Tick-borne encephalitis: symptoms

The incubation period of tick-borne encephalitis during infection through a tick bite is 5-25 (on average 7-14) days, and at the food path of infection - 2-3 days.

The main symptoms of tick-borne encephalitis and the dynamics of their development

Tick-borne encephalitis, regardless of form, in most cases begins acutely. Rarely there is a period of prodromes lasting 1-3 days.

Feverish form of tick - borne encephalitis is recorded in 40-50% of cases. In most patients, the disease begins acutely. The febrile period lasts from several hours to 5-6 days. In the acute period of the disease, the body temperature rises to 38-40 ° C and above. Sometimes a two-wave or even a three-wave fever is observed.

Patients are concerned about the following symptoms of tick-borne encephalitis: headache, general weakness, malaise, chills, fever, sweating, dizziness, pain in the eyeballs and photophobia, decreased appetite, muscle pain, bone, spine, upper and lower extremities , in the lower back, in the neck and in the joints. Nausea is typical, vomiting is possible within one or several days. Also note the injection of vessels of sclera and conjunctiva, flushing of the face, neck and upper half of the trunk, marked hyperemia of mucous membranes and oropharynx. In some cases, the pallor of the skin is noted. The phenomena of meningism are possible. At the same time, there are no inflammatory changes in the cerebrospinal fluid.

In most cases, tick-borne encephalitis results in complete clinical recovery. However, in a number of patients, after discharge from the hospital, the asthenovegetative syndrome remains.

Meningeal form is the most common form of tick-borne encephalitis. In the structure of morbidity it is 50-60%. The clinical picture is characterized by pronounced general infectious and meningeal symptoms.

In most cases, the onset of the disease is acute. Body temperature rises to high values. The fever is accompanied by chills, a feeling of heat and sweating. Characterized by a headache of varying intensity and localization. Mark anorexia, nausea and frequent vomiting. In some cases, myasthenia gravis, pain in the eyeballs, photophobia, shaky gait and tremor of hands are expressed.

Upon examination, the flushing of the face, neck and upper trunk, vascular injection of sclera and conjunctiva is revealed.

Meningeal syndrome at admission is found in half of patients. In others, he develops on the 1-5th day of stay in the hospital. Identify transient disorders due to intracranial hypertension; asymmetry of the face, anisocoria, omission of eyeballs outside, nystagmus, revival or suppression of tendon reflexes, anisoreflexia.

The pressure of the cerebrospinal fluid, as a rule, is increased (250-300 mm of water). Pleocytosis ranges from several tens to several hundred cells in 1 μl of cerebrospinal fluid. Lymphocytes predominate, neutrophils can prevail in the early periods. The content of glucose in the cerebrospinal fluid is normal. Changes in the cerebrospinal fluid remain relatively long: from 2-3 weeks to several months.

Asthenovegetative syndrome lasts longer than with febrile form. Character irritability, tearfulness. The benign course of the meningeal form of tick-borne encephalitis does not exclude the possibility of further developing a clinical picture of the chronic form of the disease.

The meningoencephalitic form is characterized by a severe course and high lethality. The frequency of this form in individual geographical regions is from 5 to 15%. For the acute period of the disease, symptoms of tick-borne encephalitis are characteristic, such as: high temperature, more severe intoxication, expressed meningeal and general cerebral symptoms, and signs of focal brain lesions.

Encephalitic form is characterized by a combination of cerebral and focal symptoms. Depending on the predominant localization of the pathological process, there are bulbar, pontinous, mesencephalic, subcortical, capsular, hemispheric syndromes. Possible disorders of consciousness, often epileptic seizures.

Characterized by deep disturbances of consciousness right up to the development of coma. In patients admitted in the unconscious and co-morbid state, motor excitation, convulsive syndrome, muscular dystonia, fibrillar and fascicular jerking in separate muscle groups are observed. Often find nystagmus. Characterized by the appearance of subcortical hyperkinesis, hemiparesis, as well as lesions of cranial nerves: III, IV, V, VI pairs, somewhat more often VII, IX, X, XI and XII pairs.

When stem lesions appear bulbar, bulbopontin syndromes, less often - symptoms of the defeat of the midbrain. There are violations of swallowing, choking, nasal shade of voice or aphonia, paralysis of the muscles of the tongue, with the spread of the process to the bridge - symptoms of damage to the nuclei of VII and VI cranial nerves. Often identify light pyramid signs, increased reflexes, clones, pathological reflexes. Brainstem lesions are extremely dangerous because of the possible development of respiratory and cardiac disorders. Bulbar disorders are one of the main causes of high mortality in meningoencephalitic form of tick-borne encephalitis.

When studying the spinal fluid, lymphocyte pleocytosis is detected. The protein concentration is increased to 0.6-1.6 g / l.

Hemiplegia among focal lesions of the nervous system occupies a special place. In the early days of the febrile period (more often in older people), the hemiplegia syndrome develops according to the central type, downstream and localized resembling vascular lesions of the nervous system (strokes). These violations are often unstable and already in the early period tend to reverse development. At 27.3-40.0% of patients develops asthenovegetative syndrome. The residual phenomena include paresis of the facial nerves.

The poliomyelitis form is the most severe form of infection. The most common in previous years, currently observed in 1-2% of patients. With this form, disability of patients is high.

