Encephalitis

Question 1

what is encephalitis

Answer 1

inflammation of brain parenchyma

Question 2

what are the causes of encephalitis

Answer 2

viral
autoimmune
paraneoplastic

Question 3

what are the viral causes of encephalitis

Answer 3

herpes simplex virus (main in UK)
varicella zoster (VZV) - may see co-occurring dermatomal rash, immunosuppression may be present
in HIV patients there are many others, including HIV itself

Question 4

what are globally important causes of viral encephalitis

Answer 4

japanese encephalitis
west nile
rabies

Question 5

what is the pathophysiology of encephalitis

Answer 5

virus invades brain (in HSV this may be via olfactory nerves, in VZV it’s via retrograde transport)
inflammation arises, different viruses affect different brain regions (HSV=temporal lobes)
secondary swelling (oedema), necrosis and in some situations haemorrhage or infarction

Question 6

what do the clinical features of encephalitis reflect

Answer 6

inflammation and necrosis

Question 7

what are the clinical features of encephalitis

Answer 7

acute onset
headache, fever, seizures, confusion, decreased consciousness, focal deficits (may include some/all)
meningism is not typical
rapid progression
decreasing consciousness
rapidly fatal if untreated

Question 8

how is encephalitis diagnosed

Answer 8

CT - low sensitivity compared to MRI, may see hypoattenuating regions
MRI - areas of oedema with or without haemorrhage
CSF - elevated lymphocytes and protein, normal glucose, conformation of a specific virus via PCR
EEG - may show slowing epileptiform discharges (spikes/sharp waves), sometimes seizures

Question 9

what is the management of encephalitis

Answer 9

antiviral therapy - aciclovir IV for 2-3 weeks, if you suspect encephalitis treat empirically (delays increase morbidity and mortality)
supportive - ICU support (coma), seizure management)
rehabilitation - cognitive impairment, dysphasia, weakness etc

Question 10

what are complications of encephalitis

Answer 10

decreased consciousness and coma
seizures (during acute phase and long-term epilepsy)
cerebral oedema, raised intracranial pressure, herniation (may require decompressive surgery)
permanent focal damage (dysphasia, motor weakness, visual field defects, impaired swallowing, amnesia, cognitive impairment)
secondary autoimmune encephalitis