**3. Dysphagia classification**

Dysphagia is commonly divided into esophageal and oropharyngeal. Based on the functional mechanisms of disease development, dysphagia is classified into:


In addition, all types of dysphagia can be divided into:

• acute

*Therapy Approaches in Neurological Disorders*

**2. Physiological aspects of the swallowing process**

cases, swallowing is performed unconsciously [3].

the pyriform sinuses into the esophagus [5, 6].

X, XI are involved at all stages of swallowing [7].

difficulty swallowing after extubation [11, 12].

perception of difficulty swallowing.

bolus is formed [3, 4].

The pharynx contracts [5].

stomach [6].

Swallowing is a sequence of coordinated voluntary and involuntary (reflex) movements that push contents of the oral cavity into the esophagus and the stomach. It is a complex process consisting of coordinated movements of the jaw, the soft palate, and the esophagus muscles. The process involves the olivary nuclei and the cerebral cortex [2]. A person swallows approximately 600 times per day. Nearly 200 times while eating, 50 times while sleeping, and 350 times in all other cases. In most

The process of swallowing can be divided into four phases: oral, oropharyngeal, pharyngeal, and esophagopharyngeal. During the first (oral) phase, food is delivered into the oral cavity. Food is chewed, it is moistened with saliva, and a food

During the second (oropharyngeal) phase, the food is accumulated at the back of the tongue, chewing is stopped, and the tongue lifts up and pushes the food bolus through the pharynx into the middle portion of the pharynx (oropharynx). At the same time, the longitudinal muscles of the tongue and the mylohyoid muscles contract and press down the tip, back, and root of the tongue sequentially to the hard palate. The tongue is pushed backwards. The soft palate lifts up as to close down the nasopharynx. The pharynx and the hyoid bone move forward and up. The epiglottis moves back and down as to close down the entrance to the trachea. Breathing stops.

During the third (pharyngeal) phase, the food bolus moves down into the middle portion of the pharynx, where the middle pharyngeal constrictor and the inferior pharyngeal constrictor contract, ensuring the bolus is squeezed and pushed downwards. At the same time, the larynx and the hyoid bone lifts up, enabling faster food bolus passing through the middle portion of the pharynx to the inferior portion. At the moment of swallowing, the reflex response enables expansion of the esophageal entrance, and the pharyngeal constrictors push the food bolus through

During the fourth (esophagopharyngeal) phase, the upper esophageal sphincter relaxes. The food bolus enters the esophagus. The esophagus contracts sequentially. The inferior esophageal sphincter opens. The food bolus enters the

The first phase is voluntary, while the others are involuntary. Cranial nerves IX,

Dysphagia (from dys- + Greek "phagein" meaning to eat, to swallow) is a clinical symptom of swallowing dysfunction: difficulty or painful passage of a food bolus from the oral cavity to the stomach [8]. Dysphagia can occur both as an independent condition or as a part of complex syndrome. Thus, dysphagia is the most important element of a bulbar or pseudobulbar palsy. Dysphagia is a subjective

Swallowing disorders are signs of various diseases. It is one of the key problems in diffuse and focal brain injuries [9]. Dysphagia occurs in 27.2% of elderly, who can take care of themselves; in 47.4% of elderly patients in intensive care units; in 51% of persons needing assistance. Dysphagia develops in 13–57% of patients suffering from dementia, in 19–81% of patients with Parkinson's disease, in 44–60% of patients with neurodegenerative diseases. Neurogenic dysphagia occurs in 25–65% of patients after stroke, provided that mortality rates among tube-fed patients with post-stroke dysphagia vary from 20 to 24% [2, 10]. In 15–17% of cases, difficulty swallowing develops after posterior fossa brain tumor surgeries and represents one of dangerous postoperative complications. Nearly 60% of patients experience

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• chronic

Based on the disease course, dysphagia can be:


## **4. Pathogenesis of neurogenic dysphagia**

In most cases, neurogenic dysphagia is oropharyngeal [14]. Neurogenic dysphagia is characterized by problems with neural control of swallowing caused by various neurological diseases.

The most common cause of neurogenic dysphagia development is a stroke [9–10, 15, 16]. Dysphagia can also occur in case of traumatic brain injury, brain tumors, encephalitis, botulism, and rabies. This type of pathology is observed at late stages of Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, other neurodegenerative diseases, severe myasthenia gravis, multiple sclerosis, Guillain– Barré syndrome, and other disorders.

