Encephalitis is defined as an inflammation of the brain tissue. Related conditions include meningitis (inflammation of the membranes that cover the brain) and encephalomyelitis (inflammation of both the brain and the spinal cord). Encephalitis is mostly caused by viral infections of the brain tissue. Encephalitis could also occur as a side-effect or complication of an immune response to some disease-causing agent or vaccine.
The symptoms of encephalitis could range from very mild to severe. Following are the symptoms associated with a bout of encephalitis:
- Altered mental status (confusion, drowsiness, sudden dementia, memory loss, loss of consciousness)
- Unsteady gait and muscular weakness
- Visual sensitivity to light
- Stiffness in neck and back muscles
Encephalitis can be life-threatening. Therefore, one should consult a doctor immediately when the above mentioned symptoms, especially any sudden changes in mental status, appear. Diagnosis of encephalitis involves MRI scans of the brain to locate any lesions, swelling, and internal bleeding in the brain. Analysis of the cerebrospinal fluid (CSF) is also done to look for signs of viral infection (using a technique called PCR) and other changes that could indicate encephalitis.
Encephalitis is mostly caused by a viral infection of the brain. However, it could be the primary disease or a side-effect of the immune response to a viral infection.
Primary encephalitis due to viral infection
Viruses such as arbovirus, poliovirus, echovirus, herpes simplex virus, rabies virus, and varicella-zoster virus can directly invade the brain and damage the nerve cells (neurons) to cause encephalitis. In some cases (like with infections with HIV, measles virus and JC virus), encephalitis symptoms may appear a long time after the viral infection.nExposure to viruses that cause encephalitis could occur via contact with infected people through body secretions and through insect bites.
Encephalitis due to complications of immune response
Encephalitis may also result from a misdirected immune response after a viral infection (measles, mumps, rubella, chickenpox, HIV, influenza, and hepatitis) or vaccination (smallpox and live-rabies vaccines). These are cases of mistaken identity in which the virus or vaccine and the nerve cells share some common proteins (antigens) that the immune system recognizes and attacks.
Treatment of encephalitis involves the following options:
This involves management of the symptoms to prevent worsening of the condition. Medications are given to treat fever and headaches. Dehydration and electrolyte imbalance is monitored and corrected. Anti-convulsants are given to prevent seizures. Corticosteroids could be given to reduce swelling and inflammation of the brain. Sedatives could be given to cope with irritability.
Anti-viral drugs are given when encephalitis is caused by direct effects of viral infection. For example, acyclovir is given if HSV infection is suspected to be the cause of encephalitis.
The success of treatment depends on the severity of encephalitis in a particular patient. In mild cases, full recovery can be expected. However, permanent neurological deficits or death may occur if the symptoms are severe. Infants are most susceptible to permanent brain damage due to encephalitis.