Slow viral infections of the central nervous system: symptoms and treatment

Slow viral infections of the central nervous system are a group of diseases with an infectious occurs after a very long incubation period, progresses rather slowly and always leads to death. This group includes a variety of diseases, the characteristics of which coincide with the definition of "slow viral infections." What infectious agents can cause the development of such diseases, what diseases do they cause and in what ways does modern medicine have them? You can learn all this by reading this article.

What is a "slow virus infection"?

The concept of "slow viral infections" has existed since 1954, when Sigurdsson published observations about a peculiar mass disease of sheep, which had the following specific features:

• a very long incubation period (from infection to the appearance of the first signs of the disease): months and even years;
• very protracted, but steadily progressing current;
• identical and rather specific changes in certain organs and tissues;
• fatal outcome.

Based on the observations of this scientist and some other specialists, it was suggested that there exists in the nature of a special group of slow viruses, which cause similar diseases. As the study of similar pathological conditions it became clear that the name does not quite correctly reflect the essence of the problem: The cause of diseases can be ordinary viruses (for example, measles, rubella), and particles of protein nature (prions) that are not viruses. However, the name of this group of diseases remained the same: slow viral infections.

To date, the group of slow viral infections is usually attributed to the disease:

• Viruses and corresponding to the above characteristics;
• caused by prions.

You can read about prion diseases here. In the same article, information on diseases of the central nervous system with a viral origin will be presented.

The slow viral infections of the central nervous system include:

• subacute sclerosing panencephalitis;
• progressive rubella panencephalitis;
• progressive multifocal leukoencephalopathy;
• Rasmussen's encephalitis.

There are also a number of diseases of the nervous system, the cause of which is supposed to be (!) A slow viral infection, so they can also be mentioned in the context of slow viral infections. These are diseases such as multiple sclerosis, amyotrophic lateral sclerosis, Vilius encephalomyelitis and several others.

Symptoms of slow viral infections

Subacute sclerosing panencephalitis

Synonyms of this disease are: encephalitis with viral inclusions, Van-Bogart leucoencephalitis, Pette-Dering nodular panencephalitis, encephalitis with Dawson inclusions. This type of slow viral infections occurs as a result of prolonged persistence (stay) in the body of the measles virus.

There is a frequency of 1 case per , 0, 00 population per year. Children are sick at the age of 5-15 years. In, times more often the disease occurs in boys than in girls. Children at risk of developing subacute sclerosing panencephalitis are those who have survived measles before the age of 2 years. Before the massive introduction of measles vaccine, the disease was much more common.

Why is the measles virus not completely destroyed? Why do some children, after suffering measles, not fall ill with subacute sclerosing panencephalitis, and others - suffer from this pathology? For not fully clarified reasons, in some children, the measles virus undergoes gene changes and acquires the capacity for prolonged "living" inside the cells of the brain. Stay inside cells "saves" the virus from the neutralizing effect of antibodies (which, by the way, when panencephalitis is very much), that is, the human immune system is not able in this case to get rid of the pathogen. Even being inside the cell, the virus can "infect" neighboring cells through direct contact or moving along the processes of nerve cells (axons and dendrites). Viral particles accumulate in the nuclei and cytoplasm of neurons, forming specific "nodules or "inclusions which are visible in the pathomorphological examination of tissue brain (hence the name "nodular"), and causing demyelination (the destruction of a substance covering the nerve processes and providing a nerve momentum). The average incubation period between the transferred measles and the onset of encephalitis is 6-7 years.

