Neurology: Encephalitis and Meningitis

Question 1

How is encephalitis definitively diagnosed?

Answer 1

Histology - inflammation of brian parenchyma

Question 2

Which age groups are most susceptible to encephalitis?

Answer 2

< 1 year and > 65 years

Question 3

What is the key feature in encephalitis?

Answer 3

Altered mental status (less prominent in meningitis)

Question 4

What features are suggestive of encephalitis?

Answer 4

1) Altered mental status e.g. confusion, disorientation, agitation
2) Fever
3) Flu-like prodromal illness
4) Early seizures

Question 5

What is the most common cause of encephalitis?

Answer 5

Herpes simplex virus type 1 (HSV1)

Question 6

What are other causes of encephalitis?

Answer 6

1) HSV2
2) CMV
3) EBV
4) VZV
5) HIV
6) Arboviruses incl. west nile virus

Question 7

Is encephalitis usually bacterial or viral?

Answer 7

Viral (can also be autoimmune)

Question 8

Which (meningitis) pathogens can sometimes progress to cause a meningoencephalitis?

Answer 8

1) Bacterial e.g. Strep pneumoniae, Neisseria meningitidis
2) Lyme disease
3) Mycoplasma
4) Severe falciparum malaria (rare)

Question 9

Which antibody is most likely to cause autoimmune encephalitis?

Answer 9

NMDA receptor antibody

Question 10

Which patients are said to be encephalopathic?

Answer 10

Patients with generalised disease of the brain not attributable to inflammation

Question 11

What are causes of encephalopathy?

Answer 11

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

Question 12

Patients with any of which presenting symptoms should be suspected of encephalitis?

Answer 12

1) Sudden onset behavioural change
2) New seizures
3) Unexplained acute headache with meningism

Question 13

What investigations should be done for work up of encephalitis?

Answer 13

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

Question 14

What might you see on CNS imaging in HSV encephalitis?

Answer 14

HSV has a predilection for the temporal lobes and bilateral multifocal haemorrhage is typical

Question 15

How do you treat suspected encephalitis?

Answer 15

Empirical - broad spectrum antimicrobial cover with:
1) 2g IV ceftriaxone
2) 10 mg/kg aciclovir TDS for two weeks

Question 16

What supportive management of complications in encephalitis is important?

Answer 16

Prompt termination of seizure activity with anticonvulsants e.g. phenytoin

Question 17

What are side effects of aciclovir?

Answer 17

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

Question 18

How does acute bacterial meningitis present?

Answer 18

1) Raised ICP
2) Acute onset
3) Fever
4) Meningism

Question 19

What investigation is done to rule out meningitis?

Answer 19

Lumbar puncture

Question 20

What investigation must be normal to carry out a lumbar puncture?

Answer 20

CT head

Question 21

What is the classic triad of symptoms that raises suspicion of meningitis until proven otherwise?

Answer 21

Fever + headache + neck stiffness

Question 22

What are risk factors for meningitis?

Answer 22

1) Young age
2) Immunosuppression

Question 23

What signs are commonly elicited examination findings in meningitis?

Answer 23

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)

Question 24

What is the gold-standard investigation to diagnose meningitis?

Answer 24

Lumbar puncture + CSF analysis and culture

Question 25

How should meningitis be treated?

Answer 25

1) All cases of suspected meningitis should be treated as bacterial until proven otherwise
2) Empirical IV abx is initiated immediately while awaiting LP findings

Question 26

How can meningitis present?

Answer 26

1) High grade fever
2) Severe headache
3) Neck stiffness
4) Non-blanching purpuric rash
5) Photophobia
6) Confusion
7) N&V
8) Focal neurology
9) Seizures
10) Reduce GCS

Question 27

What are bacterial causes of meningitis?

Answer 27

1) Strep pneumoniae
2) Neisseria meningitides
3) Haemophilus influenzae b
4) Listeria monocytogenes (patients at extremes of age)
5) Mycobacterium - TB

Question 28

What type of bacteria is Neisseria meningitides?

Answer 28

Gram negative diplococcus

Question 29

What are viral causes of meningitis?

Answer 29

1) Enteroviruses - echoviruses, coxsackie viruses A&B, poliovirus
2) HSV1 or HSV2
3) Paramyxovirus
4) Measles
5) Rubella
6) VZV
7) Arboviruses

Question 30

What is a fungal cause of meningitis?

Answer 30

Cryptococcus neoformans

Question 31

What causes of meningitis would you consider in an immunocompromised patient?

Answer 31

1) Cryptococcus neoformans
2) Mycobacterium TB

Question 32

What are parasitic causes of meningitis?

Answer 32

1) Acanthamoeba
2) Toxoplasma gondii

Question 33

What is a complication of meningitis?

Answer 33

Overwhelming sepsis - non-blanching petechial rash of impending DIC

Question 34

Which bloods do you do in suspected meningitis?

Answer 34

1) FBC
2) U&E
3) LFTs
4) ABG - includes lactate and glucose

Question 35

What investigations do you do in suspected meningitis?

Answer 35

1) Blood tests
2) Blood cultures
3) CT head
4) LP

Question 36

How do you treat suspected bacterial meningitis (meningitis is bacterial until proven otherwise) in hospital?

Answer 36

Empirical abx
1) IV ceftriaxone 2g BD
2) ± IV amoxicillin in young (< 3 months or old > 50 years to cover Listeria) - cefotaxime or chloramphenicol in penicillin allergy

Question 37

How do you treat suspected bacterial meningitis in the community or while awaiting hospital transfer?

Answer 37

IM benzylpenicillin sodium

Question 38

How do you treat viral meningitis?

Answer 38

IV aciclovir

Question 39

What are the lumbar puncture findings in bacterial meningitis?

Answer 39

1) Turbid appearance
2) Elevated opening pressure
3) Elevated WBC > 1000-2000
4) Elevated protein > 200
5) Low glucose < 40

Question 40

What are the lumbar puncture findings in viral meningitis?

Answer 40

1) Clear appearance
2) Normal opening pressure
3) WBC < 300 - lymphocytic predominance
4) Protein < 200
5) Normal glucose

Question 41

What are the lumbar puncture findings in fungal meningitis?

Answer 41

1) Clear appearance
2) Normal or elevated opening pressure
3) WBC < 500
4) Elevated protein > 200
5) Normal or low glucose