Neurogenic dysphagia: causes, symptoms, diagnosis, treatment

The function of swallowing is the precisely controlled transfer of the food bolus and liquid from the mouth to the esophagus. Since the air and food streams, crossing, have a common path in the mouth and pharynx, there is a subtle mechanism for separating them during swallowing to prevent the swallowed food from entering the airways. There is an oral preparatory phase, the actual oral phase of swallowing and a swallowing reflex. In order for the food bolus to pass through the esophagus, a reflex mechanism is activated. In this case, the essential elements of swallowing are the exclusion of the nasopharynx (nasopharynx) with the help of velopharyngeal overlap, pushing the bolus into the pharynx with the help of a pumping movement of the tongue, overlapping the larynx with the help of the epiglottis and pharyngeal peristalsis, which displaces food through the cricopharyngeal sphincter into the esophagus. Elevation of the larynx helps prevent aspiration and raises the base of the tongue, which facilitates pushing food down into the pharynx. The upper airway is closed by approximation and tension of the epiglottis, the lower by the false vocal cords and finally by the true vocal cords, which act as a valve preventing food from entering the trachea.

The entry of foreign material into the airway usually causes a cough, which depends on the tension and strength of the expiratory muscles, including the abdominal muscles, m. latissimus and m. pectoralis. Weakness of the soft palate causes a nasal tone in the voice and the entry of liquid food into the nose when swallowing. Weakness of the tongue makes it difficult to perform the important pumping function of the tongue.

Coordination of swallowing depends on the integration of sensory pathways from the tongue, oral mucosa, and larynx (cranial nerves V, VII, IX, X) and the inclusion of voluntary and reflex contractions of muscles innervated by the V, VII, and X-XII nerves. The medullary swallowing center is located in the nucleus tractus solitarius region very close to the respiratory center. Swallowing is coordinated with the phases of respiration so that swallowing apnea follows inspiration, preventing aspiration. Reflex swallowing remains normally functioning even in a persistent vegetative state.

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The main causes of dysphagia:

I. Muscular level:

1. Myopathy (oculopharyngeal).
2. Myasthenia gravis.
3. Dystrophic myotonia.
4. Polymyositis.
5. Scleroderma.

II. Neural level:

A. Unilateral injuries. Mild dysphagia (damage to the caudal group of nerves in case of a basal skull fracture, jugular vein thrombosis, glomus tumor, Garsen syndrome, rarely - in multiple sclerosis).

III. Bilateral lesions:

1. Diphtheritic polyneuropathy.
2. Tumor in the area of the base of the skull.
3. Guillain-Barre polyneuropathy.
4. Idiopathic cranial polyneuropathy.
5. Meningitis and carcinomatosis of the membranes.

III. Nuclear level:

A. Unilateral injuries:

1. Predominantly vascular lesions of the trunk, in which dysphagia is presented in the picture of alternating syndromes of Wallenberg-Zakharchenko, Sestan-Chene, Avellis, Schmidt, Tepia, Berne, Jackson.
2. Less common causes include syringobulbia, brainstem glioma, and Arnold-Chiari malformation.

B. Bilateral injuries (bulbar palsy):

1. Amyotrophic lateral sclerosis.
2. Infarction or hemorrhage in the medulla oblongata.
3. Polio.
4. Syringobulbia.
5. Progressive spinal amyotrophy (bulbar forms in children; bulbospinal form in adults).

IV. Supranuclear level (pseudobulbar palsy):

1. Vascular lacunar condition.
2. Perinatal trauma.
3. Traumatic brain injury.
4. Amyotrophic lateral sclerosis.
5. Degenerative-atrophic diseases involving the pyramidal (pseudobulbar syndrome) and extrapyramidal system (pseudo-pseudobulbar palsy), including progressive supranuclear palsy, Parkinson's disease, multiple system atrophy, Pick's disease, Creutzfeldt-Jakob disease, etc.
6. Hypoxic encephalopathy.

