Viral meningitis

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Viral meningitides correspond to a relatively common and self-limited type of CNS infection clinically diagnosed based on the cerebrospinal fluid analysis and proportionally more frequent in young children than adults. Enteroviruses represent nowadays the most common cause of viral meningitis for all ages in the developed world.

For viral infection of the brain parenchyma, please refer to the general article on viral encephalitides.

Terminology

Aseptic meningitis is a term frequently used as a synonym for viral meningitis, nonetheless, to avoid misleading interpretations, we prefer to save this term only for those noninfective inflammatory processes involving the meninges (e.g. leptomeningeal carcinomatosis, sarcoidosis, vasculitis, and connective tissue diseases).

Epidemiology

Viral meningitides are more common in young children, particularly in those with less than one year or between 5 to 10 years.

After a long term period since the implementation of highly effective conjugate ~~vaccine in the last decades~~vaccines, there has ~~changed~~been a significant change in the aetiology and the incidence and hospital admissions for viral meningitis have dropped ^1,3.

Clinical presentation

Classically, patients present with fevers and clinical signs of meningeal irritation (e.g. neck stiffness, Brudzinski sign). Other nonspecific symptoms such as vomiting, headache, anorexia, exanthems, and myalgia may be also associated. As most of the viral infections start affecting the mucosa of the respiratory or gastrointestinal tracts, symptoms involving these organs may be present ^4,5.

Neurologic dysfunction (e.g. altered state of consciousness, cranial nerve palsies, abnormal reflexes, and paralysis) is not a feature of meningitis and its presence should alert to a mixed picture with also the involvement of the brain parenchyma, meningoencephalitis ⁴.

Pathology

Most viral infections will primarily affect the respiratory and gastrointestinal tracts, as the are either inhaled (e.g. measles, mumps) or ingested (e.g. enteroviruses), and thus will have their replication in the regional lymph nodes or small bowel lymphoid tissues. From the secondary lymphoid tissues, the viruses get into the blood stream resulting in systemic infection and subsequent seeding of other organs ⁵.

Aetiology

enteroviruses ^1-5
- represent ~90% of cases of viral meningitis
- genus Enterovirus (classified as Picornaviridae) includes ⁵
  - 3 polioviruses
  - 28 echoviruses
  - 23 group A coxsackieviruses
  - 6 group B coxsackieviruses
  - 4 numbered enteroviruses
- respiratory and fecal-oral transmission

Treatment and prognosis

Most cases require only supportive management^1,3.

