Streptomycin toxico-degenerative labyrinthiasis: causes, symptoms, diagnosis, treatment

The pathogenesis of streptomycin toxic-degenerative labyrinthosis is the antibacterial property of this drug, which consists in its penetration into the microbial as well as the receptor cell and binding to the specific receptor proteins of their ribosomes. As a result, the formation of the so-called initiating substance between RNA and ribosome is disrupted, resulting in the synthesis of defective proteins in the cell, which leads to disruption of its trophism, degeneration and death. The intensity of streptomycin exposure to a microbial or receptor cell depends on the concentration of the drug and the duration of its use.

Factors that enhance the action of streptomycin on receptor cells of the inner ear include:

• applied dose; as a rule, vestibular and auditory disorders appear after the administration of 30-40 g of streptomycin into the body and more often - when this amount of the drug is exceeded; However, there are cases when transient cochleovestibular disorders occur also at lower doses, for example 3-4 g; the daily dose also is important - at 1 g / day cochleovestibular disorders occur rarely, at 2 g / day - more often, at 3 g / day - even more often with a more pronounced clinical picture;
• the route of administration; the greatest toxic effect occurs with suboccipital or intraluminal administration of the drug, and more often, faster and with more pronounced and persistent labyrinth symptoms of HBV receptor damage occurs in the first method; in some cases, the resulting deafness with decreasing the dose of the drug, stopping or changing the method of its administration acquires a reverse development, in other cases, complete irreversible deafness occurs;
• duration of application; the frequency and depth of the ototoxic effect of streptomycin is directly dependent on the duration of its use and the number of repeated courses, the need for which is dictated by the underlying disease;
• individual intolerance; observations show that this factor is of great importance; in persons susceptible to streptomycin, labyrinthine disorders may occur after application of 2-3 g of the drug; in others, administration of 100 g or more does not cause any labyrinthine disorders;
• dependence on concomitant diseases; more often and malignant streptomycin toxic-degenerative labyrinthosis is manifested with concomitant tuberculosis infection, acute or chronic purulent inflammation of the middle ear, as well as with tuberculous meningitis;
• age dependence; according to some observations, the use of streptomycin in childhood less often causes streptomycin toxic-degenerative labyrinthosis than its use in adults.

Pathological anatomy. Experimental data on animals and autopsies indicate that with streptomycin toxic-degenerative labyrinthosis peripheral receptor, radicular and central morphological changes of the nervous apparatus of the auditory and vestibular analyzers take place. These changes concern the hair cells of CpO, the spots of the vestibules of the vestibule and the ampullar cristae, the nerve fibers of the pre-vertebral nerve, the stem and subcortical centers, and the cortical zones of the auditory and vestibular analyzers. Pathomorphological changes also concern the non-receptor structures of the basilar membrane, the elements of the otolith and ampullar apparatus, the vascular stria of the cochlea. These changes cause disturbances in the trophism of the inner ear, as well as changes in the activity of the local APUD system, which results in irreversible morphological changes in the receptor and auxiliary structures of the VU.

Symptoms of streptomycin toxic-degenerative labyrinthosis. Most often streptomycin toxic-degenerative labyrinthosis begins with the gradual development of vestibular disorders, which can last for many months. With total defeat of one of the labyrinths, a pronounced lesser-like syndrome appears, manifested by dizziness, spontaneous nystagmus, a violation of statics and gait, nausea, vomiting, noise in one or both ears, and hearing loss.

Vestibular disorders eventually go through central compensation, while hearing impairment persists. As a rule, streptomycin toxic-degenerative labyrinthosis is a two-way process, therefore, vestibular disorders are not so focused on the patient's attention as hearing impairment. Usually, the largest violations of the latter occur at high frequencies of the SOC, grouping around the frequency of 4000 Hz. Along with vestibular and auditory symptoms, there are also visual disturbances.

Vestibular disorders are characterized by unsystematic behavior, as evidenced by indistinct violations of the index and march samples, spontaneous nystagmus, as a rule, absent or occurs only in the first days of intoxication. With the disappearance of spontaneous vestibular reactions, either a complete bilateral deactivation of the vestibular apparatus or, if provocative tests are possible, a symptom of "fatigue" Aubry: the disappearance of rotational or caloric nystagmus after repeated provocative tests is revealed.

Auditory disorders appear at different times, most often 1-2 months after the start of treatment, but may occur much earlier or 2-3 months after discontinuation of treatment. As a rule, cochlear disorders are bilateral and symmetrical. FUNG is constantly present, ear noise, according to different authors, is observed in 10-20% of cases.

The prognosis for the functions of the inner ear is determined by the above risk factors. The vestibular function is gradually normalized by the remaining receptors and central compensation. Hearing impairment, as a rule, is irreversible. Only in rare cases can it recover to its normal state if streptomycin treatment is discontinued at the earliest stage of streptomycin toxic-degenerative labyrinthosis and with appropriate drug treatment. With more pronounced deafness, stopping the progression of the disorder is possible only with the immediate withdrawal of streptomycin treatment and intensive medication, otherwise it may progress after stopping the drug.

Treatment of streptomycin toxic-degenerative labyrinthosis. When treating streptomycin, control over auditory and vestibular functions is necessary. The appearance of noise in the ears, deafness and dizziness serves as an indication for the suspension of this treatment and the appointment of a comprehensive treatment (pantocrine, pantogam, other neurotropic drugs, antihypoxants, glucose, ascorbic acid, B vitamins). With the progression of hearing loss, extracorporal therapy (plasmapheresis) and HBO can be used. If it is necessary to resume treatment with streptomycin, the dose is reduced to therapeutically effective and applied together with sodium pantothenate, which reduces the risk of streptomycin toxic-degenerative labyrinthosis.

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