Swallowing improvement surgeries

Purpose To discuss the different swallowing improvement surgeries that address one or more dysfunctional pharyngolaryngeal structures causing dysphagia. These surgeries reduce the risk of aspiration without sacrificing vocal function. Methods We searched the PubMed database and used Google Scholar search engine to find studies discussing the different swallowing improvement surgeries. A manual search of references in selected articles and reviews was done as well. No chronologic limitation was set for the studies; however, only articles written in English and Japanese were considered. Due to the nature of this article, no particular inclusion or exclusion criteria were set when searching for studies to be used as references; however, all relevant studies were reviewed and agreed upon by the authors for inclusion in this review article. Results/discussion Surgeries to improve swallowing function can be categorized into those that reinforce nasopharyngeal closure or pharyngeal contraction, improve laryngeal elevation or pharyngoesophageal segment opening, and those that improve vocal fold closure to protect the airway during swallowing. They are an effective alternative treatment that may significantly improve these patients’ quality of life. Swallowing rehabilitation with the altered pharyngolaryngeal structures is required post-operatively to significantly improve patients’ dysphagia. Conclusions Surgeries to improve swallowing function address specific dysfunctional sites involved in the swallowing mechanism. Choosing the most appropriate surgery for each patient requires knowledge of the pathophysiology for their dysphagia and detailed pre-operative work-up.


Introduction
The swallowing mechanism is complex and requires the coordinated movement of many structures.Dysphagia occurs when one or more of these structures is not functioning properly.If not addressed, it may lead to serious sequelae, such as malnutrition, aspiration pneumonia, or even death.The goal of all treatments for dysphagia is to ensure a safe swallow and improve patients' quality of life [1].
The first line of treatment for dysphagia is swallowing therapy and diet modification; however, this may not be effective for all patients.In these cases, surgery to improve swallowing function should be considered to address deficient sites of the swallowing mechanism or to supplement non-surgical interventions [1,2].These focus on changing laryngeal, pharyngeal, and upper esophageal structures, depending on the underlying cause of dysphagia (Fig. 1, Table 1).Others have proposed a similar classification of these surgeries according to anatomical location [2]; however, this paper will present these surgeries from a more functional classification.Specifically, these surgeries have been classified to address the following: • Reinforcement of nasopharyngeal closure.
• Improved vocal fold closure to protect the airway during swallowing.
Carmel Cotaoco and Rumi Ueha have contributed equally to this work.
The purpose of this paper is to review the different surgeries to improve swallowing function and disseminate more detailed information about them to medical professionals.

Methods and ethics
We searched the PubMed database and used the Google Scholar search engine to find studies discussing the different swallowing improvement surgeries.A manual search of references in selected articles and reviews was done as well.Due to the nature of this article, no particular inclusion or exclusion criteria were set when searching for studies to be used as references.No chronologic limitation was set for the studies; however, only articles written in English and Japanese were used for this review.All relevant studies were reviewed and agreed upon by the authors for inclusion in this review article.Although ethical issues are not applicable to narrative reviews, this study protocol was approved by the Human Ethics Committee of the University of Tokyo Hospital (No. 2022179NI) and complied with the tenets of the amended Declaration of Helsinki.Specifically, written informed consent was obtained from every patient whose treatment was presented as an illustrative case in the last section of this paper, and patient anonymity was preserved.

Pathophysiology
The disease background of patients with dysphagia is varied, and treatment options must be selected accordingly.Various surgical treatments have been applied for different pathological conditions (Fig. 1).In addition to a detailed physical examination and airway assessment, a detailed site-specific evaluation of swallowing status with swallowing function tests (fiberoptic endoscopic evaluation of swallowing, videofluoroscopic swallowing study, and high-resolution manometry) is mandatory to develop a treatment plan.

Surgical management for dysphagia
In the following sections, surgeries to improve swallowing function while preserving speech function in the adult population will be described and explained briefly (Table 1).

