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Paralysis of the Larynx and Pharynx
Symposium on Complex Surgical Problems
Paralysis of the Larynx and Pharynx Clarence T. Sasaki, M.D.*
Lesions of the vagus nerve will produce devastating effects on vital functions related to swallowing, breathing, and phonation. Complications of vagal injury can be catastrophic and life-threatening. An understanding of anatomy and function leads to a practical organization of surgical priorities useful in rehabilitating neurologic disorders of the upper aerodigestive tract.
NORMAL ANATOMY AND FUNCTION Although deglutition is a continuous process, it may be divided into three stages: oral, pharyngeal, and esophageal. During the oral stage, the bolus is stripped backward by the tongue (Fig. lA). As food enters the oropharynx, the soft palate, fauces, and posterior pharyngeal wall (all receiving vagal innervation) actively approximate to seal off the nasopharynx (Fig. IB). As the bolus further enters the pharynx, the larynx is abruptly elevated by reflex contraction of the constrictor muscles innervated by the vagus nerve. The upward movement of the larynx accentuates the shield-like configuration of the epiglottis, directing the bolus laterally into the pyriform sinuses. In so doing, swallowed matter is directed laterally and posteriorly away from the laryngeal aditus into the esophagus (Fig. 1, B to D). Relaxation of the cricopharyngeus muscle must precisely coordinate with the arrival of the bolus in order to allow its entry unimpeded into the upper esophagus. Once entering the esophagus, swallowed matter is propelled by gravity into the stomach (Fig. IE). Thus deglutition consists of three stages: a voluntarily controlled oral stage, a reflexly coordinated pharyngeal stage, and a gravitational or esophageal stage. Because the upper airway traverses the digestive tract in the region of the pharynx, intricate coordination between breathing and swallowing is necessary, rendering the pharyngeal state the most complex and thus most vulnerable stage of deglutition. 15 The degree of reflex coordination required in the second stage of deglutition can be appreciated when one recalls that the entire pharyngeal contribution is normally completed in less than 1 second. During this stage, the larynx, as well as the pharynx, plays a key role. Contrary to common opinion, the primary role of the larynx is not phonatory. Rather, its principal function is sphincteric, protecting the lower airway from the aspiration of swallowed matter. This concept is supported clinically as well as phylogenetically when in lower animals the larynx appears to act as a simple valve protecting the lungs from intrusion of foreign matter. Thus, when swallowing, the
* Associate Professor of Surgery (Otolaryngology), Yale University School of Medicine, New Haven, Connecticut Surgical Clinics of North America-Vol. 60, No. 5, October 1980
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Figure 1. Normal deglutition. A, The bolus is moved posteriorly by the tongue. B, The larynx is reflexly elevated and the nasopharyngeal port closed. C, The bolus is directed laterally around the epiglottis, posteriorly into the pyriform sinuses. D, Approximation of the false and true cords prevents the bolus from entering the trachea. E, The bolus is propelled by gravity into the stomach.
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Superior laryngeal Figure 2. The reflex arc responsible for laryngeal closure consists of the sensory limb of the vagus (superior laryngeal nerve) and the motor limb of the vagus (recurrent laryngeal nerve). Note that a small motor branch of the superior laryngeal nerve innervates the cricothyroid muscle (extrinsic adductor).
I t
Superior laryngeal nerve (motor)
Vagus nerve
Recurrent laryngeal-nerve (motor)
Table 1. Sensory Innervation of Upper Aerodigestive Tract NERVE
V IX X
Trigeminal Glossopharyngeal Vagus Pharyngeal plexus Superior laryngeal Recurrent laryngeal
DISTRIBUTION
Oral cavity (palate, tongue) Base of tongue, tonsil Oro- and hypo-pharynx Supraglottic mucosa Subglottic mucosa
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Table 2. Motor Innervation of Upper Aerodigestive Tract NERVE
V
Trigeminal
VII IX X
Facial Glossopharyngeal Vagus Pharyngeal plexus
DISTRIBUTION
Muscles of mastication and tensor of palate Muscles of facial expression Stylopharyngeus muscle
Superior laryngeal Recurrent laryngeal
Levator of palate and pharyngeal constrictors Cricothyroid (extrinsic adductor) Thyroarytenoid } Interarytenoid (intrinsic adductors) Lateral cricoarytenoid Posterior cricoarytenoid (intrinsic abductor)
larynx is reflexly elevated (see Fig. 1B) and simultaneously closed (see Fig. 1, C and D) by contraction of the intrinsic laryngeal adductor musculature. The concerned reflex pathway involves the sensory limbs of the ninth and tenth (superior laryngeal nerve) cranial nerves transmitting impulses from local pharyngeal receptors to the brain stem. In tum, instantaneous closure of the larynx is mediated by the motor limb of the tenth cranial nerve (recurrent laryngeal nerve) from the medulla (Fig. 2).U During deglutition, respiration is reflexly inhibited, thus functionally, although not anatomically, separating the act of breathing from swallowing. Furthermore, between swallows, the larynx is actively opened during inspiration by contraction of the laryngeal abductors. In fact, phasic respiratory contraction of the abductor muscles (posterior cricoarytenoid) is directly controlled by the medullary respiratory center via the motor component of the vagus nerve (recurrent laryngeal nerve). Needless to say, without coordinated activation of the abductor muscles during inspiration, considerable turbulence will result in audible stridor and possible air-hunger." Phonatory function depends upon the active approximation of the vocal cords during the expulsion of air from the lungs. Active contraction of the laryngeal adductors not only approximates the cords, but also alters their shape. The vagus nerve again plays a key role in both voice production and its modulation. 7 Tables 1 and 2 summarize the innervation of the pharynx and larynx.
