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INTRODUCTION-

Encephalitis is an inflammation of the brain tissue. The most common cause is viral infections. In rare cases it can be caused by bacteria or even fungi.

There are two main types of encephalitis: primary and secondary. Primary encephalitis occurs when a virus directly infects the brain and spinal cord. Secondary encephalitis occurs when an infection starts elsewhere in the body and then travels to your brain.

Encephalitis is a rare yet serious disease that can be life-threatening. You should call your doctor immediately if you have symptoms of encephalitis.

Encephalitis often causes only mild flu-like signs and symptoms — such as a fever or headache — or no symptoms at all. Sometimes the flu-like symptoms are more severe. Encephalitis can also cause confused thinking, seizures, or problems with movement or with senses such as sight or hearing.

In some cases, encephalitis can be life-threatening. Timely diagnosis and treatment are important because it’s difficult to predict how encephalitis will affect each individual.

Types-

Different types of encephalitis have different causes.

• Japanese encephalitis is spread by mosquitoes
• Tick-borne encephalitis is spread by ticks
• Rabies can be spread through a bite from a mammal

There is also primary or secondary encephalitis.

Primary or infectious encephalitis can result if a fungus, virus, or bacterium directly infects the brain.

Secondary, or post-infectious, encephalitis is when the immune system responds to a previous infection and mistakenly attacks the brain.

SYMPTOM-

The patient typically has a fever, headache, and photophobia (excessive sensitivity to light). There may also be general weakness and seizures.

Less common symptoms

The individual may also experience nuchal rigidity (neck stiffness), which can lead to a misdiagnosis of meningitis. There may be stiffness of the limbs, slow movements, and clumsiness. The patient may also be drowsy and have a cough.

More serious cases

In more serious cases, the person may experience very severe headaches, nausea, vomiting, confusion, disorientation, memory loss, speech problems, hearing problems, hallucinations, as well as seizures and possibly coma. In some cases, the patient can become aggressive.

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Signs and symptoms in infants

Initially, encephalitis is harder to detect in young children and babies. Parents or guardians should look out for vomiting, a bulging fontanel (the soft area on the top center of the head), incessant crying that does not get better when the baby is picked up and comforted, and body stiffness.

The symptoms of encephalitis can range from mild to severe.

Mild symptoms include:

• fever
• headache
• vomiting
• stiff neck
• lethargy (exhaustion)

Severe symptoms include:

• fever of 103°F (39.4°C) or higher
• confusion
• drowsiness
• hallucinations
• slower movements
• coma
• seizures
• irritability
• sensitivity to light
• unconsciousness

Infants and young children show different symptoms. Call a doctor immediately if your child is experiencing any of the following:

• vomiting
• bulging fontanel (soft spot in the scalp)
• constant crying
• body stiffness
• poor appetite

CAUSES-

Encephalitis can develop as a result of a direct infection to the brain by a virus, bacterium, or fungus, or when the immune system responds to a previous infection; the immune system mistakenly attacks brain tissue.

Primary (infectious) encephalitis can be split into three main categories of viruses:

1. Common viruses, including HSV (herpes simplex virus) and EBV (Epstein-Barr virus)
2. Childhood viruses, including measles and mumps
3. Arboviruses (spread by mosquitoes, ticks, and other insects), including Japanese encephalitis, West Nile encephalitis, and tick-borne encephalitis

Secondary encephalitis: could be caused by a complication of a viral infection. Symptoms start to appear days or even weeks after the initial infection. The patient’s immune system treats healthy brain cells as foreign organisms and attacks them. We still do not know why the immune system malfunctions in this way.

In more than 50 percent of encephalitis cases, the exact cause of the illness is not tracked down.

Encephalitis is more likely to affect children, older adults, individuals with weakened immune systems, and people who live in areas where mosquitoes and ticks that spread specific viruses are common.

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Common viral causes

The viruses that can cause encephalitis include:

• Herpes simplex virus (HSV). Both HSV type 1 — associated with cold sores and fever blisters around your mouth — and HSV type 2 — associated with genital herpes — can cause encephalitis. Encephalitis caused by HSV type 1 is rare but can result in significant brain damage or death.
• Other herpes viruses. These include the Epstein-Barr virus, which commonly causes infectious mononucleosis, and the varicella-zoster virus, which commonly causes chickenpox and shingles.
• Enteroviruses. These viruses include the poliovirus and the coxsackievirus, which usually cause an illness with flu-like symptoms, eye inflammation and abdominal pain.
• Mosquito-borne viruses. These viruses can cause infections such as West Nile, La Crosse, St. Louis, western equine and eastern equine encephalitis. Symptoms of an infection might appear within a few days to a couple of weeks after exposure to a mosquito-borne virus.
• Tick-borne viruses. The Powassan virus is carried by ticks and causes encephalitis in the Midwestern United States. Symptoms usually appear about a week after a bite from an infected tick.
• Rabies virus. Infection with the rabies virus, which is usually transmitted by a bite from an infected animal, causes a rapid progression to encephalitis once symptoms begin. Rabies is a rare cause of encephalitis in the United States.
• Childhood infections. Common childhood infections — such as measles (rubeola), mumps and German measles (rubella) — used to be fairly common causes of secondary encephalitis. These causes are now rare in the United States due to the availability of vaccinations for these diseases.

