Unilateral Vocal Cord Paralysis and its management
Evaluation of Results of type I Thyroplasty
 

Samant Sumit, Mohan Sharat, Young Kate, Dept. of ENT, Derbyshire Royal Infirmary , Derby DE12QY UK

 

• ¹Samant Sumit, Senior House Officer, Derbyshire Royal Infirmary
• ²Mohan Sharat, Laryngologist, Derby Voice Clinic
• ³Young Kate, Clinical Lead Speech and Language Therapist ENT, Derby Voice Clinic

Address:          Derbyshire Royal Infirmary, London Road, Derby DE1 2QY

Telephone:     01332 252543

Inquiries to:   sumitsamant@gmail.com sharat.mohan@derbyhospitals.nhs.uk kate.young@derbyhospitals.nhs.uk

 Abstract
Introduction : Unilateral vocal cord paralysis is a result of dysfunction of the recurrent laryngeal or vagus nerve. This produces a characteristically breathy voice. Another associated problem is aspiration which may be aggravated by additional superior laryngeal nerve involvement. Operations on the thyroid, cervical spine by an anterior approach, carotid body tumours and the chest carry a risk of iatrogenic vocal cord paralysis. Malignant tumours of the skull base, thyroid, oesophagus, lung and mediastinal metastases could involve recurrent laryngeal or vagus nerves. Idiopathic vocal cord paralysis is a diagnosis of exclusion when no identifiable cause is found. This is usually attributed to viral or inflammatory process. In this paper we take a look at the aetiology, presentation and evaluation of unilateral vocal cord paralysis and also review its management, complications and outcome of treatment. A retrospective outcome audit was carried out on the results of type I Thyroplasty in our department.
Purpose : The purpose of this audit was to evaluate the effectiveness of type I Thyroplasty in treating patients with symptomatic unilateral vocal cord paralysis.
Methods : Thirty two consecutive cases of unilateral vocal cord paralysis who were operated on between 1998 and 2002 by the same surgeon were included in this audit. Voice quality was assessed subjectively by double-blinded evaluation by experienced speech therapists using a modified Jennifer Oates scale (comparable to the well-researched GRBAS assessment) and by calculating the scores on patient satisfaction questionnaire. Objective evaluation involved videostroboscopy and measurement of Maximum Phonation Time.
Results : All patients had subjective improvement in voice quality (100%). 30 patients had improvement in Maximum Phonation Time (93.75%). Three patients had aphonia pre-operatively and none postoperatively (100%).
Conclusion : Thyroplasty type 1 improves voice quality and Maximum Phonation Time in patients with unilateral vocal cord paralysis.

Introduction

Unilateral vocal cord paralysis is a result of dysfunction of the recurrent laryngeal or vagus nerve. This produces a characteristically breathy voice. Another associated problem is aspiration which may be aggravated by additional superior laryngeal nerve involvement.
 
Aetiology
 

Idiopathic	34%
Malignancy	25%
Iatrogenic/trauma (non-thyroidectomy)	23%
Thyroidectomy	10%
Neurologic	8%

 
Operations on the thyroid, cervical spine by an anterior approach, carotid body tumours and the chest carry a risk of iatrogenic vocal cord paralysis. Malignant tumours of the skull base, thyroid, oesophagus, lung and mediastinal metastases could involve recurrent laryngeal or vagus nerves. Idiopathic vocal cord paralysis is a diagnosis of exclusion when no identifiable cause is found. This is usually attributed to viral or inflammatory process.
 
Clinical presentation
History:
General:
It is important to determine the onset, duration and severity of dysphonia. Dysphonia is usually sudden in onset and breathy, weak and low-pitched, although it may be high-pitched due to compensatory falsetto. There may be associated history of coughing, choking, aspiration, stridor, dyspnoea, dysphagia or odynophagia. The patient may have had previous laryngeal, other head-neck or thoracic surgery. History of previous intubation may be important as well.
Glottal incompetence causes significant air wasting. Patients may therefore experience shortness of breath or a feeling of running out of air. The loss of natural positive end-expiratory pressure (PEEP) due to glottal leak can actually cause decreased pulmonary function.
 
Vocal:
Inquiries should be made about the demands on voice at work and home, episodes of abuse and vocal hygiene i.e., smoking, water and caffeine intake, and environmental irritants.
 
