Dexamethasone in Herpes Simplex Virus Encephalitis

Inclusion Criteria:

• Suspected encephalitis criteria: Acute or subacute (up to 4 weeks) alteration inconsciousness, cognition, personality or behaviour* persisting for > 24 hours Laboratoryconfirmed HSV by positive PCR on CSF sample.

• Receiving intravenous aciclovir dosed at 10mg/kg TDS or at a reduced dose in renalimpairment

• Age ≥ 18 years

• Person affiliated to social security

• Written informed consent has been given by the patient or their legal representative

Exclusion Criteria:

• Currently receiving oral or injectable corticosteroid therapy; including treatmentwith oral or injectable corticosteroids in the last 30 days.

• History of hypersensitivity to corticosteroids

• Immunosuppression secondary to:

• Known HIV infection & CD4 count under 200cell/mm3

• Biologic therapy or other immunosuppressive agents [azathioprine, methotrexate,ciclosporin]

• Solid organ transplant on immunosuppression

• Bone marrow transplant

• Currently undergoing a course of chemotherapy or radiotherapy

• Known immunodeficiency syndrome [other than HIV]

• Known haematological malignancy

• Pre-existing indwelling ventricular devices

• Peptic ulcer disease in the last 6 months: defined as a peptic ulcer seen at previousendoscopy or an upper gastrointestinal bleed causing ≥ 2 unit haemoglobin drop

• Currently on an antiretroviral regime containing rilpivirine

• Patients under legal protection, administrative or judicial control

• Pregnancy / Breast feeding and parturient

• Subject in exclusion period of another study