Reinforcement of nasopharyngeal closure
Palatopexy, push-back surgery, and pharyngeal flap are surgeries to reinforce nasopharyngeal closure.Palatopexy involves suturing the soft palate to the posterior nasopharyngeal wall [2,3], while push-back surgery utilizes mucoperiosteal flaps of the palate to lengthen the soft palate [4].In this section, we focus on pharyngeal flap surgery as a treatment for dysphagia.a. Pharyngeal flap •

Overview
In 1973, Hirano et al. first reported performing cricopharyngeal myotomy with a pharyngeal flap for dysphagia secondary to Wallenberg syndrome [5].The most common approach is the use of a centrally located pharyngeal flap with lateral ports for air to pass, but a lateral pharyngeal flap may be more appropriate for patients with a lateral velopharyngeal gap [6,7].
In the lateral pharyngeal flap, the soft palate is incised in the midline, and its undermined posterior mucosa is sutured to a laterally based pharyngeal flap created only on the affected (paralyzed) side.The soft palate is then closed primarily, and the defect on the posterior pharyngeal wall is cov-  Hyo-mandibular suspension [14,15] Hyoid bone is approximated to the mandible, restoring continuity of hyomandibular complex Laryngeal suspension Thyro-hyoido-pexy [11,16] Thyroid cartilage is approximated to the hyoid bone, pushing the epiglottis back into a retroflexed position and shifting the larynx antero-superiorly Thyro-mandibular suspension [17] Thyroid cartilage is approximated to the mandible, shifting the larynx antero-superiorly Thyro-hyoido-mandibular suspension [16,18] Thyroid cartilage is approximated to the hyoid bone and the hyoid bone is approximated to the mandible, shifting the larynx anterosuperiorly (D) Improved pharyngoesophageal segment opening Pharyngoesophageal dilation [20−21] Circumferential splitting and stretching of stenotic areas at the pharyngoesophageal area using mercury-filled bougies, wireguided polyvinyl dilators, or balloon dilators under endoscopic or fluoroscopic guidance Cricopharyngeal myotomy [26−27] Incision through all fibers of the cricopharyngeus muscle, including some fibers of the inferior constrictor and cervical esophagus muscles, through an external approach Endoscopic cricopharyngeal myotomy [30−31] Incision through all fibers of the cricopharyngeus muscle through a transoral, endoscopic approach, most often done with a CO2 laser Zenker's diverticulum surgery [34,35] External approach: Excision or suspension of the diverticular sac Endoscopic approach: The common wall between the diverticulum and esophagus is divided using electrocautery, CO2 laser, or a stapling device ered with a polyglycolic acid sheet and fibrin glue [6].

• Expected results
Laterally based pharyngeal flaps are designed to close the defective part of the velopharynx [7] and prevent the reflux of food into the nasal cavity.The centrally located flaps may impair the motion of the unaffected side of the pharynx and allow for the escape of pharyngeal pressure through the affected side during swallowing [6].•

Overview
In 1948, Naffziger first described suturing the fascia of the carotid sheath to the midline of the larynx and cricoid to increase the stiffness of the pharyngeal wall with suturing of the posterior belly of the digastric muscle to the thyroid cartilage [8].This was the first report of such surgery to improve swallowing function.Since then, many variations have been described.
First, it is possible to perform a full-thickness resection of a portion of the pharyngeal wall with suturing of the defect on the paralyzed side [9].This may be additionally reinforced with a polypropylene mesh [10].Alternatively, resection of the lateral 1/3 of the thyroid cartilage with suturing of the pyriform sinus (lateral thyrolaminectomy) may be done [11].Another approach involves resection of pyriform sinus mucosa with advancement and suturing of the inferior constrictor muscles to the thyroid cartilage anteriorly [12].•

Expected results
The use of hypopharyngeal pharyngoplasty is most commonly reported in patients with unilateral paralysis of the pharyngeal wall, seen in conditions, such as Wallenberg syndrome or unilateral cranial nerve injuries.It is expected to improve the tone or tension of the paralyzed pharyngeal wall and decrease dead space for secretions and food residue to collect by reducing pyriform sinus mucosa.These changes improve the propulsion of the food bolus into the esophagus [2,13].•

