Encephalitis is a disease that results in inflammation of the brain. The patient’s central nervous system is affected. While the lesser symptoms include headaches and fevers, the more severe ones cause the onset of mental issues like seizures, confusion, disorientation, tremors and hallucinations. It can be caused due to bacterial or viral infections of the brain, injection of toxic substances or increased complications of an infectious disease.
Depending on the virus causing the disease and the mode of its transmission, encephalitis has been identified as different types:
- Herpes Simplex encephalitis: It is caused by the HSV-1 (Herpes simplex virus type 1) virus.
- Japanese encephalitis: It is caused by flavivirus, named after the yellow fever virus and was first identified in Japan. It is mainly transmitted through Culex mosquitoes
- West Nile encephalitis: It is caused by a virus belonging to the Flaviviridae family and is spread through mosquitoes. Its main characteristic is high fever.
- Tick borne encephalitis: Any virus that spreads through ticks to cause encephalitis is called tick-borne encephalitis
Encephalitis, in most cases, is caused by a viral infection and there are several viruses that can cause inflammation of the brain. Some common viruses known to cause the condition include polio, rabies virus, varicella zoster (chicken pox virus), mumps and rubella. Other groups of viruses include adenovirus, cytomegalovirus, West Nile virus and echovirus.
The virus can be transmitted from one person to another through:
- Consumption of contaminated food and water
- Direct contact with an affected individual
- Inhaling respiratory droplets expelled by an infected person
- Insect bites (ticks, mosquitoes)
Other causes of encephalitis include:
- Allergies to vaccination
- Parasitic infection (roundworm, toxoplasma infection)
Dr Abhijit Das, Director of Neurorehabilitation Program and consultant Neurologist, Institute of Neurosciences, Kolkata says, ‘Anybody can suffer from encephalitis, from children to elderly.’ However, the risk is greater during the first few years of life. Additionally, people with a compromised immune system and those who have increased level of autoantibodies in them are at a greater risk.
The virus reaches the brain tissue and causes inflammation. It causes swelling of the brain tissue and can even destroy the neurons. Sometimes, brain hemorrhage or bleeding is also seen.
The following symptoms may occur:
- Stiffness in the neck and the back
Apart from these Dr Das highlights the following emergency symptoms of encephalitis.
- Altered consciousness
- Weakness in hand or legs
- There may be fever
Emergency symptoms form the basis of suspecting encephalitis. But to diagnose its root cause, different tests might be needed. ‘Diagnosis involves a combination of clinical examination with the help of brain scans mainly magnetic resonance imaging (MRI). We also need electroencephalogram (EEG) along with the study of cerebrospinal fluid (CSF) obtained through a lumbar puncture,’ says Dr Das.
‘Some viral encephalitis like Herpes Simplex encephalitis and Japanese encephalitis do have definitive diagnostic tests. Some of them can be detected by serological testing, where the presence of antibodies against the virus is detected. The recent viral encephalitis caused by the West Nile virus can be diagnosed in some labs in India. For autoimmune encephalitis there are different blood tests and CSF tests,’ he explains.
The goal of the treatment is to provide supportive care and help the body fight infection. Dr Das says, ‘Treatment is usually as per the symptoms (symptomatic). Reliably tested, specific drugs against viruses (antiviral agents) are few in number and are used with limited success in treatment of viral infection, with the exception of herpes simplex encephalitis, which is treated with acyclovir.’
‘In patients who are very sick, supportive treatment such as mechanical ventilation, is equally important. Most of these patients require care in ICU setting. Corticosteroids (e.g., methylprednisolone) are used to reduce brain swelling and inflammation. Sedatives may be needed for irritability or restlessness,’ he says.
Prevention is the best way to control outbreaks. ‘In India, vaccination is available against tick-borne and Japanese encephalitis and should be considered by individuals who are at high-risk. Most of these viruses are spread by mosquito bites, so control of mosquitoes breeding is very important. In India the monsoon season is the encephalitis season. We are already seeing outbreaks in North Bengal and a lot of people are dying. To control death, awareness about mosquito control and prevention of encephalitis is important,’ he concludes.
The content has been verified by
Dr Abhijit Das
, Director of Neurorehabilitation Program and consultant Neurologist, Institute of Neurosciences, Kolkata.