Encephalitis (Inflammation Of The Brain)

Also known as brain inflammation, encephalitis is a disease caused by viruses or bacteria damaging brain tissue. It can arise due to various reasons.

What Is Encephalitis?

Encephalitis can be briefly explained as inflammation of the brain tissue. In the advanced stages of brain inflammation, which presents symptoms such as fever, behavioral disorders, and headache, some neurological symptoms may also be observed. The impact of encephalitis on patients is not fully understood, and if not treated early, it can be fatal.

Encephalitis can occur in people of all ages and genders, but it is more common in infants, individuals with AIDS and HIV, and cancer patients. Additionally, it is more frequently observed during periods of epidemic diseases.

Causes of Encephalitis

The exact causes of encephalitis are not fully known, but it is generally thought to be of viral origin. However, bacterial infections and some non-infectious inflammatory conditions can also cause encephalitis. Brain inflammations are generally divided into two groups.

Primary Encephalitis

In primary encephalitis, bacteria or viruses directly reach the brain tissue and cause infection. This type of infection may be concentrated in a specific area or spread over a large area. In viral infections, the reactivation of a previously contracted viral disease can also cause inflammation.

Secondary Encephalitis

In secondary encephalitis, the inflammation occurs in any part of the body. The immune system's response to the infection attacks not only the pathogens causing the infection but also the brain tissues, leading to brain inflammation. Secondary encephalitis typically appears 2 or 3 weeks after the illness has been contracted.

Viruses That Most Commonly Cause Encephalitis

Encephalitis is usually caused by viruses. The most common viruses that lead to this condition are as follows:

Herpes Simplex Virus

The herpes simplex virus is usually responsible for cold sores. It is also one of the most common causes of secondary encephalitis. This virus, which can lead to death in its advanced stages, is seen in 1 in 500,000 people worldwide each year and can cause permanent damage to the body.

Enteroviruses

The symptoms of diseases caused by these viruses are generally the same as those of the flu. Additionally, they can manifest as eye inflammation and abdominal pain. This virus family includes the poliovirus and coxsackie viruses. Therefore, it is possible for symptoms similar to poliomyelitis to appear in brain inflammations caused by enteroviruses.

Mosquito-Borne Viruses

Mosquitoes feed on human blood. Thus, when they bite an infected person, they can easily transmit the infection to other people. Infections caused by mosquitoes typically appear a few days after the bite.

Tick-Borne Viruses

Tick-borne viruses are spread to humans through ticks. In brain inflammations caused by tick-borne viruses, symptoms such as headache, joint pain, and high fever are commonly observed. As the disease progresses, more severe symptoms may occur.

Rabies Virus

The rabies virus, which is generally transmitted through the bite of an infected animal, can cause inflammation in the brain. However, this outcome is rarer compared to other viruses.

Childhood Infections

The most common cause of secondary encephalitis is childhood diseases such as mumps, measles, or rubella. The only way to prevent these diseases is through regular vaccinations.

Risk Factors for Encephalitis

Encephalitis, which can affect people of all ages and genders, is more common in certain risk groups.

Age

Brain inflammation is most commonly seen in infants, children, and the elderly.

Weakened Immune System

People with weakened immune systems are more vulnerable to viruses and bacteria, which increases the risk of developing encephalitis.

Season

Brain inflammations caused by mosquitoes or ticks are more common in the spring and summer seasons.

Geographic Region

In regions where mosquitoes and ticks are more common, encephalitis is also more frequently encountered.

How Is Encephalitis Diagnosed?

Diagnosing encephalitis requires a detailed medical history and a thorough physical examination. Afterward, certain tests are conducted to confirm the diagnosis.

Imaging Tests

MRI and CT scans provide detailed images of any swelling or tumors in the brain.

Lumbar Puncture

This test helps identify changes in the cerebrospinal fluid, indicating brain infections. Additionally, it can determine whether the brain infections are caused by bacteria or viruses.

Laboratory Tests

These tests examine blood, urine, and biopsy samples to check for any infections in the body.

EEG

This test measures the electrical activity of the brain, and abnormal brain waves can aid in the diagnosis of encephalitis.

