TITLE: Vocal Cord Paralysis and Vocal Cord Medialization
SOURCE: Grand Rounds Presentation, UTMB, Dept. of Otolaryngology
DATE: April 28, 2004
RESIDENT PHYSICIAN: Shashidhar S. Reddy, MD, MPH
FACULTY PHYSICIAN: Anna M. Pou, MD
SERIES EDITORS: Francis B. Quinn, Jr., MD and Matthew W. Ryan, MD
"This
material was prepared by resident physicians in partial fulfillment of
educational requirements established for the Postgraduate Training Program of
the UTMB Department of Otolaryngology/Head and Neck Surgery and was not
intended for clinical use in its present form. It was prepared for the purpose
of stimulating group discussion in a conference setting. No warranties, either
express or implied, are made with respect to its accuracy, completeness, or
timeliness. The material does not necessarily reflect the current or past
opinions of members of the UTMB faculty and should not be used for purposes of
diagnosis or treatment without consulting appropriate literature sources and
informed professional opinion."
Anatomy
The cartilages of the larynx consist of the thyroid cartilage, the epiglottis, the cricoid cartilage, and the arytenoid cartilages. The corniculate and cuneiform cartilages stiffen the aryepiglottic folds. The arytenoid cartilages articulate with the cricoid by means of a true synovial joint. This joint allows two movements of the arytenoid cartilages – rotation and lateral gliding.
There are three groups of intrinsic laryngeal musculature – the abductors, adductors, and tensors. The only abductor of the larynx is the posterior cricoarytenoid muscle and it is innervated by the recurrent laryngeal nerve. The adductors are composed of the lateral cricoarytenoid muscle, interarytenoid muscle, oblique arytenoid muscles, and thyroarytenoid muscles. Innervation of the adductors is again supplied by the recurrent laryngeal nerve. The tensors are composed of mainly the cricothyroid muscle, which is innervated by the external branch of the superior laryngeal nerve, and to a lesser extent by the thyroarytenoid muscles.
The true vocal folds have an epithelial lining that is composed of respiratory epithelium (pseudostratified squamous) on the superior and inferior aspects of the fold and nonkeratinizing squamous epithelium on the medial contact surface. The subepithelial tissues are composed of a three-layered lamina propria based on the amount of elastin and collagen fibers. The superficial layer is composed of mostly amorphous ground substance and contains a scant amount of elastin with few fibroblasts – this layer is termed Reinke’s space. The intermediate layer has an increased elastin content. The deep layer has less elastin but a greater amount of collagen fibers. The intermediate and deep layers have a higher concentration of collagen fibers and are termed the vocal ligament. Deep to the lamina propria is the thyroarytenoid (or vocalis) muscle. Reinke’s space and the epithelial covering are responsible for the vocal fold vibration.
The Vagus:
Understanding the anatomy of the vagus nerve is important because branches of the vagus nerve are responsible for innervation of the larynx. The vagus nerve has three nuclei located within the medulla:
The nucleus ambiguus is the motor nucleus of the vagus nerve. The efferent fibers of the dorsal (parasympathetic) nucleus innervate the invuluntary muscles of the bronchi, esophagus, heart, stomach, small intestine, and part of the large intestine. The efferent fibers of the nucleus of the tract of solitarius carry sensory fibers from the pharynx, larynx, and esophagus.
Vagus means "wanderer" which is appropriate for the path this nerve takes after emerging from the jugular foramen. It has two ganglia, the smaller superior ganglion and the larger inferior, or nodose, ganglion. The vagus sends small meningeal branches to the dura of the posterior fossa and an auricular branch, which innervates part of the external auditory canal, the tympanic membrane, and skin behind the ear. In the neck, the vagus runs behind the jugular vein and carotid artery to send pharyngeal branches to the muscles of the pharynx and most of the muscles of the soft palate. The superior laryngeal nerve separates from the main trunk of the vagus just outside the jugular foramen. It passes anteromedially on the thyrohyoid membrane where it is joined by the superior thyroid artery and vein (see vasculature). At approximately this level, the external laryngeal nerve leaves the main trunk. The main internal laryngeal nerve enters the thyrohyoid membrane through a hiatus. It then divides into three set of branches (ascending, transverse and descending), which communicate with the recurrent laryngeal nerve posterior to the cricoid cartilage; this is referred to as the ansa galeni. The internal superior laryngeal nerve penetrates the thyrohyoid membrane to supply sensation to the larynx above the glottis. The external superior laryngeal nerve runs over the inferior constrictor muscle to innervate the one muscle of the larynx not innervated by the recurrent laryngeal nerve, the cricothyroid muscle.