Thus, in a brief discussion of function related to the pharynx and larynx, it becomes emphatically apparent that neuromuscular dysfunction produces its most serious consequences on the vital act of deglutition. Lesser consequences are apparent in respiration and in phonation. A recognition of these relative consequences now clearly establishes therapeutic priorities.
LOW VAGAL PARALYSIS Low vagal paralysis (below nodose ganglion) rarely affects deglutition. It may, however, produce noticeable respiratory and phonatory disturbances. Generally speaking, disruption of the vagus nerve below the nodose ganglion is considered less than life-threatening.
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Unilateral Paralysis Low vagal paralysis largely spares the pharynx, its major effect being on the larynx. Thus, a unilateral lesion produces a unilateral cord paralysis involving both ipsilateral adductor and abductor muscles. The effect of sucb a lesion depends heavily upon the duration of paralysis. In early paralysis (less than one year) the involved cord assumes a paramedian position caused by the unopposed contraction of the ipsilateral cricothyroid muscle which, as an extrinsic adductor, receives its vagal innervation via the intact superior laryngeal nerve (see Fig. 2). In unilateral paralysis, neither respiration nor phonation is greatly affected (Fig. 3, A and B). The uninvolved cord abducts on inspiration and compensates across and midline on phonation providing a near-normal voice. Because sphincteric closure of the larynx is unimpaired, aspiration is rarely experienced. However, in late paralysis (greater than one year), the involved cord may move to the abducted or open position as the ipsilateral intrinsic muscles slowly atrophy. Although having no untoward effect on respira-
Figure 3. Indirect (mirror) laryngoscopy. A, In acute low vagal paralysis, the paralyzed left cord assumes a paramedian position while the innervated right cord opens on inspiration allowing air to enter the trachea. B, In acute low vagal paralysis, the innervated right vocal cord comJ!ensates on phonation by crossing the midline to meet the paralyzed left cord. C, In the late stages of low vagal paralysis, the left paralyzed vocal cord will often assume a lateralized position because of muscle atrophy. This lateralized position may also occur in high vagal paralysis when the ipsilateral cricothyroid muscle (extrinsic adductor) is denervated. D, During phonation in the late stages of low vagal paralysis, the atrophied left cord may assume such a lateralized position that the right innervated cord cannot possibly compensate. This configuration may also be seen with high vagal paralysis when the ipsilateral cricothyroid muscle has been denervated.
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Figure 4. Coronal section of the larynx. A, Muscle atrophy (arrow) has resulted in a flattened lateralized true vocal cord. B, Teflon paste injected into the paralyzed left vocal cord (arrow) reestablishes its midline position.
tion, such a configuration may result in occasional aspiration and gradually progressive hoarseness as the intact cord fails to fully compensate on adduction (Fig. 3, C and D). Effective treatment consists of vocal augmentation by the injection of Teflon paste into the paralyzed abducted cord (Fig. 4, A and B) resulting in ils more midline position. Absorbable Gelfoam paste may be used instead of Teflon if the paralysis is judged to be temporary. Vocal cord augmentation alone may be completely effective in the treatment of glottic incompetence caused by low vagal paralysis. 10
Bilateral Paralysis A bilateral low vagal lesion spares the pharynx, but paralyzes the larynx resulting in the paramedian position of both vocal cords. In such a case, deglutition is rarely impaired, aspiration being prevented by the closed position of the cords. For the same reason, voice quality may be near-normal. Breathing, however, may be turbulent. Treatment, while rarely emergent, may require tracheostomy. With the passage of time (greater than one year) the paralysis may cause sufficient bilateral cordal atrophy to result in less turbulent laryngeal air flow. However, as the atrophic vocal cords assume more lateral positions, vocal quality suffers and occasional aspiration may ensue. The early treatment of bilateral low vagal paralysis is tracheostomy. If the paralysis is considered to be permanent, that is, no functional retum in one year, two options can be pursued. First, unilateral
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Figure 5. Laryngeal reinnervation. A, A nerve-muscle pedicle from the anterior belly of the omohyoid muscle is prepared for laryngeal reinnervation. B, The nerve-muscle pedicle is sutured into the thyroarytenoideus muscle (intrinsic adductor). (From Tucker, H.M.: Human laryngeal reinnervation. Laryngoscope, 86:769-779, 1976, with permission.)