Biopsy

A brain biopsy is an extremely dangerous procedure and is only performed when absolutely necessary. Examining the tissue sample from the brain can provide a definitive diagnosis of the disease.

Symptoms of Encephalitis

Patients with viral encephalitis usually do not exhibit any symptoms. When symptoms do occur, they are similar to those of the flu. The symptoms seen in these patients include the following:

• Fatigue,
• Weakness,
• Muscle and joint pain,
• Fever,
• Headache,

In patients with severe brain inflammation, more intense symptoms may occur. These symptoms include:

• Loss of consciousness,
• Speech disorders,
• Behavioral disorders,
• Muscle weakness,
• Paralysis in certain parts of the body,
• Seizures,
• Hallucinations,
• Confusion,

The symptoms caused by brain inflammation in infants and children include:

• Stiffness in certain parts of the body,
• Unexplained anger,
• Poor feeding,
• Nausea,
• Vomiting,
• Bulging of the fontanel,

Finally, there are symptoms of encephalitis that require emergency medical intervention. These symptoms include:

• Loss of consciousness,
• High fever,
• Loss of sensation in certain parts of the body,
• Muscle weakness,
• Speech disorders,
• Behavioral disorders,
• Double vision,
• Blurred vision,
• Seizures,
• Perception of bad smells,
• Persistent and severe headaches,

Treatment of Encephalitis

The treatment of brain inflammation is determined based on the factors causing the disease. Therefore, after encephalitis is diagnosed, it is necessary to investigate and determine the underlying cause.

Antiviral Treatments

Since viral infections are the most common cause of brain inflammation, antiviral treatment is generally administered to patients. Additionally, preventive measures should be taken to protect individuals from viruses, thereby preventing the development of the disease.

During the treatment process, patients are advised to rest in bed and consume plenty of fluids. Antiviral drugs containing active ingredients such as acyclovir, ganciclovir, and foscarnet are used. However, in cases of viral diseases caused by insect bites, antiviral drugs are ineffective, and supportive treatments are administered to strengthen the immune system.

Supportive Care

In the treatment of patients with severe brain inflammation, supportive care methods are also necessary.

• Use of necessary medications to stop or reduce the frequency of seizures,
• Administration of corticosteroids to relieve swelling and pressure within the brain,
• Fluid therapy to maintain basic mineral levels,
• Inhalers to support breathing,
• Regular monitoring of heart functions,

Types of Encephalitis

The cause of approximately 40% of encephalitis cases is not fully known. The majority of the remaining 60% are caused by various viruses. Therefore, encephalitis is classified into different types. Moreover, autoimmune encephalitis cases are becoming increasingly common. As a result, encephalitis is generally divided into infectious and autoimmune types.

Infectious Encephalitis

This type, also known as infectious encephalitis, is usually caused by viruses. The frequency of diseases such as measles and chickenpox during childhood has decreased globally due to widespread vaccination. However, due to the lack of sufficient vaccination efforts to prevent encephalitis caused by other viruses, the number of cases remains high. The most common viruses causing viral encephalitis include:

• Herpes simplex virus type 1 and type 2
• Varicella zoster virus
• Enteroviruses

Additionally, certain viruses carried by insects and mosquitoes can also cause encephalitis. These viruses include:

Japanese Encephalitis Virus

JE, also known as Japanese encephalitis, is a preventable and most common type of encephalitis in Asia and the Western Pacific. Although rare among travelers to Asia, the risk factor varies depending on the season of travel, the length of stay at the destination, and the activities to be undertaken.

Most people infected with JE do not show any symptoms. Those who do exhibit symptoms tend to experience mild symptoms. A small percentage of infected individuals may develop serious symptoms, including coma, seizures, tremors, high fever, and disorientation. About 25% of cases are fatal.

West Nile Virus

The primary host of the West Nile virus is wild birds. The virus is transmitted to humans by mosquitoes after biting infected wild birds. It is not transmitted from person to person. Culex mosquitoes, which carry the West Nile virus, can cause several neurological diseases, including encephalitis.

The West Nile virus has an incubation period of up to 15 days, during which no symptoms are observed. Although most cases do not have serious symptoms or clinical conditions, some cases can be life-threatening.