The right vagus nerve passes anterior to the subclavian artery and gives off the right recurrent laryngeal nerve. This loops around the subclavian and ascends in the tracheo-esophageal groove. It tends to run with the inferior thyroid artery for part of its course before it enters the larynx just behind the cricothyroid joint. It may branch prior to this with sensory fibers supplying sensation to the glottis and subglottis. The left vagus does not give off its recurrent laryngeal nerve until it is in the thorax, where the left recurrent laryngeal nerve wraps around the aorta just posterior to the ligamentum arteriosum. It then ascends back toward the larynx in the TE groove. The vagus then continues on into the thorax and abdomen contributing fibers to the heart, lung, esophagus, stomach, and intestines as far as the descending colon.
Normal function/movement/physiology
The larynx has a variety of functions. It acts as a sphincter to close the airway during swallowing, preventing aspiration of food and liquids. This is phylogenetically the oldest and perhaps most important function of the larynx. Its function is also essential for respiration. Since the larynx is the gateway to the airway, laryngeal disease may result in obstruction of the airway. It functions during communication of both intellectual and emotional expression. Thus, voice deterioration is only one symptom of laryngeal dysfunction. It also stabilizes the thorax by preventing exhalation, this helps stabilize the arms during lifting. During coughing, lifting, and straining it compresses the abdominal cavity. Aspiration on swallowing, ineffective cough, and breathy voice are symptoms caused by the loss of sphincteric function, and can occur in addition to hoarseness in patients with true vocal fold paralysis.
Phonation is defined as the physical act of sound production by means of passive vocal fold interaction with the exhaled airstream. Basically, this sound production arises from a passive movement of the true vocal cords (TVC)s modified in terms of pitch, quality, and volume by complicated interaction of thoracic and abdominal muscles, intrinsic and extrinsic muscles of larynx, and the shaping and resonance of the upper airway and nasal passages. Contraction of the expiratory muscles produces a rise in subglottic air pressure causing rapid escape of air between the nearly apposed TVCs. Bernoulli’s effect and the elasticity of the cords causes medial displacement of the medial edges of cords and airflow is stopped. A rapid rise again in subglottic pressure causes the cords to part and the cycle is repeated. It is the escape of small puffs of air that produces the vibratory phenomenon interpreted as sound.
During phonation the lower margins of the true vocal folds separate first with formation of a volume of subglottic air. As the upper margins of the vocal folds separate a burst of air is released – the glottal puff. The lower fold then returns to midline, followed by the upper margin. This delay between closure of the lower and upper margins of the fold is termed the phase delay. The mucosal wave consists of both a horizontal movement of the folds and a vertical undulation.
The body-cover theory helps explain this mucosal wave. It states that there are two layers of the vocal folds with different structural properties. The cover is composed of stratified squamous epithelium and the superficial layer of the lamina propria (Reinke’s space). The body of the fold is composed of the intermediate and deep layers of the lamina propria (which is more fibrous than the superficial layer – the “vocal ligament”) and the thyroarytenoid (vocalis) muscle. The cover is pliable, elastic, and nonmuscular, whereas the body is more stiff and has active contractile properties that allows adjustment of stiffness and concentration of the mass. The mucosal wave occurs primarily in this loose cover of the fold. Changes in stiffness or tension in the fold alters the mucosal wave. As the stiffness in the fold increases – as by contraction of the cricothyroid muscle – the velocity of the wave increases and the pitch rises. Mucosal wave velocity also increases with greater airflow and greater subglottal pressure.
The pitch of voice is related to the fundamental frequency of vocal fold vibration (measured in hertz). The fundamental frequency of vocal fold vibration correlates with changes in vocal fold tension and subglottic pressure. Contraction of the cricothyroid muscles, which correlates positively with vocal fold tension, is the main predictor of fundamental frequency, especially at high frequency. Contraction of the thyroarytenoid may change the tension of the vocal fold cover and body and affect the fundamental frequency also. Three physical properties of the vocal folds determine frequency of vibration – mass, stiffness, and viscosity
Mass – the fundamental frequency of vocal fold vibration is inversely proportional to its mass. Decreasing the mass – thinning of the fold by longitudinal stretching (contraction of the cricothyroid muscle with elongation of the vocal folds) – increases the frequency of vibration. Increasing the mass – contraction of the thyroarytenoid muscle with increased concentration of the fold – will decrease the fundamental frequency.
