ORIGINAL ARTICLE
SEQUENTIAL EVALUATION OF SWALLOWING FUNCTION IN PATIENTS WITH UNILATERAL NECK DISSECTION Hideaki Hirai, DDS,1 Ken Omura, DDS, PhD,1 Hiroyuki Harada, DDS, PhD,1 Haruka Tohara, DDS, PhD2 1
Department of Oral and Maxillofacial Surgery, Oral Restitution, Division of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan. E-mail:
[email protected] 2 Nihon University School of Dentistry, Dysphagia Rehabilitation, Tokyo, Japan Accepted 27 August 2009 Published online 1 December 2009 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/hed.21275
Abstract: Background. Neck dissection is the most reliable treatment for cervical lymph node metastases in head and neck cancer. However, it is unknown whether neck dissection can cause dysphagia. The aim of this study was to evaluate swallowing function after neck dissection. Methods. By using videofluoroscopic and videoendoscopic methods, swallowing function was evaluated in 17 patients prior to, 1 month after, and 4 months after neck dissection. Results. In comparison with preoperative observations, swallowing function after neck dissection was affected by the following changes: a forward and downward displacement of the hyoid bone at rest and at its highest position, a decrease in the distance traversed by the hyoid bone during swallowing, and an increase in laryngeal penetration. Pharyngeal residue and aspiration were not observed in any of the patients. Conclusion. Although swallowing function is affected by neck dissection, serious clinical problems are not likely to C 2009 Wiley Periodicals, Inc. Head Neck 32: 896– occur. V 904, 2010 Keywords: unilateral neck dissection; swallowing function; videofluoroscopic swallowing study; hyoid bone; cervical lymph node metastasis
Correspondence to: H. Hirai C 2009 Wiley Periodicals, Inc. V
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Head and neck cancer or related surgery, cerebrovascular disease, or aging1,2 can cause dysphagia.3–6 Dysphagia associated with cricopharyngeal dysfunction has been diagnosed in 4.9% of patients with head, neck, or esophageal tumors.7 Cervical lymph node metastasis is the most important prognostic factor in cases of head and neck cancer, and neck dissection is the most reliable treatment for cervical lymph node metastases.8,9 Patients who have undergone neck dissection often complain about dysphagia. We hypothesize that edema, pain, scarring, and nerve injury due to neck dissection are potential factors in the pathogenesis of swallowing dysfunction.10,11 Surgical interruption of the pharyngeal plexus or any injury to the recurrent laryngeal nerve may predispose a patient to at least transient dysphagia.1 In addition, because the suprahyoid muscles sometimes are resected, a change in the hyoid bone position affects swallowing function. Such a swallowing disorder raises the risk of aspiration pneumonia that could be life-threatening. Although swallowing function in patients with neck dissection should HEAD & NECK—DOI 10.1002/hed
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Table 1. Clinical, disease, and treatment characteristics of the patients. Case No.
Age, y/Sex
Primary site
Initial treatment
Neck dissection
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
66/M 78/F 78/M 46/M 33/F 53/F 67/F 65/M 50/F 36/M 60/M 64/F 81/F 68/M 61/M 38/M 61/M
Tongue Tongue Tongue Buccal mucosa Buccal mucosa Tongue Buccal mucosa Tongue Tongue Tongue Tongue Floor of mouth Tongue Tongue Soft palate Tongue Tongue
Partial glossectomy Brachytherapy Brachytherapy Brachytherapy Tumor extirpation þ STSG Brachytherapy Tumor extirpation þ STSG Brachytherapy Brachytherapy Brachytherapy Partial glossectomy Brachytherapy Partial glossectomy Brachytherapy Brachytherapy Brachytherapy Partial glossectomy
mRND cRND mRND mRND mRND mRND mRND mRND mRND mRND mRND cRND mRND mRND mRND mRND mRND
Postoperative radiotherapy, Gy 50 50
50
50 34 50
Outcome Alive Alive DOD Alive Alive Alive Alive Alive Alive Alive Alive Alive Alive Alive Alive Alive Alive
Abbreviations: STSG, split thickness skin graft; mRND, modified radical neck dissection; cRND, classical radical neck dissection; DOD, dead of disease.
