Encephalitic meningitis: causes, symptoms, treatment

According to medical terminology, encephalitic meningitis is correctly called meningoencephalitis, since in this infectious disease the inflammatory process affects not only the membranes of the brain, but also its substance . According to ICD-10, the meningocephalitis code is G04.  [1]

Epidemiology

According to clinical statistics, in half of the cases the etiological agent of meningoencephalitis is not identified.

Listeria meningitis and encephalitis are diagnosed in 20% of cases in newborns and the elderly and have a mortality rate of 22%.

Tuberculous meningitis and encephalitis account for approximately 6% of all cases of extrapulmonary tuberculosis, but it is the most severe extrapulmonary form of this disease with a high mortality rate.  [2]

With rubella, encephalitic meningitis is considered by specialists as a neurological complication, the frequency of which does not exceed one case per five thousand patients.

Herpesvirus meningoencephalitis accounts for about 10% of all cases of this disease. The annual incidence of herpes simplex encephalitis is approximately 2 to 4 cases per 1,000,000 population worldwide. The result of the initial infection with HSV types 1 and 2 is only a third of cases of damage to the membranes and tissues of the brain, in other cases, encephalitis meningitis is associated with the activation of a latent infection already present in the body. [3]

Causes of the encephalitis meningitis

Viral, bacterial, fungal and parasitic infections are the main causes of encephalitis  meningitis .  [4]

Viral inflammation  of the membranes of the brain  (meninges) with a simultaneous inflammatory process in the medulla (cerebrum materia) can be provoked by:

• herpes simplex viruses  HSV1 and HSV2 (genital);  [5]
• Varicella zoster virus (HSV3) -  varicella zoster virus ;  [6]
• Rubella virus (RuV) of the Matonaviridae family -  rubella virus ;  [7]
• measles virus ( Morbilli virus );  [8]
• RNA arbovirus of the Flaviviridae family -  tick- borne encephalitis virus  (or arbovirus).  [9], [10]

Bacterial meningoencephalitis can be caused  by meningococci  (Neisseria meningitidis),  Listeria  (Listeria monocytogenes), bacteria Mycobacterium tuberculosis (the causative agent of tuberculosis), as well as treponema pallidum (Treponema pallidum), which leads to the development of syphilis. At the same time, gradually developing encephalitic meningitis in tuberculosis, in fact, is one of its extrapulmonary forms - tuberculosis of the nervous system, and T. Pallidum brain damage can be defined as syphilitic meningoencephalitis, meningovascular syphilis or neurosyphilis.  [11], [12]

Fungal infection associated with brain damage is represented by naturally occurring  cryptococci  (Cryptococcus neoformans) and, in rare cases, endemic fungal infection -  histoplasma  (Histoplasma capsulatum), most often causing mycosis of the lungs. However, according to some reports, with disseminated histoplasmosis in 5-10% of cases, there is damage to the central nervous system.  [13], [14], [15]

Parasitic protozoa that can infect humans and cause meningoencephalitis include:

• Fowler's negleria, a unicellular amoeba Naegleria f owleri of the Percolozoa type, inhabitant of fresh waters;
• Toxoplasma  gondii, which can be contracted through contact with food or cat feces containing oocysts of this intracellular parasite.

Risk factors

Key risk factors for meningoencephalitis are caused by problems with the immune system: the weakening of the body's defenses.

In turn, immunity decreases when fighting frequent infections of various localizations, in the presence of foci of chronic infection (for example, in the middle ear, paranasal sinuses) or progressive neoplasms, immediately after vaccinations, in connection with anticancer and immunosuppressive therapy.

The risk of developing such inflammation is increased in newborns and children of the first years of life, the elderly, pregnant women, patients with HIV, as well as with existing autoimmune diseases, serious functional organ failure, and diabetes mellitus.

The risk of neurosyphilis, as well as tuberculous meningoencephalitis, is increased in cases of untreated disease in the initial stage.

Bathing in fresh water (including in water parks) increases the risk of invasion by the amoeba Naegleria f owleri with the development of protozoal meningocephalitis, especially in children.