Stiffness – vocal fold tension is an important variable in the control of fundamental frequency at the mechanical level. Vocal fold tension is affected by the contractile forces of the vocal fold musculature and the tissue characteristics of the vocal fold body, cover, and the connecting fiber structure of the vocal folds.
Viscosity – Viscosity is inversely related to ease with which the tissue layers slip over one another in response to a shear force. Increased viscosity of the vocal folds would require greater subglottal pressure to maintain the same vibratory characteristics. Therefore, hydration of the vocal folds has effect on the voice quality and ease of voice production.
PATHOLOGY AFFECTING VOICE:
Unilateral Vocal Cord Paralysis: When one
of the vocal cords is paralyzed, the cords are not able to meet in the midline
to initiate the glottic attack. This prevents
development of the subglottic pressure needed to
initiate speech.. Also with the cords at such a distance, the mucosal
wave cannot be adequately maintained. Hoarseness and breathiness are the most
common complaints but vocal abnormalities may also include easy fatigability
and voice or pitch change. It is important not to assume that the
immobile cords are necessarily paralyzed. Arytenoid
fixation can lead to an immobile cord and direct palpation of the arytenoid cartilage and/or laryngeal EMG can rule out this
possibility. Potential return of function of an immobile cord can be
determined if the underlying cause is known and with the aid of LEMG.
This contributes significantly to the choice of surgical procedure to correct
the problem. It is also important to remember that the larynx has a
number of functions in the human and dysphonia may
not be the primary compliant. Patients may be suffering from dysphagia, coughing, or choking episodes, or stridor.
There are a number of different causes of unilateral vocal cord paralysis. Any entity affecting the vagus nerve along its course may result in decrease in function. The most common cause is non-laryngeal cancer which includes neoplasms of the head, neck, chest, and skull base. Neuritis associated with upper respiratory infection, syphilis, or other infectious sources may cause nerve dysfunction. Neurologic conditions such as CVA, multiple sclerosis and myasthenia gravis may also effect vocal cord functioning. General medical conditions such as diabetes mellitus may cause an isolated neuropathy giving rise to vocal paralysis. Lesions of the vagal nerve occurring higher in the brain and may present with multiple cranial nerve abnormalities.
Vocal Fold Bowing: The inability of the folds
to approximate at the midline decreases the ability to produce proper
speech. Though it may be a normal change in the aging patient, it is also
seen with muscular atrophy secondary to nerve sectioning or central neurologic conditions. With aging, changes in the
lamina propria include a loss of elastic fibers,
atrophy of submucous glands, increased fibrosis, and
muscle atrophy. These changes result in an increased glottic
gap and a number of perceptual changes. Geriatric patients may present
with hoarseness, low pitch, imprecise articulation, or breathiness.
PATIENT EVALUATION AND SELECTION:
-History:
GENERAL: As always, obtaining a pertinent
history is of utmost importance. One should determine the onset,
duration, and severity of the dysphonia. As
previously mentioned, the larynx is also crucial in protecting the lower
respiratory tract and is a conduit of the upper respiratory tract.
Therefore the patient may present with coughing and choking episodes,
aspiration, stridor, dyspnea,
dysphagia, or odynophagia
(2). Intubation history and previous head
and neck trauma are crucial pieces of information. It is important to
know if the patient has had any previous laryngeal surgery or other head and
neck surgery.
VOCAL: A specific vocal history is also
important. Many patients who present with vocal complaints have a disease
entity that does not warrant surgical treatment. Aside from onset, duration,
variability, and past vocal problems, history should include pertinent medical
questions such as presence of seasonal allergies, history of reflux disease,
life stress, diabetes, and medications. Many patients who present for an
initial evaluation of voice complaints are unfamiliar with questions of vocal
use and hygiene. It is important for the physician to explain these
concepts to the patient during the questioning to facilitate accurate responses
and educate the patient. Questions should include voice demands at home
and at work, recreational singing, and episodes of abuse i.e. sporting events.
Smoking, water intake, caffeine intake, and environmental irritants are
important questions about vocal hygiene.
