Laryngeal paralysis (laryngeal paresis): causes and pathogenesis

Causes of paralysis of the larynx (larynx paresis)

Paralysis of the larynx is a polyethiologic disease. It can be caused by the compressed innervation of its structures or the involvement of nerves in the pathological process developing in these organs, their traumatic damage, including surgical interventions on the neck, chest or skull.

Paralysis of the central genesis, depending on the topography of the lesion in relation to the nucleus ambiguus, is conventionally divided into naduclear (cortical and corticobulbar) and bulbar. Cortical paralysis is always bilateral in accordance with innervation from the motor nucleus; possible m causes of concussis, congenital cerebral palsy, encephalitis, bilirubin encephalopathy, diffuse atherosclerosis of cerebral vessels. Corticobulbar palsy can occur as a result of damage to the area of the cross of the corticobulbar tract, for example, with circulatory failure in the basin of the vertebral artery, occlusion of the latter. Bulbar paralysis can be a consequence of circulatory disorders in the basins of the vertebral, posterior and anterior lower cerebellar, upper, middle, lower lateral branches of the cerebellar arteries; as well as polysclerosis, syringobulbia, syphilis, rabies, encephalitis, poliomyelitis, intracerebral tumors. To develop the symptoms of laryngeal paralysis, partial damage to the nucleus is sufficient. Paralysis of the larynx of the central genesis is approximately 10% chance. The main causes of peripheral paralysis of the larynx:

• medical trauma in the operation on the neck and chest;
• compression of the nerve trunk during the tumor or metastatic process in the neck and thorax, diverticulum of the trachea or esophagus, hematoma or infiltrate in traumas and inflammatory processes, with an increase in the size of the heart and the aortic arch (tetralogy of Fallot), mitral defect, aortic aneurysm, hypertrophy of the ventricles, dilatation of the pulmonary artery);
• neuritis of inflammatory, toxic or metabolic genesis (viral, toxic (poisoning with barbiturates, organophosphates and alkaloids), hypocalcemic, hypokalemic, diabetic, thyrotoxic).

The most common cause of paralysis is the pathology of the thyroid gland and medical trauma in operations on it. With primary intervention, the incidence of complications is 3%, with the second - 9%; in the surgical treatment of thyroid cancer - 5.7%. In 2.1% of patients, paralysis is diagnosed at the preoperative stage.

Pathogenesis of laryngeal paralysis (larynx paresis)

When the larynx is paralyzed, all three functions of the larynx suffer. The severity of clinical symptoms and morphofunctional changes in the larynx depends on the degree of denervation and the nature of compensatory-adaptive changes, the position of the paralyzed vocal fold, the development of atrophic processes in the muscular apparatus of the larynx, and the condition of the periarthrosplastic joint. The severity of the disease with unilateral paralysis is due to the unobstructed vocal cicle, and with bilateral paralysis, on the contrary, the median position of the vocal folds leading to stenosis of the larynx.

The timing of the onset of atrophy of the larynx muscles is not exactly defined, they are of an individual nature and depend on the degree of denervation and removal of the vocal fold from the midline. Atrophy of the vocal fold worsens the course of unilateral paralysis of the larynx, as it leads to additional lateralization and a decrease in tone. The arythritic cartilage on the side of paralysis is often displaced to the healthy side, rotated anteriorly. The results of electromyographic studies prove that complete denervation of the vocal fold with muscle atrophy with laryngeal paralysis develops infrequently, in most cases diagnose any level of syncopeesis and reinnervation. With long-term paralysis, ankylosis of the arytenoid joint occurs during detection.

Respiratory tracts are protected from aspiration during swallowing by several reflex mechanisms, including movement of the larynx upwards and tilt it forward, adduction of vocal folds, coordination of respiration and swallowing. Such protection is disturbed by paralysis of the larynx, especially in the early stages of its development and the normal laryngeal lift during swallowing is accompanied by closure of the glottis. In patients with laryngeal paralysis, this does not happen, the undamaged vocal fold occupies a more elevated position. Compensation of lost functions with unilateral paralysis of the larynx is carried out by changing the voltage of the adductors, boosting the voice to increase the lining pressure, changing the configuration of the overboard space. Clinically, this is expressed in the displacement of the glottis during phonation in the direction of paralysis due to the movement of a healthy voice fold to the opposite side, hypertrophy of the vestibular folds. With bilateral paralysis of the larynx with an intermediate position of the vocal folds, their displacement towards the midline with the development of laryngeal stenosis usually occurs over time.

[1], [2], [3], [4], [5], [6], [7]