Generality

Encephalitis is the term by which doctors identify inflammation of the brain, which, together with the spinal cord, constitutes the central nervous system (CNS).

Encephalitis is a medical emergency, so it requires immediate treatment.

More than half of encephalitis cases arise due to unknown (or unidentifiable) causes. In the remaining portion of cases, the most common triggers are viral infections and immune system abnormalities; the cases of encephalitis sustained by bacterial, protozoan or fungal infections are less frequent.

In general, encephalitis begins with a symptomatology that resembles a simple flu. However, within 24-48 hours, they lead to the appearance of increasingly severe and debilitating symptoms.

An early and accurate diagnosis of encephalitis is very important, because it allows the doctor to start the most appropriate therapies early.

Treatment depends on the triggering causes and, in the most serious cases, also includes hospitalization of the patient.

Brief review of the central nervous system (CNS)

In vertebrates, the most important part of the entire nervous system is the central nervous system ( CNS ).

The CNS has two main components: the brain and the spinal cord .

Of soft and gelatinous consistency, both the encephalon and the spinal cord are immersed in a protective liquid ( cerebrospinal fluid or liquor ), are wrapped in different protective membranes (the so-called meninges ) and are further protected by a very hard bone covering ( the skull, for the encephalon, and the vertebral column, for the spinal marrow).

Thanks to its enormous network of neurons (ie nerve cells), the central nervous system is responsible for analyzing the information coming from the internal or external environment to the organism and for processing the most appropriate responses (to the aforementioned information).

What is encephalitis?

Encephalitis is inflammation of the brain, one of the two fundamental components that make up the central nervous system.

It is a very serious condition that is among the medical emergencies. Medical emergencies are circumstances that require immediate treatment.

ORIGIN OF THE NAME

The term encephalitis derives from the union of the Greek word "enchefalos" (ἐγκέφαλος ‚), which means" brain ", and the medical suffix" -ite "which means" inflammation ".

Epidemiology

Encephalitis is, fortunately, a very rare condition.

In fact, according to some statistical studies, in 2013, it caused the death of about 77, 000 people around the world.

Anyone can develop encephalitis; however the subjects most at risk (even of death) are those who have a weak or inefficient immune system . Generally, to this category of individuals belong very young children (because the immune defenses are still immature), the elderly (the advanced age coincides with a decrease in the effectiveness of the immune defenses) and the subjects with some serious illness that depresses the immune system (immunosuppressed).

Table. Some brief epidemiological information on encephalitis.

  • In 1990, worldwide research, similar to that carried out in 2013, reported that there were about 92, 000 deaths worldwide per year during encephalitis. Thus, 13 years later, the number of annual deaths has fallen by almost 15, 000.
  • In countries of the so-called Western world, the annual incidence of acute encephalitis (with a sudden onset and marked symptoms) is approximately 7.4 cases per 100, 000 inhabitants.
  • Herpes simplex virus encephalitis has a worldwide incidence of approximately 2-4 cases per 100, 000 inhabitants.

Causes

More than half of cases of encephalitis occur due to unknown causes .

In the remaining portion of cases, the most common triggers are viral infections ( viral encephalitis), followed by immune system abnormalities (autoimmune encephalitis), bacterial infections (bacterial encephalitis), protozoan infections (protozoan-induced encephalitis or protozoan-induced encephalitis) and fungal infections (fungal encephalitis).

VIRAL ENCEPHALITIS

Before reporting the viruses that can cause encephalitis, it should be noted that doctors have divided viral encephalitis into two categories: primary and secondary.

  • The primary viral encephalitis are those due to viruses that directly infect the brain.
  • The secondary viral encephalitis, on the other hand, are those that arise at a distance of time from the infection, due to an incorrect reaction of the immune system. In other words, in secondary viral encephalitis, the infection alters the behavior of the immune defenses of the infected individual, making them aggressive towards the body they should defend.

That said, the viruses that are most known to cause encephalitis are:

  • Herpes viruses .

    The members of this category, which cause encephalitis, are: herpes simplex virus type 1 (HSV1, or cold sore virus), herpes simplex virus type 2 (HSV2, or genital herpes virus), varicella zoster virus and Epstein-Barr virus (or mononucleosis virus).