V. Psychogenic dysphagia.

I. Muscular level

Diseases that directly affect muscles or myoneural synapses may be accompanied by dysphagia. Oculopharyngeal myopathy (oculopharyngeal dystrophy) is a variant of hereditary myopathy characterized by late onset (usually after 45 years) and manifested by weakness of a limited number of muscles, mainly slowly progressing bilateral ptosis and dysphagia, as well as voice changes. In the later stages, trunk muscles may be involved. These very characteristic clinical features serve as the basis for diagnosis.

Myasthenias debut (in 5-10%) with dysphagia as a monosymptom. The addition of fluctuating weakness in other muscles (oculomotor, facial, and muscles of the limbs and trunk), as well as electromyographic diagnostics with a prozerin test confirm the diagnosis of myasthenia.

Dystrophic myotonia as a cause of dysphagia is easily recognized based on the typical autosomal dominant type of inheritance and the unique topography of muscle atrophy (m. levator palpebre, facial, chewing including temporal, sternocleidomastoid muscles, as well as muscles of the forearms, hands and shins). Dystrophic changes in other tissues are characteristic (lens, testicles and other endocrine glands, skin, esophagus and, in some cases, the brain). A characteristic myotonic phenomenon is present (clinical and on EMG).

Polymyositis is an autoimmune disease characterized by early swallowing disorder (bulbar syndrome of myogenic nature), proximal muscle weakness with myalgia and muscle compaction, preserved tendon reflexes, high levels of CPK, changes in EMG and in muscle tissue biopsy.

Scleroderma can affect the esophagus (esophagitis with a characteristic X-ray picture), manifesting itself as dysphagia, which is usually detected against the background of a systemic process affecting the skin, joints, internal organs (heart, lungs). Raynaud's syndrome often develops. In iron deficiency anemia, atrophic changes in the mucous membrane of the pharynx and esophagus, as well as spastic narrowing of its initial part (Plummer-Vinson syndrome) are an early symptom and sometimes precede the development of anemia. Hypochromic anemia and a low color index are detected.

II. Neural level

A. Unilateral injuries

Unilateral damage to the caudal group of nerves (IX, X and XII pairs), for example, in a fracture of the base of the skull, usually causes mild dysphagia in the picture of Berne's syndrome (jugular foramen syndrome, manifested by unilateral damage to the IX, X and XI pairs). This syndrome is also possible with thrombosis of the jugular vein, glomus tumor. If the fracture line passes through the adjacent canal for the hypoglossal nerve, then a syndrome of unilateral damage to all caudal nerves (IX, X, XI and XII nerves) with more pronounced dysphagia (Vernet-Sicard-Collé syndrome) develops. Garsen's syndrome is characterized by the involvement of the cranial nerves on one side (the "half-base" syndrome) and therefore, in addition to dysphagia, has many manifestations of the involvement of other cranial nerves. Multiple sclerosis can be a rare cause of unilateral damage to the roots of the caudal cranial nerves and is accompanied by other characteristic symptoms of this disease.

B. Bilateral lesions

Bilateral lesions of the trunks of the caudal cranial nerves are characteristic mainly of some polyneuropathies and meningeal processes. Diphtheritic polyneuropathy, as well as AIDP or some other variants of polyneuropathies (post-vaccination, paraneoplastic, with hyperthyroidism, porphyria) can lead to severe tetraplegia with sensory disorders, boulevard and other brainstem disorders up to paralysis of the respiratory muscles (Landry type) and complete loss of the ability to swallow independently.

