Encephalitis

What are the sequelae of encephalitis? All the information about this disorder: causes, symptoms, and treatments.

Symptoms and Causes

Encephalitis refers to a set of disorders characterized by inflammation of the brain tissue. It is an infrequent but very serious condition with a high mortality rate, thus constituting a medical emergency.

Depending on the origin of the inflammation, two main types of encephalitis are distinguished:

Infectious encephalitis: caused by a viral or bacterial infection.
Autoimmune encephalitis: caused by a reaction of the immune system.

Encephalitis is further classified based on the areas where the inflammation occurs:

Meningoencephalitis: inflammation of the brain and meninges.
Encephalomyelitis: inflammation of the brain and spinal cord.
Limbic encephalitis: inflammatory process localized in the limbic system.
Lethargic encephalitis: affects the brain, midbrain, and basal ganglia.

Symptoms

The symptoms of infectious encephalitis vary greatly. Its acute phase lasts for one to two weeks, and common symptoms include:

Digestive symptoms: before the encephalitis-specific symptoms manifest, nausea, vomiting, diarrhea, or abdominal pain may appear.
Acute febrile syndrome: in the early stage, encephalitis presents with symptoms similar to the flu, such as fever, headache, weakness, muscle or joint pain, and general malaise.
Neck and back stiffness, if the meninges are affected.
Seizures.
Personality changes.
Confusion.
Numbness or paralysis in certain parts of the face or body, if the spinal cord is affected.
Incontinence.
Abnormal movements and motor coordination issues.
Auditory, olfactory, or visual hallucinations.
Aphasia: the inability to produce or understand language.
Extreme sudden drowsiness: a typical symptom of lethargic encephalitis.
Loss of consciousness.
Coma.

The symptoms of autoimmune encephalitis develop more slowly over several weeks:

Personality changes.
Memory loss.
Psychotic episodes.
Hallucinations.
Seizures.
Loss of sensitivity.
Sleep disorders.
Vision problems.
Difficulty walking.
Abnormal movements.
Incontinence.

In babies and young children, common symptoms include:

Bulging fontanels: the soft spots of the skull.
Nausea, vomiting.
Irritability and frequent crying.
Body stiffness.
Insufficient feeding.

Causes

In most cases, infectious encephalitis is viral, caused by a virus directly infecting the brain. The viruses that can cause encephalitis include:

Herpesviruses (causing herpes encephalitis), such as herpes simplex virus type 1 and 2, Epstein-Barr virus, varicella-zoster virus, or cytomegalovirus.
Enteroviruses, such as poliovirus, hepatitis virus, or coxsackievirus.
Arboviruses: transmitted by arthropod bites (mosquitoes, fleas, or ticks). These include La Crosse virus, alphavirus genus viruses (responsible for equine encephalitis), West Nile virus, St. Louis virus, Powassan virus, flavivirus genus viruses (causing Japanese encephalitis), chikungunya virus, and Zika virus.
Rabies virus: transmitted through animal bites.
Paramyxoviruses, such as mumps virus and measles virus.

Infectious encephalitis can also result from the reactivation of a virus that caused a previous infection in the body, typically herpes simplex virus type 1, varicella-zoster virus, JC virus, or paramyxovirus. Reactivation may occur years after the primary infection.

In rare cases, bacterial encephalitis is caused by various pathogens:

Borrelia bacteria, transmitted by ticks, responsible for Lyme disease.
Treponema pallidum, causing syphilis.
Toxoplasma, a protozoan causing toxoplasmosis.
Bacteria causing meningitis, such as Mycoplasma pneumoniae or Neisseria meningitidis.
Plasmodium parasites, causing malaria and transmitted by mosquitoes.
Listeria monocytogenes, causing listeriosis.
Rickettsia bacteria, transmitted by fleas, lice, or ticks, responsible for diseases like typhus or Rocky Mountain spotted fever.

In autoimmune encephalitis, inflammation is caused by an erroneous immune system response: the immune system releases antibodies that act against certain neurotransmitter receptors or neuronal surface proteins, frequently targeting the NMDA receptor or myelin (in acute disseminated encephalomyelitis). Common triggers for this immune response include:

Previous viral infections (post-infectious encephalitis): caused by enteroviruses, Epstein-Barr virus, hepatitis A and B viruses, HIV (human immunodeficiency virus), or influenza virus.
Vaccines.
Benign or malignant tumors (paraneoplastic encephalitis).