    Among these viral agents, the most clinically dangerous (can irreparably damage the brain or even cause death) are: HSV1 and HSV2. Fortunately, it is very rare for these viruses to reach the brain once they have infected an individual.

  • Some enteroviruses .

    Enteroviruses capable of reaching the brain and inducing inflammation are poliovirus and coxsackievirus.

  • Several viruses that are transmitted by the bite of mosquitoes (or other bloodsucking insects - blood suckers).

    Among the viral agents belonging to this category, particularly known are: the West Nile virus, the La Crosse virus, the equine encephalitis virus, the Japanese encephalitis virus and the Saint Louis encephalitis virus.

  • Viruses that are transmitted by tick bites .

    These viral agents belong to the Flavivirus category (the same in which dengue and yellow fever viruses fall).

    The encephalitis that arise after a tick bite is called TBE, an acronym of the English definition Tick-Borne Encephalitis (ie tick bite encephalitis).

  • The rabies virus .

    Men contract this virus after being bitten by infected animals.

    Human infection with rabies virus is currently very rare.

  • Measles virus, mumps virus and rubella virus .

    Responsible for what were once (prior to vaccination prophylaxis) the classic infections of young age, these viruses may be responsible for some forms of secondary encephalitis.

  • The AIDS virus ( HIV ).

    HIV infections can cause chronic encephalitis (chronic encephalitis), called chronic progressive encephalitis.

  • The JC virus .

    Although very rarely, this viral agent can cause chronic encephalitis, known as progressive multifocal leukodystrophy.

Secondary encephalitis (or post-infectious) and vaccination

Some individuals may develop a form of secondary viral encephalitis after being subjected to certain vaccinations (for example against measles).

It should be pointed out that these are very rare events, not comparable to the risk of encephalitis that occurs in individuals without the aforementioned vaccinations.

ENCEFALITES AUTOIMMUNE

Table . The main viruses that can cause secondary encephalitis.

  • Measles virus
  • Rubella virus
  • Mumps virus (mumps)
  • Influenza virus
  • Epstain-Barr virus
  • Varicella zoster virus
  • Cytomegalovirus
  • HIV

Autoimmune encephalitis belongs to the category of autoimmune diseases .

Autoimmune diseases are characterized by an exaggerated and improper response of the immune system.

For unclear reasons, in individuals with an autoimmune disease, the elements that make up the immune system (mostly cells and glycoproteins) attack perfectly healthy organs and tissues, causing even very serious damage.

During the study of autoimmune encephalitis, doctors noted that there is a certain association between the aforementioned diseases and the presence of a tumor, in an internal organ of the body. The possibility that the neoplasm may alter the behavior of the immune system is yet to be demonstrated and only further future research can clarify it definitively.

What is the immune system?

The immune system is an organism's defensive barrier against threats from the external environment - such as viruses, bacteria, parasites, etc. - but also from within - such as, for example, cells that have gone mad (cancer) or malfunctioning.

The defense tools of the immune system are very particular cells and glycoproteins, capable of acting in concert to be even more effective.

BACTERIAL ENCAFALITES

The bacteria that can most frequently cause encephalitis are: Borrelia burgdorferi (also known as "the bacterium of Lyme disease "), Bortella henselae and Mycoplasma pneumoniae .

Bacterial encephalitis is very rare.

PROTOZOARY ENCEPHALITIS

Among the protozoa that can determine encephalitis, fall

  • The protozoan of toxoplasmosis, also known as Toxoplasma gondii .
  • The plasmodium of malaria .
  • Naegleria fowleri, also known as "the protozoan of primary amoebic encephalitis".

RISK FACTORS

Anyone can develop encephalitis, but they are particularly at risk:

  • Very young individuals and the elderly, who, although healthy, have a less efficient immune system than normal.
  • Immunodepressed subjects . Immunodepressed people have a pathologically less efficient immune system than normal.

    A classic example of an immunodepressed subject, which can develop encephalitis, is the AIDS patient. In fact, the virus that causes this infection (HIV) reduces the immune defenses of the infected organism.

  • Individuals living where mosquitoes and ticks are widespread, capable of transmitting those infections described above. This means that there are geographical areas that are riskier than others.