Idiopathic cranial polyneuropathy (idiopathic multiple cranial neuropathy) is less common and can be unilateral or bilateral. It is characterized by an acute onset with headache or facial pain, most often in the periorbital and frontotemporal areas. The pain is of a constant aching nature and cannot be classified as either vascular or neuralgic. Usually, after a few days, a picture of sequential or simultaneous involvement of several (at least two) cranial nerves (III, IV, V, VI, VII nerves; involvement of the II pair and the caudal group of nerves is possible) is observed. The olfactory and auditory nerves are not involved. Both monophasic and recurrent course are possible. Pleocytosis in the cerebrospinal fluid is not typical; an increase in protein is possible. A good therapeutic effect of glucocorticoids is typical. The disease requires exclusion of symptomatic cranial polyneuropathy.

Meningeal carcinomatosis is characterized by bilateral sequential (with an interval of 1-3 days) involvement of cranial nerves. Tumors of the skull base (including in Garsen syndrome), Blumenbach's clivus or caudal parts of the brainstem are accompanied by involvement of V-VII and IX-XII and other nerves. In these cases, dysphagia is observed in the picture of damage to several cranial nerves. Neuroimaging is of decisive diagnostic importance.

III. Nuclear level

A. Unilateral injuries

Unilateral damage. The most common cause of unilateral damage to the nuclei of the caudal group of nerves is vascular lesions of the brainstem. In this case, dysphagia is presented in the picture of alternating syndromes of Wallenberg-Zakharchenko (more often), or (very rarely) Sestan-Chene, Avellis, Schmidt, Tepia, Berne, Jackson. The course of the disease and the characteristic neurological symptoms in these cases rarely give cause for diagnostic doubts.

Less common causes of unilateral caudal brainstem damage include syringobulbia, brainstem glioma, and Arnold-Chiari malformation. In all cases, neuroimaging provides invaluable diagnostic assistance.

B. Bilateral damage (bulbar palsy)

Bilateral damage (bulbar palsy) at the nuclear level can be caused by vascular, inflammatory and degenerative diseases affecting the caudal parts of the brainstem (medulla oblongata). The bulbar form of amyotrophic lateral sclerosis already at the early stages of the disease manifests itself in swallowing disorders, which, as a rule, is accompanied by dysarthria, EMG signs of motor neuron disease (including in clinically intact muscles) and a progressive course of the systemic process.

Infarction or hemorrhage in the medulla oblongata with bilateral damage always manifests itself with massive general cerebral and focal neurological symptoms, and dysphagia is a characteristic part of it.

Poliomyelitis in adults is usually not limited to damage to bulbar functions; however, in children, a bulbar form is possible (usually neurons of the VII, IX and X nerves are affected). In diagnostics, in addition to the clinical picture, it is important to take into account the epidemiological situation and serological research data.

Syringobulbia is characterized by symptoms of damage not only to the motor nuclei of the IX, X, XI and XII nuclei (dysphonia, dysarthria, dysphagia; with higher localization, the facial nerve may also be involved), but also by characteristic sensory disturbances on the face of a segmental type. The slow progression of the disease, the absence of conduction symptoms in this form and the characteristic picture on CT or MRI make the diagnosis not very difficult.

Progressive spinal amyotrophy, manifested by dysphagia, occurs in different forms in children and adults.

Facio-Londe syndrome, also called progressive bulbar palsy in children, is a rare inherited disorder that affects children, adolescents, and young adults. The disease usually begins with respiratory (stridor) problems, followed by diplegia facialis, dysarthria, dysphonia, and dysphagia. Patients die within a few years of the onset of the disease. Upper motor neuron function is usually spared.

Adult bulbospinal amyotrophy, called Kennedy syndrome, is observed almost exclusively in men (X-linked inheritance), most often at the age of 20-40 years, and is characterized by a rather unusual combination of distal atrophy (first in the arms) with mild bulbar signs. Mild paretic syndrome is noted, sometimes - episodes of general weakness. There are fasciculations in the lower part of the face. Gynecomastia is quite typical (approximately 50%). Tremor is possible, sometimes - crampi. The course is quite benign.