A
B
arytenoidectomy, resulting in the permanent lateralization of one paralyzed cord, will allow restoration of air flow through the larynx so that the tracheostomy tube can be removed. Is The greater the lateralization achieved, the greater the chance for aspiration and the greater the degree of hoarseness. For the same reason, bilateral arytenoidectomy is contraindicated because aspiration can be catastrophic . Second, reinnervation ofthe paralyzed vocal cord may successfully alleviate turbulent inspiration (Fig. 5). 17 By transferrring a nerve-muscle pedicle from the omohyoid muscle to the paralyzed posterior cricoarytenoid, phasic vocal cord abduction may be restored. In this case inspiratory activity of the omohyoid, mediated by the ansa cervicalis, is transferred to the paralyzed laryngeal abductor, the posterior cricoarytenoid muscle.
HIGH VAGAL PARALYSIS Whether unilateral or bilateral, high vagal paralysis (above nodose ganglion) is clearly catastrophic. Not only is the larynx paralyzed, but the
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Figure 6. Barium swallow. A, A lateral view shows characteristic aspiration due to high vagal paralysis. B, In high vagal paralysis, an anteroposterior view shows that the paralyzed vocal cord (small arrow) has assumed an open position. The atonic ballooned pyriform sinus (large glottis.arrow) allows swallowed matter to "spill over" into the trachea across an incompetent
pharyngeal muscles are also dennervated. Because high vagal paralysis involves motor impairment of both the superior and recurrent laryngeal nerves, a slightly abducted paralyzed cord results. The open position of the vocal cord invites aspiration (see Fig. 3, C and D). Meanwhile, simultaneous pharyngeal paralysis produces ballooning of the atonic constrictor muscles resulting in a reservoir of secretions capable of contaminating an incompetent larynx and soiling the lungs (Fig. 6). More importantly, the combined absence of sensory cues from pharynx, larynx, and upper trachea produces total impairment of the pharyngeal stage of deglutition resulting in further life-threatening aspiration pneumonitis (Fig. 7). The paralysis may be caused by a variety of intracranial or extracranial events: inflammatory, vascular, traumatic, or neoplastic. In most clinical situations, it is therefore not uncommon to encounter widespread cranial nerve involvement. Associated paralysis of the fifth, seventh, ninth, and twelfth cranial nerves represents a crippling threat to life.
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Figure 7. A, Massive aspiration pneumonitis may be life-threatening. B, A follow-up chest roentgenogram demonstrates an evolving lung abscess (arrows).
The overriding therapeutic concern is the prevention of aspiration. Treatment must be prompt and effective in order to be life-saving. A trial and error approach to treatment is to be condemned. Patients may be divided into two broad therapeutic categories of unilateral paralysis or bilateral paralysis.
Unilateral Paralysis Prompt treatment consists of the following measures in combination: 1. A cuffed tracheostomy allows a temporary means of averting aspiration while providing adequate pulmonary toilet. Long-term cuffed tracheostomy invites stomal infection, 13 tracheal stenosis, 1 esophageal erosion, 2 and innominate artery fistulization. H For this reason, cuffed tracheostomy alone does not serve a useful long-term solution to this problem. Not infrequently the cuffed tube introduces catastrophic complications of its own. 2. Nasogastric tube feeding provides a temporary solution to impaired deglutition. However, long-term nasogastric feeding is not only uncomfortable but invites nasal, esophageal, and laryngeal injury. 3. Vocal cord augmentation by Teflon injection aids in transforming a lateralized cord into a more median position. 10 By aiding glottic closure during deglutition, gross tracheal contamination is minimized. However, vocal cord injection alone is never completely effective in correcting aspiration caused by high vagal paralysis.
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rynx
Cricopharyngeus muscle
Figure 8. A cricopharyngeal myotomy is performed by dividing the cricopharyngeus muscle extramucosally as close to the midline as possible.
