The etiology, clinical manifestations, diagnosis, and differential diagnosis of viral meningitis in children will be reviewed here. The epidemiology, pathogenesis, management, prognosis, and prevention are discussed separately. (See "Viral meningitis: Epidemiology, pathogenesis, and etiology in children" and "Viral meningitis: Management, prognosis, and prevention in children".)
●Meningitis – Meningitis is inflammation of the meninges, manifest by cerebrospinal fluid (CSF) pleocytosis (ie, an increased number of white blood cells [WBC]) .
Aseptic meningitis is the clinical syndrome of meningeal inflammation with negative cultures for routine bacterial pathogens in a patient who did not receive antibiotics before lumbar puncture [1-4]. Aseptic meningitis has a number of infectious and noninfectious causes (table 1). Viruses (usually enteroviruses) are the most common cause (table 2). Because viruses are the most common cause of aseptic meningitis, the terms aseptic meningitis and viral meningitis are sometimes used synonymously.
●Encephalitis – Encephalitis is inflammation of the brain parenchyma that produces neurologic dysfunction (eg, altered mental status, behavior, or personality; motor or sensory deficits; speech or movement disorders; hemiparesis; and paresthesias) . Encephalitis may occur during or after a viral infection. (See "Acute viral encephalitis in children and adolescents: Clinical manifestations and diagnosis", section on 'Viral etiologies'.)
●Myelitis – Myelitis is inflammation of the spinal cord, manifest by flaccid paralysis and reduced or absent reflexes. (See "Disorders affecting the spinal cord", section on 'Acute viral myelitis'.)
The presence or absence of normal brain function distinguishes meningitis from encephalitis. Certain viruses usually cause isolated meningitis or isolated encephalitis. Others cause less discrete manifestations of central nervous system (CNS) infection, described as meningoencephalitis or encephalomyelitis . Although the distinction between meningitis and encephalitis is sometimes blurred, it is important to try to distinguish between them because the likely causes differ (table 2). The discussion that follows will focus on viruses that most often cause meningitis. (See "Acute viral encephalitis in children and adolescents: Clinical manifestations and diagnosis", section on 'Viral etiologies'.)