IV. Supranuclear level (pseudobulbar palsy)

The most common cause of dysphagia in the picture of pseudobulbar syndrome is a vascular lacunar condition. There is a picture of not only bilateral damage to the corticobulbar tract, but also bilateral pyramidal signs, gait disturbances (dysbasia), oral automatism reflexes, and often urination disorders; cognitive impairment is often detected, and MRI shows multiple foci of softening in the cerebral hemispheres in a patient with vascular disease (most often hypertension).

Pseudobulbar syndrome is often encountered in perinatal trauma. If the latter is accompanied by spastic tetraplegia, severe speech disorders, respiratory difficulties and dysphagia are possible. As a rule, other symptoms are also present (dyskinetic, ataxic, impaired mental maturation, epileptic seizures and others).

Traumatic brain injury can lead to various types of spastic paralysis and severe pseudobulbar syndrome with a disorder of bulbar functions, including swallowing.

Lateral amyotrophic sclerosis at the onset of the disease (the "high" form) may be clinically manifested only by signs of the upper motor neuron (pseudobulbar syndrome without signs of atrophy and fasciculations in the tongue). Dysphagia is caused by spasticity of the muscles of the tongue and pharynx. Actually, bulbar paralysis sometimes joins in a little later. A similar picture is possible with such a form of lateral amyotrophic sclerosis as primary lateral sclerosis.

Dysphagia can be observed in the picture of various forms of multiple systemic degeneration and parkinsonism (idiopathic and symptomatic). We are talking about progressive supranuclear palsy, multiple system atrophy (in its three variants), diffuse Lewy body disease, corticobasal degeneration, Parkinson's disease, vascular parkinsonism and some other forms.

In most of the above forms, the clinical picture of the disease includes Parkinsonism syndrome, among the manifestations of which dysphagia sometimes occurs, reaching a noticeable degree of severity in some patients.

The most common etiologic form of parkinsonism accompanied by dysphagia is Parkinson's disease, the diagnostic criteria of which are also unified, as are the diagnostic criteria of progressive supranuclear palsy, multiple system atrophy, corticobasal degeneration and diffuse Lewy body disease. In general, parkinsonism in the picture of multisystem degeneration is characterized by the absence of resting tremor, early development of postural disorders, rapid rate of progression, low efficiency of dopa-containing drugs.

Rarely, dysphagia is caused by dystonic spasm of the pharynx (“spastic dysphagia”) or other hyperkinesis (dystonic, choreic), for example, with tardive dyskinesia.

V. Psychogenic dysphagia

Dysphagia in the picture of conversion disorders sometimes acts as the main clinical syndrome, leading to a significant decrease in body weight. However, the analysis of mental and somatic status always reveals polysyndromic disorders (at the time of examination or taking into account the anamnesis), developing against the background of current (and childhood) psychogenia in a person prone to demonstrative reactions. However, "neurological forms" of hysteria, as a rule, are observed in the absence of pronounced personality disorders. Concomitant visual, pseudo-ataxic, sensorimotor, speech (pseudo-stuttering, mutism), "lump in the throat" and other (including various vegetative) disorders are revealed, the provocation of which allows to clarify their phenomenology and facilitates diagnosis. It is always necessary to exclude somatic causes of dysphagia with an X-ray examination of the act of swallowing. Mild dysphagia is very common in the population of psychiatric patients.

Differential diagnosis is carried out with other forms of neurogenic dysphagia, refusal to eat food in negativism syndrome, visceral disorders (somatogenic dysphagia).

Diagnostic tests for dysphagia

Clinical and biochemical blood tests, esophagoscopy and gastroscopy, X-ray examination of the upper gastrointestinal tract, chest X-ray, tomography of the mediastinum, EMG of the tongue muscles (with a test for myasthenia), CT or MRI of the brain, cerebrospinal fluid examination, thyroid hormone examination, EEG, consultation with a therapist, endocrinologist, psychiatrist.

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