acute viral encephalitis is used to describe restricted CNS involvement (namely, involvement of the brain, sparing the meninges)

Viral encephalitis is a medical emergency The spectrum of brain involvement and the prognosis are dependent mainly on the specific pathogen and the immunological state of the host.

Although specific therapy is limited to only several viral agents, correct immediate diagnosis and introduction of symptomatic and specific therapy has a dramatic influence upon survival and reduces the extent of permanent brain injury in survivors Epidemiologic studies estimate the incidence of viral encephalitis at 3.5 to 7.4 per 100,000 persons per year. Overall, viruses are the most common cause of encephalitis.

The Centers for Disease Control and Prevention (CDC) estimates an annual incidence of approximately 20,000 new cases of encephalitis in the United States; most are mild in nature. The mortality depends largely on the etiologic agent of the encephalitis.

Herpes simplex virus (HSV) encephalitis (HSVE) is the most common cause of sporadic encephalitis in humans. More than 90% of HSVE cases are attributable to HSV type-1 (HSV-1). Approximately 5% of them are caused by HSV type-2 HSVE is a severe disease, often leading to high morbidity (40%) and mortality (up to 15% in treated cases and 70% in untreated cases) Patients with encephalitis have an altered mental status ranging from subtle deficits to complete unresponsiveness. The typical clinical presentation includes a rapid onset of fever and impaired consciousness, often accompanied by focal neurologic signs and seizures.

The current treatment of choice is the viral replication inhibitor acyclovir. Although highly effective in reducing mortality, it only results in complete recovery in one-half of patients . Steroid therapy as an adjunctive therapy in HSVE has good anti inflammatory effect. Steroid therapy has both anti inflammatory and immunosuppressive property.

The diagnosis of viral encephalitis is suspected in the context of a febrile disease accompanied by headache, altered level of consciousness, and symptoms and signs of cerebral dysfunction. These may consist of abnormalities that can be categorized into four: cognitive dysfunction (acute memory disturbances), behavioural changes (disorientation, hallucinations, psychosis, personality changes, agitation), focal neurological abnormalities (such as anosmia, dysphasia, hemiparesis, hemianopia etc.) and seizures. After the diagnosis is suspected, the approach should consist of obtaining a meticulous history and a careful general and neurological examination.

Inclusion Criteria:

• Pediatric patients who attending Neurology unit in Assiut University Children Hospital and diagnosed as viral encephalitis.
• Age 1month : 18 year .
• Both sexes.
• Diagnosis of viral encephalitis will be confirmed by clinical picture ,investigations and exclusion of other causes of encephalopathy

Exclusion Criteria:

• Autoimmune encephalitis
• Renal failure (any patient with abnormal renal function tests will be excluded)
• Hepatic failure ( any patient with abnormal liver function tests will be excluded)
• Metabolic disorders (any patient with abnormal level of ammonia and lactate )