Viral meningitis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Ahmed Elsaiey, MBBCH [2]

Viral meningitis is a condition in which the layers lining the brain, or meninges, become inflamed due to a viral infection. Meningitis is diagnosed on a history of characteristic symptoms and certain examination findings (e.g. Kernig’s sign). Investigations should show an increase in the number of leukocytes present in the cerebrospinal fluid (CSF), obtained via lumbar puncture.

Meningitis was first discovered by Hippocrates. Wallgren described aseptic meningitis in 1924 and defined it as a disease with acute onset that had typical systematic symptoms of meningeal involvement, in association with a cerebrospinal fluid (CSF) typical of meningitis (typically with a mononuclear cell predominance). Additionally, there was absence of bacteria on stain and culture and there was no identifiable parameningeal infection.

There is no specific classification to the viral meningitis. However, it may be classified based on the age into child and adult viral meningitis. It may be also according to the causative virus like enterovirus, arbovirus, mumps and herpes simplex viruses.

Viral meningitis pathophysiology may differ from virus to another and depends on many factors like age, immune status and gene expression. Invasion into the meninges by a pathogen can set up a local inflammatory response. The clinical signs are due to this meningeal irritation. Kernig’s sign is due to pain produced by stretching of the inflamed meninges.

Viral meningitis is caused by many viruses. The most important and the most common virus group that causes meningitis is Enteroviruses group. There are other viruses cause meningitis as arbovirus and herpes simplex virus groups but not common as the enteroviruses.^[1][2][3]

The differential diagnosis of viral meningitis includes two step approach. First is differentiating viral meningitis from other diseases which have similar clinical presentation as viral meningitis such as encephalitis, brain abscess, subarachnoid hemorrhage, and brain tumour. Second step involves CSF examination and differentiating viral meningitis from bacterial, fungal and other causes of meningitis

Viral meningitis affect around 26,000 to 42,000 individual annualy with incidence 11 per 100,000 population. There is no gender or racial predilection.

Viral meningitis risk factors rely particularly on the exposure to the infection itself and the route of transmission like respiratory droplet and feco-oral transmission. However, there are people at risk to be infected by the disease as children less than 5 years and immunocompromised patients.^[4]

Viral meningitis is a self resolved disease if left untreated. It takes around 10 days to be resolved. Seizures and loss of consciousness are the most important complications that may appear in the infants younger than 3 months. It has an excellent prognosis.

Viral meningitis symptoms are varied, depending on the causative organism. The symptoms of viral meningitis usually last from 7 to 10 days, and people with normal immune systems usually recover completely. A rash may be present, which could suggest a particular virus e.g. varicella zoster. However, a non-blanching purpuric rash is not associated with meningitis and suggests systemic bacterial infection. The more common symptoms of meningitis are fever, severe headache, stiff neck, bright lights hurting the eyes, drowsiness or confusion, and nausea and vomiting. In babies, the symptoms are more difficult to identify. They may include fever, irritability, difficulty in awakening the baby, or the baby refuses to eat. The symptoms of meningitis may not be the same for every person.

Viral meningitis patients appear lethargic and may be not well oriented. They also appears feverish grading (40°C/104°F). The signs may differ according to the patient age and the virus causing the disease as well. Different signs can be noticed like photophobia, phonophobia, nuchal rigidity, altered mental status, and skin rash.

Viral meningitis lab tests include non specific blood tests like the CBC, blood culture, PT and PTT tests. Other tests include some tissues swabbing like the throat and nose swab to detect the viruses. PCR is also recommended for virus detection. CSF studies is the most important specific diagnostic test for the viral meningitis and it also differs between the various types of meningitis.

Viral meningitis diagnosis depends on mainly the CSF studies. CT scan is required for imaging before applying the lumbar puncture to see if there is any contraindication for the procedure. However, CT scan may be performed to exclude other brain diseases that can be misinterpreted with the viral meningitis.^[5]

Viral meningitis diagnosis depends on mainly the CSF studies.However, MRI scan may be performed to exclude other brain diseases that can be misinterpreted with the viral meningitis.

There are no ultrasound findings associated with viral meningitis.

There are no x-ray findings associated with viral meningitis.

There is no other imaging findings to diagnose the viral meningitis.

There is no other diagnostic studies for the viral meningitis.