Conditionally subacute sclerosing panencephalitis is divided into several stages:

• I stage lasts for several weeks or months. There are nonspecific symptoms, such as changes in behavior and mood, general weakness, poor tolerance of physical and mental stress. Children become depressed, silent, do not want to play or, conversely, acquire emotional instability, irritability. Possible unmotivated outbursts of anger or aggression. Along with psychological changes, neurological micro-symptoms appear. It can be a small blur of speech, a change in handwriting, flinches, muscle trembling. This stage often goes unnoticed and does not force parents to seek medical help (all explained by spoiling or stress);
• II stage is characterized by the appearance of pronounced neurological disorders. The child becomes awkward, sluggish, coordination of movements is disrupted. There are involuntary movements: hyperkinesis. Initially, they occur 1 time per day, for example, when going to sleep or waking up. Gradually, their frequency and amplitude increase. Hyperkinesis can cause sudden falls. As the disease progresses, there are epileptic seizures, muscle weakness, which makes it difficult to perform simple actions (dressing, bathing, eating). Intellect suffers, memory worsens. Characteristic visual disturbances: double vision, gradual loss of vision. Possible so-called cortical blindness: the patient sees the object, but does not notice and does not recognize it (for example, if you put a chair on the path of the patient, he will bypass it, but will say that there is no obstacle It was). At the end of this stage tetraparesis (expressed weakness in all extremities) is formed with increased muscle tone, mental disorders reach the degree of dementia. The duration of stage II is 2-4 months;
• III stage: the patient becomes bedridden, practically does not contact with others, does not talk, can only turn his head to sound or light. Tactile touch can cause a smile or crying. The frequency and amplitude of involuntary movements decrease. At this stage, vegetative disorders become more pronounced: fever, sweating, increased heart rate, indomitable hiccup, irregular breathing. Swallowing is disturbed;
• IV stage - terminal - comes in 1-2 years from the appearance of the first signs of the disease. The patient can not even move. Only the movements are preserved by the eyes, and then they are not purposeful, but wandering and aimless. There is pathological laughter and crying, periods of seizures throughout the body (hyper-necrosis). Gradually, patients fall into a coma, trophic disorders (bedsores) join. In the end, the patients die.

Very rarely happens that the disease lasts more than 2 years, while the staginess of the process remains, only each of the stages has a longer duration. The outcome is in any case deadly.

Progressive rubella panencephalitis

This is an extremely rare consequence of rubella transmitted in utero or in early childhood. In total, only a few dozen cases are described in the world, and all are registered only in boys. The incubation period is very long: from 8 to 19 years (!). Mostly children and adolescents are ill, somewhat less often - people over 18 years old. By which mechanisms the rubella virus performs the defeat of the central nervous system, is still a mystery.

The disease begins gradually with nonspecific symptoms. Character and behavior change, which is often associated with a transitional age. The child becomes uncontrollable. School performance falls, memory and attention worsen. Gradually, these disorders are joined by disorders of balance, the gait becomes unstable, movements - inaccurate, miss. Possible hyperkinesis and epileptic seizures. Visual impairment is noted. The most pronounced and "conspicuous" at this stage are coordination disorders.

However, the disease does not stop there, because, like all slow viral infections, it is characterized by a slow but steady progression. There are problems with speech (both reproduction and understanding), tetraparesis (weakness in all four limbs) is formed. Mental disorders reach the extent of dementia. Man ceases to control urination and defecation.

In the terminal stage, which usually develops in 2-3 years from the onset of the disease, the patient is completely chained to bed, often in a coma. The disease ends with death.

Progressive multifocal leukoencephalopathy

This type of slow viral infection develops as a result of brain damage by the JC virus, which is related to papovaviruses. About 80-95% of the world's population is infected with these viruses, but they do not cause disease in most people.

Progressive multifocal leukoencephalopathy (subcortical encephalopathy) develops only with a marked decrease in immunity in the body. This happens in the presence of tumor formations, with HIV infection, tuberculosis, collagen diseases (connective tissue diseases), after operations for kidney transplantation. In such cases, the virus can be reactivated and attack the cells of the neuroglia, which leads to a violation of myelin synthesis and, consequently, demyelination. The process is diffuse, covering almost the entire central nervous system, which is manifested by a multitude of symptoms.