Risk factors

Anyone can develop encephalitis. Factors that may increase the risk include:

• Age. Some types of encephalitis are more common or more severe in certain age groups. In general, young children and older adults are at greater risk of most types of viral encephalitis.
• Weakened immune system. People who have HIV/AIDS, take immune-suppressing drugs or have another condition causing a weakened immune system are at increased risk of encephalitis.
• Geographical regions. Mosquito- or tick-borne viruses are common in particular geographical regions.
• Season of the year. Mosquito- and tick-borne diseases tend to be more common in summer in many areas of the United States.

DIAGNOSIS

Your doctor will first ask you about your symptoms. They may perform the following tests if encephalitis is suspected.

Spinal tap or lumbar puncture

In this procedure, your doctor will insert a needle into your lower back to collect a sample of spinal fluid. They will test the sample for signs of infection.

Brain imaging with CT scan or MRI

CT scans and MRI detect changes in brain structure. They can rule out other possible explanations for symptoms, such as a tumor or stroke. Certain viruses have a tendency to affect certain areas of the brain. Seeing what parts of your brain are affected can help determine what type of virus you have.

Electroencephalograph (EEG)

An EEG uses electrodes (small metal discs with wires) attached to the scalp to record brain activity. An EEG does not detect the virus that causes encephalitis, but certain patterns on the EEG may alert your neurologist to an infectious source of your symptoms. Encephalitis can lead to seizures and coma in later stages. That’s why the EEG is important in determining the areas of the brain that are affected and the types of brain waves that occur in each area.

Blood tests

A blood test can reveal signs of a viral infection. Blood tests are rarely performed alone. They usually help diagnose encephalitis along with other tests.

Brain biopsy

In a brain biopsy, your doctor will remove small samples of brain tissue to test for infection. This procedure is rarely performed because there’s a high risk of complications. It’s usually only done if doctors can’t determine the cause the brain swelling or if treatment isn’t working.

When to see a doctor

Get immediate care if you are experiencing any of the more-severe symptoms associated with encephalitis. A severe headache, fever and altered consciousness require urgent care.

Infants and young children with any signs or symptoms of encephalitis should receive urgent care.

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Complications

The complications of encephalitis vary, depending on factors such as:

• Your age
• The cause of your infection
• The severity of your initial illness
• The time from disease onset to treatment

People with relatively mild illness usually recover within a few weeks with no long-term complications.

Complications of severe illness

Inflammation can injure the brain, possibly resulting in a coma or death.

Other complications — varying greatly in severity — may persist for months or be permanent. These complications can include:

• Persistent fatigue
• Weakness or lack of muscle coordination
• Personality changes
• Memory problems
• Paralysis
• hearing defect
• vision defect

TREATMENT-

Treatment for encephalitis focuses on alleviating symptoms. There are only a limited number of reliably tested specific antiviral agents that can help, one of which is acyclovir; success is limited for most infections except when the condition is due to herpes simplex.

Corticosteroids may be administered to reduce the brain’s inflammation, especially in cases of post-infectious (secondary) encephalitis. If the patient has severe symptoms, they may need mechanical ventilation to help them breathe and other supportive treatment.

Anticonvulsants are sometimes given to patients who have seizures. Sedatives can be effective for seizures, restlessness, and irritability. For patients with mild symptoms, the best treatment is rest, plenty of fluids, and Tylenol (paracetamol) for fever and headaches. Tylenol is available to purchase online.

Prevention

Keeping up-to-date with vaccines is the most effective way of reducing the risk of developing encephalitis. These include vaccines for measles, mumps, rubella, and if the virus exists in those areas, Japanese encephalitis and tick-borne encephalitis.

In areas known to have mosquitoes that carry encephalitis-causing viruses, individuals should take measures to reduce the risk of being bitten. This may include wearing appropriate clothing, avoiding mosquito-infested areas, avoiding going outside at specific times during the day when there are large numbers of mosquitoes about, keeping the home mosquito-free, using mosquito repellent, and making sure there is no stagnant water around the home.

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