Symptoms of West Nile virus include:

• Flu-like symptoms
• Headache
• Back pain
• Diarrhea
• Muscle weakness
• Rash
• High fever
• Nausea and vomiting
• Severe swelling of lymph nodes
• Central nervous system involvement
• Drowsiness
• Inability to hold the neck upright
• Mental confusion
• Muscle twitching
• Tremors
• Coma
• Convulsions
• Meningitis
• Encephalitis
• Paralysis

Powassan Virus

The Powassan virus is a type of virus spread to humans by ticks. Although rare, recent years have seen an increase in Powassan virus cases. It is a serious disease that can cause both encephalitis and meningitis.

St. Louis Virus

Another mosquito-borne virus is the St. Louis virus, which is related to the Japanese encephalitis virus and is particularly prevalent in Hawaii, the Greater Antilles, Canada, and Mexico.

It typically presents with symptoms such as mild headache and fever. However, in some cases, significant and serious symptoms can occur, including:

• Severe headache
• Neck stiffness
• High fever
• Drowsiness
• Disorientation
• Tremors
• Occasional seizures
• Spastic paralysis
• Coma

The mortality rate for cases of St. Louis virus ranges from 3% to 30%.

La Crosse Virus

The La Crosse virus, frequently found in the Upper Midwest, Mid-Atlantic, and Southeastern United States, is spread by mosquitoes. Although it can cause encephalitis in some individuals, it typically does not present with a serious clinical picture. The majority of severe cases are observed in children under the age of 16. The first symptoms in individuals with La Crosse virus appear 5 to 15 days after being bitten by a mosquito, including:

• Headache
• Nausea and vomiting
• Fatigue
• Drowsiness
• Increased sleepiness
• Encephalitis
• High fever
• Neck stiffness
• Disorientation
• Coma
• Tremors
• Seizures
• Muscle weakness
• Vision loss
• Paralysis

After treatment, the La Crosse virus can leave damage to the central nervous system. Therefore, cognitive and behavioral disorders and seizures may persist after treatment. The mortality rate for La Crosse virus is less than 1%.

Chikungunya Virus

Another virus transmitted by mosquitoes is the Chikungunya virus. The same mosquitoes that cause Dengue fever also spread this virus. Although rare, transmission from mother to baby during childbirth can occur in some cases. The symptoms of Chikungunya virus include:

• Fever
• Joint pain
• Headache
• Muscle pain
• Swelling in the joints
• Rash

While some patients recover within a week, joint pain may persist for months in others.

In addition to viruses, fungi, parasites, and bacteria can also cause encephalitis, though these cases are rare.

Autoimmune Encephalitis

Autoimmune encephalitis is a clinical condition that occurs when a person's immune system attacks brain cells. Specifically, antibodies target specific proteins in the brain, allowing the identification of the type of autoimmune encephalitis. As a result, autoimmune encephalitis is divided into three groups.

• In cases of anti-NMDA receptor encephalitis, the immune system attacks NMDA receptors in the brain.
• In VGKC complex antibody encephalitis, the immune system attacks VGKC brain proteins, including the LGI-1 and CASPR2 subtypes.
• GABA-A and GABA-B receptors are also attacked by the immune system.
• Although the cause of autoimmune encephalitis is not fully known, in some cases, it is associated with benign tumors. In cases of autoimmune encephalitis, such as acute disseminated encephalomyelitis (ADEM), it can be triggered by an infection.

Difference Between Encephalitis and Meningitis

The three membranes that cover the brain and spinal cord are known as the meninges. Meningitis is a disease caused by inflammation of the meninges. Encephalitis, on the other hand, is the inflammation of the brain. The different areas of inflammation help distinguish between the two diseases. However, in some cases, both the brain and meninges may become inflamed, a condition known as meningoencephalitis.

Both diseases can be caused by bacteria, viruses, and parasites. Another similarity between meningitis and encephalitis is that the infection can present with acute or chronic symptoms and can be fatal in some cases.

Another similarity between the two diseases is that the swelling caused by inflammation can damage brain tissue and lead to permanent damage in the affected area. Additionally, both diseases can compromise the blood-brain barrier, allowing large molecules, toxins, immune system chemicals, and white blood cells to reach the brain.