CNS Infections Flashcards
What can happen if a CNS infection is left untreated?
Brain herniation and death
Cord compression and necrosis with subsequent permanent paralysis
Name some examples of CNS infections
Encephalitis, meningitis, meningoencephalitis, encephalomyelitis, epidural abscess, neuritis, sepsis syndrome due to infection elsewhere
How is meningitis classified?
Acute pyogenic (bacterial) meningitis, acute aseptic (viral) meningitis, acute focal suppurative infection (brain abscess, subdural and extra dural empyema), chronic bacterial infection (TB)
Describe the pathology of pyogenic meningitis
Pyogenic meningitis shows a thick layer of suppurative exudate covers the leptomeninges over the surface of the brain
Microscopically - neutrophils in the subarachnoid space
Name some pathogens that cause bacterial meningitis
Neonates - listeria, group B strep, E.coli
Children - haemophilus influenzae
10-21 - neisseria meningitidis
Over 21 - strep pneumoniae > neisseria meningitidis
Over 65 - strep pneumoniae > listeria
How is bacterial meningitis treated if the organism has not been identified?
10 days treatment with:
Ceftriaxone IV 2g BD +
Dexamethasone IV 10mg QDS
If listeria add amoxicillin IV 2g 4 hourly (co-trimoxazole if penicillin allergic)
If recent travel to country with high rates of penicillin resistant pneumococci then add vancomycin or rifampicin
How is meningococcal bacterial meningitis treated?
5 days of ceftriaxone (chloramphenicol if allergic) IV 2g BD + stop dexamethasone
How is pneumuococcal bacterial meningitis treated?
10 days ceftriaxone (IV 2g BD) + 4 days dexamethasone (IV 10mg QDS)
How is penicillin/cephalosporin resistant pneumococcal bacterial meningitis treated?
14 days ceftriaxone + vancomycin + 4 days dexamethasone
How is listeria bacterial meningitis treated?
21 days amoxicillin + stop dexamethasone
How is haemophilus influenzae bacterial meningitis treated?
10 days of ceftriaxone + stop dexa
When is viral meningitis prevalent and what usually causes it?
Late summer and autumn
Enteroviruses e.g. ECHO viruses
How is viral meningitis diagnosed and treated?
Viral stool culture, throat swab and CSF PCR
Treatment is generally supportive as it is self-limiting
What questions would you consider asking in a patient with suspected encephalitis?
Current or recent febrile or flu-like illness, altered behaviour or cognition, altered consciousness, new onset seizures, focal neurological symptoms, rash, others in the family, travel history, recent vaccination, contact with animals, contact with fresh water, exposure to tick or mosquito bites, immunocompromised, HIV?
What are the clinical features of encephalitis?
Insidious onset, sometimes sudden Meningismus Stupor, coma Seizures, partial paralysis Confusion, psychosis Speech, memory symptoms
How is encephalitis investigated?
LP, EEG + MRI
If delay start pre-emptive acyclovir as prompt therapy improves outcomes
What should be suspected in a patient with fever and a non-blanching rash?
Septicaemia - medical emergency
What are some of the common signs and symptoms of meningitis and septicaemia?
Fever, cold hands and feet Stiff neck Altered consciousness Vomiting Drowsiness, difficult to wake Severe muscle pain Confusion and irritability Pale, blotchy skin, rash Severe headache Photophobia Convulsions/seizures
What are some risk factors for bacterial meningitis?
Decreased cell mediated immunity - listeria monocytogenes, strep pneumoniae, neisseria meningitidis
Neurosurgery/head trauma - staphylococcus, staph epidermidis, aerobic GNR
Fracture of the cribriform plate - strep pneumoniae, H.influenzae, GABHS
What are some complications of meningitis?
Purulence - clusters at the base of the brain. Exudate around CN III, VI
Invasion - pia mater prevents meningitis becoming abscess. Abscesses can cause secondary ventriculitis and hence meningitis
Cerebral oedema
Ventriculitis/hydrocephalus
Describe the pathogenesis of bacterial meningitis
- Nasopharyngeal colonisation
- Direct extension of bacteria - parameningeal foci (sinusitis, mastoiditis or brain abscess), across skull defects/fracture
- From remote foci of infection e.g. pneumonia, UTI
What causes meningococcal meningitis and how does it occur?
Neisseria meningitidis is the cause - found in the throat of healthy carriers
Bacteria probably gain access to the meninges via the bloodstream
Bacteria may be found in leukocytes in CSF
Symptoms are due to endotoxins
Disease occurs most often in young kids
What does H.influenzae require for growth and in which age group is it most common?
H.influenzae require blood factors for growth
Type B is the most common cause of meningitis in children under 4 y/o
A conjugated vaccine directed against the capsular polysaccharide antigen is available
Where is strep pneumoniae commonly found and who are most susceptible to it?
Commonly found in the nasopharynx
Hospitalised patients, patients with CSF skull fractures, diabetics/alcoholics and young children are most susceptible to S.pneumoniae meningitis
There is a conjugate vaccine for this that provides protection in kids