Examination:
Indirect laryngoscopy and flexible laryngoscopy or videostroboscopy are performed while the patient phonates a high pitched /ee/ sound which elongates the vocal cords and moves the larynx superiorly. This aids complete visualization of the larynx. A direct laryngoscopy with palpation of the arytenoids to rule out joint fixation is essential before surgery. It is important to remember that incomplete transaction, variable reinnervation and compensatory hypertrophy may confound examination findings. Recurrent laryngeal nerve injury generally leaves the vocal cord in a paramedian position while superior laryngeal nerve involvement moves the posterior glottis ipsilaterally and produces a bowed and flaccid cord.
A thorough examination of the neck and chest is also mandatory.
The lateral manual compression test is an easy office-based procedure which is particularly useful in determining whether a patient with a wide glottic gap from unilateral vocal cord paralysis or vocal bowing will benefit from a medialization thyroplasty.   To perform the test, the neck is palpated to find the superior notch and the inferior margin of the thyroid ala.  The vocal cords are located along a horizontal line drawn at the midpoint of these two landmarks.  The patient is asked to sustain an /a/ phonation and pressure is applied to the lateral aspects of the thyroid cartilage.  The concept is to approximate the vocal folds and decrease the glottic gap.  A subjective improvement in voice quality is sufficient to state that the patient would benefit from a medialization thyroplasty though acoustic, aerodynamic, and videostroboscopic studies can be done to quantify improvement.  The limitations to this test are older patients who have calcification of the thyroid cartilage, patients with obese necks, and patients with scarring of the vocal folds.
 
Relevant anatomy & Pathophysiology
The recurrent laryngeal nerve is involved in both abduction and adduction of the vocal cords. The left vagus nerve gives off the recurrent nerve as it crosses the aortic arch. The latter then loops under the ligamentum arteriosum and travels superiorly in the tracheo-oesophageal groove, passes deep to the inferior cornu of the thyroid cartilage and enters the larynx. This is a short space where the nerve lies between the thyroid and cricoid cartilages and where it is vulnerable to trauma from a high or over-inflated endotracheal or tracheostomy tube cuff. The right recurrent laryngeal nerve arises at the level of subclavian artery and loops around it to reach the tracheo-oesophageal groove.
An understanding of both the internal and external laryngeal anatomy is important for the surgical treatment of unilateral vocal cord paralysis. For patients who receive a vocal fold injection, an appreciation and thorough understanding of the anatomy of the membranous vocal fold, process of the arytenoid cartilage, and paraglottic space is crucial for successful treatment.
Laryngeal framework surgery requires an understanding of the relationship and anatomy of the thyroid cartilage and cricoid cartilage. This is especially true regarding the relationship of the membranous vocal fold and paraglottic space to the external landmarks of the thyroid cartilage. For the more advanced laryngeal framework surgery techniques (eg, arytenoid adduction, cricothyroid subluxation), thorough knowledge of the anatomy of the cricothyroid joint and cricoarytenoid joint are required to be successful.
Natural history of the paralyzed fold depends on the aetiology and severity of the paralysis, the extent of reinnervation and compensation by the contralateral vocal cord. Flaccid paralysis immediately follows transaction of the nerve and is followed by atrophy of the cord and fibrillation potentials. If the cut ends are close, reinnnervation usually occurs in 6-12 months, indicated by polyphasic potentials and manifested as synkinetic movements.
Bowing of the vocal cords is a result of changes in the lamina propria viz., a loss of elastic fibres, muscle and submucous gland atrophy and increased fibrosis. These changes produce an increased glottic gap. Bowing may be a normal change in an ageing patient or it may be due to muscle atrophy secondary to nerve sectioning or central neurological conditions.
Bilateral vocal cord adduction causes glottal closure and this, together with subglottic airflow, induces vocal cord vibration. Unilateral vocal cord paralysis, therefore, results in weak and uncoordinated vibration that causes dysphonia.
 
Imaging
If the aetiology is uncertain, posteroanterior and lateral chest radiographs are the first step in evaluation. These may reveal a Pancoast tumour, mediastinal mass or cardiomegaly as the cause. If radiography is normal, a CT scan from skull base to mid chest on the left and the clavicle on the right should be done to evaluate the entire length of the vagus and recurrent laryngeal nerves.  If the patient is a child, pregnant, or suspected to have a generalized neurologic problem, an MRI is advised instead.  A barium swallow may be done to evaluate swallowing mechanism and associated dysphagia.  Radioactive thyroid uptake scan or ultrasound may be done to evaluate for the presence of a nodule or tumor. 
 
Evaluation
1. Subjective:
a) Laryngoscopy
Indirect or fiberoptic laryngoscopy reveals information about vocal cord anatomy and mobility and allows for immediate diagnosis of mass lesions or asymmetric stiffness abnormalities (unilateral paralysis).
 
b) Patient satisfaction
In addition to patient history regarding functional aspects of voice use and voice demands, a standardized voice-related outcome measure can be used to assess the patient's vocal limitations and disability. The voice handicap inventory has been shown to be a reliable and useful patient-based survey instrument, quantifying the patient's voice handicap due to their voice disorder.
 
c) Evaluation by Speech therapist
Even the most modern tests cannot replace a trained ear. Qualitative assessment of the patient’s voice looks at qualities such glottic fry, hard glottal attacks, breathiness, diplophonia, pitch breaks, phonation breaks, and tense phonation. 
 