Complications
Although complications with this procedure are rare, possible complications include an anastomotic leak and infection [12].
3. Improved laryngeal elevation level (Fig. 2) a. Hyo-mandibular suspension In 1959, both Edgerton and McKee and Desperez and Kiehn reported on the use of a suspensory tie and fascia lata strips, respectively, connecting the hyoid bone to the mandible for cases of extensive head and neck malignancies that disrupted the hyomandibular complex.Hyo-mandibular suspension is useful in cases where the suprahyoid muscles or hypoglossal nerve is disrupted.It approximates the hyoid bone to the mandible and restores the integrity of the hyomandibular complex [14,15].The muscular process of the arytenoid is sutured and secured anteriorly to the apex of the thyroid cartilage, simulating the action of the lateral cricoarytenoid muscle b.Laryngeal elevation surgery (Thyro-hyoido-pexy, thyro-mandibular suspension, thyro-hyoido-mandibular suspension) • Overview Laryngeal elevation surgery (laryngeal suspension) was first described in 1948 by Naffziger who sutured the posterior belly of the digastric muscle to the thyroid cartilage in a patient with unilateral paralysis of the ninth-to-twelfth cranial nerves [8].Variations of laryngeal suspension were subsequently developed, which involved the suspension of either the hyoid bone [11,16], thyroid cartilage [17], or both [16,18] to the mandible (Fig. 2).Suspension is done using a variety of materials, including non-absorbent and absorbent threads, steel wires, polytetrafluoroethylene (Teflon) tape, or expanded polytetrafluoroethylene (Goretex).
A thyro-hyoido-pexy compresses the tissues in the preepiglottic space and pushes the epiglottis into a retroflexed position, offering protection of the glottic opening during swallowing [11,16].Thyro-mandibular suspension elevates the larynx without hindering the mobility of the hyoid bone [17].Thyro-hyoido-mandibular suspension is used in cases with severely impaired laryngeal elevation, where the thyroid cartilage is approximated to the hyoid bone and the hyoid bone is then approximated to the mandible [16,18].
Transection of the infrahyoid muscles is often done in conjunction with this surgery to prevent downward traction of the larynx [16], as well as cricopharyngeal myotomy to further improve the passage of the food bolus [18,19].•

Expected results
The purpose of laryngeal elevation is to lift the laryngeal framework upward and anteriorly, approximating it more closely to the hyoid bone or mandible.This improves the closure of the laryngeal vestibule by laying the epiglottis backward, and it contributes to the opening of the upper esophageal sphincter (UES), assisting the passage of the food bolus into the esophagus [18].•

Complications
Complications include damage or infection of the thyroid cartilage and airway obstruction by the epiglottis and base of the tongue if the larynx is lifted excessively or due to laryngeal edema; therefore, concurrent tracheostomy is recommended [17,18].

Improved pharyngoesophageal segment opening a. Pharyngoesophageal dilation • Overview
Pharyngoesophageal dilation became more widespread in 1902, when Chevalier Jackson designed a distally lighted esophagoscope which allowed relatively safer antegrade bougienage through the oral cavity under direct visualization [20].Later on, retrograde [21] (via gastrostomy tract) and combined antegrade and retrograde approaches were developed and done under endo- scopic or fluoroscopic guidance to improve the safety and success of this procedure [22].
Pharyngoesophageal dilation is most commonly done for strictures in the pharyngeal, cricopharyngeal, or upper cervical esophageal areas.In all approaches, the stenotic segment is identified and a dilator is passed through the lumen in gradually increasing diameters to slowly dilate it [22].Dilators used include mercury-filled bougies, wire-guided polyvinyl dilators, or controlled radial expansion balloon dilators, which are usually left in place for a few minutes.In general, the rule is not to pass more than 3 dilators of sequential size once moderate resistance is felt [23].Others consider the identification of a mucosal tear during the procedure as a sign to cease further dilation [24].•

