CNS Infections Flashcards
What are some clinical consequences of untreated infections of the CNS?
Brain herniation and death Cord compression and necrosis with subsequent permanent paralysis
List infections of the CNS
Encephalitis Meningitis Meningoencephalitis Encephalomyelitis Epidural abscess Neuritis Sepsis syndrome due to infection elsewhere
Name different classifications of meningitis
Acute pyogenic (bacterial) meningitis Acute aseptic (viral) meningitis Acute focal suppurative infection (brain abscess, subdural and extradural empyema) Chronic bacterial infection (tuberculosis) Acute encephalitis
What is acute encephalitis?
An infection of the brain parenchyma
What does the brain look like when infected by pyogenic meningitis?
Thick layer of suppurative exudate covering the leptomeninges
What is seen microscopically in pyogenic meningitis?
Neutrophils in the subarachnoid space
What pathogens cause bacterial meningitis?
Pneumococcus Meningococcus Haemophilus influenza
What other pathogen can cause bacterial meningitis in patients >60 or immunocompromised?
Listeria spp
What antibiotics are used to treat bacterial meningitis?
Ceftriazone IV + Dexamethasone IV If P allergy: chloramphenicol IV
What antibiotic can be added to cover listeria infection?
Amoxicillin IV P allergy: co-trimoxazole
Why does H. influenza rarely cause meningitis?
Vaccination
Which bacteria is diplococcus, gram positive and stains purple?
Strep pneumonia
Which bacteria is gram-negative (stains pink) and is intracellular?
Neisseria meningitidis
Which bacteria is gram positive, bacillus (rod-shaped) and occurs in over 60s and alcoholics?
Listeria monocytogenes
Which bacteria is gram negative and bacillus?
H. influenzae
Which pathogen causes viral meningitis?
Enteroviruses e.g. ECHO virus
How is viral meningitis diagnosed?
Viral stool culture Throat swab CSF PCR
What is the treatment for viral meningitis?
Supportive Self-limiting
What questions should you ask when taking a history from a patient with suspected encephalitis?
Current or recent febrile, flu-like illness? Altered behaviour, personality change or altered consciousness? New onset seizures? Focal neurological symptoms? Rash? Family/neighbours affected? Travel history? Recent vaccinations? Animals (rabies)? Fresh water (leptospirosis)? Mosquito/tick bites? Immunocompromised? HIV?
What are the clinical features of encephalitis?
Insidious onset Stiffness in head/neck Stupor, coma Seizures, partial paralysis Confusion, psychosis Speech, memory symptoms
Which disease is coma more likely to present in, encephalitis or meningitis?
Encephalitis
What are the investigations for encephalitis?
Lumbar puncture EEG MRI
Should acyclovir be given pre-emptively if there is a delay in treating encephalitis?
Yes- prompt therapy improves outcomes
What are the common signs and symptoms of meningitis?
Fever, cold hands + feet Drowsy Severe muscle pain Severe headache Dislike bright lights Vomiting Confusion + irritability Pale, blotchy skin Spots/rash Stiff neck Convulsions/seizures
Which bacteria commonly infects neonates with community acquired bacterial meningitis?
Listeria Group B Streptococci E.coli
Which bacteria commonly infects children with community acquired bacterial meningitis?
H. influenza
Which bacteria commonly infects children aged 10-21yrs with community acquired bacterial meningitis?
Neisseria menigitidis
Which bacteria commonly infects >21yrs with community acquired bacterial meningitis?
Streptococcus pneumonias > Neisseria meningitidis
Which bacteria commonly infects >65yrs with community acquired bacterial meningitis?
Streptococcus pneumonia > Listeria
Which bacteria commonly infects patients with decreased cell mediated immunity with community acquired bacterial meningitis?
Listeria monocytogenes
Which bacteria commonly infects neurosurgery/head trauma patients with community acquired bacterial meningitis?
Staph aureus Staph epidermis Aerobic GNR
Which bacteria commonly infects fracture of cribriform patients with community acquired bacterial meningitis?
Streptococcus pneumoniae
Which bacteria commonly infects CSF shunt patients with community acquired bacterial meningitis?
Staph epidermidis Staph aureus Aerobic GNR Propionibacterium acnes
What percentage of those who survive meningitis with have life-altering after effects. Give examples
25% Limb loss Blindness Deadness Cerebral palsy Quadriplegia Severe mental impairement
What is the pathogenesis of bacterial meningitis?
Nasopharyngeal colonisation Direct extension of bacteria- parameningeal foci (sinusitis, mastoiditis or brain abscess) or across skull defects/fractures From remote foci of infection (endocarditis, pneumonia, UTI)
Which bacteria causes meningococcal meningitis?
Neisseria meningitidis Found in throats of healthy carriers
What indicates the presence of n. meningitidis in CSF?
Bacteria found in leukocytes
Which type of H. influenza meningitis is most common in children under 4?
Type B
How does the vaccine for H. influenza work?
Conjugated vaccine directed against capsular polysaccharide antigen
Which groups of people are most susceptible to s. pneumoniae meningitis?
Hospitalised patients Patients with CSF skull fractures Diabetics Alcoholics Young children
Which vaccine is given to children to protect against pneumococcal meningitis?
Pneumococcal pneumonia vaccine
What is a gram positive bacilli (+blood cultures)?
Listeria monocytogenes
What is the antibiotic of choice for listeria monocytogenes?
IV ampicillin/amoxicillin Ceftriaxone has no value
Who is affected most by TB meningitis?
Reactivation Elderly
How is TB meningitis treated?
Isoniazid + rifampicin (add pyrazinamide + ethambutol)
What are features of cryptococcal meningitis?
Fungal Mainly in HIV disease CD4 <100 Disseminated infection
What is found on investigation of a patient with cryptococcal meningitis?
Subtle neurological presentation Aseptic on CSF Serum and CSF cryptococcal antigen
Which antibiotics should be given for cryptococcal meningitis?
IV amphotericin B/ Flucytosine Fluconazole
What should be measured when taking a CSF sample?
Opening pressure Microscopy, culture +sensitivity Meningococcal and pneumococcal PCR Protein Glucose Lactate
What further tests should be performed in suspected meningitis?
Bacterial- PCR on CSF Viral- PCR on CSF for: HSV1/2, VSZ, enterovirus Stool Throat swab
What is the algorithm for meningitis?
