECREASED CELL MEDIATED IMMUNITY: LISTERIA MONOCYTOGENES
NEUROSURGERY/ HEAD TRAUMA: STAPHYLOCOCCUS, GRAM NEGATIVE BACILLI
FRACTURE OF THE CRIBIFORM PLATE: STREPTOCOCCUS PNEUMONIAE
clinical features of pyogenic meningitis
fever, stiff neck, alteration in consciousness, headache, vomiting, pyrexia, photophobia, lethargy, confusion, petechial or purpuric rash, seizures,
neurological features of meningitis
focal neurological deficit, abnromal eye movement, facial palsy, balance problems/hearing impairment
clinical features of infants with meningitis
hypothermia, irritability, lethargy, poor feeding, apnoea, bulging fontanelle. high pitched cry
what are your first line investigations in meningitis?
CT lumbar puncture (CSF analysis)
what other investigations could you consider in meningitis?
blood cultures, throat swab, blood EDTA for PCR
management of pyogenic meningitis
Ceftriaxone 2g bd + Dexamethasone
add ampicillin/amoxicillin if listeria suspected, or aciclovir if encephalitis
what are the indications for hospital admission?
signs of meningeal irritation, an impaired conscious level, petechial rash, who are febrile or unwell and have had a recent fit, Any illness, especially headache, and are close contacts of patients with meningococcal, infection, even if they have received a prophylactic antibiotic
what are the common prophylactic regimes of pyogenic meningitis?
600 mg rifampicin orally 12-hourly for four doses (adults and children over 12 years), 10 mg/kg orally 12-hourly for four doses (aged 3-11 months) (IV).
500 mg ciprofloxacin orally as a single dose for adults and children aged more than 12 years (IV)
250 mg ceftriaxone intramuscularly as a single dose in adults, 125 mg iv as a single dose in children under 12 years
What is the management of penicillin allergic pyogenic meningitis?
If there is a clear history of anaphylaxis to beta-lactams give chloramphenicol iv 25 mg/kg 6-hourly with vancomycin iv 500 mg 6-hourly or 1g 12-hourly.
If listeria suspected and penicillin allergy co-trimoxazole alone has been used successfully for this infection.
when should you give steroids in the management of pyogenic meningitis?
give to all patients suspected of bacterial meningitis (10mg iv 15-20 min before or with the first dose of antibiotic and then every 6 hours for 4d)
do not give in post-surgical meningitis, severe immunocompromise, meningococcal or septic shock or those hypersensitive to steroids
What is an causative organism of cryptococcal meningitis?
cryotococcus neoformo=us
risk factor for cryptococcal meningitis
HIV
management of cryptococcal meningitis
IV amphotericin B/flucytosine
Fluconazole
clinical features of cryptococcal meningitis
subtle neurological presentation
disseminated infection
aseptic CSF
what does aseptic meningitis mean?
non-pyogenic bacterial meningitis
general features of CSF of aseptic meningitis
low WBC,
minimally elevated protei
normal glucose
What are the common causes of viral meningitis
human enteroviruses - 5 subgernera coxsackieviruses echoviruses polioviruses herpes viruses - HSV1 (encephalitis), HSV2 (meningitis) arboviruses
risk factors of viral meningitis
exposure to mosquito or tick vector unvaccinated for mumps use of swimming pools and ponds immunosuppression exposure to rodents
clinical features of viral meningitis
headache, nausea and vomiting, photophobia, neck stiffness, fever, rask, kernigs sign, brudzinskis sign
investigations for viral meningitis
viral stool culture, throat swab, CSF PCR
treatment for viral meningitis
self limiting, supportive
aciclovir only if herpes
What are 2 types of brain abscesses?
single or multiple
pathological features of single abscesses
occur adjacent to source
pathological features of multiple abscesses
haematogenous spread
causes of single abscesses
local extension (e.g. mastoiditis) direct implantation of infectious agent (skull fracture)
causes of multiple abscesses
bronchopneumonia, bacterial endocarditis
risk factors for development of abscesses
sinus and dental infections, penetrating trauma, pulmonary infections, congenital heart disease, HIV, transplantation, neutropenia
symptoms of a brain abscess
fever, ICP
symptoms of underlying cause
investigations for a brain abscess
CT or MRI
Aspiration for culture
management of brain abscess
Aspiration and antibiotics
CSF features of bacterial meningitis
Appearance - cloudy Pressure - raised WBC - 500-10000 neutrophils Glucose - decreased Protein - >150
CSF features of viral meningitis
Appearance - clear Pressure - normal WBC - 10-100 lymphocytes Glucose - normal Protein - raised
CSF features of fungal meningitis
Appearance - clear/cloudy Pressure - normal WBC - 10-500 mononuclear cells Glucose - decreased Protein - >1000
CSF features of TB meningitis
Appearance - opaque Pressure - rasied WBC - 50-500 neutrophils/monocytes Glucose - decreased Protein - >100
CSF of crytococcal meningitis
Appearance - clear Pressure - raised WBC - 100-200 lymphocytes Glucose - decreased Protein - 50-200
