Viral meningitis

Viral meningitis
Other names	Aseptic meningitis
Viral meningitis causes inflammation of the meninges.
Specialty	Neurology

Viral meningitis, also known as aseptic meningitis, is a type of

In most cases, there is no specific treatment, with efforts generally aimed at relieving symptoms (headache, fever or nausea).[6] A few viral causes, such as HSV, have specific treatments.

In the United States, viral meningitis is the cause of more than half of all cases of meningitis.^[7] With the prevalence of bacterial meningitis in decline, the viral disease is garnering more and more attention.^[8] The estimated incidence has a considerable range, from 0.26 to 17 cases per 100,000 people. For enteroviral meningitis, the most common cause of viral meningitis, there are up to 75,000 cases annually in the United States alone.^[8] While the disease can occur in both children and adults, it is more common in children.^[1]

Signs and symptoms

Viral meningitis characteristically presents with

Symptoms can vary depending on the virus responsible for infection. Enteroviral meningitis (the most common cause) typically presents with the classic headache, photophobia, fever, nausea, vomiting, and nuchal rigidity.[15] With coxsackie and echo virus' specifically, a maculopapular rash may be present, or even the typical vesicles seen with Herpangina.^[15] Lymphocytic choriomeningitis virus (LCMV) can be differentiated from the common presenting meningeal symptoms by the appearance of a prodromal influenza-like sickness about 10 days before other symptoms begin.^[15] Mumps meningitis can present similarly to isolated mumps, with possible parotid and testicular swelling.^[15] Interestingly, research has shown that HSV-2 meningitis most often occurs in people with no history of genital herpes, and that a severe frontal headache is among the most common presenting symptoms.^[16][15] Patients with varicella zoster meningitis may present with herpes zoster (Shingles) in conjunction with classic meningeal signs.^[15] Meningitis can be an indication that an individual with HIV is undergoing seroconversion, the time when the human body is forming antibodies in response to the virus.^[1]

Causes

The most common causes of viral meningitis in the United States are non-polio

Mechanism

Viral Meningitis is mostly caused by an

The diagnosis of viral meningitis is made by clinical history, physical exam, and several diagnostic tests.^[21] Kernig and Brudzinski signs may be elucidated with specific physical exam maneuvers, and can help diagnose meningitis at the bedside.^[15] 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.^[22] 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.^[23] Increasingly, cerebrospinal fluid PCR tests have become especially useful for diagnosing viral meningitis, with an estimated sensitivity of 95-100%.^[24] Additionally, samples from the stool, urine, blood and throat can also help to identify viral meningitis.^[22] CSF vs serum c-reactive protein and procalcitonin have not been shown to elucidate whether meningitis is bacterial or viral.^[14]

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.^[1] 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.^[14]

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.^[14]

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.

Herpes simplex virus, varicella zoster virus and cytomegalovirus have a specific antiviral therapy. For herpes the treatment of choice is aciclovir.^[26] If encephalitis is suspected, empiric treatment with IV aciclovir is often warranted.^[14]

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.^[10]

The majority of people that have viral meningitis get better within 7–10 days.^[27]

Epidemiology

From 1988 to 1999, about 36,000 cases occurred each year in the United States.^[28] As recently as 2017, the incidence in the U.S. alone increased to 75,000 cases per year for enteroviral meningitis.^[8] With the advent and implementation of vaccinations for organisms such as Streptococcus pneumoniae, Haemophilus influenza type B, and Neisseria meningitis, rates of bacterial meningitis have been in decline, making viral meningitis more common.^[14] Countries without high rates of immunization still carry higher rates of bacterial disease.^[14] While the disease can occur in both children and adults, it is more common in children.^[1] Rates of infection tend to reach a peak in the summer and fall.^[29] During an outbreak in Romania and in Spain viral meningitis was more common among adults.^[30] While, people aged younger than 15 made up 33.8% of cases.^[30] In contrast in Finland in 1966 and in Cyprus in 1996, Gaza 1997, China 1998 and Taiwan 1998, the incidence of viral meningitis was higher among children.^{[31][32][33][34]}

Recent research

It has been proposed that viral meningitis might lead to inflammatory injury of the vertebral

While there is some emerging evidence that bacterial meningitis may have a negative impact on cognitive function, there is no such evidence for viral meningitis.[38]

References