NS Infection - Meningitis/Encephalitis

Question 1

Causes of Meningitis?

Answer 1

• Infective
• Inflammatory e.g. Sarcoid
• Drugs Induced e.g. NSAIDs & IVIG
• Malignant (Metastatic or Leukemia)

Question 2

Investigations for meningitis

Answer 2

• Blood Cultures & Gram Stain
• LP (CSF culture & Microscopy)
• Only image if LP is contraindicated

Question 3

Investigations for encephalitits?

Answer 3

• Blood Culture
• CT/MRI
• LP (PCR of the CSF for viral DNA)
• EEG

Question 4

When would an LP be contraindicated?

Answer 4

You don’t do it if there’s sign of a mass or swelling as the pressure could cause herniation when you repressurise by puncturing it.

• Focal Neuro deficits
• New Seizures
• Papilloedema
• GCS<10
• Severe Immunocompromisation

Question 5

What would you find on an LP in meningititis?

Answer 5

Bacterial:

• raised pressure
• Raised cell count (Mainly Neutrophils)
• Low Glucose (Bacteria consume it)
• Very High Protein

Viral:

• Normal/raised pressure
• Raised Cell Count (Mainly Lymphocytes)
• Normal glucose (~60% of blood glucose)
• Slightly raised protein

Question 6

Causes of Encephalitis?

Answer 6

• Infective (HSV is main cause of encephalitis, Enterovirus etc)
• Inflammatory (i.e. autoimmune)
• Metabolic (Hepatic, uraemic, hyperglycaemic)
• Malignant, either a metastases or a paraneoplastic syndrome
• Post Ictal (After Seizure)

Question 7

What microorganisms cause infective meningitis?

Answer 7

Neisseria Meningitidis (Meningococcus)
Streptococcus Pneumoniae (Pneumococcus)

Enteroviruses

Question 8

How do we treat viral encephalitis?

Answer 8

Aciclovir based on clinical suspicion of Viral encephalitis.

Question 9

How does HSV cause encephalitis?

Answer 9

It goes latent, in your trigeminal or sacral ganglion

It reactivates later and encephalitis is a rare complication, which mostly results from Type 1 HSV

Question 10

Name some enteroviruses and how you spread/test for them in encephalitis?

Answer 10

Polioviruses, coxsackie virus, echovirus

Faecal-oral spread

Do PCR of a stool sample if you suspect

Question 11

Other than HSV and Enteroviruses what else causes infectious encephalitis?

Answer 11

Arbovirus Encephalitides

Common in other parts of the world they are vector-transmitted (tick or mosquito) so a travel history is important

E.g. West Nile Virus (Location name viruses dont relate to current geographical distribution)

Question 12

How does Meningitis Present?

Answer 12

Classic Triad of Fever, neck stiffness and altered mental status
Also:
- Short history of headache
- Meningism (Stiff neck, photophobia, N&V)

Cerebral dysfunction e.g. confusion is common and many have a lowered GCS

Cranial Nerve Palsies, Seizures and focal neuro deficits can occur

Question 13

What presentation of meningitis is specific to which cause?

Answer 13

Petechial Skin Rash

A hallmark of meningococcal meningitis (But can occur in viral)

Question 14

How does Encephalitis Present?

Answer 14

Flu-like Prodrome for 4-10 days

• Progressive Headache with Fever
• ~Meningism
• Progressive cerebal dysfunction (Seen as confusion, memory issues, behaviour etc)
• Seizures
• Focal Signs

Question 15

How is viral encephalitis different from bacterial meningitis?

Answer 15

It has a slower onset and more prominent cerebral dysfunction…generally

Question 16

Describe the types of auto-immune encephalitis?

Answer 16

Anti-VGKC (Voltage Gated K Channel) antibodies:

• Seizures, Amnesia & Altered mental state
• Usually in temporal lobe

Anti-NMDA receptor antibodies:

• Flu like prodrome
• Prominent Psych features
• Altered Mental state & Seizures
• Progresses to a movement disorder then coma
• Looks more like viral encephalitis