Pathogenesis

Answering the question whether encephalitis meningitis is contagious or not, experts point out that a person can become infected with the viruses (mentioned earlier) from someone else, but encephalitis itself is not transmitted from person to person.

But meningococci (Neisseria meningitidis) can be infected from a patient - during the prodromal period of meningoencephalitis (which lasts 4-6 days). In syphilitic meningoencephalitis, damage to the membranes and tissues of the brain is the result of reactivation of treponema with untreated syphilis (which is infected sexually and through everyday life). Although the pathogenesis of neurosyphilis is not fully understood, it is assumed that an infection that spreads through the blood and lymph can accumulate in tissues adjacent to the vessels, followed by inflammation and obliteration (narrowing of the lumen) of the vessels that supply blood to the brain and its membranes.

Listeria can be transmitted through contaminated food. These bacteria infect the leukocytes of the blood and lymph, and with them, overcoming the blood-brain barrier, penetrate into the brain. There they multiply, forming granulomas, which leads to focal tissue necrosis.

Virions of viruses, in contact with the cells of the mucous membranes, attach to receptors on their surface and - by phagocytosis, direct release of genomic nucleic acids or fusion of the virus capsid with the membrane of the host cell - affect tissues, cause a protective antigenic reaction in the form of inflammation.

The tick-borne encephalitis virus is transmitted transmissively: with the bites of ixodid ticks. And the pathogenesis lies in the degeneration of brain neurons and their necrosis as a result of the penetration of the virus into the general circulation through the vascular endothelium, the cells of which are damaged by viral cytolytic enzymes. Once in the cerebrospinal fluid, the virus attacks the meninges and neuroglia. 

Cryptococci, as well as histoplasmic spores, enter the body with inhaled air, and the mechanism of their action is due to the defeat of phagocytic cells, inside which the infection passes through the BBB (microbiologists call this path the Trojan horse mechanism), penetrates into the blood and cerebrospinal fluid, and then into the brain, where fungi continue to multiply, forming colonies.

When water contaminated with Naegleria fowleri trophozoites enters the nasal cavity, the infection lingers on the olfactory epithelium, affecting its receptors and penetrating along the cranial olfactory nerve beyond the cribriform plate of the bone between the cavities of the nose and skull, and then into the cerebral membranes and tissues. Amoebic trophozoites absorb brain tissue cells, destroying them with a whole set of their enzymes.

Symptoms of the encephalitis meningitis

Depending on the causative agent of encephalitis meningitis, its first signs appear after different times and are expressed with different intensity. Most often it is weakness, general malaise, headache and a sharp increase in temperature (˂ + 39 ° C). 

Then there are stiffness (rigidity) of the neck muscles, sensitivity to bright light, blurred vision and double vision, problems with speech or hearing.

Symptoms  of tick-borne meningoencephalitis  occur one to three weeks after a tick bite (often people simply do not notice it) and may include headache, fever, myalgia and arthralgia, nausea, and confusion. This is followed by convulsions, loss of sensation or paralysis of certain areas of the face or body; patients may fall into a coma.  [16]

Meningoencephalitis due to HSV1 also begins with headache and fever for 5-6 days, followed by tremors and convulsions, muscle weakness, hallucinations, mental and behavioral disturbances.

Hemorrhagic inflammation of the cerebral membranes and tissues in amoebic meningoencephalitis develops rapidly, in most cases with a fatal outcome.

When Listeria monocytogenes is affected, purulent encephalitic meningitis can develop with subcortical abscesses in structures such as the thalamus and medulla oblongata.

Encephalitic meningitis in children of the first year is manifested by such symptoms as fever, lethargy, lack of awakening for feeding, vomiting, spasticity of the skeletal muscles of the body, irritability, and bulging of the large fontanel.  [17]

Complications and consequences

Encephalitic meningitis is dangerous for its complications and consequences,  [18]which include:

• hydrocephalus , leading to intracranial hypertension;
• damage to the cranial nerves, which leads to problems with speech, swallowing, vision, hearing, coordination of movements, memory;
• the formation of an intracerebral cyst;
• convulsive seizures of varying intensity, up to generalized;
• shutdown of the functions of the cerebral cortex with the development  of apallic syndrome .
• memory problems, personality and behavior changes, speech and language problems

Children have disorders of mental and mental development, and with herpesvirus etiology of inflammation, tissues of the frontal lobes of the brain often suffer, causing behavioral and personality changes.

