Epidemiology

• Viral meningitis is common, especially in children.
• Neonates are at greatest risk and have the most significant risk of morbidity and mortality.²
• A study from Finland reported an incidence of approximately 200 per 100,000 in infants.
• In the UK it is estimated at 5-15 cases per 100,000.³
• In children, hospitalisation is highest immediately after birth with a further secondary peak at age 5.⁴
• It may present identically to bacterial meningitis, but the two can be distinguished by cerebrospinal fluid (CSF) analysis.

Causes^3,5

• Enteroviruses (the most common cause of aseptic meningitis apart from in neonates less than 7 days old).²
• Herpes simplex viruses (HSV).
• Varicella zoster virus (HZV).
• Human immunodeficiency virus (HIV).
• Epstein-Barr virus.
• Mumps virus.
• Measles.
• Cytomegalovirus (CMV): occurs mostly in immunocompromised patients.⁶
• Travel related, e.g. tick-borne meningoencephalitis.

Enteroviruses⁵

• The name relates to how the virus enters the human body, i.e. via the gastrointestinal tract..
• They are a large group and include Coxsackie A and B viruses, echoviruses, polioviruses and enterovirus 71 (more recent).
• They all can invade the neurological system and cause inflammation.
• The most common enteroviruses causing viral meningitis include Coxsackie B and echoviruses.
• It occurs mostly at a young age and infection is highest in summer and autumn in temperate areas.
• Viral meningitis from enteroviruses is self-limiting but headache can be severe and continue for days. It may also require admission for opiate analgesia.

HSV types 1 and 2

• HSV type 1 (HSV-1) is a cause of encephalitis but HSV type 2 (HSV-2) more often causes meningitis.⁷
• Both HSV-1 and HSV-2 have been implicated in Mollaret's meningitis.⁷
• HSV meningitis is associated with primary genital HSV infection and HIV infection.⁷
• HSV meningitis is usually a self-limiting illness in immunocompetent people.⁵

HIV viral meningitis⁸

• Seen in 5-10% of HIV infected patients.
• Meningitis can occur at the time the virus is acquired or during seroconversion.
• CSF findings are indistinguishable from other viral meningitides and so it is difficult to diagnose HIV at the time. Peripheral anti-HIV antibodies are likely to be negative during seroconversion.

Presentation

Presentation is similar to bacterial causes of meningitis.

Symptoms

• Fever.
• Headache.
• Photophobia.
• Neck stiffness.
• Confusion/delirium.
• Rarely - seizures, fluctuation in Glasgow Coma Scale (GCS).
• Specific features relating to causative virus, e.g. vesicles in Coxsackie viruses or herpes-related infections, rash in HIV seroconversion.

Also, enquire about recent travel, sexual history, and vaccinations received.

Signs

• High temperature.
• Neck stiffness.
• Pharyngitis.
• Lymphadenopathy.
• Focal neurological signs are usually not present.
• Specific features relating to causative virus, e.g. vesicles in Coxsackie viruses or herpes-related infections, sacral radiculomyelitis in HSV-2 meningitis.

Differential diagnosis

• Other causes of meningitis or meningoencephalitis, e.g. bacterial or tuberculosis meningitis
• Any cause of headache, e.g. subarachnoid haemorrhage, migraine.
• Other causes of aseptic meningitis (bacterial cultures from CSF are negative:⁹
  • Other infections, e.g. fungal, parasitic, rickettsial.
  • Post vaccinal, e.g. following rubella vaccine.
  • Drugs, e.g. non-steroidal anti-inflammatory drugs, azathioprine, allopurinol.
  • Systemic disorders, e.g. sarcoidosis, vasculitic disorders.
  • Neoplasia.

Investigations

• Full blood count, renal function and liver function tests may all be unremarkable.
• CT brain scan is also likely to be unremarkable.
• Lumbar puncture - cerebrospinal fluid (see separate Cerebrospinal Fluid article):
  • White cell count is raised but usually lymphocytes predominate unlike bacterial causes.
  • Cerebrospinal fluid (CSF) glucose to plasma glucose ratio is usually >0.5.
  • CSF protein raised (but <1 g per litre, thus not as high as in bacterial meningitis).
  • CSF samples for virology - viral culture or polymerase chain reaction (PCR) (more sensitive) looking for enteroviruses, herpes simplex virus (HSV), etc.⁵

Management

• The general principles of management for all viral meningitis include supportive therapy, e.g. analgesia, antipyretics, nutritional support and hydration.
• Intravenous antibiotics should be started promptly and continued until bacterial meningitis has been excluded.
• Enteroviral meningitis: usually self-limiting and no specific therapy is required unless there is hypogammaglobulinaemia (immunoglobulins required).
• Acyclovir is considered beneficial in treating herpetic viral infections but only if given very early in the course of the infection, and evidence for benefit is limited. Intravenous acyclovir should be started immediately if there is any suspicion of herpes simplex encephalitis.
• Ganciclovir is effective for cytomegalovirus (CMV) infections but, because of toxicity, should be reserved for severe cases with positive CMV culture, congenital infection, or an AIDS-related infection.²

Complications

Complications are rare but more likely in infants and young children.

• Communicating hydrocephalus.
• Syndrome of inappropriate ADH secretion (SIADH).
• Long-term neurological complications include seizure disorders, sensorineural hearing loss, weakness, paralysis, cranial nerve palsy, learning disabilities, blindness, behavioural disorders, and speech delay.²
• There have been rare reports of deaths in children with viral meningitis relating to cerebral oedema and cardiopulmonary collapse.¹⁰

Prognosis²

• The prognosis for viral meningitis is usually excellent, with complete resolution usually within 10 days.
• Neonates who develop viral meningitis have an increased mortality and morbidity.
• Associated encephalitis is also associated with a worse prognosis.

Prevention

Vaccines are available for the prevention of some causes of viral meningitis, such as mumps, measles, influenza, varicella and poliomyelitis.

Document references

1. Notifications of Infectious Diseases (NOIDs), Health Protection Agency
2. Vokshoor A et al; Viral Meningitis, eMedicine, Oct 2009
3. Chadwick DR; Viral meningitis. Br Med Bull. 2006 Feb 10;75-76:1-14. Print 2005. [abstract]
4. Hviid A, Melbye M; The epidemiology of viral meningitis hospitalization in childhood. Epidemiology. 2007 Nov;18(6):695-701. [abstract]
5. Logan SA, MacMahon E; Viral meningitis. BMJ. 2008 Jan 5;336(7634):36-40.
6. Rafailidis PI, Kapaskelis A, Falagas ME; Cytomegalovirus meningitis in an immunocompetent patient. Med Sci Monit. 2007 Sep;13(9):CS107-109. [abstract]
7. Razonable RR et al; Meningitis, eMedicine, Jun 2010
8. de Almeida SM, Letendre S, Ellis R; Human immunodeficiency virus and the central nervous system. Braz J Infect Dis. 2006 Feb;10(1):41-50. Epub 2006 Jun 2. [abstract]
9. Lee BE, Davies HD; Aseptic meningitis. Curr Opin Infect Dis. 2007 Jun;20(3):272-7. [abstract]
10. Krous HF, Chadwick AE, Miller DC, et al; Sudden death in toddlers with viral meningitis, massive cerebral edema, and neurogenic pulmonary edema and hemorrhage: report of two cases. Pediatr Dev Pathol. 2007 Nov-Dec;10(6):463-9. [abstract]