Encephalitis

Contents

• Encephalitis 1
• HSV encephalitis 1

• Epidemiology 1

• Pathogenesis 1

• Clinical manifestations 1

• Diagnosis 1

• Treatment 1

• Prognosis 1

Clinical Features

• The main difference from meningitis is a change in the level of consciousness
• This ranges from confusion to coma
• Personality changes, behavioural disorders and psychotic symptoms can occur
• Seizures are common

Aetiology

• Herpesviruses
• HSV (more often HSV-1 c.f. meningitis HSV-2)
• VZV
• EBV
• Arbobviruses
• JE
• Murray valley encephalitis
• West-nile (USA)
• Other
• Enteroviruses (up to 70% of cases)
• CMV
• Mumps
• HIV (rare)
• Rabies

Diagnosis

Clues to aetiology

• Parotitis – mumps
• Scan body for vesicles to suggest VZV
• Imaging
• Temporal lobe involvement is relatively specific for HSV (not 100%)

Enteroviruses

• Echovirus, Coxsakie virus
• More commonly cause meningitis, but still common cause of encephalitis
• ?RX Pecornoril

HSV encephalitis

Epidemiology

• A (?the) major cause of viral encephalitis
• 10-20%
• Incidence ? 2.2/million/year
• Most common cause of focal encephalitis

Pathogenesis

• HSV-1 or HSV-2 can cause disease in neonates, however essentially all HSV-1 in adults
• Age <20yrs – usually primary infection
• Adults Usually due to reactivation of latent virus in the brain
• Preferentially affects temporal lobe

Clinical manifestations

• Headache (~70%)
• Altered mentation and LOC
• Focal signs (75%)
• Hemiparesis
• Dysphasia
• Focal cranial nerve deficits
• Ataxia
• Seizures
• Behavioural symptoms
• Including hypomania
• Fever
• Late features
• Diminished comprehension
• Paraphasic speech
• Impaired memory
• Loss of emotional control

Diagnosis

• CSF
• Same as viral meningitis
• Lymphocytosis rarely >500/ul (10% may be normal on initial sample)
• Mild protein elevation
• Normal glucose
• CSF PCR
• Sensitivity 96%
• Specificity 99%
• CSF cell culture
• Usually negative and of little use
• CSF antibodies
• Become positive after one week
• May therefore be useful in patients presenting with prolonged disease who are PCR negative
• MRI
• Hyperintensity on T2 and diffusion
• Frontotemporal
• Cingulate or insular regions
• Some changes present in 90%
• EEG
• PLEDs over temporal lobe
• Often on flattened background.
• Abnormal in >90%

Treatment

• Acyclovir
• IV 10mg/kg Q8H for 14 days (to 21 days)
• Consider ongoing treatment if they remain PCR positive – controversial
• Oral alternatives are being trialled but not currently recommended

Prognosis

• 5-10% relapse
• This is probably most often anti-NMDA encephalitis
• From one trial (NIAID-CASG)
• 81% survived of which
• 46% had only minor sequalae
• 12% were moderately impaired
• 42% were severely impaired
• Older patients do worse