The consequences of syphilitic meningoencephalitis (neurosyphilis) are dorsal tabes (Tabes dorsalis), general paresis, spastic and progressive paralysis, ophthalmic disorders, partial loss of cognitive abilities.

Lower motor neuron involvement and spinal arachnoiditis, in addition to gait disturbance and cognitive changes, are serious complications of cryptococcal meningoencephalitis.

Due to severe edema and damage to the brain, a coma develops with encephalitis meningitis, for details, see -  Cerebral coma .

Diagnostics of the encephalitis meningitis

The sooner meningoencephalitis is diagnosed, the sooner treatment is started, increasing the chances of patients to recover.

First of all, an examination is carried out, an anamnesis is taken and clinical symptoms are identified. Analyzes are taken: a complete blood count, a blood test for antibodies (IgM and IgG) to viruses, for RW; serological analysis of blood serum; general, PCR and  microbiological analysis of cerebrospinal fluid  (CSF) - to determine the type of pathogenic infection.

Instrumental diagnostics are used: neuroimaging using  computed tomography of the brain  or magnetic resonance imaging (MRI), and  electroencephalography  (EEG) to monitor the electrical activity of the brain. [19]

Differential diagnosis

Differential diagnosis includes viral encephalomyelitis, autoimmune encephalitis, meningeal carcinomatosis, CNS vasculitis, etc. It is also important to differentiate between viral and bacterial (or fungal) meningocephalitis.

Treatment of the encephalitis meningitis

Treatment of meningoencephalitis, like the  treatment of meningitis  , involves addressing the underlying cause, relieving symptoms, and maintaining bodily functions. Usually inflammation of the membranes and tissues of the brain is treated in the intensive care unit.  [20]

How is meningococcal meningocephalitis treated, read the publication -  Meningococcal infection

Read more about the treatment of listeriosis meningoencephalitis with antibiotics in the article -  Listeriosis

In case of tuberculous etiology of inflammation, the antibiotic Rifampicin ( Makoks ) is used, and in cases of neurosyphilis - Penicillin and Ceftriaxone (Cefamed, Triaxon).

With encephalitic meningitis of viral etiology, glucocorticosteroids are administered, for example,  Dexamethasone . And if meningoencephalitis is caused by HSV1, HSV2 or Varicella zoster viruses, the antiviral agent Acyclovir or Ganciclovir is administered parenterally.

Cryptococcal meningoencephalitis is treated in the same way as  cryptococcal meningitis : with the polyene antibiotic Amphotericin B and the fungicide Flucytosine.

Liposomal Amphotericin B is also used to treat encephalitic meningitis caused by histoplasma; then a long-term intake of the fungicidal preparation Itraconazole (Itracon, Sporagal) in encapsulated form or Ketoconazole tablets is prescribed.

The annual incidence of herpes simplex encephalitis is approximately 2 to 4 cases per 1,000,000 population worldwide. The result of the initial infection with HSV types 1 and 2 is only a third of cases of damage to the membranes and tissues of the brain, in other cases, encephalitis meningitis is associated with the activation of a latent infection already present in the body.

In addition, intensive care is given by intravenous infusion to maintain bodily functions and relieve symptoms.

Prevention

Fortunately, the prevention of encephalitis meningitis is not limited to personal hygiene and the use of repellents to repel ticks, which can prevent infection. [21]

There are effective vaccines, so you need to be  vaccinated against tick-borne encephalitis , chicken pox,  and meningococcal infection .

Forecast

Not all cases of encephalitic meningitis have a favorable prognosis: it varies depending on the specific infection, the severity of the disease, and the timely initiation of treatment. 

In mild cases with mild symptoms, patients recover in a few weeks, although it may take months for the neurological effects to resolve. [22]

In severe cases, irreversible brain damage or death can occur. The lethal outcome in inflammation of the cerebral membranes and tissues is estimated at about 10% of cases, with encephalitic meningitis caused by HSV - in 20%, and with damage to the brain by the amoeba Naegleria fowleri - in almost 98%.