The onset of the disease is difficult to grasp, as development occurs against the background of the already existing other somatic disease. At first, the parameters of higher brain functions deteriorate: concentration of attention decreases, forgetfulness appears, it is difficult for a person to count in the mind, consistently state his thoughts. And then other neurological symptoms join in. It can be said that progressive multifocal leukoencephalopathy can manifest itself by any symptoms of the nervous system, so extensive is the brain damage by the virus:

• various epileptic seizures;
• speech impairment;
• violation of swallowing and perception of sounds;
• loss of visual fields and reduced visual acuity right up to blindness;
• impaired sensitivity;
• muscle weakness;
• increased muscle tone;
• the appearance of involuntary movements;
• impaired coordination and balance;
• violent laughter and crying;
• decrease in intelligence to the extent of dementia;
• loss of control over the functions of the pelvic organs;
• hallucinations and delirium and so on.

Within 6-12 months the patient falls into a coma, from which it no longer leaves. Death comes from joined intercurrent diseases on the background of a decrease in immunity.

Encephalitis of Rasmussen

The disease is the name of an American neurosurgeon who described this condition in 1958. This ailment presumably refers to slow viral infections, since the exact cause is not defined and to the present. It is suggested that cytomegalovirus infection and the Epstein-Barr virus may play a role in the onset of Rasmussen's encephalitis. The possibility of autoimmune disorders is not excluded.

Very often, Rasmussen's encephalitis develops in a few weeks or months after a nonspecific viral infection.

The disease affects children and adolescents more often. The median age at onset of the disease is 6 years, the latest at the beginning is 58 years. Encephalitis Rasmussen is a special form of epilepsy, very resistant to treatment with anticonvulsant drugs. With it develops the atrophy of one of the cerebral hemispheres. In such children there are involuntary movements in the limbs, the so-called hyperkinesis. Over time, they become convulsive seizures with loss of consciousness. Seizures are quite similar: at the beginning of the disease involuntary movements occur in the same limbs (right or left). However, as the disease progresses, the picture becomes more polymorphic, seizures become more diverse. Gradually, due to the often recurrent seizures, hemiparesis is formed in the limbs, which persists during the inter-rush period. In addition, epileptic seizures lead to speech disturbance, loss of visual fields, mental defects. A special feature of the course of the disease in adults is the bilateral defeat of the cerebral hemispheres.

During the disease, three stages are distinguished. Let's call them.

• Prodromal: on average it lasts about 7-8 months. Cases up to 8 years are described. In this stage, mainly hyperkinesis is observed, convulsive seizures are rare;
• acute: also lasts an average of 8 months. It is characterized by an aggravation of symptoms with an increase in muscle weakness in the limbs and frequent convulsive attacks, which lead to a violation of speech and visual fields;
• Residual: the frequency of seizures decreases, there remains persistent paresis in the limbs and speech defects.

The peculiarity of convulsive seizures with Rasmussen's encephalitis is the lack of effect from all antiepileptic drugs, therefore, to eliminate this symptom in In some cases, surgical treatment is performed: the connection of one hemisphere to another is cut, which does not allow the epileptic excitation to spread to the "healthy" hemisphere.

Rasmussen's encephalitis, to date, is the only disease among slow viral infection, the course of which does not necessarily end in a lethal outcome within a few years from the beginning disease. Part of the patients (usually this happens in the early debut of the disease) dies in a few years from the onset of the disease, and in some, the condition stabilizes as a residual stage. It is difficult to predict the course of the disease.

Treatment of slow viral infections

Unfortunately, to date, medicine knows no effective ways to combat slow viral infections. All patients who have such diseases are treated exclusively with symptomatic treatment, which only alleviates suffering, but does not affect life expectancy.

Attempts have been made to use antiviral drugs, immunotropic drugs (immunoglobulin intravenously), glucocorticoids, plasmapheresis, but none of them was not successful success.

Slow viral infections of the central nervous system are very rare, but, unfortunately, deadly diseases. All of them have a long incubation period, they always progress and end with death. Effective ways to combat them do not exist, and, in view of the rare occurrence, a single treatment strategy has not been developed.