2. Objective
a) Laryngeal ElectroMyoGraphy (LEMG)
This is the only objective measurement of laryngeal innervation in vocal fold paralysis. Though not routinely performed, it is an excellent evaluation of specific muscle functioning. This is an invasive test that relies on accurate placement of electrodes into the laryngeal musculature. Results hold prognostic importance. Fibrillation potentials are usually seen within three weeks of denervation while reinnervation potentials seen between six and twelve months after the injury. It can also differentiate between vocal cord paralysis and arytenoid joint fixation.
 
b) Electroglottography
This records vocal cord adduction by measuring the current from an electrode on one side of the larynx across the glottis and into the opposite electrode. A closed glottis provides the least amount of resistance and is associated with the greatest amount of current flow. When the vocal cords are abducted, the resistance is high and the current is low. The output is a wave representing glottic resistance plotted against time, and since glottic resistance relates to the area between the cords, the output represents vocal cord position versus time. Alterations in the normal pattern can reflect mass lesions or asymmetric stiffness disorders. In the normal voice, the closed time is about 50% of the cycle. In the breathy voice, the closed time represents a significantly decreased portion of the cycle. In the tense voice, the closed time occupies a greater portion of the cycle. The disadvantage of this technique is that the information is a product of both vocal folds and is therefore imprecise.
 
c) Photoglottography
This is similar to EGG in that the amount of light trans-illuminated through the glottis is measured and plotted against time. It is complementary to EGG because the peaks of the cycle correspond to the abducted glottis and therefore measures vocal fold opening.
 
d) Aerodynamic Measurements
Subglottic pressure and translaryngeal airflow can be measured noninvasively with a facemask. Since pressure is equivalent to the product of flow and resistance, the resistance can be calculated. Glottic resistance is often altered in vocal fold stiffness pathology. Decreased resistance often accompanies the paralyzed larynx.
 
e) Acoustic Analysis
Acoustic evaluation is the quantitative measurement of various voice characteristics.  Having the patient sustain a single tone, the fundamental frequency (Fo), variations in amplitude (shimmer), and variations in pitch (jitter) can be measured.  Fo may be decreased in patients with vocal abuse or poor approximation of the vocal folds.  Shimmer alteration is due to decreased stability of the vocal folds.  Abnormal jitter correlates with the subjective quality of harshness.  Another area where pathology is demonstrated is in the relative level of noise; soft, breathy voices often have more associated noise and tend to have more energy in the fundamental frequency and less in the harmonics.
 
f) Videostroboscopy
Videostroboscopy utilizes flashes of light at a frequency determined by either the pitch of phonation or a frequency generator. This creates the impression that the folds are vibrating in slow motion. It provides detailed information about vocal fold mobility, mass lesions, and the status of the mucosal wave. It allows for dynamic assessment of the vocal cords and differentiation between functional voice problems and those caused by subtle structural abnormalities. Amongst other variables, evaluation of the symmetry of movement, aperiodicity, glottic closure configuration, and horizontal excursion is done. If the cords are functioning symmetrically, they should essentially be mirror images of each other.  The lateral excursion and timing of opening/closing should be identical.  Aperiodicity is a measure of irregularities in vocal fold movement. The glottis may also be assessed for gap, shape, and appropriate closure.  The shape of the glottis may be characterized as complete, anterior chink, irregular, bowed, posterior chink, hourglass, or incomplete.  Horizontal excursion is a measurement of the amplitude of the cords.  Measurement both pre and post-operatively can provide objective data for evaluating improvement.  An additional benefit is reviewing the results with the patient immediately after performing the examination.  Giving the patient a visual image of the problem helps considerably in motivation for behavioral treatment and development of goals for improvement. 
 
Management
Dysphonia is the main indication for treatment. Treatment may be more imperative if patients are aspirating. Treatment should be determined based on the patient's functional needs and demands. Some patients do not notice any significant functional limitation possibly because of minimal voice demands or coexisting morbidities that occur during postoperative recovery.
 
1. Conservative:
a) Medical therapy:
Concomitant gastro-oesophageal reflux disease or sinonasal allergic disease needs to be treated.
 
b) Voice therapy:
Assessment of patients by a speech pathologist allows for maximal conservative treatment to be implemented before considering surgical treatment.  Some patients develop hyperfunctional compensatory mechanisms which lead to the common complaints of voice strain, neck discomfort, and fatigue.  Speech pathologists can help eliminate these habits and educate the patient on proper compensation techniques.  Relaxation exercises, aerobic conditioning, voice exercises and other methods are all practiced by the patient to improve voice quality.  Once vocal therapy has been maximized and further voice improvement is desired, surgical options may be considered.  Utilizing voice therapy in treatment of unilateral vocal cord paralysis is crucial to ensuring the greatest improvement in voice. 
 
2. Surgical
History of Surgery
Phonosurgery is a relatively young field with the first medialization procedure coming in 1911 and our modern concept of laryngeal framework surgery arising only 20 years ago.
 
