Unilateral vocal cord paralysis (UVCP) may be caused by lower laryngeal nerve damage or high vagal paralysis (HVP). HVP are rare and refer to the region of the nerve from the jugular foramen through the branching of the auricular (Arnold’s branch) and the pharyngeal branch¹. Patients suffering from unilateral HVP secondary to neurological disorders, trauma, skull base or other head and neck tumors or surgeries often have an incompetent larynx as a result of disru-ption of sensory and motor pathways. If dysfunction in the vagus nerve is presented, it will cause vocal- fold paralysis, discoordination of the pharyngeal musculature, and loss of relaxation of the cricopha-ryngeus muscle, leading to swallowing disability, which is referred to as cricopharyngeal dysphagia¹. If HVP is superimposed with deficits in other cranial nerves, marked deglutition and airway morbidity will occur, which increases mortality.

Glottic insufficiency resulting from UVCP may cause impairment of most laryngeal functions, including airway protection, breathing, and stabilization of the body core during physical activity and phonation². Patients may have aspiration and dysphagia if the vocal folds are widely abducted or if substantial sensory loss occurs in the lower pharynx and larynx. Aspira-tion complicates rehabilitation and recovery of these patients; many require a gastrostomy tube for feeding and/or tracheotomy as a pulmonary outlet.

Quality of life is impacted in patients with UVCP but conditions can be improved with adequate mana-gement. The goal of UVCP management is to decrease the glottal gap and restore phonation and swallowing function. Medialization thyroplasty and injection laryn-goplasty are the most common surgical treatments for cases of uncompensated UVCP. The role of mediali-zation thyroplasty with or without arytenoid reposi-tioning and injection laryngoplasty is to re-establish glottal closure. In patients with HVP, cricopharynx myotomy and pharyngoplasty can also be used to manage glottal insufficiency to decrease the risk of aspiration by increasing the transit time of the phary-ngeal bolus. Our aim in this study was to further define whether office-based injection laryngoplasty or media-lization thyroplasty is more effective to treat UVCP caused by HVP.

1. Patients

We retrospectively reviewed the medical records of patients with cricopharyngeal dysphagia caused by lower cranial nerve deficits that were treated in Yeouido St. Mary’s Hospital from March 2002 to February 2010. Of the 46 consecutive patients with cricopharyngeal dysphagia in our database, 28 patients with UVCP caused by HVP were reviewed. Study approval was granted by the Institutional Review Board of our institution. Flexible laryngoscopy and videofluoroscopic swallowing studies (VFSS) were performed to evaluate the degree of dysfunction at the first visit to the dysp-hagia clinic for patients with UVCP caused by HVP. Positional change was applied to the patients during VFSS to minimize aspiration. Various airway protection maneuvers were trialed with varying textures and consistencies to develop a therapeutic swallowing and exercise program. The most commonly used positional change was head rotation to the paralyzed side followed by the chin down position. Therapy included the Mendelsohn maneuver, tongue base exercises, and a head lifting exercise. Vocal fold augmentation was done with either injection laryngo-plasty or medialization thyroplasty if there was a large glottic gap. If a patient has a glottal level difference on phonation, medialization thyroplasty with or with-out an arytenoid adduction was chosen, in order to overcome the glottal level difference and glottal inco-mpetency. If a patient has no glottal level difference on phonation, injection laryngoplasty was chosen. If aspiration persisted, cricopharyngeal release using cricopharyngeal myotomy or BOTOX^Ⓡ (Allergan, Irvine, CA, USA) injection into the cricopharyngeus muscle was performed. The patient continued to use a naso-gastric tube as the primary source of nutrition and hydration. Oral alimentation was then initiated using pureed food with daily speech and chest therapy. A gastrostomy tube was placed when a patient was unable to demonstrate the ability to maintain adequate hydration and nutrition through oral means alone for at least 4 weeks and for so long as there was any concern about swallowing safety. The follow-up period was 2-97 months (mean, 29.9 months).

2. Videofluoroscopic swallowing studies

Videofluoroscopic images were recorded and analyzed with a model 7200 digital swallowing workstation (Kay Pentax, Lincoln Park, NJ, USA). Three consis-tencies of food were given to each patient: water mixed with liquid barium (Polibar Plus liquid, barium sulfate suspension; Therapex) in a 3:1 ratio presented in a cup; approximately 10 ml of pudding mixed with barium paste (Esobar, barium sulfate cream; Therapex) in a 3:1 ratio presented in a spoon; and one-quarter of a digestive cookie coated with barium paste. Two trials of each consistency were performed while video-fluoroscopic recording took place. All patients con-sumed much of the three consistencies of food as possible, with some consistencies excluded for certain patients because of anatomical constraints (i.e., absence of dentition) or the clinician perceived a clinical risk to the patient.