4. To facilitate the passage of swallowed matter from oropharynx into the upper esophagus, a cricopharyngeal myotomy is essential (Fig. 8). 9 More importantly, myotomy minimizes stasis of saliva and secretions within the atonic paralyzed pharynx, secretions that can be aspirated if regurgitated. 5. Salivary production can be reduced by bilateral chorda tympani and tympanic nerve sections (Fig. 9). 16 Neurectomy is accomplished transtympanically under local anesthesia. The control of excessive saliva remains effective for months using this method, which interrupts pre-
Tympanic membrane
tympani nerve
Stapes Figure 9. Tympanic neurectomy. A transcanal tympanotomy allows ready access to the chorda tympani nerve and the tympanic nerve.
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ganglionic parasympathetic innervations to the submandibular (chorda tympani nerve) and parotid (tympanic nerve) salivary glands. Rarely in unilateral high vagal paralysis is any single procedure completely successful in preventing life-threatening respiratory complication owing~ to aspiration. However, when used in combination, sufficient rehabilitation can be expected, allowing one to remove both tracheostomy and nasogastric tubes in the satisfactory rehabilitation of deglutatory function.
Bilateral Paralysis Bilateral paralysis is incompatible with life. It is therefore mandatory that the extent of deficit be clearly defined. One cannot assume that measures successful in rehabilitating unilateral paralysis will suffice in averting massive aspiration and death. There is simply no place for vocal augmentation, cricopharyngeal myotomy, or transtympanic neurectomy. Rather, the following definitive surgical steps are urgently required.'1 1. Tracheostomy is performed to support respiration and provide pulmonary toilet. 2. Gastrostomy minimizes aspiration of food or fluid taken by mouth and is better tolerated than nasogastric feeding over long-term recovery. 3. Surgical closure of the larynx represents the single most important step in preventing aspiration in those patients who have suffered progressive loss of sphincteric and phonatory laryngeal control. Surgical closure of the larynx is theoretically reversible should sufficient neuromuscular function retum in any given patient. Numerous surgical techniques have been devised to separate the upper respiratory from digestive tract. Each technique has met with diverse success in the hands of most surgeons. The epiglottic flap operation of Rahal,~ Lindeman's diversion procedure,' and Montgomery's glottic closure 6 procedure have all been successful in the prevention of aspiration when reflex closure of the larynx is severely impaired. A variation of Montgomery's procedure greatly improves the chances of successful surgical closure and for this reason is described below.' 1 TECHNIQUE. A permanent tracheostomy is first performed over an endotracheal tube, after which general anesthesia may be delivered through the tracheostomy cannula for the remainder of the surgical procedure. A permanent tracheostomy ensures a safe airway if the tracheostomy tube is accidentally dislodged after surgical closure of the larynx has been accomplished. The larynx is approached through a horizontal skin incision made over the thyroid cartilage (Fig. lOA). Skin flaps are developed by subcutaneous dissection superficial to the sternohyoid muscle, avoiding, if possible, communication with the tracheostomy. The sternohyoid muscles are separated from each other in the midline, exposing the underlying thyroid notch and cricothyroid membrane. A vertical midline thyrotomy is created, using a No. 15 surgical blade if cartilage is un-ossified. If ossification has occurred, an oscillating saw is used to create the vertical incision through the thyroid cartilage (Fig. lOB). Before the lumen of the larynx is entered, the cricothyroid mem-
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Figure 10. Surgical closure of the larynx. 3 •14 A, A horizontal skin incision is made over the thyroid cartilage. B, The thyroid cartilage is opened vertically (arrows). C, The thyroid alae are retracted laterally to expose the true and false cords as well as the laryngeal ventricles. D, The free edges of the fulse cords are approximated in a first layer of closure. E, A superiorly based stemohyoid muscle pedicle is sutured into the midline posterior commissure (arrows). The free edges of the true vocal cords are then approximated in a third layer of closure. F, The thyroid alae are reapproximated and the skin is closed over a drain. (From Glenn, W.L., Haak, B., Sasaki, C.T., and Kirchner, j.A.: Characteristics in management of respiratory complications accompanying pathologic lesions of the brain stem. Ann. Surg., in press, 1980, with permission.)