 

1911	Brunings introduced paraffin injection into the vocal cord for medialization
1915	Payr described a technique of a posterior, vertical incision through the thyroid cartilage to allow medialization with lateral pressure
1952	Meurman uses an anterior, vertical thyroid cartilage incision to allow the placement of autologous rib
1962	Arnold described Teflon injections for medialization
1975	Isshiki introduced the concept of alloplastic materials to implant for medialization procedures
1987	Brandenburg et al. reported the first use of autologous fat injection for glottic insufficiency
1999	Zeitels described cricothyroid subluxation

 
Timing of surgery
Acute medialization is indicated at the time of skull-base surgery if resection of the vagus is carried out and may prevent a tracheotomy. If no etiology is identified it is advisable to wait a year before any medialization technique is performed. For other identifiable pathologies six to twelve months is often said to be reasonable. However, reversible procedures such as Gelfoam medialization may be done more acutely.
Intraoperatively, the voice quality is observed both perceptually and with laryngeal examination via flexible fibreoptic nasopharyngoscopy. This allows the surgeon to control or adjust the surgery to optimize the voice quality at the end of the procedure. This is an essential to high-quality phonosurgery and is the reason why these procedures in general should not be conducted under general anaesthesia.
 
Contraindications
No contraindications exist for the nonsurgical treatment of unilateral vocal cord paralysis. Contraindications for the surgical treatment of unilateral vocal cord paralysis include medical problems, such as severe cardiac or pulmonary limitations or anticoagulation therapy. A careful and detailed medical history and evaluation are required prior to deciding on surgical treatment. Often, the most complete history is obtained in conjunction with an internal medicine physician and an anaesthetist. A poorly abducting contralateral vocal cord is a relative contraindication for surgical treatment of unilateral vocal cord paralysis because of the airway reduction that occurs with surgical medialization of the paralyzed vocal fold.
 
a) Cord injection
A variety of substances are used including autogenous fat, collagen, and Gelfoam. Teflon had been the primary method of treatment for the past thirty years, but is no longer acceptable due to significant long-term complication rate for Teflon granuloma formation. Proper technique is essential in injection medialization, and poor results can usually be traced to errors here. Once the larynx is reached, the needle is obliquely directed through the floor of Morgagni's ventricle three millimetres in depth. The injected material in instilled in one millilitre aliquots in the space between the vocalis muscle and thyroid cartilage. Complications include overinjection, underinjection, improper placement, migration, and granuloma formation.
 
i. Temporary
Gelfoam
The main indications for the use of Gelfoam are temporary paralysis with glottic incompetence, augmentation to a re-innervation procedure, contraindication to an open procedure, and as a test run before injecting a non-absorbable material.   
Approximately 1g of Gelfoam powder is mixed with 4 cc of saline immediately prior to vocal fold injection.  The less viscous the solution, the quicker it will be reabsorbed. 
Gelfoam is effective in decreasing aspiration and returning the ability to cough in patients.  Voice can be improved in most patients without the aid of speech therapy.   The amount of Gelfoam present in the cord is constant for approximately one month and is fully absorbed in 8 to 10 weeks.  The slow resorption allows for a gradual compensation in speech and swallowing.  There is a mild mucosal edema and erythema that occurs in some patients and rare reported cases of airway compromise. 
 
ii. Permanent
Collagen
Collagen injections are derived from bovine collagen which is modified to minimize host immune response.  Collagen implants are assimilated into the surrounding tissues by an invasion of fibroblasts and deposition of new host collagen. Collagen is placed within the histologically similar deep layer of the lamina propria. Resorption of the collagen is offset by deposition of host collagen thereby providing long term voice improvement.  Resorption of the cartilage may be precipitated by an upper respiratory infection.  There have been reports of hypersensitivity reactions with rare cases of airway compromise.  Some authors still advocate the use of dermal skin tests to test for possible allergic reaction to the injections.  In a series by Ford and Bless, 2 of 80 patients had a positive skin test which is consistent with the reported incidence of 3%.  Recently, an increased used of Zyplast collagen, a GAX collagen,  has decreased the incidence of allergic reactions. 
 
