Overview

Encephalitis is a serious medical condition involving inflammation of the brain. It often presents with symptoms that affect mental clarity, coordination, behavior, and other vital functions. While some cases may be mild, others can become life-threatening without prompt medical care. Each year, thousands of people are hospitalized due to encephalitis, and quick intervention can mean the difference between recovery and long-term disability or death.

Types of Encephalitis

Encephalitis is typically categorized by its root cause. Understanding the type is crucial for determining appropriate treatment.

Infectious encephalitis

This is the most common form, caused by pathogens like viruses, bacteria, fungi, or parasites. Among these, viral encephalitis is most frequently diagnosed, with herpes simplex virus (HSV) being the leading cause in many countries.

Other infectious organisms include:

  • Arboviruses (spread by mosquitoes or ticks)

  • Enteroviruses

  • Epstein-Barr virus

  • Adenoviruses

  • Herpes zoster (shingles)

  • Rabies virus

  • Hepatitis viruses

  • Malaria parasites

Symptoms usually appear suddenly and worsen quickly. Diagnosing the specific microorganism is essential to guide therapy.

Autoimmune encephalitis

In autoimmune encephalitis, the body’s immune system mistakenly attacks brain tissue. It has become more widely recognized in recent years, though many cases still go undiagnosed or misdiagnosed. Antibodies targeting certain brain receptors are often present.

Common subtypes include:

  • Anti-NMDA receptor encephalitis: Found especially in younger women; symptoms include mood swings, hallucinations, seizures, and irregular heartbeat.

  • Anti-LGI1 encephalitis: More common in older men; usually affects memory and causes seizures.

  • Rasmussen’s encephalitis: A rare condition that typically affects children and causes seizures and progressive neurological decline on one side of the brain.

Paraneoplastic encephalitis

Some cancers can lead to immune system dysfunction that targets the brain, even if cancer itself hasn't spread there. This is called paraneoplastic encephalitis and is commonly associated with cancers like:

  • Lung

  • Breast

  • Ovarian

  • Lymphoma

Key Symptoms

The symptoms of encephalitis vary based on the part of the brain involved and the severity of the condition. In many cases, symptoms progress rapidly.

Common symptoms include:

  • Fever

  • Confusion or disorientation

  • Seizures

  • Headache

  • Memory loss

  • Muscle weakness

  • Speech or coordination difficulties

  • Tremors or involuntary movements

  • Vision disturbances

  • Behavioral changes

  • Mood swings

In infants, encephalitis may cause:

  • Poor feeding

  • Vomiting

  • Irritability

  • Bulging soft spot on the head

  • Lethargy or unresponsiveness

  • Seizures

Some autoimmune-related forms may develop gradually over weeks or months and may mimic psychiatric conditions.

Underlying Causes

Despite extensive testing, up to 50% of encephalitis cases have no clear cause. When identifiable, causes may include:

  • Viral infections (e.g., HSV, JE virus, arboviruses)

  • Autoimmune reactions

  • Post-infectious complications

  • Parasitic infections (e.g., malaria)

  • Reactivation of latent viruses

Factors that may increase the risk:

  • Travel to regions with endemic viruses

  • Weak immune system (e.g., due to HIV, cancer, diabetes)

  • Close contact living environments (e.g., dormitories)

  • Lack of vaccination

Diagnosis

To diagnose encephalitis, symptoms must persist for at least 24 hours without another identifiable cause. Diagnosis often involves ruling out other critical conditions such as:

  • Meningitis

  • Sepsis

  • Stroke

  • Brain tumor

  • Drug overdose

  • Electrolyte imbalances

Diagnostic tools and procedures:

  • MRI or CT scan to detect inflammation

  • Lumbar puncture (spinal tap) to analyze cerebrospinal fluid (CSF)

  • Blood and urine tests for signs of infection

  • EEG to detect abnormal brain activity or seizures

  • Autoantibody panels for autoimmune forms

  • Chest X-rays or other imaging to look for signs of systemic infection or cancer

Treatment Options

Treatment must begin promptly, even before all test results are available.

Targeted treatment

  • Antivirals (e.g., IV acyclovir for HSV)

  • Antibiotics (for bacterial causes)

  • Antiparasitic drugs (for parasitic infections)

  • Steroids to reduce brain inflammation (in autoimmune cases)

  • Immunoglobulin therapy (IVIG)

  • Plasmapheresis (removing harmful antibodies from the blood)

  • Immunosuppressants (e.g., cyclophosphamide, rituximab)

For paraneoplastic cases, tumor removal is key.

Supportive care

  • Hospitalization in ICU if necessary

  • Anticonvulsants for seizures

  • Ventilation support if breathing is compromised

  • Fluids and medications for swelling

  • Pain and fever management

Recovery and Rehabilitation

Recovery may take weeks, months, or even longer, depending on the severity and underlying cause. Many patients benefit from long-term rehabilitation services:

  • Physical therapy: To regain strength and coordination

  • Occupational therapy: To assist with daily living tasks

  • Speech therapy: To improve language and swallowing difficulties

Ongoing support is essential, and some people may require assistive devices or home care. Medications may be continued to manage seizures or inflammation.

Long-Term Complications

While some patients recover fully, others experience lifelong complications:

  • Memory loss

  • Difficulty speaking

  • Personality or mood changes

  • Seizure disorders

  • Muscle weakness

  • Vision or hearing impairment

  • Cognitive decline

Autoimmune encephalitis may increase the risk of other autoimmune diseases like Hashimoto’s thyroiditis or lupus.

Prevention Tips

Not all cases of encephalitis can be prevented, but precautions can significantly reduce risk:

  • Vaccination: Get routine and travel vaccines (e.g., MMR, Japanese encephalitis)

  • Mosquito control: Use insect repellent, wear protective clothing, and eliminate standing water

  • Hygiene: Wash hands regularly and avoid sharing food or drinks

  • Safe food and water: Especially when traveling

  • Timely treatment: For infections to prevent complications