Expected results
Pharyngoesophageal dilation essentially splits stenotic segments in the pharyngeal or upper esophageal areas and causes circumferential stretching, facilitating the passage of the food bolus through this area.It should be noted that the effects of the dilation are most often temporary and need to be performed as a series of dilations [22].•

b. Cricopharyngeal myotomy • Overview
Kaplan in 1951 is generally considered to be the first to have performed a cricopharyngeal (CP) myotomy through an external approach for patients with hypopharyngeal paresis due to bulbar poliomyelitis.Since then, this technique has been applied widely to address oropharyngeal dysphagia associated with neurogenic, myogenic, structural, and idiopathic diseases [26,27].
In the external approach, the CP muscle is exposed and may be stretched in a variety of ways (esophagoscope, bougies, balloons, etc.) to better expose its fibers, which are then transected up to the mucosa.Many surgeons advocate to extend the myotomy 1-2 cm cranially and caudally to include muscle fibers from the inferior constrictor and cervical esophagus, as these contribute to the UES as a unit [27][28][29].
• Expected results CP myotomy assists in the passage of the food bolus by decreasing the resistance of the UES and increasing the length of time that food may pass through the sphincter, instead of being limited to the brief relaxation time in a normal swallow [28,29].•

Complications
Complications that may occur with an external approach are esophageal perforation, recurrent laryngeal nerve injury, pharyngocutaneous fistula formation, or wound infection [26].Many also consider severe gastroesophageal reflux a contraindication to CP myotomy, as the protective function of the UES is lost and refluxate material from the esophagus may spill into the hypopharynx [18,28].c.Endoscopic cricopharyngeal myotomy •

Overview
An endoscopic or transmucosal approach to CP myotomy using electrocautery was done by Dohlman and Mattsson as early as 1960 as part of the treatment for Zenker's diverticulum [30].In 1994, Halvorson and Kuhn performed an endoscopic CP myotomy using a potassium-titanyl-phosphate (KTP) laser [31].Since then, the carbon dioxide (CO2) laser has increased in popularity and is more frequently used to incise the CP muscle [32].
Once the CP muscle is exposed and identifiable as a posterior bulge, often called "the cricopharyngeal bar", it is cut transmucosally in the midline layer by layer until the buccopharyngeal fascia [32] or prevertebral fatty tissue [30] is seen.•

Expected results
The expected results are similar to that of the external approach; however, it avoids the scar seen with an external approach and allows for a shorter operating time, quicker recovery, and shorter hospital stay [32].•

Complications
The most common complication associated with an endoscopic approach is an esophageal perforation with entry into the neck spaces and possible abscess formation or mediastinitis [26,30].It should also be noted that this approach is not suitable for patients that have difficulty with neck extension, as it would be difficult to expose and visualize the cricopharyngeal area transorally [33].d.Zenker's diverticulum surgery •

Overview
Zenker's Diverticulum (ZD) may be approached externally through simple excision (diverticulotomy) or suspension (diverticulopexy) of the pouch.In the endoscopic approach, the common wall between the diverticulum and esophagus is exposed transorally and divided using electrocautery, a carbon dioxide laser, or a stapling device [34].Although the endoscopic technique is said to be simpler with a shorter operating time, its use is precluded in cases where the diverticulum cannot be visualized adequately [35].•

Expected results
In all approaches to surgery for ZD, the goal is to prevent the accumulation of food and other debris in the pouch.Concurrent cricopharyngeal myotomy is said to decrease the recurrence of the diverticulum, as the pressure at the UES is decreased [35].•
In patients with unilateral vocal fold paralysis that experience dysphagia, the injection is applied to the paraglottic space to medialize the entire vocal fold.The adequate amount of injected material can be confirmed visually and by asking the patient to phonate (for awake procedures) [42,43].•

Expected results
IL is used in cases of unilateral vocal fold paralysis with glottic insufficiency, resulting in improved glottic closure and decreasing the chances of aspiration during swallowing.However, some postulate that improved glottic closure may also increase the intrapharyngeal pressure during swallowing, triggering the swallow reflex and improving bolus clearance [42].•

Complications
The most common complications from IL are extrusion, migration, inflammation, and granuloma formation due to the injected substances [42].
b. Laryngeal framework surgery •

Overview
Medialization (type I) thyroplasty became the preferred treatment for unilateral vocal fold paralysis when Isshiki reported on it in 1974 [44].Medialization thyroplasty is done by creating a window on the thyroid ala of the affected side at the level of the vocal folds to access the paraglottic space.Once the window is created, an implant [silicone [45], expanded polytetrafluoroethylene (Gore-Tex) [46], fascia [47], etc.] is placed into the paraglottic space to medialize the entire vocal fold.Correct positioning can be confirmed by asking the patient to phonate and visually using a flexible videolaryngoscope [48].Arytenoid adduction is usually done concurrently with medialization thyroplasty.The muscular process of the arytenoid is identified, and a suture is passed through it then secured anteriorly to the apex of the thyroid cartilage.This essentially simulates the action of the lateral cricoarytenoid muscle [48,49].•