Please note: for infections transmitted by mosquitoes and ticks, the season of the year is also important. In fact, it is easier to contract the aforementioned infectious diseases in spring and summer.

Symptoms and Complications

To learn more: Symptoms of Encephalitis

Encephalitis usually begins with a series of flu-like symptoms, such as high fever (at least 38 ° C), headache, nausea, vomiting and joint pain.

Therefore, after 24-48 hours from the first manifestations, the symptomatic picture worsens drastically and determines:

  • Changes in mental status, such as confusion, disorientation and drowsiness
  • Attacks of epilepsy
  • Personality changes and behavioral alterations
  • Loss of knowledge

LESS COMMON SYMPTOMS

Some forms of encephalitis can also cause:

  • Photophobia, that is sensitivity to light
  • Inability to speak
  • Inability to control body movements
  • Neck stiffening
  • Hallucinations
  • Loss of sensitivity in some parts of the body
  • Partial or total loss of sight
  • Involuntary eye movements
  • Skin rash (or skin rash or rash). This sign is characteristic of some viral infections, therefore it represents a valid diagnostic element.

The presence of some of these manifestations depends on the encephalic area involved or on the concomitant involvement of the meninges, the latter condition known as meningoencephalitis .

To know what entails and how to recognize inflammation of the meninges, or meningitis, it is advisable to consult the dedicated article.

COMPLICATIONS

If treated with delay, an encephalitis can have permanent consequences on neurological functions and, in some cases, even lead to death.

The main complications of encephalitis include:

  • Memory problems . They represent a rather frequent complication. In fact, according to some studies, they characterize about 7 cases out of 10.
  • Permanent personality and behavioral changes . They emerge in more than half of the clinical cases.
  • Aphasia (language problems). Its response is in one patient every 3.
  • Permanent epilepsy . Among adult patients, it characterizes one case every 4; among those of young age, one case every 2.
  • Frequent mood swings
  • Permanent difficulties in attention, concentration and planning skills
  • Serious motor and physical difficulties
  • Depression
  • Sense of persistent fatigue

Diagnosis

Diagnosing encephalitis is always quite complex, since, especially in the initial phase, the symptoms are non-specific. The symptoms, in fact, could be mistaken for the manifestations of an influenza or another similar morbid condition.

Excessive delays in diagnosing a morbid condition such as encephalitis take time away from therapies, which should begin as soon as possible.

In general, for the recognition of an encephalitis, the following are fundamental: the physical examination, some instrumental tests to scan the brain, blood tests, a lumbar puncture and an electroencephalogram.

EXAMINATION OBJECTIVE

A thorough physical examination requires the doctor to visit the patient, looking for any external clinical signs on it and asking him about the symptoms (if the patient is a child, the people questioned are the parents or adults who spend more time with him).

For diagnostic purposes, a careful investigation of symptoms and signs is a must, because it allows to determine which more specific tests are required.

ENCUSPHALO INSTRUMENTAL TESTS OF SCANNING

Instrumental brain scan tests are needed by the doctor to:

  • Make sure that the symptoms are due to an encephalitis and not to a stroke, a brain tumor or an aneurysm (NB: these are all equally serious and equally symptomatic).
  • In case of confirmed encephalitis, study the degree of extension of inflammation to the brain.

Among the instrumental tests for scanning the brain, the most widely used are the cerebral CT and the cerebral nuclear magnetic resonance (or brain MRI)

While CT scan exposes the patient to a non-negligible dose of ionizing radiation, the brain MRI is totally harmless and non-invasive.

BLOOD TESTS

Thanks to the collection and analysis of a sample of blood from the patient, a doctor can trace the type of infectious agent that triggered encephalitis, because, in the blood, it is possible to find its presence.

LUMBAR PUNCTURE

The lumbar puncture consists in taking a sample of cerebrospinal fluid (or liquor ) and in its laboratory analysis. To take liquor, the doctor uses a needle that inserts between the lumbar vertebrae L3-L4 or L4-L5.

Like blood tests, the lumbar puncture supports the identification of the triggering causes. In fact, it provides useful information regarding the infectious agent that triggered the inflammation of the brain.

ELECTROENCEPHALOGRAM

The electroencephalogram is the recording, completely safe and painless, of the electrical activity of the brain.