Autologous fat
It is an outstanding and efficacious method to medialize paralyzed vocal folds, especially those that are in the median or paramedian position with mild-to-moderate atrophy. However, patients with severe glottal incompetence because of a lateralized, atrophic, and shortened vocal fold are not good candidates. Fat injections have been used successfully in patients with vocal cord paralysis, vocal fold scarring, vocal fold atrophy, and intubation defect. Under general anesthesia, fat is harvested from the lower abdominal pannus, the fat is cut into 1mm pieces separating it from connective tissue and rinsed with ringer’s lactate followed by a methylprednisolone solution.  It is then loaded into a syringe.  The actual location of fat placement is dictated by the underlying pathology.  For those patients with vocal cord atrophy and paralysis, the antero- and posterolateral areas of the middle third of the cord are injected.  Injection is continued until a 50% overcorrection and convex bowing of the affected cord is seen. Overinjection is recommended because a certain percentage of fat will atrophy over time.   
Autologous fat is well tolerated in the vocal cord and repeated injections can be done if necessary. Postoperative analysis reveals an improvement in glottic closure and mucosal wave production.  Though breathiness improves, roughness may persist after the procedure.  Anterior defects have a better postoperative outcome than posterior defects. 
Early failure is believed to be due to a large glottal gap or a posterior defect not corrected with fat injection.  Late failure is attributed to absorption of the fat supported by an initial improvement in voice quality. 
There are still a few concerns and questions about fat injection. It is not known whether improved vocal function is due to the amount of fat injected or softening of the vocal cords.  Another uncertainty is the rate of fat absorption by the vocal tissue.  If initially effective, the benefits of fat injection may last anywhere from three months to several years.  Some studies have shown that despite absorption of the fat, lipocytes and fibrous connective tissue retain the contour of the vocal cord and provide long term benefit.  The exact method of harvesting and preparation of the fat and its relation to absorption is still unknown.  Effort should be made to minimize that amount of trauma to the fat during extraction. 
 
Fascia lata
Minced Fascia lata is also used for the purpose of injecting into the vocal fold to medialize the vocal cord. Research into freeze-dried Fascia lata is currently under way.
 
Bioplastique
BioplastiqueTM is a textured polymer (polymethylsiloxane elastomer) that is also being used for vocal cord medialization by injection. It has good biocompatibility.
 
Teflon
Teflon is no longer an acceptable material for cord injection due to a significant long-term complication rate for Teflon granuloma formation. Its incidence was estimated to be over 50% with long-term follow-up, and the treatment of this complication usually required surgery (often several) and permanent diminution in vocal function.
 
b) Laryngeal framework surgery
i. Medialization Thyroplasty

The indications for a Type I thyroplasty are unilateral or bilateral vocal fold paralysis or paresis, vocal fold bowing, and incomplete glottic closure with aspiration. Type I thyroplasty is contraindicated in patients with a previous hemilaryngectomy.  Without the support of the thyroid cartilage, the silastic implant is ineffective in medializing the scarred side.  Vocal fold injection is indicated in this case.  The second contraindication is previous laryngeal irradiation due to extensive scarring.
There are many variations in this procedure championed by several authors.  The technique described below is favoured by many authors e.g., Netterville et al.  A horizontal incision is made over the midportion of the thyroid cartilage and the cartilage exposed. A window is created in the thyroid ala approximately 8mm posterior to the anterior commissure and 3mm superior to the inferior border of the cartilage. This provides a sufficient strut inferiorly to support the implant. After the window is made, the cartilage is removed. Incisions are made in at the inferior, posterior and superior aspects of the inner perichondrium thereby creating a flap. The perichondrium is elevated from the medial aspect of the thyroid ala. While viewing the cords via fiberoptic laryngoscopy, a depth gauge is used to medialize the cords in the anterior, middle, and posterior aspects of the window and the measurements are recorded. These measurements are also taken at the superior and inferior aspects of the window to find the relation between the true and false vocal cords. Using these measurements, an implant is fashioned from a silastic block. The point of maximal medialization is at the level of the vocal process. Very minimal medialization is designed at the anterior commissure to prevent a strained voice. The inferior aspect of the implant is placed in the window and rotated into place. The patient is asked to phonate and voice is assessed. If medialization is not optimal, the implant can be removed and modified. The time of intralaryngeal elevation and implant placement should be minimized to prevent vocal interference by intraoperative edema. 
It is important to note that the implant design using medialization laryngoplasty must simultaneously address the treatment of the paralyzed vocal fold in the medial-lateral, superior-inferior, and anterior-posterior dimensions. Optimal voice results from medialization laryngoplasty involve appropriate consideration and treatment of the paralyzed vocal fold in all 3 of these dimensions with the implanted material.  
 

