Encephalitis

Question 1

Define encephalitis

Answer 1

inflammation of brain parenchyma

Question 2

What is encephalitis most commonly caused by?

Answer 2

Viral infection- HSV-1 most common

Question 3

What else can it be caused by?

Answer 3

Bacterial, fungal, parasitic infections
Also in immunocompromised patients or those with autoimmune/ paraneoplastic syndrome

Question 4

What demographics is it most common in?

Answer 4

bimodal distribution:
age <1 years
age >65 years

Question 5

What risk factors of encephalitis

Answer 5

immunosuppresion
viral infections
body fluid exposure
organ transplantation
animal or insect bites
travel
season

Question 6

What are the clinical features?

Answer 6

Initial symptoms are flu-like with pyrexia and headache and persist
. altered mental state (this symptom distinguish it from meningitis)
. fever + malaise
. rash
. focal neurological deficits like personality and behaviour change, difficulty speaking, weakness or loss of movement, loss of consciousness
. seizure
. meningism (headaches, photophobia, neck stiffness)
. positive kernig test

Question 7

What issue may arise secondary to encephalitis?

Answer 7

Raised ICP

signs of this:
. cushing triad: widened pule pressure, bradycardia, irregular breathing
. papilloedema (swelling of the optic nerve at the back of the eye caused by increased pressure inside the skull)

Question 8

What invasive investigation do we do and what would it show?

Answer 8

CSF analysis via lumbar puncture
. high lymphocyte
. high protein
. normal glucose

Question 9

What cell types predominate in virus vs bacteria

Answer 9

virus- lymphocytes
bacteria- neutrophils

Question 10

What do we need to do before lumbar puncture

Answer 10

Do CT before to exclude significantly raised ICP

Question 11

What investigation will confirm the presence of HSV

Answer 11

CSF viral PCR

Question 12

What other investigations should you do?

Answer 12

Bloods: hyponatraemia, raised WCC, elevated LFTs
Blood culture- detect bacteria infections
Throat swab- detect virus
MRI/CT brain- exclude any mass lesions. CT head may also show temporal lobe changes of HSV. MRI will show swelling and increased brain signals

Question 13

What’s the first line for HSV or viral encephalitis

Answer 13

IV aciclovir (antiviral)
supportive care

Question 14

What’s the first line for non-viral encephalitis

Answer 14

treatment of underlying cause e.g. Abx for bacteria
Supportive care

Question 15

Complication of prognosis

Answer 15

Death
Seizures
Hypothalamic dysfunction –> DI, SIADH