In the presence of an encephalitis, the recording presents anomalies, which only a medical expert in the field is able to interpret and decipher.

Treatment

In the presence of encephalitis, doctors prescribe a therapy valid for any type of inflammation of the brain ( non-specific therapy ), associated with a specific treatment, depending on the causes.

In general, if the symptoms are mild and the situation is under control, the patient's treatment can take place at home; if instead the symptomatology is severe and the critical situation, the care of the patient must take place in the hospital, in an intensive care unit .

ASPECIFIC THERAPY

Non-specific therapy includes:

  • A period of absolute rest
  • The constant supply of liquids, to avoid dehydration phenomena (which are very common)
  • The administration of anti-inflammatories, such as paracetamol and NSAIDs (naproxen sodium and / or ibuprofen). They are used to relieve headaches and fever.

SPECIFIC THERAPY IN THE CASE OF VIRAL ENCEPHALITIS

Patients with primary viral encephalitis require treatment based on antiviral drugs, including especially acyclovir, ganciclovir and foscarnet .

Administered intravenously, these medicines have some merits, but, unfortunately, also some limitations. In fact, they are particularly effective against herpes simplex virus and varicella zoster virus infections, while they are almost completely useless against viruses transmitted by mosquito bites.

Side effects of antiviral drugs and corticosteroids.
Side effects of antiviral drugs:
  • Nausea
  • He retched
  • Diarrhea
  • Pain or numbness in the muscles and joints
  • Kidney dysfunctions
  • Liver dysfunctions
  • Suppression of bone marrow activity

Side effects of corticosteroids:

  • Hypertension
  • Diabetes
  • Bone weakening or osteoporosis
  • Glaucoma
  • Overweight or obesity
  • Gastric ulcers

The treatment of secondary viral encephalitis is slightly different and usually involves the administration of corticosteroids (especially prednisone). Corticosteroids are powerful anti-inflammatory drugs, which, if taken for long periods or at high doses, can cause unpleasant side effects.

If the corticosteroid therapy does not give the desired results, the doctor must vary the treatment and resort to immunoglobulin injections (to regulate the functioning of the immune system) and to perform a plasmapheresis (to remove part of the immune cells that are causing inflammation).

SPECIFIC THERAPY IN THE CASE OF AUTOIMMUNE ENCEPHALITES

In the presence of autoimmune encephalitis, doctors prescribe the administration of:

  • Corticosteroids, to reduce inflammation, e
  • Immunosuppressants, to reduce immune defenses (whose abnormal functioning triggers inflammation of the brain). A widely used immunosuppressant is cyclosporine .

Main side effects of cyclosporine:

  • Numbness and tingling
  • Hypertension
  • Tremors
  • Muscle aches and cramps

If the situation does not improve and the symptoms persist, several injections of immunoglobulins and the execution of a plasmapheresis may be useful (again).

SPECIFIC THERAPY IN THE CASE OF BACTERIAL ENCEPHALITIS, PROTOZOARY AND FUNGINE

Antibiotic therapy is essential for bacterial encephalitis. The choice of the most suitable antibiotic is up to the doctor and depends on the bacterium that caused the inflammation of the brain.

For protozoan encephalitis, a pharmacological treatment based on antiprotozoans is required,

Finally, for fungal encephalitis, a treatment based on antifungal (or antifungal ) medicines is essential.

WHAT DOES HOSPITALIZATION SEE?

When encephalitis is particularly severe or when symptoms persist, despite treatment, it is imperative to proceed with hospitalization of the patient.

During admission, doctors will:

  • Administer the previously mentioned drugs (depending, of course, on the specific case).
  • Support breathing.
  • Provide, via tube, all the nutrients a patient in serious health conditions needs, such as an individual with severe encephalitis.

Prognosis

In the absence of treatments or when these are ineffective, encephalitis has a negative prognosis.

According to a recent statistic, one case of encephalitis out of 10 is fatal (that is, it causes the death of the patient) and there are many subjects, who, despite all the necessary care, develop one or more complications.

In the case of healing, the path to symptom resolution can be very long, lasting several months.

Prevention

Today, it is possible to prevent, with good results, only some forms of encephalitis, in this case those supported by infectious agents for which there is a vaccine.