-<p><strong>Viral meningitides</strong> correspond to a relatively common and self-limited type of <a title="CNS infections" href="/articles/cns-infectious-diseases">CNS infection</a> clinically diagnosed based on the cerebrospinal fluid analysis and proportionally more frequent in young children than adults. Enteroviruses represent nowadays the most common cause of viral meningitis in the developed world. </p><p>For viral infection of the brain parenchyma, please refer to the general article on <a title="Viral encephalitides" href="/articles/viral-encephalitides">viral encephalitides</a>. </p><h4>Terminology</h4><p>Aseptic meningitis is a term frequently used as a synonym for viral meningitis, nonetheless, to avoid misleading interpretations, we prefer to save this term only for those noninfective inflammatory processes involving the meninges (e.g. <a title="Leptomeningeal carcinomatosis" href="/articles/leptomeningeal-metastases">leptomeningeal carcinomatosis</a>, <a title="Sarcoidosis (head and neck manifestations)" href="/articles/sarcoidosis-head-and-neck-manifestations-1">sarcoidosis</a>, vasculitis, and connective tissue diseases).</p><h4>Epidemiology</h4><p>After a long term implementation of highly effective conjugate vaccine in the last decades has changed the aetiology and </p><h4>Treatment and prognosis </h4><p>Most cases require only supportive management. <br> </p>
+<p><strong>Viral meningitides</strong> correspond to a relatively common and self-limited type of <a href="/articles/cns-infectious-diseases">CNS infection</a> clinically diagnosed based on the cerebrospinal fluid analysis and proportionally more frequent in young children than adults. Enteroviruses represent nowadays the most common cause of viral meningitis for all ages in the developed world. </p><p>For viral infection of the brain parenchyma, please refer to the general article on <a href="/articles/viral-encephalitides">viral encephalitides</a>. </p><h4>Terminology</h4><p>Aseptic meningitis is a term frequently used as a synonym for viral meningitis, nonetheless, to avoid misleading interpretations, we prefer to save this term only for those noninfective inflammatory processes involving the meninges (e.g. <a href="/articles/leptomeningeal-metastases">leptomeningeal carcinomatosis</a>, <a href="/articles/sarcoidosis-head-and-neck-manifestations-1">sarcoidosis</a>, vasculitis, and connective tissue diseases).</p><h4>Epidemiology</h4><p>Viral meningitides are more common in young children, particularly in those with less than one year or between 5 to 10 years. </p><p>After a long term period since the implementation of highly effective conjugate vaccines, there has been a significant change in the aetiology and the incidence and hospital admissions for viral meningitis have dropped <sup>1,3</sup>. </p><h4>Clinical presentation</h4><p>Classically, patients present with fevers and clinical signs of meningeal irritation (e.g. neck stiffness, Brudzinski sign). Other nonspecific symptoms such as vomiting, headache, anorexia, exanthems, and myalgia may be also associated. As most of the viral infections start affecting the mucosa of the respiratory or gastrointestinal tracts, symptoms involving these organs may be present <sup>4,5</sup>. </p><p>Neurologic dysfunction (e.g. altered state of consciousness, cranial nerve palsies, abnormal reflexes, and paralysis) is not a feature of meningitis and its presence should alert to a mixed picture with also the involvement of the brain parenchyma, meningoencephalitis <sup>4</sup>. </p><h4>Pathology </h4><p>Most viral infections will primarily affect the respiratory and gastrointestinal tracts, as the are either inhaled (e.g. measles, mumps) or ingested (e.g. enteroviruses), and thus will have their replication in the regional lymph nodes or small bowel lymphoid tissues. From the secondary lymphoid tissues, the viruses get into the blood stream resulting in systemic infection and subsequent seeding of other organs <sup>5</sup>. </p><h5>Aetiology</h5><ul><li>enteroviruses <sup>1-5</sup><ul>
+<li>represent ~90% of cases of viral meningitis </li>
+<li>genus <em>Enterovirus</em> (classified as <em>Picornaviridae</em>) includes <sup>5</sup><ul>
+<li>3 polioviruses</li>
+<li>28 echoviruses</li>
+<li>23 group A coxsackieviruses</li>
+<li>6 group B coxsackieviruses</li>
+<li>4 numbered enteroviruses</li>
+</ul>
+</li>
+<li>respiratory and fecal-oral transmission </li>
+</ul>
+</li></ul><h4>Treatment and prognosis </h4><p>Most cases require only supportive management <sup>1,3</sup>. <br> </p>

References changed:

2. Maller V, Bathla G, Moritani T, Helton K. Imaging in Viral Infections of the Central Nervous System: Can Images Speak for an Acutely Ill Brain? Emerg Radiol. 2017;24(3):287-300. <a href="https://doi.org/10.1007/s10140-016-1463-5">doi:10.1007/s10140-016-1463-5</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/27853972">Pubmed</a>
3. Martin N, Iro M, Sadarangani M, Goldacre R, Pollard A, Goldacre M. Hospital Admissions for Viral Meningitis in Children in England over Five Decades: A Population-Based Observational Study. Lancet Infect Dis. 2016;16(11):1279-87. <a href="https://doi.org/10.1016/S1473-3099(16)30201-8">doi:10.1016/S1473-3099(16)30201-8</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/27527749">Pubmed</a>
1. Logan S & MacMahon E. Viral Meningitis. BMJ. 2008;336(7634):36-40. <a href="https://doi.org/10.1136/bmj.39409.673657.AE">doi:10.1136/bmj.39409.673657.AE</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/18174598">Pubmed</a>
4. Romero J & Newland J. Viral Meningitis and Encephalitis: Traditional and Emerging Viral Agents. Semin Pediatr Infect Dis. 2003;14(2):72-82. <a href="https://doi.org/10.1053/spid.2003.127223">doi:10.1053/spid.2003.127223</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/12881794">Pubmed</a>
5. Swanson P & McGavern D. Viral Diseases of the Central Nervous System. Curr Opin Virol. 2015;11:44-54. <a href="https://doi.org/10.1016/j.coviro.2014.12.009">doi:10.1016/j.coviro.2014.12.009</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/25681709">Pubmed</a>

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