Encephalitis (viral encephalitis)

• What is Encephalitis (Viral Encephalitis)
• Statistics on Encephalitis (Viral Encephalitis)
• Risk Factors for Encephalitis (Viral Encephalitis)
• Progression of Encephalitis (Viral Encephalitis)
• Symptoms of Encephalitis (Viral Encephalitis)
• Clinical Examination of Encephalitis (Viral Encephalitis)
• How is Encephalitis (Viral Encephalitis) Diagnosed?
• Prognosis of Encephalitis (Viral Encephalitis)
• How is Encephalitis (Viral Encephalitis) Treated?
• Encephalitis (Viral Encephalitis) References

What is Encephalitis (Viral Encephalitis)

Encephalitis is an inflammation of the brain parenchyma (the functional part of the brain). Patients affected have widespread or focal disability of the neurological and psychological function. Encephalitis is different from meningitis, although, clinically, the 2 often occur together with signs and symptoms of meningitis, such as fear of light, headache, or stiff neck. Encephalitis usually has a viral cause however, it can occur as a result of bacterial or fungal meningitis. Common viral causes of encephalitis include Herpes Simplex virus (HSV – most common cause), ECHO, Coxsackie, mumps and Epstein-Barr viruses. A well known case in Australia is the Ross River virus.

Statistics on Encephalitis (Viral Encephalitis)

The occurence rate of encephalitis is about 1 in 200,000 per year. The most commonly affected groups are children, the elderly, and those with suppressed immune systems. Approximately 850 cases of encephalitis were reported in 1994. The true statistics of these infections are difficult to obtain because the diagnosis may not be considered, many cases are unreported, or a specific viral cause is never confirmed.

Risk Factors for Encephalitis (Viral Encephalitis)

Exposure to viruses can occur through insect bites, food or drink contamination, inhalation of respiratory droplets from an infected person, skin contact, and extremely rarely, vaccinations.

Progression of Encephalitis (Viral Encephalitis)

Most episodes of encephalitis are mild and patients will recover by themselves. In a small number of cases, the disease can be very serious, leading to brain damage, coma and death. In general however, the fevers and headaches associated with the illness last for 1-2 weeks before gradually improving. Full recovery may take weeks to months.

How is Encephalitis (Viral Encephalitis) Diagnosed?

Tests which may help make the diagnosis of encephalitis include:

• Lumbar puncture: a needle is used to collect fluid from within the spine, and this is analysed.
• EEG: a scan of brain activity, which may be abnormal.
• A CT or MRI scan of the head.
• Special tests can also be done to help identify the cause of the encephalitis.

Prognosis of Encephalitis (Viral Encephalitis)

The prognosis depends on the type of virus and the condition of the patient e.g. general health, age, immune status, and pre-existing brain conditions.

How is Encephalitis (Viral Encephalitis) Treated?

The goals of treatment are to provide supportive care and relieve symptoms. Antiviral medications may be prescribed for herpes encephalitis or other severe viral infections. Most of the time, however, no specific antiviral drugs are available to combat the infection. Antibiotics may be prescribed when the infection is caused by bacterial organisms. Anti-epileptic medications are used to suppress seizures if they happen to occur. On rare occasions, potent anti-inflamatory drugs called “steroids” (such as dexamethasone) are used to reduce brain swelling. Sedatives may be needed to treat irritability or restlessness. Supportive care (rest, nutrition, fluids) allows the body to fight the infection. After the acute illness physiotherapy and speech therapy may be needed for rehabiliation.

Encephalitis (Viral Encephalitis) References

1. Anderson DC, Kozak AJ: Meningitis, encephalitis, and brain abscess. In: Tintinalli JE, et al, eds. Emergency Medicine: A Comprehensive Study Guide. 4th ed . McGraw-Hill; 1997.
2. Centers for Disease Control and Prevention. Summary of notifiable diseases, United States 1994. MMWR 1994;43(53):1-80.
3. Gutierrez KM, Prober CG. Encephalitis: Identifying the specific cause is key to effective management. Postgrad Med 1998; 103(3): 123-5, 129-30, 140-3.
4. Koskiniemi M, Rautonen J, Lehtokoski-Lehtiniemi E, et al. Epidemiology of encephalitis in children: a 20-year survey. Ann Neurol 1991;29(5):492-7
5. Lazoff M. Encephalitis [online]. 2005 [citec 2006 Jan 29]. Available from: URL: http://www.emedicine.com/emerg/topic163.htm
6. UpToDate: Johnson RP, Gluckman SJ. Overview of viral infections of the central nervous system [online]. 2005 [cited 2006 Jan 28]. Available from: URL: http://www.utdol.com/application/topic.asp?file=cns_infe/2236&type=A&selectedTitle=1~68
7. Walls RM: Adult meningitis, encephalitis, and intracranial abscess. In: Rosen P, ed. Emergency Medicine: A Comprehensive Study Guide. 3rd ed. Mosby; 1992.