be studied thoroughly, few studies have evaluated the pharyngeal stage of swallowing in detail after neck dissection.10 Videofluoroscopic swallowing study (VFSS) and videoendoscopic swallowing study (VESS) are well-established tools for analysis of swallowing functions and detection of subtle swallowing abnormalities.12,13 VFSS is the definitive technique for studying swallowing function, because the imaging method defines both physiology and anatomy and can be viewed at reduced speeds.14,15 Furthermore, VFSS permits the examiner to observe oral, pharyngeal, and esophageal phases of swallowing.16 In fact, VFSS allows for detection of pharyngeal aspiration and decisions regarding rehabilitation exercise that correspond to swallowing dysfunction. VESS is safer and more accessible than VFSS, because VESS equipment is portable and does not require the use of radiographic techniques.16 Therefore, VESS can be used effectively as a primary tool to screen large numbers of patients with dysphagia, to image patients during treatment, and for follow-up of patients after surgery.17 These methods allow for spatial and temporal analysis of swallowing function, such as the position of the hyoid bone and pharyngeal transit time. Moreover, accumulation of objective data allows for meaningful comparisons of swallowing function between patients. The purpose of this preliminary study was to evaluate the sequential effects of neck dissection
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on swallowing function. By using VFSS and VESS, we focused specifically on changes in the position of the hyoid bone.
PATIENTS AND METHODS Patients. The present study was approved by the Institutional Review Board of the Tokyo Medical and Dental University Hospital of Dentistry. All patients gave written informed consent for participation in the study before clinical examination. Seventeen patients who underwent unilateral neck dissection in the department of Oral and Maxillofacial Surgery at the Tokyo Medical and Dental University Hospital of Dentistry from June 2006 to June 2008 were included in this study (Table 1). Each patient had developed cervical lymph node metastasis after treatment of the primary lesion alone. The study cohort consisted of 10 men and 7 women, ranging in age from 33 to 81 years, with an average age of 59.1 years. Primary tumor site was the tongue in 12 patients, the buccal mucosa in 3 patients, the floor of the mouth in 1 patient, and the soft palate in 1 patient. Eleven patients received brachytherapy for the primary tumor, whereas the other patients received surgical excision as their initial treatment. Four patients with tongue carcinoma underwent partial glossectomy with primary
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closure, and 2 patients with buccal carcinoma underwent tumor resection with skin graft; postoperatively, however, none of the patients exhibited any symptoms associated with the oral stage of swallowing. The length of time that passed before subsequent cervical lymph node metastasis was detected ranged from 1 to 13 months (mean, 6 months). Fifteen of the neck dissections performed were modified radical neck dissections (type I),11 whereas 2 neck dissections involved radical surgery. In all cases, the anterior and posterior bellies of the digastric muscle, the stylohyoid muscle, the sternocleidomastoid muscle, and the omohyoid muscle were resected. Videofluoroscopic
Swallowing
Study
and
We evaluated swallowing function using VFSS and VESS. All patients were examined at 3 points in time: before neck dissection, 1 month after, and 4 months after neck dissection. Patients were seated comfortably in a chair, as if they were eating at a table. We evaluated the following anatomic and physiologic parameters: (1) the position of the hyoid bone at rest; (2) the highest position to which the hyoid bone was elevated at the time of deglutition; (3) the maximal anteroposterior diameter of the upper esophageal sphincter (UES) opening; (4) pharyngeal transit time; (5) pharyngeal residue; and (6) laryngeal penetration and aspiration. To assess the pharyngeal stage of swallowing, VFSS (Medix-900DR, Hitachi Medical Corp, Tokyo, Japan) was performed from a lateral projection. To calibrate the image, a radiopaque ball marker made of lead (12.8 mm diameter) was attached to the neck of each patient. Also, as a reference point for Camper’s plane,18 radiopaque disk markers (gold-silver-palladium alloy, 5 mm diameter, 1 mm thickness) were attached to the base of the nose (Point A) and to the inferior margin of the tragus (Point B) (Figure 1). A bolus of 4 mL of a 50% (w/v) aqueous solution of barium sulfate solution (Barytgen solution, Fushimi Pharmaceutical Co., Kagawa, Japan) was given as contrast medium to each patient. One technician administered the barium sulfate solution orally with a 10-mL disposable plastic syringe. Each patient was instructed to hold the bolus in his or her mouth until given a cue to begin swallowing the bolus. The VFSS image was recorded on a digital video recorder (GV-D1000, NTSC, SONY, Tokyo, Videoendoscopic
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FIGURE 1. Camper’s plane and the distance of the hyoid bone. A, base of the nose; B, inferior margin of the tragus; M, the highest position to which the hyoid bone was elevated at the time of deglutition; R, the position of the hyoid bone at rest; XM – XR, forward distance; YM – YR, upward distance.