 
Variations/Controversies:
Removal of the cartilage window: Some authors feel that the cartilage, if left in place can migrate superiorly and medialize the false vocal cord or ventricle. If the cartilage migrates inferiorly, it may cause overmedialization of the cord resulting in a persistently strained voice quality. 
Inner perichondrium: Some authors prefer to leave the inner perichondrium intact stating that it decreases the incidence of graft extrusion. Netterville states that the reason for increased implant extrusion is injury to the ventricle. This occurs more frequently if a paramedian incision is used near the anterior commissure where the ventricle is located very close to the inner perichondrium. He argues that incising the inner perichondrium does not increase implant extrusion secondary to the development of a fibrous capsule around the implant.   
Implant material: Though some authors feel that a carved implant allows for precise results, Montgomery et al. reports certain benefits to a pre-made implant. The inner aspect, which medializes the cord, is made of a softer plastic closer to the consistency of the surrounding tissue. The outer half is made of a harder plastic which locks into the thyroid cartilage. This prevents displacement of the cords and eases revision.  Hydroxylapatite is a pre-made implant which has minimal tissue reactivity and good biocompatibility with the surrounding tissue. Gore-tex (ePTFE) is another material reported to be of benefit in medializing a paralyzed vocal cord. This material has excellent biocompatibility and can be used to medialize the cord in an incremental fashion. This technique does not require extreme precision in creating the thyroid window or shaping the implant. 
Type I thyroplasty has had excellent results in voice improvement. The procedure helps to re-establish the mucosal wave in the paralyzed vocal fold. By approximating the vocal membranes, normal anatomic position is re-established and the cords are able to produce sound. The return of an intact mucosal wave is a large reason that this procedure is so effective in improving voice. This improvement is illustrated by an increased Fo and maximum phonation time. Other objective variables such as glottic closure and cord symmetry are also improved. The improvement in aspiration symptoms is even more consistent than the improvement in voice quality.  Additional benefits include the ability to monitor vocal improvement during the procedure if performed under local anesthesia. Using a nasopharyngoscope, the surgeon can ensure the implant is at the level of the true vocal cords and not medializing the false cords or the ventricle. It is both adjustable and potentially reversible. The reversibility of the procedure allows its use in a patient with potential return of vocal cord function. The implant can also be revised if the vocal cord continues to atrophy over time. When performing a Type I thyroplasty, it is important to council the patient on the expected voice changes post-operatively. Though initially strong in the operating room, perioperative edema will cause the patient to be hoarse for the first ten days after the procedure. Some have noted an additional period of voice difficulty occurs 4 to 6 weeks after surgery. This eventually improves and the patient’s voice may continue to improve for the next year. Primary medialization thyroplasty occurs at the time of extirpative surgery with known sacrifice of the recurrent laryngeal nerve in the neck.  This procedure is done under general anesthesia and therefore negates the benefit of intraoperative voice evaluation. It is performed primarily in hope to eliminate the need for a tracheotomy and decrease the postoperative rehabilitation time (swallowing and speech) of patients with loss of multiple cranial nerves.
Complications of Type I thyroplasty include persistent dysphonia, airway obstruction, implant migration, extrusion, hematoma, and infection. Poor voice quality post-operatively may be due to inadequate medialization or over-medialization of the cords. Appropriate voice assessment can only take place 4 to 6 weeks after the operation when all edema has resolved. Despite various techniques to prevent migration, occasionally the implant may move superiorly and medialize the false cord and ventricle. This calls for removal of the implant and replacement with a larger prosthesis. Extrusion into the airway is a serious complication. Though it does not occur frequently, suspicion should warrant a fiberoptic laryngoscopy and subsequent endoscopic extraction if found. Extrusion laterally can be avoided by securing the prosthesis firmly in the thyroid cartilage. In general, complications can be reduced by careful handling of the tissues, limited operative time, and meticulous hemostasis. 
Type I thyroplasty may not be sufficient to close a large posterior gap. It may difficult to know pre-operatively whether posterior approximation will be needed. One method proposed by Omori et al. is to obtain videostroboscopic measurements prior to surgery. They assessed the posterior glottic gap as a percentage of the membranous vocal fold length. They found that is the posterior glottic gap was larger than 10% of the membranous vocal fold length, the post-operative outcome was worse and a posterior closure procedure may be warranted. If it is determined that the posterior gap is too large either pre or intra-operatively, the surgeon has the option of either creating an implant with a large posterior component or performing an arytenoid adduction (discussed later). Implants that were originally fashioned to medialize the posterior cord did so by pressing on the vocal process of the arytenoid cartilage. It has since been shown that it is more effective to fashion the implant to apply pressure to the muscular process of the arytenoid. Simply stated, the implant should have a large posterior flange, approximately 5mm in thickness to fit between the muscular process and the thyroid ala. The major advantage of this procedure is, unlike arytenoid adduction, that it does not hinder mobility of the vocal folds.
 
