Encephalitis

Question 1

Define encephalitis

Answer 1

Inflammation of the brain parenchyma associated with neurological dysfunction

Question 2

Aetiology of encephalitis

Answer 2

Infection
Viral:
- Herpes, HSV (most common UK) - retrograde axonal transport
- West Nile virus (becoming a leading cause)
- Arbovirus (most common worldwide) - haematogenous

Bacterial: Neisseria meningitides (most common bacterial) | TB | Syphilis | Listeria | Bartonella
Fungal: Cryptococcus | Ciccidiodes | Histoplasma | Blastomycosis | Candida |Nocardia
Parasitic: Toxoplasma gondii | Cysticerosis | Amoebic |Naegleria | Entamoeba histolytica

Para-infectious: acute disseminated encephalomyelitis (ADEM) | Acute haemorrhagic leukoencephalitis
Prion disease: Creutzfeldt-Jakob disease
Paraneoplastic syndromes: Anti-NMD R encephalitis | Anti GABA R encephalitis
Chronic traumatic
Liver cirrhosis

Question 3

Risk factors for encephalitis

Answer 3

Age: <1 or >65
Immunodeficiency
Viral infection
Blood/bodily fluid exposure
Organ transplant
Animal/insect bite
Recent travel
Season
Swimming in warm freshwater

Question 4

Symptoms of encephalitis

Answer 4

Often a self-limiting mild disease
Confusion
Altered mental state
Fever
Seizure
Symptoms of the underlying cause e.g. rash with HSV

No headache in pure encephalitis as there are no pain receptors in the brain
Headache in encephalitis suggests meningo-encephalitis

Question 5

What cause is suggested by the following symptoms:
Parotitis
Lymphadenopathy
Optic neuritis
Acute flaccid paralysis
Movement disorders
Cough
GI infection
Seizures
Biphasic illness
Autonomic/hypothalamic disturbance
Myocarditis/pericarditis
Jaundice
Arthritis
Retinitis
Parkinsonism

Answer 5

Parotitis: mumps
Lymphadenopathy: Bartonella
Optic neuritis: ADEM
Acute flaccid paralysis: West Nile Virus - arbovirus, rabies
Movement disorders: Creutzfield Jakob, anti-NMDA
Autonomic/hypothalamic disturbance: Anti-NMDA
Cough: RTI
GI infection: enterovirus, rotavirus
Seizures: HSV
Biphasic illness: enterovirus
Myocarditis/pericarditis: enterovirus, mumps
Jaundice: leptospirosis
Arthritis: Lyme disease, SLE
Retinitis: CMV, toxoplasmosis
Parkinsonism: arbovirus, toxoplasmosis

Question 6

Signs of encephalitis on examination

Answer 6

Fever
Rash (Vesicular eruption, Maculopapular eruption, Malar rash, Petechial rash, Erythema migrans, Erythema nodosum, Erythema multiforme, Mucous membrane lesions, Pharyngitis, Conjunctivitis, Gumma, Kaposi’s sarcoma, Non-healing skin lesions, Genital lesions)
Altered mental state/fluctuating GCS
- Mild somnolence (sleepiness) to coma
- Cognitive dysfunction with acute memory disturbance and behavioural manifestations (withdrawal, apathy, abulia, akinetic mutism, personality changes, psychotic behaviour, disorientation, hallucination)
Focal neurological deficit
- Aphasia
- Hemianopia
- Hemiparesis
- Ataxia
- Brisk reflexes
- Babinski’s sign
- Cranial nerve deficits

Question 7

Investigations for encephalitis

Answer 7

Based on symptoms: urine culture | sputum culture | throat swab | stool culture | NPA for PCR

FBC: raised WCC (infection) | suppressed WCC (HIV/immunosuppression) | lymphocytosis (viral ) Eosinophilia (parasitic)
U&Es: hyponatraemia (SIADH, rickettsial)
LFTs: rickettsia, coxiella, tick-borne, EBV, CMV
Blood gas
Blood cultures
HSV serology

CT brain: considered in all patients with altered mental state
MRI brain: recommended
CXR: ?TB, sarcoid
EEG: BG slowing
LP

Question 8

Management for encephalitis

Answer 8

1. A-E assessment
2. Fluid resuscitation
3. Sepsis 6: cultures, abx, fluids, oxygen, urine output, lactate
4. IV aciclovir (10mg/kg) TDS + IV ceftriaxone
   - >50yo or immunocompromised IV → amoxicillin

Question 9

Complications of encephalitis

Answer 9

Death
Hypothalamic and autonomic dysfunction
Encephalitis lethargica
Neuro: seizures, cerebral haemorrhage, ischaemic stroke, cerebral vein thrombosis, cerebral vasculitis, hydrocephalus
Long term morbidity: fatigue, cognitive impairment, attention and deficit disorders, dysphasia, motor impairment, ataxia, epilepsy, and personality changes.

Question 10

Prognosis for encephalitis

Answer 10

Depends on underlying aetiology, immune status and extent and location of anatomic lesions
Severe disability occurs in more than half of survivors. In children, long-term morbidity occurs in up to two-thirds of patients.
Post-encephalitic epilepsy occurs in 10% by 5 years and 20% by 20 years