Study.
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Japan). The image was recorded at 30 frames per second. After VFSS images were recorded, they were stored on a personal computer as AVI format movie files and manipulated for quantitative analysis (Adobe Premiere, Adobe Photoshop, and Adobe Systems, San Jose, CA). To evaluate the act of swallowing, analysis of images was performed in slow motion and frame-by-frame on a computer. After VFSS, we also conducted VESS on all patients. A fiberoptic rhinolaryngoscope (FNL10RP3, HOYA Corporation PENTAX Life Care Business Division, Tokyo, Japan) attached to a CCD camera (AR-T10E, Olympus, Tokyo, Japan), color video system (OTV-SC, Olympus), and light source (CLH-SC, Olympus), was inserted gently through the nasal floor. The scope was then deflected downward and passed into the oropharynx until the whole laryngopharynx could be viewed. The general conditions of the pharynx and larynx were recorded on the digital video recorder, as described previously. We also examined patients for the presence of residue from the barium sulfate solution. Position and Elevation Time of the Hyoid Bone. We determined the position of the hyoid bone at rest and the highest position to which it was elevated at the time of deglutition after observing several complete acts of swallowing, both in real time and frame-by-frame. We also measured the time that had elapsed from the start of hyoid bone elevation to its return to the starting position, hereafter referred to as hyoid bone elevation time.
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Upper Esophageal Sphincter: Maximal Anteroposterior Diameter of Upper Esophageal Sphincter Opening and Opening Time. We measured the maximal diameter of the narrowest portion of the UES between cervical spine 3 (C3) and cervical spine 6 (C6) (Figure 2), and the time that elapsed between the opening of the UES and its closure, which we refer to as the opening time of the UES.
FIGURE 2. The maximal anteroposterior diameter of the upper esophageal sphincter (UES) opening. The maximal distention of the narrowest portion of the UES opening between C3 and C6 during bolus passage.
