NS Infection - Encephalitis

Question 1

Causes of Encephalitis? [5]

Answer 1

• 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 2

How do we treat viral encephalitis?

Answer 2

Aciclovir based on clinical suspicion of Viral encephalitis.

Question 3

How does HSV cause encephalitis?

NB encephalitis is a rare complication, which mostly results from Type 1 HSV

Answer 3

It goes latent, in your trigeminal or sacral ganglion

It reactivates later

Question 4

How does Encephalitis Present? [6]

Answer 4

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
• Peripheral lesions eg cold sores (but no relation if HSV present)

Question 5

How is viral encephalitis different from bacterial meningitis in presentation?

Answer 5

It has a slower onset and more prominent cerebral dysfunction in viral encephalitis
Bacterial meningitis is a medical emergency

Question 6

Describe the types of auto-immune encephalitis? State 3 features of each respective disorder.

Answer 6

Anti-VGKC (Voltage Gated K Channel) antibodies:
- Seizures, Amnesia & Altered mental state

Anti-NMDA receptor antibodies:

• Flu like prodrome with prominent Psych features
• Altered Mental state, Seizures
• Progresses to a movement disorder then coma

Question 7

What are infective causes of encephalitis:
Viral [8]
Bacterial [6]
Fungal [1]
Parasitic [2]

Answer 7

• Viral: herpes simplex virus (HSV-1), CMV, adenovirus, influenza, polio, rubella, rabies, VZV
• Bacterial: TB, mycoplasma, listeria, Lyme, neurosyphillis, any cause of bacterial meningitis
• Fungal: Cryptococcus
• Parasitic: African trypanosomiasis, toxoplasmosis

Question 8

Investigations

Answer 8

Bloods
LP
CT head
MRI
EEG

Question 9

What blood investigations to do? [5]

Answer 9

• PCR for HSV
• FBC and film
• LFT
• glucose
• ESR, CRP

Question 10

What would you see on an LP? [3]

Answer 10

• lymphocytosis
• normal or high protein
• PCR for HSV, VZV and enteroviruses

Question 11

What would you see on:

• CT head [2]
• MRI [2]
• EEG [1]

Answer 11

• CT head: medial temporal and inferior frontal changes e.g. petechial haemorrhages, excl. SOL
• MRI: demyelination and oedema
• EEG: lateralised periodic discharges at 2Hz

Question 12

Complications [5]

Answer 12

SIADH, DIC, cardiac and respiratory arrest, epilepsy, neuropsychiatric impairment

Question 13

Cerebral abscess
Onset
Symptoms [5]
Signs [3]

Answer 13

Onset: sudden or subacute

• Fever, headache
• Altered mental state
• Focal neuro deficit
• Gen tonic-clonic seizures
• N+V, neck stiffness

Signs:

• fever
• focal motor or sensory deficits, ataxis
• elevated ICP

Question 14

Ruptured abscess signs [2]

Answer 14

Ruptured abscess:

- Suddenly worsening headache then emerging signs of meningism

Question 15

Cerebral abscess investigations:
Blood results [3]
2 other investigations

Answer 15

Bloods:

• FBC (leucocytosis)
• ESR, CRP, cultures (at least 2 before abx started)
• U&E and creatinine (hyponatraemia due to SIADH)
• CT head with contrast
• Abscess aspiration for culture or biopsy

Question 16

What would you see on CT of a cerebral abscess? [2]

Answer 16

• distinctive ring enhancement as abscess wall thickens

- surrounded by oedema

Question 17

Management [2]

Answer 17

• Drainage or excision: burr hole craniotomy

- Empirical antibiotics

Question 18

Antimicrobial therapy
Duration
Bacterial [3]
Fungal [2]
Toxoplasmosis [2]

Answer 18

Antimicrobials for 4w with IV for at least 1st week
o Bacterial: CEFTRIAXONE, METRONIDAZOLE and VANCOMYCIN
o Fungal: AMPHOTERICIN or FLUCONAZOLE
o Toxoplasmosis: PYRIMETHAMINE and SULFADIAZINE