Neurological status is characterized by significant polymorphism. In patients with poliomyelic form of the disease, sudden development of weakness in any limb or the appearance of numbness in it is possible. Subsequently, motor disorders develop in these extremities. Against the background of fever and cerebral symptoms, such symptoms of tick-borne encephalitis develop as: flaccid paresis of the cervico-humeral musculature and upper limbs. Often the pareses are symmetrical and cover the entire musculature of the neck. The raised hand falls passively, the head hangs down on the chest. Tendon reflexes are not caused. At the end of the second week atrophy of the affected muscles develops. Paresis and paralysis of the lower limbs are rare.

The course of the disease is always heavy. Improvement of general condition is slow. Only half of the patients have moderately recovered lost functions. In CSF, pleocytosis is detected from several hundreds to thousands of cells in 1 μl.

Residual effects in the poliomyelitis form are characteristic for all patients. The weakness of the muscles of the neck and upper limbs, the symptom of the "drooping" head, the paresis of the muscles of the upper extremities, the hypotrophy of the muscles of the neck, the shoulder girdle, the forearms, the intercostal muscles are noted.

Polyradiculoneuritic form is diagnosed in 1-3% of patients. The leading symptoms are mononeuritis (facial and sciatic nerves), cervico-shoulder radiculoneuritis, and polyradiculoneuritis with or without ascending flow. Symptoms of tick-borne encephalitis of this form are the following: neuralgia, radicular symptoms, tenderness of muscles and nerves, peripheral paralysis or paresis. Patients have pain along the nerve trunks, paresthesia (a feeling of "crawling," tingling).

Two-wave fever occurs in all forms of the disease, but more often with meningeal form. This type of fever is more typical for diseases caused by the Central European and East Siberian genotypes of the virus. For the first febrile wave, there must be a pronounced infectious-toxic syndrome. There is an acute onset, a sudden increase in temperature to 38-39 ° C, accompanied by a headache and general weakness. After 5-7 days, the condition of the patients improves, the body temperature normalizes, but after several days it rises again. Often against the background of the second wave, meningeal syndrome appears in patients.

Chronic progression is observed in 1-3% of patients. Chronic forms occur several months, and sometimes years after the acute period of the disease, mainly with meningoencephalitic, less often meningeal forms of the disease.

The main clinical form of the chronic period is kozhevnikovskaya epilepsy, which is expressed in permanent myoclonic hyperkinesias, which primarily involve the muscles of the face, neck, and shoulder girdle. Periodically, especially with emotional stress, paroxysmal enhancement and generalization of myoclonus occurs or their passage into a large tonic-clonic attack with loss of consciousness. There is also a syndrome of chronic subacute poliomyelitis caused by a slowly progressive degeneration of the peripheral motor neurons of the anterior horns of the spinal cord, which is clinically characterized by increasing atrophic paresis of the extremities, mainly the upper ones, with a constant decrease in muscle tone and tendon reflexes.

Hyperkinetic syndrome is characterized by the appearance of spontaneous rhythmic muscle contractions in individual muscle groups of the parietal limbs already in the acute period of the disease. Often progredient forms are accompanied by disorders of the psyche right up to dementia. Often, clinical symptoms are mixed, when the progression of hyperkinesis is combined with increasing amyotrophy and, sometimes, mental disorders. As the severity of symptoms increases, patients are disabled.

In recent years, relatively severe clinical forms of an acute period have been relatively rare, which does not preclude the development of a chronic, progressive form of the disease.

The course and prognosis of tick-borne encephalitis

Symptoms of tick-borne encephalitis grow within 7-10 days. Then focal symptoms of tick-borne encephalitis begin to weaken, the cerebral and meningeal symptoms gradually disappear. With a meningeal form, recovery occurs 2-3 weeks later without consequences. May be an asthenic syndrome for several months. With poliomyelitic form of complete recovery, without neurological disorders, there are no, atrophic paresis and paralysis, mainly cervical myotomes, are preserved.

With encephalic form, the impaired functions are restored slowly. The recovery period can last from several months to 2-3 years. The most severe course was noted with meningoencephalitic form with a violent onset, a rapidly onset comatose condition and a lethal outcome. High mortality (up to 25%) occurs with encephalitic and poliomyelitic forms with bulbar disorders.

In recent decades, due to extensive preventive measures, the course of tick-borne encephalitis has changed. Heavy forms began to appear much less often. Predominant are mild symptoms of tick-borne encephalitis, meningeal and febrile forms with a favorable outcome.

Classification of tick-borne encephalitis

The clinical classification of tick-borne encephalitis is based on the definition of the form, severity and nature of the course of the disease. Forms of tick-borne encephalitis:

• Inpatient (subclinical):
• febrile;
• meningeal;
• meningoencephalitic;
• poliomyelitis;
• polyradiculoneuritic.

The course of tick-borne encephalitis can be erased, light, of medium severity and severe.

According to the nature of the current distinguish between acute, two-wave and chronic (progredient) flow.

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Mortality and causes of death

Lethality in tick-borne encephalitis is associated with the development of bulbar and convulsive-coma syndromes. The frequency of deaths depends on the genotype of the circulating virus and varies from single cases in Europe and the European part of Russia to 10% in the Far East.