In our measurements of hyoid bone displacement, we used Camper’s plane as the coordinate. The line passing through point A and point B (defined above) was assigned as the anteroposterior (x) axis. The vertical (y) axis was defined as a line perpendicular to the X-axis, intersecting it at point B. Based on movements of the radiopaque ball marker (12.8 mm diameter) attached to each patient’s neck, we calculated the actual distance traversed by the hyoid bone during the act of swallowing. In the present study, we used the preoperative position of each patient’s hyoid bone at rest as a reference point. Perpendicular lines were drawn from the most anterior point of the body of the hyoid bone in the lateral image to the x- and y-axes. The points at which these lines intersected their respective axes were recorded as the X and Y values (Figure 1). The position of the hyoid bone at rest (R) and its highest position at the time of deglutition (M) were indicated as points XR, YR, XM, and YM. From the coordinates observed at each measurement time, we calculated the distance that the hyoid bone moved during the act of swallowing. 1. Coordinates of the position of the hyoid bone at rest (XRi–XR1, YRi–YR1) [i ¼ 1, 2, 3; 1: preoperative; 2: 1 month postoperative; 3: 4 months postoperative] 2. Coordinates of the highest position of the hyoid bone at the time of deglutition (XMi–XR1, YMi–YR1) 3. The hyoid bone displacement (XMi–XRi, YMi–YRi)
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Pharyngeal Transit Time. The pharyngeal transit time began at the moment when the head of the bolus passed the point where the inferior border of the mandible crosses the base of the tongue, and ended the moment the tail of the bolus passed through the UES. Pharyngeal Residue. After the final swallow of the single bolus, pharyngeal residue was evaluated at the base of the tongue, the epiglottic vallecula, and the pyriform fossa. Also, we used VESS to evaluate pharyngeal residue, because VESS is better than VFSS for detecting small amounts of pharyngeal residue.19 Laryngeal Penetration and Aspiration. We evaluated movies of each deglutition in real time, slow motion, and frame-by-frame, looking for laryngeal penetration, aspiration, or sensorimotor reactions, such as coughing or throat-clearing during aspiration. RESULTS Displacement of and Distance Traversed by the
The displacement of the hyoid bone is shown in Figure 3. One month after surgery,
Hyoid Bone.
FIGURE 3. The displacement of the hyoid bone. The position of the hyoid bone at rest in the preoperative exams expressed as the baseline. The hyoid bone underwent a gradual anteroinferior displacement with time after neck dissection.
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Table 2. The distance traversed by the hyoid bone (mm). Forward distance Preoperative 1 month postoperative 4 months postoperative
7.8 2.8 6.5 3.1 6.5 2.9
Upward distance *
*
10.1 4.1 9.3 3.9 (NS) 8.8 3.3 (NS)
Abbreviation: NS, not signficant. Wilcoxon signed rank test. * p < .05.
Table 4. Pharyngeal transit time (s). Preoperative 1 month postoperative 4 months postoperative
0.78 0.12 0.82 0.15 (NS) 0.85 0.18 (NS)
Abbreviation: NS, not significant. Wilcoxon signed rank test.
significantly different from those at the preoperative exam.
the hyoid bone at rest was displaced, on average, 3.7 mm forward and 3.1 mm downward. At the same postoperative exam, the highest position of the hyoid bone at the time of deglutition was displaced, on average, 2.3 mm forward and 4.0 mm downward. The distance traversed by the hyoid bone during the act of swallowing is shown in Table 2. The hyoid bone moved in the forward direction, on average, 7.8 2.8 mm, 6.5 3.1 mm, and 6.5 2.9 mm at the preoperative exam, the 1month postoperative exam, and the 4-month postoperative exam, respectively. Similarly, the hyoid bone moved in the upward direction, on average, 10.1 4.1 mm, 9.3 3.9 mm, and 8.8 3.3 mm at the preoperative exam, the 1month postoperative exam, and the 4-month postoperative exam, respectively. The distances traversed by the hyoid bone during swallowing, in both the forward and the upward directions, decreased after surgery. The change in forward movement is of particular interest because the difference was statistically significant; in contrast, the change in upward movement was not statistically significant.