-Physical:
It is important to do an entire exam with emphasis on
palpation of the neck to assess for any neck mass or goiter and cranial nerve
testing. An indirect laryngeal exam, as well as a flexible laryngoscopy
or videostrobe should be performed. The patient should phonate a high
pitched /ee/ sound. This causes elongation of
the vocal folds and causes the larynx to move superiorly. These movements
aid in obtaining a complete view of the larynx. In addition to assessing
vocal fold position and mobility, it is crucial to rule out carcinoma of the
larynx in a patient presenting with hoarseness. A direct laryngoscopy with palpation of the arytenoids to ensure
joint fixation is absent should be done prior to any surgical procedure.
The manual compression test is an easy non-invasive
office procedure to help evaluate a number of voice disorders. The
lateral manual compression test 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 should be 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.
-Vocal Assessment:
Despite the recent outburst of technology used to
measure and quantitatively assess voice, there is no substitute for the trained
ear. Taking a history gives ample time for the physician to make a
qualitative assessment of the patient’s voice. Qualities such glottic fry, hard glottal attacks, breathiness, diplophonia, pitch breaks, phonation breaks, and tense
phonation can be assessed.
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 hoarseness.
Videostrobolaryngoscopy
(VSL) should be performed whenever possible. It allows for dynamic
assessment of the vocal folds. With this view, the physician is able to
differentiate between functional voice problems and those caused by subtle
structural abnormalities. Pulses of light allow us to watch various parts
of successive cycles to obtain a complete picture of vocal cord activity.
The physician is able to evaluate symmetry of movement, aperiodicity,
glottic closure configuration, and horizontal
excursion amongst other variables. 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. If the frequency of the strobe light is equal to the
fundamental frequency, no vocal fold movement should be seen. If movement
is observed followed by a static period, aperiodicity
is present. The glottis may also be assessed for gap, shape, and
appropriate closure (11). 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.
Electromyography (EMG), though not routinely
performed, is an excellent evaluation of specific muscle functioning. By
placing electrodes into laryngeal muscles (thyroarytenoid,
cricothyroid), EMGs help
elucidate whether there is any re-innervation of
muscles which are thought to be paralyzed. It can also help to
differentiate paralysis from arytenoid joint
fixation. EMGs are also used to identify
excessive muscle activity prior to the use of BOTOX for spasmodic dysphonia.
-Diagnostic Tests:
If indirect or stroboscopic exam demonstrates a
unilateral vocal cord paralysis with no known etiology, a specific battery of
tests should be considered.
TREATMENT OPTIONS:
The most important aspect of rehabilitating voice is
defining the patient's goals.
--VOICE THERAPY :
Assessment of patients by a speech pathologist allows
for maximal medical treatment to be implemented before consideration is given
to surgical treatment. Some patients develop hyperfunctional
compensatory mechanisms which lead to the common complaints of voice strain,
neck discomfort, and fatigue (16). 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.
--CORD INJECTION:
Teflon
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. Histologically, the collagen is similar
to the deep layer of the lamina propria.
Therefore, the collagen is placed within this layer of the vocal fold.
Though there is some resorption of the
collagen, this is offset by the deposition of host collagen thereby
providing long term voice improvement. Resorption
of the collagen may be precipitated by an upper respiratory infection.
There have been reports of hypersensitivity reactions with rare cases of airway
compromise with the use of Bovine collagen, Zyderm.
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 Cymetra,
a form of collagen composed of micronized homologous alloderm, has decreased the incidence of allergic reactions
and lengthened the period of benefit.
Autologous Fat
In 1987, Brandenburg et al. reported the first use of autologous fat injection for glottic
insufficiency. Since then, fat injection for a variety of etiologies has
become very popular.
Hsiung et al. (12) divided
failure into two categories, early and late. With early failure, it was
believed that it was due to 1) a large glottal gap or 2) a posterior defect not
corrected with fat injection. Late failure was 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. Knowing that there will be some reabsorption of the fat, the cord needs to be overinjected. This leads to the question of exactly how much fat results in an optimal change in voice. It is also 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.
Synthetic Injectables:
Calcium Hydroxyapatite (Radiance FN; BioForm) is an injectable material made of small spherules of CaHydroxyapatite. No granuloma formation occurs with this agent. Long term efficacy is currently under study.
Polydimethylsiloxane gel (Bioplastique;
Bioplasty) is widely used in
--TYPE I THRYOPLASTY
-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. (10) 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.