Viral meningitis has no specific treatment as most of the patients recover within 7-10 days. General supportive measures are recommended to manage the cases and prevent proceeding to serious conditions like the brain edema. These measures include: analgesics for the pain, acetaminophen for the fever and electrolytes management However, antiviral medical therapy can be provided for the patients caused with specific viruses like the enteroviruses or the influenza. In severe cases, the patients will need to be hospitalized.

Surgical intervention has no role in the management of viral meningitis.

Primary prevention of viral meningitis depends mainly on the self hygiene and some measures that should be considered like: washing hands regularly, avoid touching face, avoid close contact with suspected individuals, and staying home when feeling sick. There are no vaccines against the enteroviruses but other viruses like influenza should be vaccinated to prevent the development of the disease. There is no secondary prevention for viral meningitis.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2]Ahmed Elsaiey, MBBCH [3]

Meningitis was first discovered by Hippocrates. Wallgren described aseptic meningitis in 1924 and defined it as a disease with acute onset that has typical systematic symptoms of meningeal involvement, in association with a cerebrospinal fluid (CSF) typical of meningitis (typically with a mononuclear cell predominance). Additionally, there was absence of bacteria on stain and culture and there was no identifiable parameningeal infection.^[1]

• Meningitis was described first by the hippocrates, but it was first accurately identified by the Swiss Vieusseux (a scientific-literary association) during an outbreak in Geneva, Switzerland in 1805.^[2]
• In 1661, Thomas Willis first described the inflammation of meninges and an epidemic of meningitis.
• In 1891, Heinrich Quincke provided an early analysis of CSF by introducing a new technique of lumbar puncture.
• In early 19th century, detailed profile of CSF analysis in meningitis was explained by William Mestrezat, and H. Houston Merritt.
• Wallgren first described aseptic meningitis was in 1924.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Ahmed Elsaiey, MBBCH [2]

There is no specific classification to the viral meningitis. However, it may be classified based on the age into child and adult viral meningitis. It may be also according to the causative virus like enterovirus, arbovirus, mumps and herpes simplex viruses.

There is no specific classification to the viral meningitis. However, it can be classified according to the age and the causative virus.

• Age:
  • Infantile viral meningitis
  • Adult viral meningitis

• Causative viruses:
  • Enteroviruses
  • Arboviruses
  • Mumps
  • Herpes simplex viruses

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2],Ahmed Elsaiey, MBBCH [3]

Viral meningitis pathophysiology differs from virus to another and depends on many factors like age, immune status and gene expression. Invasion into the meninges by a pathogen can set up a local inflammatory response. The clinical signs are due to this meningeal irritation – for example, Kernig’s sign is due to pain produced by stretching of the inflamed meninges.

• The causative viral agents can reach the nervous system via the blood or the nerves themselves. There is a difference in both pathways pathogenesis. Viral spreading through the blood (viremia) is more common in viral meningitis pathogenesis. The viruses enter to the pulmonary and intestinal mucosa at which they spread into the blood to reach the lymph nodes where viral replication takes place and this is called primary viremia. At this point, the host cells try to prevent further replication from happening and if they fail to stop the replication, secondary viremia will take place and the viruses can spread to the nervous system causing many clinical manifestations.^[1]

• Enteroviruses:
  • They include coxsackievirus A&B, echovirus, hepatitis A, and poliovirus.
  • Infection can be started in the nasal mucosa and after that it can be ingested in the stomach. It attaches to the enterocytes then the viruses reach the peyer’s patches of the lamina propria where the replication takes place.
  • The replication which occurs at this site causes viremia to further organs like the lung, brain and liver at which another replication takes place at these organs causing more viremia. Infection of the nervous system can occur via this viremia which is responsible for the clinical manifestaions of the disease.

• Arboviruses:
  • Common arvboviruses in the United States^[2]:
    • St. louis encephalitis virus (Flavivirus)
    • Western equine encephalitis virus (Alphavirus)
    • Colorado tick fever virus (Coltivirus)
  • They commonly cause encephalitis. However, they are responsible for causing viral meningitis.
  • Pathogenesis is similar to the enteroviruses pathogenesis. The difference between them is in the start process of the infection. The infection starts by the arthropod bite to the skin then virus replication takes place in the lymph nodes then viremia occurs in the distant organs and finally the virus reaches the brain.

