Infections of the nervous system Flashcards
What is meningitis?
Inflammation of the meninges.
What are the symptoms and signs of meningitis?
Symptoms:
- photophobia
- N/V
Signs –> classical triad:
- fever
- neck stiffness
- altered mental status
(Also petechial skin rash - hallmark of meningococcal meningitis)
What are the main organisms that cause meningitis?
Bacterial:
- Neisseria meningitidis (meningococcus)
- Strep pneumoniae (pneumococcus)
Viral:
- enterovirus
Which investigations would you do for suspected meningitis?
- blood cultures looking for bacteraemia
- lumbar puncture: culture CSF and do microscopy looking for bacteria
Don’t need to use imaging unless there are CI’s to LP.
What are CI’s to LP?
- presence of focal signs/symptoms suggest a focal brain mass
- reduced consciousness level suggests a raised ICP
–> in both cases, CT before LP
How can meningococcal meningitis be treated?
IV ceftriaxone.
What is encephalitis?
Inflammation of the brain.
What are the signs and symptoms of encephalitis?
Signs:
- fever
- meningism
- progressive cerebral dysfunction
- focal signs
Symptoms:
- flu-like prodrome
- progressive headache
What is the most common type of encephalitis in Europe?
HSV encephalitis - mostly type 1 HSV, but in neonates type 2.
How is HSV encephalitis diagnosed?
Lab diagnosis by PCR of CSF for viral DNA.
How is HSV encephalitis treated?
Aciclovir - over 70% mortality and high morbidity if untreated.
Where does HSV remain latent?
Trigeminal or sacral ganglion after primary infection.
Which family viruses can cause non-paralytic meningitis?
Enteroviruses: faecal-oral soread. Includes polioviruses.
Which organisms are the main cause of encephalitis in other parts of the world?
Arboviruses - mosquito or tick-borne. Importance of travel history.
What is a brain abscess?
Localised area of pus within the brain.
What is a subdural empyema?
A thin layer of pus between the dura and arachnoid membranes over the surface of the brain.
What are the symptoms and signs of brain abscess/empyema?
Symptoms:
- headache that is worse in the morning
- coughing
- sleeping
Signs:
- raised ICP (papilloedema, depressed conscious level)
- fever
- meningism
What causes a brain abscess/empyema?
- penetrating head injury
- spread from adjacent infection (dental, otitis media)
- blood-borne infection eg bacterial endocarditis
How are brain abscess/empyema investigated?
- Imaging: CT/MRI
- Blood cultures
- Drainage of pus
Which organisms cause brain abscess?
Streptococci in 70% of cases, especially the Strep milleri group (Strep anginosis, Strep intermedius and Strep constellatus). Usually anaerobic organisms - bacteriodes, Prevotella etc.
How are brain abscesses managed?
- Surgical drainage if possible
- Penicillin/ceftriaxone for Strep
- Metronidazole for anaerobes
–> need high doses to penetrate the BBB
Which illnesses indicate HIV?
- cerebral toxoplasmosis
- aseptic meningitis/encephalitis
- primary cerebral lymphoma
- cerebral abscess
- Cryptococcal meningitis
HIV encephalopathy –> HIV-associated dementia
How is HIV diagnosed?
HIV PCR. Can also do CMV PCR, JC virus PCR, toxo serology (IgG) etc.
Describe Cryptococcal meningitis.
Mostly caused by C.neoformans. Most clinical cases present with meningoencephalitis - common in people with AIDS or on high doses of immunosuppression.