--ARYTENOID ADDUCTION:
There are two major indications for an arytenoid adduction. The first reason is to close a
posterior glottic gap. Given that the cricoid overlaps the thyroid posteriorly,
a posterior window is not effective in medializing
the posterior vocal cord. The traditional Type I thyroplasty
has been shown to be ineffective in medializing the
posterior cord. 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. The second reason is if the vocal folds are not at the same
caudal-rostral level. The vocal process of the arytenoid cartilage moves inferior with adduction and
superior with abduction. This is due to the cylindrical shape of the cricoarytenoid joint. Some surgeons advocate an
intra-operative assessment of the vocal cord medialization.
If after the silastic implant has been placed, there
is a persistent posterior gap, an arytenoid adduction
is performed.
The procedure is described as it is performed by Isshiki. Using a horizontal neck incision at the
level of the vocal cords, the posterior border of the thyroid cartilage is
exposed by transecting the strap muscles and detaching the inferior constrictor
from the thyroid. 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 violating the piriform recess. Cricoarytenoid
joint is then opened allow exposure of the muscular process. The
posterior cricoarytenoid muscle is identified and 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.
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.
Arytenoid adduction can be
used in conjunction with medialization thyroplasty and re-innervation surgery.
Currently, no other procedure corrects for a discrepancy in vocal cord level
and few other procedures effectively address a wide posterior chink.
--REINNERVATION
SURGERY WITH ANSA CERVICALIS:
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.
Recently a modification has been proposed to the
recurrent laryngeal nerve – ansa recurrent laryngeal
anastomosis procedure. Paniello
(16) 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
Bilateral Vocal Cord Paralysis:
In contrast to unilateral vocal cord paralysis, voice quality is not the primary concern in patients with bilateral vocal cord paralysis. The significant problem is airway compromise. This can range from unnoticeable to, more commonly, dyspnea and stridor. The patient's voice quality is usually only mildly affected (if just the recurrent laryngeal nerves are involved) because the paralyzed cords tend to assume the natural position for phonation.
There are three basic ways that bilateral vocal cord paralysis is managed:
Tracheotomy:
Tracheotomy has the advantages of providing immediate relief of airway restriction. It can be performed under local anesthesia, and has relatively little reduction in voice quality. Disadvantages include the creation of a stoma that has both cosmetic and long-term care problems, and the need to occlude the tube or wear a speaking valve to phonate. This may be the best option for many patients because it controls the airway while preserving voice quality. In many patients, the tracheotomy can be occluded the majority of the time. In times of exertion, while sleeping, or when the patient has a cold or other respiratory condition, the tracheotomy can simply be unplugged.
Vocal Cord Lateralization:
This involves several techniques that surgically widen the glottic opening. While this improves the airway, the patient's voice quality suffers. The three most commonly utilized techniques are arytenoidectomy, arytenoidopexy, and cordectomy/cordotomy.
Arytenoidectomy:
Classic arytenoidectomy involves removal of some or all of the arytenoid cartilage. This procedure can be performed in a variety of ways, from endoscopically by microsurgical or laser technique to an external, lateral neck approach (Woodman). The Woodman procedure involves a lateral neck incision, exposure of the arytenoid cartilage posteriorly with removal of the majority of the cartilage, sparing the vocal process. A suture is then placed into the remnant of vocal process and fixed to the lateral thyroid ala. This technique seems to cause less voice deficit than other approaches.
Arytenoidopexy:
Arytenoidopexy displaces the vocal fold and arytenoid without surgical removal of any tissue. It can be done endoscopically with a suture passed around the vocal process of the arytenoid and secured laterally. This procedure, however, has a relatively high failure rate and is technically difficult.
Cordectomy:
Dennis and Kashima (1989) introduced the posterior partial cordectomy procedure using the carbon dioxide laser. This involves excising a C-shaped wedge from the posterior edge of one vocal cord. If this posterior opening is not adequate after 6-8 weeks, the procedure can be repeated or a small cordectomy can be performed on the other vocal cord. Laser cordotomy removes a smaller posterior portion of the true vocal cord and better preserves voice.
Reinnervation:
Tucker proposed a nerve-muscle transfer to the posterior cricoarytenoid muscle for the treatment of bilateral vocal cord paralysis. The technique is similar to the one used for unilateral vocal cord paralysis. Prerequisites are that the cricothyroid joint not be fixed and that the necessary nerve for the graft not have been affected by the process that caused the paralysis. Tucker reports a high success rate.
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Deborah, “Vocal Cord Paralysis,” Quinn Grand Rounds Archive,
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