3. Voice evaluation

All acoustic examinations were performed by the same voice analyst in a computerized speech laboratory with a multidimensional voice program (Kay Elemetrics Corp., Pine Brook, NJ, USA). Fundamental frequency, jitter (frequency of perturbation), shimmer (amplitude of perturbation) and, noise-to-harmonic ratio (NHR) were recorded. All patients were instructed to produce the vowel “a” for at least 3 seconds in a quiet room. Maximum phonation time (MPT) was assessed during sustained vowel “a” after deep inspiration at a conversational pitch and loudness level using a stopwatch.

4. Office-based injection procedures

All injection laryngoplasties were performed percu-taneously under local anesthesia by the same surgeon. Each patient inhaled a 4% lidocaine nebulizer for 10 min before the procedure. An extra nozzle was used to spray additional 4% lidocaine onto the pharynx, larynx, and nose. The cricothyroid approach was performed through the cricothyroid membrane, dire-ctly into the vocalis muscle, using a disposable 25G- long needle under transnasal flexible fiberscopic moni-toring (Olympus laryngobronchoscope type triiodo-thyronine). The appropriate needle location was confir-med through a flexible fiberscope before injection. The tip of the needle could be seen submucosally and was then withdrawn slightly for injections. The injection was started slowly into the vocalis muscle in front of the vocal process and continued until slight over-correction was achieved. A small number of patients underwent additional injections if they had complaints of recurrent aspiration and were noted to have glottic insufficiency on follow-up examinations.

5. Medialization procedures

All patients underwent the same surgical procedure under local anesthesia. After a horizontal incision was made at the level of the thyroid cartilage, the straight prelaryngeal musculature was dissected and displaced laterally. Then, the perichondrium of the thyroid car-tilage was elevated from the anterior edge to the dorsolateral side of the thyroid lamina. The upper corner of the window was set 7 mm from the anterior edge. In all patients, the window was placed as cau-dally as possible, preserving a minimum of 2 mm of cartilage at the lower border of the thyroid lamina. The cartilage window was then drilled out, preserving the inner perichondrium. The inner perichondrium was widely undermined in all directions. Then, the vocal fold was medialized using different sized tem-plates. According to the size of the chosen template, the permanent hydroxyapatite implant was inserted and locked with displacement.

6. Statistical analysis

Differences between the voice analysis data were analyzed by Student’s t-test. A P<0.05 was considered significant. All calculations were performed using SPSS ver. 16.0 software (SPSS, Chicago, IL, USA).

Mean subject age was 54 years (range, 15-74 years); there were 44 males and one female. The causes of the HVP varied. Skull base surgery was the cause in 15 patients, cerebral vascular diseases in five, infections such as varicella zoster virus in two patients, trauma in one patient, and unknown cause in five patients. The patient characteristics are summarized in Table 1. All patients used feeding tubes for a mean of 6 months (range, 0.5-28 months) after being diagnosed with high vagal lesions. The main abnormalities during VFSS were delayed pharyngeal swallowing, decreased pharyngeal contraction, decreased laryngeal elevation and some aspiration due to incomplete laryngeal closure and residues in the pyriform sinus.

Table 1 . Profiles of patients with unilateral high vagal paralysis..

Case	Age (yrs)	Gender	Cause of high vagal paralysis	Lower cranial nerve deficits	Surgical modality	Feeding tube
1	38	M	Skull base paraganglioma	IX, X, XI	MT	GT
2	47	M	Skull base fracture with C-spine injury	X	IL	GT
3	22	M	Idiopathic	X	MT	NGT
4	58	M	Subdural hemorrhage	IX, X	MT	GT
5	69	F	Parapharyngeal space paraganglioma	IX, X, XI	MT	NGT
6	15	M	Skull base meningioma	IX, X, XI, XII	MT	GT
7	58	F	Intracranial hemorrhage	IX, X	MT	NGT
8	39	F	Skull base glomus tumor	IX, X	MT	GT
9	49	M	CP angle acoustic neuroma	IX, X	IL	NGT
10	73	M	Skull base glomus tumor	VII, IX, X	IL	NGT
11	62	M	Intracranial hemorrhage	IX, X, XII	IL	GT
12	61	M	Intracranial hemorrhage	IX, X	IL	NGT
13	43	M	Subarachnoid hemorrhage	VII, IX, X	MT	GT
14	63	M	Idiopathic	IX, X	IL	NGT
15	59	F	Skull base glomus tumor	X	IL	NGT
16	51	F	CP angle acoustic neuroma	IX, X	IL	NGT
17	66	M	Skull base glomus tumor	X	IL	NGT
18	60	F	Skull base glomus tumor	IX, X, XII	IL	NGT
19	52	F	Parapharyngeal space paraganglioma	X	ML	NGT
20	68	M	Idiopathic	X	IL	NGT
21	69	M	Skull base meningioma	IX, X	MT	NGT
22	37	M	Skull base glomus tumor	IX, X, XI	MT	NGT
23	56	M	Idiopathic	X	IL	NGT
24	18	F	Cerebellar hemangioblastoma	X	IL	NGT
25	74	M	Varicella zoster infection	VII, VIII, IX, X	IL	NGT
26	73	M	Varicella zoster infection	VII, VIII, IX, X, XII	IL	NGT
27	64	F	Idiopathic	X	IL	NGT
28	54	F	Skull base meningioma	X, XII	IL	NGT

MT: medialization thyroplasty, IL: injection laryngoplasty, GT: gastrostomy tube, NGT: nasogastric tube..