Pharyngeal Transit Time. Mean pharyngeal transit times were 0.78 0.12 seconds, 0.82 0.15 seconds, and 0.85 0.18 seconds at the preoperative exam, the 1-month postoperative exam, and the 4-month postoperative exam, respectively (Table 4). Pharyngeal transit times observed at the postoperative exams were not significantly different from those at the preoperative exam. Timing of Pharyngeal Stage. The relationships among pharyngeal delay time, pharyngeal transit time, hyoid bone elevation time, and UES opening time are presented in Figure 4. No significant changes in these durations in the pharyngeal stage from the preoperative exam to the postoperative exams were observed. The relationship between the timing of bolus transition and pharyngeal swallowing was not affected by unilateral neck dissection. Pharyngeal Residue, Laryngeal Penetration, and Aspiration. Our observations of pharyngeal residue, laryngeal penetration, and aspiration are
Maximal Anteroposterior Diameter of the Upper Esophageal Sphincter Opening. The mean maximal anteroposterior diameters of the UES opening were 6.0 1.2 mm, 5.9 1.3 mm, and 6.3 1.4 mm at the preoperative exam, the 1-month postoperative exam, and the 4-month postoperative exam, respectively (Table 3). The diameters observed at the postoperative exams were not
Table 3. The maximal anteroposterior diameter of the upper esophageal sphincter opening (mm). Preoperative 1 month postoperative 4 months postoperative
6.0 1.2 5.9 1.3 (NS) 6.3 1.4 (NS)
Abbreviation: NS, not significant. Wilcoxon signed rank test.
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FIGURE 4. The timing of the pharyngeal stage. We defined the onset of hyoid bone elevation as a baseline. Each of the items measured at the 1-month and 4-month postoperative exams had a value similar to its preoperative value. No decrease in timing occurred in association with neck dissection.
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Table 5. The incidence of pharyngeal residue, laryngeal penetration, and aspiration. Each of these incidents was the first such experienced by the patient.
Preoperative 1 month postoperative 4 months postoperative
Pharyngeal residue
Laryngeal penetration
Aspiration
0 0 0
2 3 3
0 0 0
presented in Table 5. Neither pharyngeal residue nor aspiration was seen at any of the 3 examinations for any patient. In 2 cases, laryngeal penetration was observed already at the preoperative exam. In 6 cases, although laryngeal penetration was not observed at the preoperative exam, laryngeal penetration was observed after surgery. Three of these cases exhibited laryngeal penetration at the 1-month postoperative exam, whereas 3 cases exhibited laryngeal penetration at the 4-month postoperative exam.
DISCUSSION Deglutition. There are many reports of deglutition disorders after primary surgery, especially for tongue cancer and laryngeal cancer. Although deglutition disorder after neck dissection is seldom reported, prediction of the extent of deglutition disorder after neck dissection is just as important as it is after other surgery for oral cancer. Anatomic Markers for Spatial Analysis. In the present study, we used Camper’s plane, passing through the inferior margin of the tragus and the base of the nose, nearly parallel to the maxillary occlusal plane, as 1 of the anatomic markers for spatial analysis.18 As all reference points of Camper’s plane lie on the upper jaw, they are unaffected by the shape of the cervical spine, presence of cervical osteophytes, or loss of teeth. As such, Camper’s plane is a reliable standard plane for use in both young and elderly patients. Furthermore, the use of Camper’s plane allows for minimizing unnecessary radiation exposure of patients during VFSS. Other standard planes, including the Frankfort plane and the sella-nasion plane, require wider radiation exposure, because their reference points include the porion and orbitale, and the sella turcia and nasion, respectively.
