CNS Infection Flashcards
What is acute encephalitis?
Infection of brain parenchyma
What are the classifications of CNS infection?
Acute pyogenic (bacterial) meningitis
Acute aseptic (viral) meningitis
Acute focal suppurative infection (abscess, empyema)
Chronically bacterial infection (tuberculosis)
Describe the morphology of pyogenic meningitis?
Thick layer of suppurative exudate covering leptomeninges
Exudate in basal and convex surface
Neutrophils in subarachnoid space
What are the features of viral meningitis?
Common
Late summer/autumn
Enteroviruses e.g. ECHO virus
Diagnosis- viral stool culture, throat swab and CSF PCR
Treatment is supportive as is self limiting
What are the causes of viral encephalitis?
Causes: herpes simplex (aciclovir), varicella zoster (aciclovir), CMV, HIV, measles, rabies, west Nile, tick borne,
What are the clinical features of encephalitis?
Insidious onset (sometimes sudden) Meningismus Stupor, coma Seizures, partial paralysis Confusion, psychosis Speech, memory symptoms
What investigations should be done for encephalitis?
LP, EEG, MRI
What are the MRI features of encephalitis?
Inflamed portion of the temporal lobe, involving the uncus and adjacent parahippocampal gyrus in the brightest white on MR.
What are the common causes of bacterial meningitis in Neonates?
Listeria, group b strep, E. coli
What is the commonest cause of bacterial meningitis in children?
H. Influenza
What is the commonest cause of bacterial meningitis in 10-21 yr olds?
Meningococcal
What is the commonest cause of bacterial meningitis in adults?
Pneumococcus
What is the commonest cause of bacterial meningitis in elderly?
Pneumococcus
Name some of the sequelae of meningitis.
Limb loss, blindness, cerebral palsy, quadriplegia, mental impairment
Describe the pathogenesis of bacterial meningitis
Nasopharyngeal colonisation
Direct extension of bacteria
Remote foci of infection
Name the agents of meningitis in immunocompromised patients
Conventional agents Listeria monocytogenes Mycobacterium tb Nocardia asteroides Crytococcus neoformans
What is the antibiotic of choice for listeria monocytogenes meningitis
IV ampicillin/ amoxicillin
What is the treatment of choice for tuberculous meningitis
Isoniazid and rifampicin (with pyrazinamide and ethambutol)
What is the treatment for cryptococcal meningitis
IV amphotericin, b/flucytosine, fluconazole
What are the clinical signs of bacterial meningitis?
Fever, stiff neck, alteration of consciousness
What are the signs and symptoms of bacterial meningitis?
Headache Vomiting Pyrexia Neck stiffness Photophobia Lethargy Confusion Rash
What are the CSF features of viral meningitis?
Lymphocytes
Negative gram stain
Normal or slightly high protein
Normal glucose
What are the CSF findings in bacterial meningitis?
Polymorphs
Positive gram stain
High protein
Low glucose
What is the empirical treatment in suspected bacterial meningitis?
IV ceftriaxone
(+IV ampicillin/amoxicillin if listeria suspected)
Steroids before or with first dose of antibiotics