The surgical procedures included 17 (60%) injection laryngoplasties and 11 (40%) medialization thyro-plasties.(Table 2) Twenty-four office-based injection laryngoplasties were attempted on 17 patients. Eleven patients were injected with synthetic calcium hydro-xylapatite and six were injected with hyaluronic acid. On average, 0.81 ml of injectate was used in each setting. Cricopharyngeal release using BOTOX^Ⓡ inje-ction or cricopharyngeal myotomy was performed in five patients (3 patients in the injection laryngoplasty group and 2 patients in the medialization thyroplasty group) who failed to swallow after proper positional changes, swallowing maneuvers, and laryngoplasties.

Table 2 . Type of intervention..

Intervention	Number	%
Injection
Calcium hydroxylapatite	11	39
Hyaluronic acid	6	21
Total	17	60
Medialization
With arytenoid adduction	3	11
Without arytenoid adduction	8	29
Total	11	40

All but one patient resumed complete nutritional intake by mouth, and the feeding tube was removed (100% in the injection laryngoplasty group vs. 91% in the medialization thyroplasty group). The one patient with persistent ipsilateral vagal and hypoglossal para-lysis required a gastrostomy tube for >1 year from the date of medialization thyroplasty despite a well- medialized vocal fold. The results of the voice analysis in 14 patients who underwent nine injection laryngo-plasties and five medialization thyroplasties are shown in Table 3. Shimmer (P=0.001) and NHR (P=0.050) in the injection laryngoplasty group was significantly different preoperatively than postoperatively. A signi-ficant difference was observed between preoperative and postoperative MPT in the injection laryngoplasty group (P=0.001). The acoustic analysis demonstrated significant postoperative change in jitter (P=0.029) in the medialization thyroplasty group. Moreover, MPT values were significantly different between preoperative and postoperative measurements (P=0.001).

Table 3 . Results of acoustic voice analysis..

Parameter	Surgical modality	Preoperative	Postoperative	P-value
MPT	IL	5.40±2.78	16.20±6.93	0.001*
	MT	6.49±2.71	16.10±2.72	0.001*
	Total	5.79±2.71	16.16±5.64	<0.001*
F0	IL	154.15±39.63	138.27±27.22	0.337
	MT	210.90±173.95	173.95±44.70	0.150
	Total	174.42±44.43	151.01±37.22	0.143
Jitter	IL	6.81±5.88	2.40±2.55	0.055
	MT	6.17±2.20	2.97±1.55	0.029*
	Total	6.58±4.78	2.60±2.20	0.009*
Shimmer	IL	9.09±3.88	3.63±1.35	0.001*
	MT	11.59±6.51	6.78±2.85	0.169
	Total	9.98±4.88	4.75±2.47	0.001*
NHR	IL	0.30±0.20	0.15±0.04	0.051
	MT	0.27±0.12	0.20±0.07	0.287
	Total	0.29±0.17	0.17±0.58	0.020*

MPT: maximum phonation time, NHR: noise to harmonic ratio, MT: medialization thyroplasty, IL: injection laryngoplasty..

*Significant at P<0.05..