In many cases, no specific trigger for autoimmune encephalitis is identified, as is the case with Rasmussen encephalitis or Hashimoto's encephalitis.

Risk Factors

The likelihood of developing encephalitis increases in the following situations:

Compromised immune system, more susceptible to infections.
Exposure to arthropods.
Summer season: viral transmission by arthropods is more common in warmer months.
Autoimmune disorders: increase the risk of autoimmune encephalitis.
Age: in general, viral encephalitis is more common in children and the elderly.
Cancer or tumor processes.

Complications

While mild forms of encephalitis can recover within a few weeks, more severe forms can lead to death or long-lasting, even permanent sequelae, including:

Memory loss.
Loss of muscle control.
Weakness.
Loss or alteration of sensitivity.
Speech, hearing, or vision impairments.
Personality changes.
Persistent fatigue.
Learning disorders.

Prevention

The most effective way to prevent encephalitis is to take measures to protect oneself from infections:

Vaccination: stay up to date with mandatory and recommended vaccinations, and get necessary vaccines when traveling to other countries, as well as vaccinating pets against rabies.
Maintain proper hygiene, including frequent handwashing with soap and water.
Avoid sharing personal items such as toothbrushes, cutlery, razors, drinks, etc.
Strengthen the immune system by maintaining a healthy diet and exercising regularly.
Protect against mosquito and tick bites:

Apply DEET-based mosquito repellent on skin and clothing.
Use insecticides containing permethrin on clothing and other items, but not on skin.
Use mosquito nets.
Wear long-sleeve clothing and long pants in high-risk areas.
Avoid areas with stagnant water.
Keep water-accumulating areas at home clean and dry, such as pots or gutters.
Avoid unnecessary exposure to areas with frequent mosquito or tick activity.

What doctor treats encephalitis?

Encephalitis is evaluated and treated in the neurology unit.

Diagnosis

When characteristic symptoms are present, the following tests are performed to confirm the diagnosis of encephalitis and identify the causative agent:

Imaging tests such as MRI or CT scans to detect brain inflammation. They also help rule out conditions with similar symptoms, such as stroke or brain tumors.
Electroencephalogram (EEG): electrodes placed on the scalp measure the brain's electrical activity, allowing detection of abnormalities characteristic of encephalitis.
Lumbar puncture: a needle is inserted into the lumbar area to collect cerebrospinal fluid and measure white blood cell levels, which are elevated in cases of encephalitis. Infections or antibodies associated with autoimmune encephalitis can also be detected.
Blood analysis: blood tests can identify the microorganisms responsible for encephalitis.
Polymerase chain reaction (PCR) test: a sample of blood, saliva, mucus, or tissue is taken, and polymerase is added to replicate its genetic material millions of times. The sample also contains genetic material from the infectious agent, which can then be identified.
Brain biopsy: in severe cases where symptoms worsen and treatment is ineffective, a sample of brain tissue may be taken for analysis.

Treatment

Encephalitis treatment depends on its cause and severity. Options include:

Anti-inflammatory drugs, such as ibuprofen, to alleviate headache and fever in cases of mild encephalitis.
Antivirals, if encephalitis is caused by a viral infection. Common antivirals include acyclovir, ganciclovir, and foscarnet.
Antibiotics, if the causative agent is bacterial.
Anticonvulsants, if encephalitis causes seizures.
For autoimmune encephalitis, treatment includes:

Corticosteroids, such as prednisone or methylprednisolone, to inhibit the immune response and reduce inflammation.
Immunomodulators: drugs that regulate immune response.
Immunosuppressants: drugs that inhibit immune response.
Intravenous immunoglobulin: antibodies from healthy donor plasma are injected.
Plasmapheresis: a procedure that removes abnormal antibodies from the blood by extracting the patient’s blood, separating plasma from blood cells in a centrifuge or filter, discarding the plasma, and returning the cells with a replacement fluid, such as albumin.

Rehabilitation therapy: if neurological sequelae persist after encephalitis resolution, physiotherapy, occupational therapy, speech therapy, or psychotherapy can be applied to recover brain function, motor skills, and speech, as well as to acquire adaptation strategies and behavioral techniques to improve quality of life.