Neurology: Encephalitis and Meningitis Flashcards
How is encephalitis definitively diagnosed?
Histology - inflammation of brian parenchyma
Which age groups are most susceptible to encephalitis?
< 1 year and > 65 years
What is the key feature in encephalitis?
Altered mental status (less prominent in meningitis)
What features are suggestive of encephalitis?
1) Altered mental status e.g. confusion, disorientation, agitation
2) Fever
3) Flu-like prodromal illness
4) Early seizures
What is the most common cause of encephalitis?
Herpes simplex virus type 1 (HSV1)
What are other causes of encephalitis?
1) HSV2
2) CMV
3) EBV
4) VZV
5) HIV
6) Arboviruses incl. west nile virus
Is encephalitis usually bacterial or viral?
Viral (can also be autoimmune)
Which (meningitis) pathogens can sometimes progress to cause a meningoencephalitis?
1) Bacterial e.g. Strep pneumoniae, Neisseria meningitidis
2) Lyme disease
3) Mycoplasma
4) Severe falciparum malaria (rare)
Which antibody is most likely to cause autoimmune encephalitis?
NMDA receptor antibody
Which patients are said to be encephalopathic?
Patients with generalised disease of the brain not attributable to inflammation
What are causes of encephalopathy?
1) Encephalitis
2) Hypoglycaemia
3) Hepatic encephalopathy
4) DKA
5) Drug-induced encephalopathy
6) Uraemic encephalopathy
7) SLE
8) Hypoxic encephalopathy
9) Beri-Beri
- Each subtype may have suggestive clinical features and associations which may aid diagnosis
Patients with any of which presenting symptoms should be suspected of encephalitis?
1) Sudden onset behavioural change
2) New seizures
3) Unexplained acute headache with meningism
What investigations should be done for work up of encephalitis?
1) Routine panel of blood tests
2) Blood cultures
3) Viral PCR - including CSF sample
4) Malaria blood films if exposure is suspected
5) CNS imaging may be helpful
What might you see on CNS imaging in HSV encephalitis?
HSV has a predilection for the temporal lobes and bilateral multifocal haemorrhage is typical
How do you treat suspected encephalitis?
Empirical - broad spectrum antimicrobial cover with:
1) 2g IV ceftriaxone
2) 10 mg/kg aciclovir TDS for two weeks
What supportive management of complications in encephalitis is important?
Prompt termination of seizure activity with anticonvulsants e.g. phenytoin
What are side effects of aciclovir?
Common:
1) Generalised fatigue/malaise
2) GI disturbance
3) Photosensitivity and urticarial rash
Less common:
4) Acute renal failure
5) Haematological abnormalities
6) Hepatitis
7) Neurological reactions
How does acute bacterial meningitis present?
1) Raised ICP
2) Acute onset
3) Fever
4) Meningism
What investigation is done to rule out meningitis?
Lumbar puncture
What investigation must be normal to carry out a lumbar puncture?
CT head
What is the classic triad of symptoms that raises suspicion of meningitis until proven otherwise?
Fever + headache + neck stiffness
What are risk factors for meningitis?
1) Young age
2) Immunosuppression
What signs are commonly elicited examination findings in meningitis?
1) Kernig’s sign - pain on passive extension of the knee when hips are flexed to 90 degrees in supine position
2) Brudzinski’s sign - reflex flexion of the hip and knee when the neck is passively flexed in the supine position (bend forwards)
What is the gold-standard investigation to diagnose meningitis?
Lumbar puncture + CSF analysis and culture