On rare occasions, neurogenic dysphagia can be the sole manifestation. However, in most cases it is a component of bulbar or pseudobulbar palsy (**Tables 1** and **2**).

Bulbar palsy occurs in case of bilateral or unilateral injury of cranial nerve nuclei IX, X, and XII and their roots. Isolated nuclear palsy is not common due to close proximity of anatomical structures of the caudal part of the medulla. Bulbar palsy elements are also included in some alternating syndromes. By its nature, bulbar palsy is peripheral paralysis of the pharynx. In addition to dysphagia, bulbar palsy is


### **Table 1.**

*Bulbar dysfunction scale.*


### **Table 2.**

*Variants of bulbar dysfunctions (swallowing function).*

characterized by dysarthria (speech disorder resulting from an injury of the nerves responsible for articulation), atrophy of the pharynx and tongue muscles, and aphonia. As a rule, breathing pattern disorders (aspiration syndrome, Lambert–Eaton myasthenic syndrome, respiratory failure) develop in critically ill patients suffering from bulbar palsy, which often leads to death [17]. This is caused by close proximity of the caudal group of cranial nerve nuclei to the respiratory and vasomotor centers [7].

Pseudobulbar palsy is a neurological syndrome caused by bilateral disturbance of the corticonuclear tracts. In contrast to bulbar palsy, pseudobulbar palsy is central paralysis of the pharynx. Pseudobulbar palsy is characterized by the same triad of symptoms as bulbar palsy: dysarthria, dysphonia, and dysphagia. However, in pseudobulbar palsy, swallowing disorders are less severe: there is no muscles atrophy, primitive oral reflexes are present, and pharyngeal reflex does not

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*Dysphagia Associated with Neurological Disorders DOI: http://dx.doi.org/10.5772/intechopen.96165*

onset and before oral eating [9, 23].

gia assessment are the following ones:

pneumonia [26].

grades (**Tables 3**–**5**) [15, 27].

method of aspiration [10, 29].

detection of dysphagia occurrence [24, 25].

disappear. Pseudobulbar palsy is characterized by compulsive crying or laughing. Pseudobulbar palsy can be often combined with signs of central hemiparesis or

A special form of oropharyngeal dysphagia called "postextubation dysphagia" (PED) was first observed in 1991 during myography of oral cavities of extubated patients. PED is one of the signs of post-intensive care syndrome (PICS) [2, 19–21]. The pathogenesis of PED is characterized by the "learned non-used" phenomenon characterized by three-phase swallowing impairment associated with long-term intubation (>48 h) or due to the absence of subglottal pressure in case of a cannula bearing [17, 22].

Dysphagia assessment procedures are selected depending on patient characteristics, severity of swallowing disorder, and procedure availability. Patients with stroke shall be screened for dysphagia during the first 24 hours after the disease

Swallowing assessment protocol was developed by the American Speech– Language–Hearing Association (ASHA). The main tests for oropharyngeal dyspha-

• Water swallow test (three-swallow test): inexpensive and potentially useful basic screening test together with the data obtained from medical history and physical examination. The test has prognostic sensitivity of >95% as applied to

• Videofluoroscopy ("modified barium swallow"), which is a gold standard for oropharyngeal dysphagia assessment. The swallowing process is video recorded during fluoroscopy. Monitoring of patient's swallowing motions is provided. This procedure can be beneficial in predicting the risk of aspiration

• Upper gastrointestinal tract endoscopy. Endoscopy is not a sensitive method for detection of impaired swallowing function and is not effective for aspiration detection. At the same time, this method is effective for dysphagia monitoring [27].

• Fiberoptic endoscopic evaluation of swallowing (FEES), which is a modified method that includes visual examination of the larynx and pharynx structures using flexible transnasal fiberoptic endoscope when a patient is eating or drinking. This method is the most commonly used in real clinical practice [28].

• Overall estimate of dysphagia severity is based on summing up PAS and FEDS

• Automated impedance-manometry (AIM), which is combination of impedance-manometry and high-resolution manometry. This method provides valuable diagnostic information. These measurements represent reliable prognostic

• High-resolution pharyngoesophageal manometry, which is quantitative

assessment of pressure and time of the pharynx contraction and time of upper esophagus relaxation. It can be used in combination with videofluoroscopy in order to gain better understanding of involved movements and pressure [30].

tetraparesis, due to the pyramidal tracts involvement [6, 7, 18].

