Encephalitis (N)

Question 1

Define encephalitis.

Answer 1

Inflammation of the brain parenchyma associated with neurological dysfunction, such as altered state of consciousness, seizures, personality changes, cranial nerve palsies, speech problems, and motor and sensory deficits

Question 2

What are the causes of encephalitis? (4)

Answer 2

• most commonly viral infection (HSV-1 most common)
• non-viral infections: bacterial, fungal, parasitic (syphilis, S. aureus)
• also in immunocompromised patients (CMV, toxoplasmosis, Listeria)
• also in those with autoimmune/paraneoplastic syndromes (associated with certain antibodies: anti-NMDA, anti-VGKC)

Question 3

What is the most common cause of viral encephalitis?

Answer 3

HSV-1

Question 4

What are some other causes of viral encephalitis? (8)

Answer 4

• HSV-1
• VZV
• mumps
• adenovirus
• Coxsackie
• EBV
• HIV
• Japanese encephalitis

Question 5

What demographics is encephalitis most common in?

Answer 5

Bimodal distribution:

• age <1y
• age >65y

Question 6

Describe the onset and severity of encephalitis.

Answer 6

• subacute onset (hours to days)
• self-limiting and mild (in most cases)

Question 7

What are the clinical features of encephalitis? (8)

Answer 7

• initial flu-like symptoms with pyrexia and headache that persist
• altered mental state
• fever + malaise
• rash
• headache
• focal neurological deficits - depending on which area of brain is inflamed
• seizures
• meningismus - headache, photophobia, neck stiffness

Question 8

What are some focal neurological deficits you might see in encephalitis? (4)

Answer 8

• changes in personality or behaviour
• difficulty speaking, dysphagia
• weakness or loss of movement / hemiplegia
• loss of consciousness

Question 9

What are some signs of meningism you might find in encephalitis? (3)

Answer 9

• headache
• photophobia
• neck stiffness

Question 10

What might you see on examination in encephalitis? (9)

Answer 10

• altered mental state + reduced consciousness
• bizarre encephalopathic behaviour
• deteriorating GCS
• acute flaccid paralysis
• seizures
• pyrexia
• meningism - headache, photophobia, neck stiffness, Kernig’s test +ve
• signs of raised ICP (Cushing’s triad, papilloedema)
• focal neurological signs

Question 11

What might MMSE reveal in encephalitis?

Answer 11

Cognitive/psychiatric disturbance

Question 12

What issue may arise secondary to encephalitis, and what are the features of this?

Answer 12

Raised ICP:

• Cushing’s triad:
  
  • widened pulse pressure (hypertension)
  • bradycardia
  • irregular breathing
• papilloedema

Question 13

What key clinical features distinguish encephalitis from meningitis? (2)

Answer 13

• altered mental state (and personality change)
• seizures

Question 14

What do we need to remember to ask about in encephalitis?

Answer 14

Travel history

Question 15

What are some risk factors for encephalitis? (9)

Answer 15

• age <1 or >65
• immunosuppression
• post-infection / viral infection
• bodily fluid exposure
• organ transplantation
• animal/insect bites
• travel
• season
• nasal/sinus irrigation

Question 16

What are the first-line investigations for encephalitis? (5)

Answer 16

• lumbar puncture for CSF analysis
• FBC
• peripheral blood smear - detection of Plasmodium falciparum and Ehrlichia
• serum electrolytes - SIADH (hyponatraemia)
• LFTs - elevated

Question 17

What does FBC show in encephalitis? (3)

Answer 17

• high lymphocytes - viral
• neutrophilia - bacterial
• eosinophilia - parasitic

Question 18

What is the main investigation that we do in encephalitis and what would it show?

Answer 18

CSF analysis via lumbar puncture:

• high lymphocytes
• high protein
• normal glucose

Question 19

What cell types would predominate in viral vs bacterial encephalitis in CSF analysis?

Answer 19

• virus - lymphocytes
• bacteria - neutrophils

Question 20

What do we need to do before lumbar puncture in encephalitis?

Answer 20

Do CT before to exclude significantly raised ICP

Question 21

What investigation will confirm the presence of HSV in encephalitis?

Answer 21

CSF - viral PCR (95% specific for HSV-1)

Question 22

What other investigations are there for encephalitis? (4)

Answer 22

• bloods - hyponatraemia, raised WCC, elevated LFTs
• blood culture - to detect bacterial infections
• throat swab - to detect viruses
• MRI/CT brain - exclude any mass lesions

Question 23

What might MRI/CT head show in encephalitis? (2)

Answer 23

• MRI will show swelling and increased brains signals
• CT head may also show temporal lobe changes of HSV

Question 24

What might EEG show in encephalitis?

Answer 24

Often shows background slowing

Question 25

What are some differential diagnoses for encephalitis? (7)

Answer 25

- aseptic meningitis - no altered mental status or neurological signs - encephalopathy (toxic/metabolic) - normal CSF and MRI, EEG shows diffuse slowing and triphasic waves - status epilepticus - CNS vasculitis - pseudomigraine with pleocytosis - malignant hypertension - intracranial tumours and cysts

Question 26

What is the first-line treatment for viral encephalitis (HSV or other virus)?

Answer 26

- **IV acyclovir** - supportive care (admit, ICU, corticosteroids for elevated ICP, elevate head, hyperventilation, hyperosmolar therapy)

Question 27

What is the first-line treatment for non-viral encephalitis?

Answer 27

- treatment of underlying cause e.g. Abx for bacteria - syphilis = benzylpenicillin - Listeria = ampicillin + gentamicin - Mycoplasma pneumoniae = doxycycline - supportive care

Question 28

What do we give along acyclovir if viral encephalitis and immunocompromised?

Answer 28

IV acyclovir + foscarnet + ganciclovir

Question 29

What are some complications of encephalitis? (7)

Answer 29

- death - seizures - hypothalamic and autonomic dysfunction (diabetes insipidus, SIADH) - ischaemic stroke - encephalitis lethargica - neurological sequelae (e.g. behavioural, motor) - hydrocephalus

Question 30

What is the prognosis of encephalitis like?

Answer 30

Often poor

Question 31

What does a CT head showing temporal lobe changes suggest (encephalitis)?

Answer 31

HSV encephalitis

Question 32

What can encephalitis be complicated by?

Answer 32

Temporal lobe seizure (motionless staring, confusion and disorientation, altered ability to respond to others; accompanied by an aura - jamais vu = feeling of unfamiliarity)

Question 33

What does HIV + neurological symptoms + multiple brain lesions with ring enhancement suggest?

Answer 33

Toxoplasmosis (cause of encephalitis in immunocompromised patients)