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Hyoid Bone: Displacement and Distance Traversed. Forward and upward displacement of the
hyoid bone contributes to airway protection and transport of the bolus to the esophagus. In other words, displacement of the hyoid bone helped epiglottic tilt and airway closure, thereby enhancing protection of the larynx from the bolus. Also, displacement of the hyoid bone eased transport of the bolus to the esophagus by pulling the cricopharyngeus muscle open within the context of a relaxed UES. It has been suggested that superior displacement of the hyoid is more strongly associated with closure and protection of the laryngeal vestibule, and that the anterior is more strongly associated with the pulling motion on the cricopharyngeus muscle, which allows its opening within the UES.20,21 In the present study, the position of the hyoid bone at rest was displaced farther forward and downward over time. Forward displacement was greater than downward displacement. We consider that resection of muscles that support the hyoid bone may have caused this observation. In neck dissection, we generally ablate the anterior and posterior bellies of the digastric muscles and the stylohyoid muscle, because many lymphatic vessels are present near these muscles.22 All cases in the present study involved an ablation of the supraomohyoid muscle as well. We consider that resection of the posterior belly of the digastric muscle, the stylohyoid muscle, and the omohyoid muscle, all of which exert a backward tractive force on the hyoid bone, could have contributed to the anterior displacement of the hyoid bone. Furthermore, we propose that postoperative edema and scar formation may cause dysmotility of the hyoid bone. Similarly, Kurita et al6 reported that, if the submandibular region is resected, the hyoid bone moves in an anterior direction. The highest position of the hyoid bone at the time of deglutition was associated with its position at rest. The distance traveled upward by the hyoid bone hardly changed at all, although its absolute location was displaced significantly downward. We presume that this is due to the downward displacement of the starting position (ie, the position of the hyoid bone at rest) of the attollens muscle. Although we predicted that the upward movement of the hyoid bone would be reduced by the decrease in upward tractional force on the hyoid bone, due to resection of certain muscles, this reduction in upward
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movement was not statistically significant. The mild reduction in upward movement may result from either the conservation of the geniohyoid muscle, which greatly affects the elevation of the hyoid bone, or compensation by the suprahyoid muscles on the intact side of the neck. The distance traversed by the hyoid bone during deglutition is directly related to the volume of the bolus swallowed.21,23 Dodds et al21 reported that a significant, direct relationship existed between the distance traversed by the hyoid and graded increases in the volume of a bolus from 0 to 10 mL. For volumes of 15 and 20 mL, however, there was no additional increase in movement beyond that observed for a 10 mL bolus. In contrast, another study reported that the upward movement, but not the forward distance, of the hyoid bone was directly related to the volume of the bolus.24 Clearly, any study aiming to measure the distance traversed by the hyoid bone before and after a surgical intervention should utilize a constant volume of bolus swallowed. Accordingly, in the present study, each measurement was taken using a 4 mL bolus. Because our observations of the distance traversed by the hyoid were not affected by variation in the volume of the bolus swallowed, we are confident that the measurements we obtained were accurate and meaningful. Upper Esophageal Sphincter Opening. An adequate UES opening allows a bolus to pass into the esophagus, whereas an incomplete opening can obstruct bolus transit. In healthy individuals, pharyngeal residue is rarely observed at the pyriform fossa after deglutition. Therefore, when obvious residue is observed at the pyriform fossa, incomplete opening of the UES is suspected. The UES is composed of cartilage and striated muscle. The major component of the UES is the cricopharyngeus muscle, which attaches to the lateral margins of the posterior aspect of the cricoid cartilage and encircles the lumen. Opening of the UES during deglutition is due to relaxation of the cricopharyngeus muscle and the traction forces imparted on this muscle by contraction of the thyrohyoid and suprahyoid muscles. Abnormalities of these components may result in a reduction in the size of the UES opening during deglutition. In particular, reduction of the forward movement of the hyoid bone, which causes loss of forward traction forces, is
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strongly related to a decrease in size of the UES opening.20,25 In the present study, forward movement of the hyoid bone was diminished, but the highest position of the hyoid bone at the time of deglutition was displaced forward. Thus, little difference in the maximal anteroposterior diameter of the UES opening may occur after surgery. In addition, as measurements in our study were made using low volume boluses (4 mL) that patients could swallow in 1 deglutition movement, the UES opening may not have been affected visibly. Furthermore, the location of the UES as observed on a VFSS remains controversial. Previously, the UES has been defined as a point 1.5 cm below the top of the tracheal air column, a point corresponding at rest to a high-pressure zone.20 We assume, however, that the position of the UES may change among individuals, depending on the person’s body size and perhaps other variables. For these reasons, we defined the maximal UES opening as the maximum diameter of the narrowest portion of the UES between the cervical vertebrae, C3 and C6. Previous studies have demonstrated that the maximal UES opening was proportional to bolus size.24,26 For example, Leonard et al24 reported that maximal openings of the UES in normal subjects swallowing boluses of 1, 3, and 20 mL were 3.9 1.9 mm, 5.1 1.5 mm, and 8.9 2.8 mm, respectively. Given that all measurements were taken of 4 mL boluses, and because our measurement values were similar to previously published results, we surmise that neck dissection did not influence maximal UES opening.