**5. Neurogenic dysphagia diagnoses and monitoring**

*Dysphagia Associated with Neurological Disorders DOI: http://dx.doi.org/10.5772/intechopen.96165*

*Therapy Approaches in Neurological Disorders*

**Sensitivity of pharyngeal mucosa**

Grade 2 Partially preserved Partially

Grade 4 Not observed Grossly

**Bulbar dysfunctions**

**Table 1.**

**Variant Clinical profile**

*Bulbar dysfunction scale.*

feeding arises.

pneumonia.

characterized by dysarthria (speech disorder resulting from an injury of the nerves responsible for articulation), atrophy of the pharynx and tongue muscles, and

1st Partially preserved sensitivity of the laryngeal mucosa and the epiglottic mobility; the

swallowed; patients do not require tube feeding.

respiratory failure and grunting breathing.

form of difficulty breathing.

*Variants of bulbar dysfunctions (swallowing function).*

swallowing function is preserved. On rare occasions, choking starts when liquid food is

**Swallowing function**

impaired

impaired

Grade 5 Not observed Not observed Lower (epiglottic paralysis)

Grade 1 Partially preserved Preserved Upper (normal)

Grade 3 Not observed Impaired Upper

**Epiglottis position (evaluation of the** 

**epiglottic paresis grade)**

Upper

Medium

mucosa; patients experience significant limitations. These patients can be fed by small portions (using a teaspoon) with food of cream, puree, and jelly-like consistency. When a patient has impaired critical judgment and weak ability to concentrate on performed actions, a need for tube

2nd Mild impairment of swallowing function with partially preserved sensitivity of the laryngeal

3rd Severe impairment of laryngeal mucosa sensitivity and severe impairment of swallowing function, which require tube feeding. This variant is the most dangerous in terms of underestimation of case severity, because the epiglottis is in its upper position and it does not block breathing. Aspiration of the oropharynx contents into the trachea is common. Due to impairment of laryngeal and tracheal mucosa sensitivity and cough reflex suppression, aspiration is manifested at late stages in the form of respiratory failure and rapidly progressive

4th Severe impairment of laryngeal mucosa sensitivity, severe impairment of swallowing function; the epiglottis is in its middle position and usually does not block breathing. In this variant, aspiration is manifested quite soon after failure of respiratory tract protection in the form of

5th Severe impairment of laryngeal mucosa sensitivity, no swallowing function. The epiglottis rests

at the inferior wall of the larynx, i.e., in its lower position. The glottis can be examined only using a fiberscope or via direct laryngoscopy (during intubation). Respiratory failure in such patients is usually manifested immediately after failure of respiratory tract protection (extubation) in the

of the corticonuclear tracts. In contrast to bulbar palsy, pseudobulbar palsy is central paralysis of the pharynx. Pseudobulbar palsy is characterized by the same triad of symptoms as bulbar palsy: dysarthria, dysphonia, and dysphagia. However, in pseudobulbar palsy, swallowing disorders are less severe: there is no muscles atrophy, primitive oral reflexes are present, and pharyngeal reflex does not

aphonia. As a rule, breathing pattern disorders (aspiration syndrome, Lambert–Eaton myasthenic syndrome, respiratory failure) develop in critically ill patients suffering from bulbar palsy, which often leads to death [17]. This is caused by close proximity of the caudal group of cranial nerve nuclei to the respiratory and vasomotor centers [7]. Pseudobulbar palsy is a neurological syndrome caused by bilateral disturbance

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**Table 2.**

disappear. Pseudobulbar palsy is characterized by compulsive crying or laughing. Pseudobulbar palsy can be often combined with signs of central hemiparesis or tetraparesis, due to the pyramidal tracts involvement [6, 7, 18].

A special form of oropharyngeal dysphagia called "postextubation dysphagia" (PED) was first observed in 1991 during myography of oral cavities of extubated patients. PED is one of the signs of post-intensive care syndrome (PICS) [2, 19–21]. The pathogenesis of PED is characterized by the "learned non-used" phenomenon characterized by three-phase swallowing impairment associated with long-term intubation (>48 h) or due to the absence of subglottal pressure in case of a cannula bearing [17, 22].
