Anatomy, Physiology, and Pathology of the Organs of Hearing, Vision, and Speech - Shvetsov A.G. 2006

Anatomy, Physiology, and Pathology of Voice and Speech Production
Pathology of Voice Production
Pathology of the Vocal Apparatus

Phonation is The primary function of the Larynx. Developmental anomalies of the larynx are most commonly associated with structural abnormalities of the epiglottis, but epiglottic defects usually have no significant impact on voice production.

A congenital laryngeal web is very rarely observed—a thin membrane between or below the true vocal folds that leaves a small opening for respiratory air to pass through. Consequently, the primary symptoms are varying degrees of breathing difficulty, hoarseness, and other voice defects.

Acute inflammation of the laryngeal mucosa (acute laryngitis) most commonly develops as part of a diffuse Upper Respiratory Tract infection during Influenza or seasonal catarrh. The onset of the inflammatory process in the larynx is promoted by general and local exposure to cold, while risk factors include smoking and vocal strain. The disease manifests as a dry, scratchy sensation in the throat, followed by a dry cough; the voice becomes hoarse and is sometimes lost completely (aphonia).

In children, acute laryngitis is often accompanied by "false croup"—a significant Swelling of the laryngeal mucosa above the true vocal folds, leading to a narrowing of the glottis. The child develops a "barking" cough, and often labored breathing in the form of choking fits. These attacks usually occur suddenly at night, lasting 1-2 hours, after which breathing is typically restored on its own, providing immediate relief. In some cases, however, urgent medical intervention is required.

The main danger of false croup is failing to recognize true diphtheritic croup, which shares very similar symptoms.

Frequent episodes of acute laryngitis and prolonged vocal strain lead to the gradual development of chronic laryngitis, the primary sign of which is dysphonia (voice alteration)—ranging from a slight loss of vocal Resonance to severe hoarseness and even aphonia. Accompanying symptoms include a "tickling" or scratchy sensation in the throat and a dry cough. With excessive and prolonged vocal strain, so-called nodules can form on the true vocal folds—localized swellings located symmetrically on the free edge of the folds. This prevents their complete closure during phonation. A gap forms between the folds, through which air leaks, making the voice hoarse. Vocal fold nodules are sometimes observed in children who scream frequently and loudly, in singers with untrained voices, and in choir members who excessively force their voices while singing. Frequent acute laryngitis is a predisposing factor.

A laryngeal fibroma (polyp) is a rounded, smooth-surfaced mass that typically forms on the free edge of one of the true vocal folds. Its size can range from that of a millet seed to a pea. By preventing tight closure of the folds, the fibroma causes hoarseness. Treatment is exclusively surgical.

Laryngeal papilloma is a benign tumor that appears as bumpy, cluster-like growths resembling cauliflower, located on the true or false vocal folds. It is more common in children aged 2 to 8 years, grows slowly, and leads to progressive hoarseness. In advanced cases, complete loss of voice (aphonia) and breathing difficulties may develop. Treatment is surgical.

Laryngeal Cancer is more common in people over 40, while Sarcoma (a proliferation of Connective Tissue) can also develop in childhood. Treatment usually involves a total laryngectomy, followed by training in voice production using air swallowed or drawn into the Esophagus and Stomach.

Paralysis and paresis of the laryngeal Muscles are relatively rare and usually occur as concomitant complications of central or peripheral neurological disorders. Paralysis of the recurrent laryngeal nerve and its branches is accompanied by damage to all intrinsic Muscles of the corresponding half of the larynx, both those that narrow and those that widen the glottis. The true vocal fold assumes a semi-open position that does not change during phonation and Respiration. As a result of the incomplete closure of the true vocal folds during phonation, air leaks through the open glottis, severely disrupting voice production, causing aphonia, and making only whispered speech possible. In unilateral recurrent laryngeal nerve lesions, partial compensation of vocal function often gradually occurs due to the healthy vocal fold. Although aphonia resolves, the voice remains weak and muffled. Bilateral recurrent laryngeal nerve paralysis results in complete aphonia.

In paralysis of individual Branches of the recurrent laryngeal nerve, only the function of the muscles innervated by these branches is affected. Thus, in paralysis of the thyroarytenoid Muscle, which forms the body of the true vocal fold, the glottis gapes during phonation, and the voice becomes hoarse or sometimes voiceless. In persistent bilateral paralysis of the true vocal folds, a compensatory function of the false vocal folds develops as they begin to close. However, the resulting voice is usually hoarse and weak.

Paralysis of the muscle that widens the glottis leads to immobility of the corresponding half of the larynx. During breathing, the true vocal fold remains in the median position, just as during phonation; although this has practically no effect on voice production, breathing difficulties may occur during physical exertion because the laryngeal lumen is narrowed by half. If the condition is bilateral, severe respiratory distress and even suffocation can occur because the glottis does not open to allow sufficient air to pass.