In meningitis, the barrier is disrupted, so once viruses have entered the brain, they are isolated from the immune system and can spread. This leads to elevated intracranial pressure, cerebral edema, meningeal irritation, and neuronal death. Diagnosis
The diagnosis of viral meningitis is made by clinical history, physical exam, and several diagnostic tests. Kernig and Brudzinski signs may be elucidated with specific physical exam maneuvers, and can help diagnose meningitis at the bedside. Most importantly however, cerebrospinal fluid (CSF) is collected via lumbar puncture (also known as spinal tap). This fluid, which normally surrounds the brain and spinal cord, is then analyzed for signs of infection. CSF findings that suggest a viral cause of meningitis include an elevated white blood cell count (usually 10-100  cells/µL) with a lymphocytic predominance in combination with a normal glucose level. Increasingly,  cerebrospinal fluid PCR tests have become especially useful for diagnosing viral meningitis, with an estimated sensitivity of 95-100%. Additionally, samples from the stool, urine, blood and throat can also help to identify viral meningitis. CSF vs serum c-reactive protein and procalcitonin have not been shown to elucidate whether meningitis is bacterial or viral.In certain cases, a CT scan of the head should be done before a lumbar puncture such as in those with poor immune function or those with increased intracranial pressure.
If the patient has focal neurological deficits, papilledema, a Glasgow Coma Score less than 12, or a recent history of seizures, lumbar puncture should be reconsidered.Differential diagnosis for viral meningitis includes meningitis caused by bacteria, mycoplasma, fungus, and drugs such as NSAIDS, TMP-SMX, IVIG. Further considerations include brain tumors, lupus, vasculitis, and Kawasaki disease in the pediatric population. Treatment
Because there is no clinical differentiation between bacterial and viral meningitis, people with suspected disease should be sent to the hospital for further evaluation. Treatment for viral meningitis is generally supportive. Rest, hydration, antipyretics, and pain or anti-inflammatory medications may be given as needed. However, if there is initial uncertainty as to whether the meningitis is bacterial or viral in origin, empiric antibiotics are often given until bacterial infection is ruled out.Herpes simplex virus, varicella zoster virus and cytomegalovirus have a specific antiviral therapy. For herpes the treatment of choice is aciclovir. If encephalitis is suspected, empiric treatment with IV aciclovir is often warranted.Surgical management is indicated where there is extremely increased intracranial pressure, infection of an adjacent bony structure (e.g. mastoiditis), skull fracture, or abscess formation.The majority of people that have viral meningitis get better within 7–10 days. Epidemiology
From 1988 to 1999, about 36,000 cases occurred each year. As recently as 2017, the incidence in the U.S. alone increased to 75,000 cases per year for enteroviral meningitis.