• Mumps:
  • Infection occurs through respiratory droplet that infects first the parotid gland causing parotitis.
  • After the infection, viremia takes place and the virus reaches the brain causing meningitis.

• Human herpes viruses:^[3]
  • They include: Herpes simplex virus 1, Herpes simplex virus 2, human herpes virus 1, Cytomegalovirus, epstein barr virus and human herpes virus 8.
  • Primary infection by the herpes viruses is like the other viral infections by invasion through the respiratory and gastric mucosa and the replication followed by the viremia till reaching the brain causing meningitis.
  • Latent infection may occur when the virus is stimulated again by tissue damage or exposure to ultraviolet light.

Infectious transmission is different among the viruses causing viral meningitis:

• Enteroviruses: Feco-oral transmission and may be transmitted by the respiratory droplet
• Herpes simplex virus: Inter-human transmission
• Arboviruses, such as West nile virus : Transmitted through mosquitoes bite
• Mumps: Transmitted via the blood
• Influenza: Postinfections – airborne transmission
• Lymphocytic choriomeningitis virus: Transmitted from the rodents

There is no genetic inheritance correlated with the viral meningitis.

Microscopic pathological findings in viral meningitis may include the following:

• Pleocytosis (10-1000 cells/µl)
• Polymorphous population of lymphocytes
• Activated lymphocytes
• Plasma cells may be binuclear or multinuclear
• Activated monocytes

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ahmed Elsaiey, MBBCH [2]

Viral meningitis is caused by many viruses. The most important and the most common virus group that causes meningitis is Enteroviruses group. There are other viruses cause meningitis as Arbovirus and herpes simplex virus groups but not common as the enteroviruses.^[1][2][3]

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Ahmed Elsaiey, MBBCH [2]

The differential diagnosis of viral meningitis includes two step approach. First is differentiating viral meningitis from other diseases which have similar clinical presentation as viral meningitis such as encephalitis, brain abscess, subarachnoid hemorrage, and brain tumour. Second step involves CSF examination and differentiating viral meningitis from bacterial, fungal and other causes of meningitis

Viral meningitis may mimick other diseases in terms of clinical signs and symptoms. It is important to differentiate viral meningitis from other diseases with similar presentation. Once the diagnsis of meningitis is confirmed, the next step may be to differentiate different types of meningitis on the basis of CSF examnination:^{[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]}

Bacterial meningitis may be differntiated from other causes of meningitis by cerebrospinal fluid examination:^{[21][22][23][24][25]}

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Ahmed Elsaiey, MBBCH [2]

Viral meningitis affect around 26,000 to 42,000 individual annualy with incidence 11 per 100,000 population. There is no gender or racial predilection.

• Viral meningitis is associated with an estimated 26.000-42.000 hospitalizations annually in the United States.^[1]
• The incidence of the viral meningitis is 11 per 100.000 population per year.
• Enteroviruses are responsible for 85-95% of the viral meningitis cases. They are the cause in the summer and fall seasons.

Viral meningitis can occur in any age but it is more common in the infants and children.

Men and women are affected equally by viral meningitis.

There is no racial predilection for viral meningitis.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Ahmed Elsaiey, MBBCH [2]

Viral meningitis risk factors rely particularly on the exposure to the infection itself and the route of transmission like respiratory droplet and feco-oral transmission. However, there are people at risk to be infected by the disease as children less than 5 years and immunocompromised patients.^[1]

Viral meningitis most common risk factors include the following:

• Children less than 5 years
• Immunocompromised patients
• Direct contact with meningitis patients
• Touching surfaces and objects that were touched by infected patients

• Taking chemotherapy medications
• Organ transplant
• Bone marrow transplant

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Ahmed Elsaiey, MBBCH [2]

There is no screening for viral meningitis.

There is no screening for viral meningitis.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Ahmed Elsaiey, MBBCH [2]

Viral meningitis is a self resolved disease if left untreated. It takes around 10 days to be resolved. Seizures and loss of consiousness are the most important complications that may appear in the infants younger than 3 months. It has an excellent prognosis.

If left untreated, viral meningitis usually will be self resolved within 10 days. Unlike the bacterial meningitis that may lead to critical medical conditions.

Although viral meningitis is a self resolved disease in most cases, some complications may take place in the infants younger than 3 months. These complications include the following:^[1]

• Seizures
• Loss of consiousness

Viral meningitis prognosis is excellent as the disease usually resolve within 10 days.