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

o This ranges from Confusion to coma

· Personality changes, behavioural disorders and psychotic symptoms can occur

· Focal and generalized seizures are common

Aetiology

o Herpesviruses

§ HSV (more often HSV-1 c.f. meningitis HSV-2)

§ VZV

§ EBV

o Arbobviruses

§ JE

§ Murray valley encephalitis

§ West-nile (USA)

o Other

§ Enteroviruses (up to 70% of cases)

§ CMV

§ Mumps

§ HIV (rare)

§ Rabies

Diagnosis

Clues to aetiology

· Vaccination for mumps

· Parotitis – mumps

· Scan body for vesicles to suggest VZV

· Imaging

o 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
1. Lymphocytosis rarely >500/ul (10% may be normal on initial sample)
2. Mild protein elevation
3. Normal glucose
• CSF PCR
1. Sensitivity 96%
2. Specificity 99%

o CSF cell culture

1. Usually negative and of little use

o CSF antibodies

1. Become positive after one week

2. May therefore be useful in patients presenting with prolonged disease who are PCR negative

· MRI

o Hyperintensity on T2 and diffusion

o Frontotemporal

o Cingulate or insular regions

o Some changes present in 90%

· EEG

o PLEDs over temporal lobe

o Often on flattened background.

o 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 - ?reactivation vs inadequate treatment
• 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