ii. Arytenoid adduction
This is an adjunctive procedure for instances in which either type I thyroplasty fails to provide adequate medialization of the posterior glottis or when the vocal cords are at   a different level. It is often combined with a type I thyroplasty in high vagal lesions because the asymmetric cricothyroid contraction places the cords at different levels and creates a large posterior glottic gap.
Many authors are firm believers in this partnership because medialization laryngoplasty addresses the position and bulk of the membranous vocal cord while operations on the arytenoid address tension and length of the paralyzed vocal cord. Addressing all of the distinct and important features of the paralyzed vocal cord yields the best surgical result for this condition.
A simple way to assess if an arytenoid adduction is necessary is to see if the vocal processes of the arytenoid cartilages touch in the midline when the patient phonates.  If after the silastic implant has been placed, there is a persistent posterior gap, an arytenoid adduction is performed. 
As performed by Isshiki, a horizontal neck incision is made at the level of the vocal cord and the posterior border of the thyroid cartilage is exposed. It is important to identify the recurrent laryngeal nerve in this area to avoid any damage. The cricothyroid joint is then opened to allow access to the muscular process of the arytenoid cartilage. The piriform sinus mucosa is then elevated with great care to avoid violating the piriform recess. In order to gain access to the cricoarytenoid joint the posterior and lateral cricoarytenoid muscles are separated.
Posterior cricoarytenoid muscle is ligated from the muscular process.  Two 3-0 nylon sutures are placed around the muscular process and the surrounding soft tissue.  The sutures are then pulled anteriorly through the thyroid ala.  The patient is asked to phonate and the appropriate force is determined to provide optimum voice results. 
Woodson and Zeitels have proposed modifications to the Isshiki procedure to enhance the arytenoid repositioning. The former suggests the placement of a second suture on the muscular process of the arytenoid and securing it to the lateral-inferior aspect of the cricoid to simulate the pull of the vertical belly of the posterior cricoarytenoid muscle.
The only significant variation is whether or not to open the thyroarytenoid joint.  Some authors believe that opening the joint results in prolapse of the arytenoid cartilage into the laryngeal lumen with overadduction of the posterior commissure. Though this is a technically difficult procedure and requires the opening of the cricoarytenoid joint, making it irreversible, currently, no other procedure corrects for a discrepancy in vocal cord level and few other procedures effectively address a wide posterior chink.
Arytenoid adduction may also be indicated in patients with aspiration pneumonia due to incompetence of the posterior glottis.
 
iii. Cricothyroid subluxation
This procedure involves anteriorly displacing the ipsilateral inferior cornu of the thyroid cartilage. This is performed by placement of a suture that runs from the inferior cornu of the thyroid cartilage to the midline of the cricoid cartilage. This effectively rotates the thyroid cartilage on the cricoid cartilage, providing additional length to the paralyzed vocal fold.
 
iv. Reinnervation
These techniques were described by Tucker in 1977 and modified by Crumley in 1988 and allow a more physiologic approach to rehabilitation of the paralyzed vocal cord. This procedure can improve stabilization of the arytenoid cartilage, and present a more normal mass, tension, and position of the paralyzed vocal fold. The procedure described by Tucker involves taking a segment of omohyoid muscle with its attached ansa hypoglossus nerve and placing it adjacent to the vocalis muscle via a window in the thyroid cartilage identical to that of a type I thyroplasty. Crumley's modification involves attaching the proximal ansa cervicalis to the distal stump of the recurrent laryngeal nerve. These reinnervation procedures are performed rarely and can be done in combination with other medialization procedures. A mobile arytenoid cartilage is a prerequisite for these procedures. This procedure cannot be performed on a patient who has had disruption of the ansa cervicalis. It is not useful in patients with aspiration because of limited medialization.
Neuromuscular pedicle reinnervation: An incision is made in the lower half of the thyroid ala extending to the sternocleidomastoid muscle.  The ansa cervicalis is identified overlying the jugular vein and is traced to its insertion to the anterior belly of the omohyoid muscle.  Two stay sutures are placed 2-3mm proximal and distal from the insertion site.  A window is made is similar to that used for a Type I thyroplasty.  The inner perichondrium is opened and the thyroarytenoid is incised superficially.  Using the stay sutures, the muscle pedicle is sown in place.  It is crucial to avoid excessive tension on the pedicle. 
Ansa Cervicalis – Recurrent Laryngeal Anastomosis: The ansa cervicalis is exposed overlying the great vessels or within the carotid sheath and is traced to either the omohyoid or sternothyroid.  The nerve is sectioned at its insertion to the muscle and transposed to the tracheoesophageal groove.  The recurrent laryngeal nerve is identified by retracting the superior thyroid neurovascular bundle and followed to its insertion into the larynx.  It is ligated 7 –10mm from its insertion in the larynx to ensure a tension free anastomosis.  The nerves are anastomosed with a neurorrhaphy (epineural repair) with 10-0 suture under magnification. 
Reinnervation surgery provides tone to the thyroarytenoid muscle and gives tension to the vocal cord. Another reason to perform reinnervation is to prevent vocal fold atrophy.  Medialization procedure may need to be revised 2 to 3 years later because cord atrophy has resulted in an increased glottic gap.  Laryngeal reinnervation maintains the bulk of the paralyzed fold. Patients with no spontaneous reinnervation would be more likely to benefit from operative reinnervation. 
A universal criticism of reinnervation is the 4 to 6 month period required for the procedure to be effective.  Many authors advocate the concurrent use of a medialization procedure, either Gelfoam injection or thyroplasty.  Tucker has described removing the posterior inferior aspect of the implant in order to allow room for the muscle-pedicle implant to be placed.
When comparing the two methods of reinnervation, it is currently unclear which procedure produces the best results.  Preliminary work by Hall et al. indicates that the muscle pedicle allows for more rapid innervation and stronger contractile force.  Current research is directed toward understanding the role of cell adhesion markers in the role of nerve regrowth.  This research will likely have a significant impact on the methods of reinnervation surgery. 
Paniello has proposed a recurrent laryngeal – hypoglossal nerve anastomosis.  The theoretical advantage is that these are the only two nerves involved in swallowing and phonation.  Other advantages are an abundance of axons in the hypoglossal nerve, use in patients in which ansa is unavailable, and low donor site morbidity.  Initial work with the procedure suggests that it results in a stronger reinnervation and sphincter-like action on swallowing.  Though there is denervation of the ipsilateral tongue, no increase in aspiration has been shown.
 