Pharyngeal Transit Time. In healthy subjects, regardless of food consistency, normal pharyngeal transit time is reported to have a range of less than 1 second.27–29 The duration of pharyngeal transit of a bolus is important, because prolonged pharyngeal transit times have been associated with an increased incidence of aspiration in several patient populations. Kendall et al12 reported that observed pharyngeal transit times for bolus swallows of 1, 3, and 20 mL were 0.91 0.3 seconds, 0.86 0.23 seconds, and 0.85 0.17 seconds, respectively. In the present study, all measurements were taken using bolus swallows of 4 mL. All pharyngeal transit times we observed were in accordance with the results of Kendall et al.30
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Therefore, we conclude that neck dissection had no influence on pharyngeal transit time. Timing of the Pharyngeal Stage. The pharyngeal stage began when the swallowing reflex was induced. A delay in onset of the pharyngeal stage increased the risk of aspiration. The present study suggests that neck dissection had minimal influence on the timing of the pharyngeal stage. Moreover, tongue and UES functions were normal in all patients. Neck dissection caused displacement, but not a change in elevation time, of the hyoid bone. Therefore, neck dissection without tongue or pharyngeal resection usually does not cause aspiration due to poor pharyngeal coordination in swallowing. Pharyngeal Residue. Oral and pharyngeal residue represents symptoms of dysphagia. Pharyngeal residue is particularly critical as it may result in aspiration pneumonia, which is a major cause of death among elderly patients.29 An increase in patient age is accompanied by increases in pharyngeal residue quantity.31 Ono et al32 reported that pharyngeal residue can be caused by a decline in mastication, which affects bolus formation. In our study, we used VESS because it allows us to detect small amounts of residue that are undetectable by VFSS, and because VESS is the most important tool for estimating the risk of surgery-related complications, such as aspiration pneumonia. In the present study, no pharyngeal residue was observed during any examination by either VFSS or VESS. Studies that aim to evaluate pharyngeal residue should use VESS in addition to VFSS in order to achieve an accurate diagnosis. Laryngeal Penetration and Aspiration. Laryngeal penetration is defined as the passage of material into the larynx, but not below the vocal folds.33–35 In the present study, we observed postoperative laryngeal penetration in 6 patients. All laryngeal penetrations, which were detected during swallowing, indicated dysfunction of airway closure.16 Dysfunction of airway closure was most likely caused by decreased function of organs that participate in airway closure, such as the epiglottis. In turn, decreased function of the epiglottis was caused by reduction of the distance traversed by the hyoid bone and by scar formation following surgery. In these 6 patients, laryngeal penetration did not evoke sensorimotor
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responses, perhaps because the penetration was shallow. Despite the fact that laryngeal penetration is often observed in normal subjects, it is not an abnormal finding, unless the patient also experiences aspiration. Aspiration is defined as the passage of material below the level of the vocal folds.10,33–35 In older patients, aspiration is an important cause of death because of the potential for aspiration pneumonia. Although the frequency of laryngeal penetration increases with age, the frequency of aspiration does not rise in direct proportion to age.33 In the present study, neck dissection appeared to increase the rate of laryngeal penetration caused by dysfunction of the airway closure, did not increase the rate of aspiration.
CONCLUSIONS
Although the number of cases examined in the current study was small, we performed a detailed analysis of the influence of neck dissection on swallowing function. The effects of unilateral neck dissection on swallowing function include the forward and downward displacement of the hyoid bone at rest and at its highest position during deglutition, a decrease in hyoid bone distance, and an increase in laryngeal penetration. However, none of our patients exhibited deglutition disorder. Further study is necessary to confirm the validity of our findings.
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Swallowing in Patients with Unilateral Neck Dissection
HEAD & NECK—DOI 10.1002/hed
July 2010
