Salivation disorder: causes, symptoms, diagnosis, treatment

A feeling of dry mouth - xerostomia, hyposalivation (these terms are more often used to denote conditions of decreased secretion without distinct clinical manifestations detected experimentally) - or excess saliva (sialorrhea, hypersalivation) - is possible both with a neurogenic secretion disorder (organic or psychogenic in nature) and with various somatic diseases. Hypo- and hypersalivation can be constant or paroxysmal; the severity of the disorder, as well as the degree of salivation, normally depends on the functional states of the brain in the sleep-wake cycle. The volume of secretion during sleep is significantly lower, it also decreases with directed attention. When eating, saliva production increases as a result of conditioned and unconditioned reflexes. Unconditioned reflexes arise from olfactory, taste and tactile receptors. Usually 0.5-2 liters of saliva are produced per day.

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Brief physiology of salivation and pathogenesis of its disorders

The participation of sympathetic and parasympathetic innervation in the regulation of salivation is not the same, the leading role belongs to parasympathetic mechanisms. Segmental parasympathetic innervation is represented in the brainstem by secretory salivary nuclei (n.salivate rius sup. et inf.). From the brainstem, parasympathetic fibers go as part of the VII and IX glossopharyngeal nerves, synaptically interrupted in the submandibular and otic ganglion, respectively. The submandibular and sublingual salivary glands receive postganglionic fibers from the submandibular ganglion, and the parotid glands - from the otic ganglion. Sympathetic postganglionic fibers go from the superior cervical ganglion and end in the vessels and secretory cells of only the submandibular salivary glands.

Sympathetic and parasympathetic innervation of the salivary glands do not have reciprocal relationships, i.e. peripheral sympathetic activation does not cause peripheral suppression of secretion. Any suppression of secretion, for example during stress, is mediated by central inhibitory effects by reducing the activation of efferent pathways. Afferent fibers are part of the nerves innervating the masticatory muscles and taste fibers. Normally, reflex secretion of saliva is carried out with a predominance of parasympathetic impulses, which causes increased secretion of saliva and vasodilation as part of the secretory process. Mediators in the endings of the parasympathetic nerves are acetylcholine, vasoactive intestinal polypeptide (VIP) and substance P. The effect of sympathetic activation is carried out by the mediator norepinephrine, while there is no mobilization of fluid, but the protein composition of saliva changes by increasing exocytosis from certain cells. Sympathetic fibers terminate mainly in those cells that receive parasympathetic innervation, which provides a synergistic effect. Although some sympathetic fibers regulate vascular tone, this largely depends on independent central control and is not directly involved in reflex secretory mechanisms.

The reflex activity of the salivary glands can change when any part of the reflex is disrupted (its afferent, central or efferent part), as well as when the effector organ is damaged.

Insufficient afferentation from the masticatory muscles explains xerostomia in old age and that which occurs with a long-term sparing diet. In severe cases, atrophy of the salivary glands is possible.

Reflex salivation is under the complex control of higher brain regions, the influence of which is realized, in particular, in changes in the secretion of saliva depending on the functional state of the brain in the sleep-wake cycle. Examples of suprasegmental influences on the salivary function may also be psychogenic hypo- and hypersalivation, unilateral suppression of secretion in hemispheric tumors, the central action of hypotensive drugs, anorexigenic agents.

Damage to the efferent vegetative pathways explains xerostomia in progressive autonomic failure syndrome; similarly, dry mouth is caused by pharmacological denervation with anticholinergics. Damage to the effector organ, i.e., the salivary glands, causes dry mouth in Sjögren's syndrome and post-radiation xerostomia. Dry mouth in diabetes mellitus is associated with a decrease in the secretion of the liquid portion of saliva due to plasma hyperosmolarity, as well as in connection with polyuria.

Drooling is possible not only with increased secretion of saliva, but also when its normal outflow is disrupted. Thus, discoordination of oral muscles causes drooling in children with cerebral palsy; subclinical swallowing disorders due to increased tone of the axial muscles can lead to sialorrhea in Parkinsonism (with this disease, however, another mechanism is possible - activation of central cholinergic mechanisms); in patients with boulevard syndrome, drooling is caused by a disruption of the reflex act of swallowing.

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Salivation

Drooling may occur both with increased and normal secretion of the salivary glands; in this case, depending on the predominant activation of parasympathetic or sympathetic mechanisms, secretion of liquid or thick saliva occurs, respectively. The following most well-known forms of salivation can be distinguished.

Psychogenic hypersalivation

Rarely observed. Occurs without apparent cause, with no signs of organic damage to the nervous system. Salivation is sometimes dramatic; the patient is forced to carry a jar to collect saliva. Psychoanamnesis, demonstrative features in the presentation of the symptom, its combination with other functional-neurological manifestations or stigmas are important.

Drug-induced hypersalivation

Most drugs that affect salivation cause mild or moderate xerotomy. At the same time, the use of some drugs may be accompanied by a side effect in the form of salivation. A similar effect has been described with lithium, nitrazepam - an anticonvulsant used to treat various forms of epilepsy. In the latter case, salivation develops as a result of a violation of the reflex function of swallowing. Withdrawal or reduction of the drug dose usually eliminates drug hypersalivation.

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Hypersalivation in Parkinsonism

The most common form of hypersalivation, often combined with other autonomic disorders characteristic of Parkinsonism (seborrhea, lacrimation), can be one of the early manifestations of the disease. Sialorrhea in Parkinsonism is most pronounced at night and in the supine position. As a rule, taking antiparkinsonian drugs (especially anticholinergics) reduces salivation.