3. Postoperative and Follow up care
Patients after lipoinjection are placed on voice rest typically for 6-7 days to enhance the survival of the transplanted fat. No or minimal voice rest is used after laryngeal framework procedures.
 
Evaluation following surgical treatment should include a patient-based assessment of the voice function and head and neck examination, including indirect laryngoscopy and voice evaluation by a speech pathologist. The latter is important to assist in deciding whether the patient would be best served with postoperative voice therapy.
 
4. Complications
Complications of surgical treatment include poor voice outcome, airway difficulties, and migration of the medialization implant. Manipulation of the airway may result in swelling or a hematoma from either laryngeal framework surgery or vocal fold injection and consequent airway difficulties. Prevention of this complication involves meticulous and precise surgical technique and the use of preoperative and postoperative steroids. A greater risk exists for a bilateral procedure.
Unless the surgery is performed strictly for aspiration, most surgical procedures are elective in nature and are aimed at improving voice quality. No improvement should therefore be considered a complication of the procedure and can often be rectified with revision medialization laryngoplasty, with or without an arytenoid adduction procedure.
The most common reason for poor voice quality following medialization laryngoplasty is improper placement of the thyroplasty implant in a too anterior and/or too superior direction. In addition, the implant size can be either too large or too small. Perioperative oedema might mislead the surgeon into placing too small an implant. This can be prevented by the use of preoperative steroids, as well as expedient surgery.
Thyroplasty implant migration can occur postoperatively, either medially into the airway or laterally into the neck. The former obviously is of great concern but appears to be rare.
 
5. Outcome
Expected voice outcome following the treatment for unilateral vocal cord paralysis is excellent. Most patients resume normal speaking activities and functions and are able to meet all normal voice demands. Singing is a higher demand than speaking and may not be restored to its premorbid condition. The ability to project one's voice over a large area in a loud manner is also often never fully restored despite optimal medical, behavioral, and surgical treatment. Most patients should have normal or near-normal speaking voice ability with minimal to no functional limitations of their everyday voice use following successful treatment.
 
6. Future Considerations
Laryngeal modelling, from canine larynges to mathematical modeling, is being actively pursued with the ultimate goal of designing a mechanical neolarynx. Selective reinnervation of adductors and abductors is the other treatment avenue being studied.
 
Type I Thyroplasty Audit
A retrospective outcome audit on the results of type I Thyroplasty was carried out in our department. The questions this audit addressed were:
1. Did type I Thyroplasty improve voice quality?
2. Did it improve the phrase length?
3. Did patient satisfaction improve following the procedure?
 
Methods:
The audit included 32 consecutive patients with unilateral vocal cord paralysis who underwent type I Thyroplasty between 1998 and 2002. Voice evaluation protocol for the purpose of this audit was devised following principles mentioned earlier in this paper and included subjective and objective analysis.
i. Subjective analysis: Voice quality was assessed subjectively by double-blinded evaluation by experienced listeners using a modified Jennifer Oates scale. This scale scores the parameters of breathiness, harshness, diplophonia, falsetto and phonation breaks from zero to five and is comparable to the well-researched GRBAS assessment. Patients were also given a satisfaction questionnaire both before and after the operation.
ii. Objective analysis: Objective evaluation involved videostroboscopy and measurement of the Maximum Phonation Time.
 
Results:
i. patient satisfaction: all patients had subjective improvement in voice quality (100%). Three patients had aphonia pre-operatively and none postoperatively (100%).
ii. Modified Jennifer Oates scale: evaluation by experienced speech therapists in a double-blinded fashion revealed that breathy quality of voice improved as did phonation breaks, these improvements being more significant than those in other parameters evaluated. As can be seen in the following table, these improvements represented trends rather than statistically significant changes.
 

 
iii. Maximum Phonation Time: 30 patients had improvement in Maximum Phonation Time (93.75%). The trend is shown in the following table.
 

 

Complications:
Two patients developed postoperative wound infection which responded well to treatment with systemic antibiotics. One patient developed early postoperative stridor due to soft tissue oedema, for which he required a tracheostomy. The tracheostomy was reversed five days later when the oedema had settled and the subsequent postoperative recovery was uneventful.
 
Conclusions of the Audit:
This audit concluded that type I Thyroplasty improves voice quality and Maximum Phonation Time in patients with unilateral Vocal cord paralysis.
 
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