Expected results
Expected results are the same as for IL, but arytenoid adduction is more effective in cases with a vocal fold height difference and a wide posterior glottic gap [1,48].
The effect of a Type I thyroplasty is permanent although reversible since the implant material is not resorbed [48].•

Complications
Complications in Type I thyroplasty include extrusion, migration, or foreign body reaction to the implant, as well as airway compromise if there is impaired motion of the contralateral vocal fold.Arytenoid adduction has a higher risk for airway compromise due to edema of the posterior glottis, and pyriform sinus perforation is another associated but rare complication [48].
It must be emphasized that improved swallowing function cannot be achieved immediately through surgery alone.Rehabilitation of the modified pharyngolaryngeal complex with swallowing exercises in the post-operative period is necessary.

Choosing the appropriate surgery for patients with severe dysphagia
Here, we provide some specific examples to illustrate in which clinical situations it is appropriate to use the different swallowing improvement surgeries described in the article.
1. Dysphagia in a 66-year-old man with traumatic head injury leading to a subarachnoid hemorrhage and skull base fracture with multiple lower cranial nerve deficits.Swallowing evaluation revealed severely impaired pharyngeal contraction and laryngeal elevation, as well as impaired bolus passage through the UES.Paralysis (paramedian position) and atrophy of the right vocal fold was also seen with insufficient glottic closure.Nasopharyngeal valve closure was only slightly impaired.A bilateral cricopharyngeal myotomy, thyro-mandibular suspension, and autologous fat injection at the right vocal fold was performed for this patient, and his oral intake status improved post-operatively (Fig. 3).2. Dysphagia in a 62-year-old man with Wallenberg syndrome.The patient had severe left-sided velopharyngeal insufficiency, left vocal fold paralysis (median position), poor laryngeal elevation, severely decreased pharyngeal contraction, and impaired bolus passage through the UES.Patient's oral intake status improved after a lateral pharyngeal flap on the left, thyro-mandibular suspension, and bilateral cricopharyngeal myotomy (Fig. 4).3. Dysphagia in a 76-year-old man after contracting COVID-19.One year after COVID-19 treatment, he still had impaired laryngeal elevation, decreased pharyngeal contraction, an excessive osteophyte at the cervical spine, and impaired bolus passage through the UES.His oral intake status improved after thyro-mandibular suspension, removal of cervical spine osteophyte, and left-sided cricopharyngeal myotomy (Fig. 5).

Conclusion
Surgeries to improve swallowing function address specific dysfunctional sites involved in the swallowing mechanism, namely the velopharyngeal closure, pharyngeal wall contraction, pharyngoesophageal inlet opening, laryngeal elevation level, or vocal fold closure.Choosing the most appropriate surgery for each patient requires knowledge of the pathophysiology for their dysphagia and detailed pre-operative work-up.Swallowing rehabilitation with the altered pharyngolaryngeal structures is required post-operatively to significantly improve patients' dysphagia.

Fig. 1
Fig. 1 Anatomic sites addressed with swallowing improvement surgeries.Swallowing improvement surgeries focus on changing laryngeal, pharyngeal, and upper esophageal structures, depending on the underlying cause of dysphagia

Fig. 2
Fig. 2 Surgeries to improve laryngeal elevation.Normal anatomy (a).Approximation of hyoid to mandible (b), thyroid cartilage to hyoid (c), thyroid cartilage to mandible (d), and thyroid cartilage to hyoid and hyoid to mandible (e)

5 .
Improved vocal fold closure to protect the airway during swallowing (medialization of the vocal fold).a. Vocal fold injection

Fig. 3
Fig. 3 Videofluoroscopic swallowing study findings.a Preoperative: inability of contrast to flow past upper esophageal sphincter (UES, white arrowhead); b post-operative: contrast flows smoothly past UES (white arrowhead)

Table 1
Summary of surgeries to improve swallowing function