Drooling in bulbar and pseudobulbar syndrome

In bulbar and pseudobulbar syndrome of various etiologies (tumors, syringobulbia, poliomyelitis, vascular pathology, degenerative diseases), salivation may be observed, the degree of which depends on the severity of bulbar disorders. Salivation may be abundant (up to 600-900 ml/day); saliva is thick. Patients are forced to hold a handkerchief or towel to their mouths. Most authors explain sialorrhea by a violation of the reflex act of swallowing, as a result of which saliva accumulates in the oral cavity, although irritation of the bulbar salivary center is also possible.

Drooling in patients with cerebral palsy

Associated with discoordination of the oral muscles and difficulty swallowing saliva, it often significantly complicates the lives of patients.

Hypersalivation in somatic pathology

Increased secretion of saliva is observed in ulcerative stomatitis, helminthic invasion, and toxicosis of pregnancy.

Xerostomia, or dry mouth

Xerostomia in Sjögren's syndrome

A sharply expressed constant dryness in the mouth is one of the main manifestations of Sjögren's syndrome ("dry syndrome"). The disease refers to systemic autoimmune diseases, observed more often in women over 40 years old. The parotid salivary glands periodically swell. In this case, xerostomia is combined with xerophthalmia, dryness of the mucous membrane of the nose, stomach and other mucous membranes, joint syndrome, changes in reactivity.

Drug-induced xerostomia

Taking medications is the most common cause of salivary gland hypofunction. More than 400 drugs (anorexics, anticholinergics, antidepressants, sedatives and hypnotics, antihistamines, hypotensives, diuretics, etc.) can cause this effect. Usually, there is mild or moderate dryness in the mouth - depending on the dose, duration and mode of taking the drug. Hypofunction of the salivary glands is reversible.

Post-radiation xerostomia

Observed after irradiation of the salivary glands during radiation therapy for head tumors.

Psychogenic xerostomia

A transient feeling of dry mouth when worried or in stressful situations. Usually observed in anxious, emotionally unstable individuals.

Dry mouth has also been described in depressive states (however, dryness is not associated with taking medications).

Xerostomia in acute transient total dysautonomia

In 1970, selective damage to the vegetative (sympathetic and parasympathetic) fibers of infectious-allergic nature with subsequent recovery was described for the first time. Parasympathetic dysfunction, in addition to xerostomia, is manifested by decreased secretion of tears, lack of pupillary response to light, decreased activity of the gastrointestinal tract, detrusor of the urinary bladder, which leads to insufficient emptying, etc. Sympathetic dysfunction is manifested by insufficient dilation of the pupils in the dark, orthostatic hypotension with fainting, fixed heart rate, lack of sweating, etc.

Xerostomia in glossodynia

Disorders of salivation are observed in 80% of patients with glossodynia; most often these disorders are represented by hyposalivation, which may be the first manifestation of the disease (before the development of algic phenomena). Dry mouth most often bothers at night.

Xerostomia in congenital absence of salivary glands

Congenital absence of salivary glands is a rare pathology that is sometimes combined with a decrease in tear production.

Xerostomia due to limited chewing

Insufficient salivation and a feeling of dry mouth may develop in people who are on a diet and eat only pureed and liquid food, for example, after maxillofacial surgery, in elderly people. With prolonged adherence to such a diet, atrophy of the salivary glands is possible.

Xerostomia in diabetes mellitus

Dry mouth may be one of the first manifestations of the disease; thirst, increased appetite, polyuria and other manifestations of diabetes occur simultaneously.

Xerostomia in gastrointestinal diseases

Hyposalivation can be observed in chronic gastritis and hepatocholecystitis.

Hyposalivation in some focal brain lesions

Salivary secretion in hemispheric tumors and brain abscesses decreases on the side of the lesion, while in subtentorial tumors, there is bilateral suppression of secretion, more pronounced on the side of the tumor. The most pronounced suppression of secretion is noted in patients in a serious condition, apparently due to the effect of the tumor on the brainstem. Complete suppression of secretion is an extremely unfavorable prognostic sign. However, it should be remembered that the experimentally detected decrease in salivary secretion in the clinical picture occupies a very modest place against the background of gross neurological defects.

Treatment of salivation disorders

The choice of therapy for hypersalivation and its effect largely depend on the form of hypersalivation.

Drug-induced hypersalivation usually requires only discontinuation or reduction of the drug dose.

In psychogenic hypersalivation, pharmacological agents (tranquilizers, antidepressants - amitriptyline is preferable, since it has anticholinergic activity), various forms of psychotherapy are used; in particular, improvement with hypnotherapy has been described.

Salivation in Parkinsonism usually decreases significantly with antiparkinsonian therapy (especially when using anticholinergics in doses typical for this disease), but is sometimes difficult to treat.

Special programs for teaching children to correct salivation in children with cerebral palsy have been created. In severe cases, surgical treatment is indicated. Various surgical treatment methods include removal of the salivary glands, duct dotting, their transposition, and various procedures for denervation of the salivary glands.

Treatment of xerostomia may be aimed at:

1. to eliminate the cause of hypofunction of the salivary glands (treatment of the underlying disease in Sjögren's syndrome; dose reduction, change in the regimen of taking medications or their discontinuation; insulin therapy in diabetes mellitus; diet expansion, exercises involving the masticatory muscles in deafferentation xerostomia);
2. to stimulate the function of the salivary glands: pilocarpine (capsules of 5 mg once a day sublingually: at this dosage there is no noticeable effect on blood pressure and heart rate); nicotinic acid (0.05-0.1 g 3 times a day), vitamin A (50,000-100,000 IU/day), potassium iodide (0.5-1 g 3 times a day as a mixture);
3. to change the consistency of saliva: bromhexine (1 tablet 3-4 times a day).

As a replacement therapy, the following are used: various compositions of artificial saliva when other forms of treatment are ineffective (mainly for Sjögren's syndrome, severe forms of post-radiation xerostomia).