UVCP caused by high vagal lesions is rare. The incidence of HVP is not well established, but is estimated to be about 10% of UVCP cases³. The causes of high vagal lesions may result from cerebro-vascular accidents, skull base tumors or trauma, cervical spinal cord damage, or complications from surgery. In addition to motor dysfunction, sensations of the larynx are also impaired by high vagal lesions. In our series, skull base surgery (54%) was the most common cause of high vagal lesions followed by cerebral vascular diseases (18%) and unknown cause (18%). UVCP leads to valvular incompetence that cau-ses a constant pressure leak into the airway making voice production and swallowing more difficult. UVCP can lead to voice, respiratory, and swallowing symptoms. Cough and choking on liquids or saliva are the most common manifestations of dysphagia in UVCP. Choking with solids is less frequent, but may also occur in some patients, particularly those with HVP. Patients may have aspiration and dysphagia if the vocal folds are widely abducted or if substantial sensory loss occurs in the lower pharynx and larynx. The goal of surgical treatment of patients with glottal insufficiency is to restore valve closure to re-establish airway protection during the swallow. The role of injection laryngoplasty and medialization thyroplasty with or without arytenoid repositioning is to re-establish glottal closure. In HVP patients, Cricopharyneal myo-tomy and pharyngoplasty can also be used in the management of glottal insufficiency to decrease the risk of aspiration by increasing the transit time of the pharyngeal bolus. Thus, managing UVCP of high vagal origins should differ considerably from managing UVCP caused by recurrent laryngeal nerve damage. Low vagal paralysis (i.e., isolated recurrent laryngeal nerve paralysis) leads to denervation of the laryngeal adductors and abductors and so a vocal fold is paralyzed and displaced laterally. However, HVP (i.e., combined paralysis of the superior laryngeal nerve and the recurrent laryngeal nerve) leads to additional sensory deficits, and also additional paralysis of the cricothyroid muscle with a consequent loss in vocal fold tension, bowing of the vocal fold, and a vertical mismatch in the levels of the two vocal folds⁴. In 11 cases undergoing medialization thyroplasty, three patients showed the level difference of the paralyzed vocal fold preoperatively and received arytenoid adduction with medialization thyroplasty.

Injection laryngoplasty was introduced in 1911 by Brunings⁵. Arnold introduced Teflon injection, and it remained the standard treatment for UVCP^6,7. Long- term complications of granuloma formation and sig-nificant difficulty in revision surgery have essentially excluded its use in modern laryngology. Many other materials have been used for injection laryngoplasty, but the ideal material has yet to be found⁶. Since Isshiki⁸ introduced the type I thyroplasty, it has become the gold standard treatment for UVCP^9,10. Media-lization thyroplasty is the preferred surgical treatment in patients with longstanding vagus nerve palsy. It is a time-tested procedure that yields excellent voice and swallowing function improvement by restoring glottal competence. The procedure is usually reserved for patients that have not had recovery of vocal fold mobility after 9 months to 1 year from the initial nerve injury or patients with significant vocal atrophy that desire a long-term solution for symptoms of glottal insufficiency. Patients who have documented iatrogenic injury or tumor involvement of the vagal nerve are candidates for early medialization thyroplasty. Additional medial displacement of the vocal fold can be achieved with arytenoid repositioning. However, this requires access to the posterior portion of the thyroid cartilage, division of the inferior constrictor muscles, and dissection of the pyriform sinus to reveal the muscular process of the posterior cricoa-rytenoid muscle. Laryngeal framework surgery for treating UVCP is a long-term solution in patients with dysphagia related to glottal insufficiency. In comparison to injection laryngoplasty, patients usually undergo a single procedure to improve glottal closure. Injection laryngoplasty of the vocal folds increases the bulk of an immobile or paretic vocal fold. Hence, the surface area of contact with the contralateral fold is restored at the midline. It restores glottal closure at the time of the pharyngeal phase of the swallow, preventing material from penetrating through the glottis. Injec-tion laryngoplasty is an immediate but temporary and reversible solution to restore glottal insufficiency. It can be used in the outpatient as well as the hospital setting in patients who have symptoms of dysphagia due to glottal insufficiency. Although medialization thyroplasty was considered the standard procedure for UVCP, the neck scar that is left behind discou-rages some patients. In our study, 17 patients accepted injection laryngoplasties instead of medialization thyroplasty. All patients gained swallowing benefits from this treatment. Furthermore, the results of acoustic analysis, including shimmer, NHR, and MPT were significantly improved after the injection lary-ngoplasties. Favorable functional results were ob-tained because of the biocompatibility and viscosity of the injected material. We suggest that injection lary-ngoplasty could be alternative treatment option for patients with UVCP caused by HVP and can achieve similar outcomes to those of medialization thyroplasty.

The present study had some limitations, including the retrospective analysis, small sample size, unequal distribution of treatment groups, and short median follow-up period. In addition, some data that might add more value to the study were not available, such as follow-up VFSS study that might add more value to the study were not available because the tests r-equired for calculating them were not routinely per-formed. Accordingly, we suggest that an additional prospective investigation be conducted in a larger number of patients.

Office-based injection laryngoplasty or medialization thyroplasty in combined with a therapeutic swallowing and exercise program are the basic modalities succe-ssfully used to surgically treat UVCP caused by HVP. Office-based injection laryngoplasty can be considered a safe, quick, and efficient procedure for improving swallowing and voice function.

Study approval was granted by the Institutional Review Board of Yeouido St. Mary’s Hospital (No. HC10RIS10042).

None.

YH Joo-Conceptualization, Formal analysis, Metho-dology Writing - original draft, HB Kim - Data curation, Formal analysis, Writing - review & editing, YH Park - Conceptualization, Data curation, Formal analysis, Writing - review & editing.