brane is opened horizontally for a short distance (1 em) in order to visualize the anterior commissure of the larynx from below as the laryngeal airway is gradually opened sagittally. By using small skin hooks, the thyroid alae may be retracted allowing accurate division of the anterior commissure in the midline under direct vision (Fig. 10C). A self-retaining retractor can be inserted for continued exposure. For purposes of hemostasis, lidocaine 1 per cent with epinephrine 1: 100,000 is infiltrated into both true and false cords. Mucous membrane between the free edges of the false and true cords is resected. Mucous membrane is thereby removed from the glottis circumferentially. Specific attention must be paid to the removal of mucous membrane from both laryngeal ventricles and their superior saccular extensions. The free edges of both false and true cords are undermined, 1 to 2 mm, to facilitate their midline approximation. The glottis is then closed superiorly in a first layer by approximating denuded margins of both false cords with interrupted 4-0 Dexon suture, vertically mattressed (Fig. lOD). A superiorly-based sternohyoid muscle pedicle is then routed through the thyroid notch. It may be necessary to resect a margin of alar cartilage in order to widen the notch for the comfortable insertion of the muscle
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pedicle. The leading edge of the muscle flap is anchored to the interarytenoideus muscle in the midline posterior commissure before the free edges of the true vocal cords are approximated inferiorly with vertically mattressed 4-0 Dexon suture (Fig. lOE). A superiorly-based muscle pedicle avoids disrupting its attachment to the posterior commissure as the thyrohyoid complex repeatedly rises and falls with each swallow. In this regard, the viable muscle flap provides a dual function. On the one hand, it obliterates a large dead space created by the apposition of the ventricular concavities. On the other hand, three rather than two layers of closure are accomplished without tension. The thyroid alae are re-approximated with several absorbable sutures and the wound closed over a drain (Fig. lOF). Surgical closure of the larynx, while theoretically reversible, should be reserved only for those patients in whom aspiration is clearly lifethreatening. Those who suffer bilateral high vagal paralysis clearly fall into this category. Those patients with unilateral high vagal paralysis may require such a procedure if the combination of recommended conservative measures fails to control aspiration. The associated involvement of cranial nerves five, seven, nine, or twelve increases the severity of pharyngeal dysfunction in unilateral high vagal paralysis, thus increasing the likelihood for surgical closure of the larynx.
SUMMARY Widespread neurologic dysfunction of the pharynx and larynx is catastrophic. Aspiration pneumonitis, resulting from laryngeal and pharyngeal incompetence, is incompatible with life. In· such cases, surgical intervention plays a key role and may be clearly life-saving. A system of surgical management has evolved based upon an understanding of functional priorities, leading to an organized plan of treatment and rehabilitation.
REFERENCES J., and Pearson, F. G.: Incidence and pathogenesis of tracheal injury following cuffed tube tracheostomy with assisted ventilation: Analysis of a two-year prospective study. Ann. Surg., 173:249-263, 1971. Flege, J, B.: Tracheoesophageal fistula caused by cuffed tracheostomy tube. Ann. Surg., 166:153-156, 1967. Glenn, W. L., Haalk, B., Sasaki, C. T., et al.: Characteristics and management of respiratory complications accompanying pathologic lesions of the brainstem. Ann. Surg., in press. Habal, M. B., and Murray, j. E.: Surgical treatment of life-endangering chronic aspiration pneumonia. j. Plast. Reconstr. Surg., 49:305-311, 1972. Lindeman, R. C.: Diverting the paralyzed larynx: A reversible procedure for intractable aspiration. Laryngoscope, 85:157-180, 1975. Montgomery, W. W.: Surgery to prevent aspiration. Arch. Otolaryngol., 101:679-682, 1975. Negus, V. E.: Comparative Anatomy and Physiology of the Larynx. New York, Hafner Publishing Co., Inc., 1962, pp. 128-154, ch. 10. Reich, M. P., and Rosenkrantz, J, G.: Fistula between innominate artery and trachea. Arch. Surg., 96:401-402, 1968.
1. Andrews, M.
2. 3. 4. 5. 6. 7. 8.
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9. Rontal, M., and Rontal E.: Lesions of the vagus nerve: Diagnosis, treatment, and rehabilitation. Laryngoscope, 87:72-86, 1977. 10. Ron tal, E., Rontal, M., Morse, G., et al.: Vocal cord injection in the treatment of acute and chronic aspiration. Laryngoscope, 86:625-634, 1976. 11. Sasaki, C. T.: Physiology of the larynx. In English, G. (ed.): Otolaryngology. Hagerstown, Maryland, Harper and Row Publishers, Inc., 1977. 12. Sasaki, C. T., Fukuda, H., and Kirchner, J. A.: Laryngeal abductor activity in response to varying ventilatory resistance. Trans. Am. Acad. Ophthalmol. Otolaryngol., 77:403410, 1973. 13. Sasaki, C. T., Horiuchi, M., and Koss, N.: Tracheostomy-related subglottic stenosis: Bacteriologic pathogenesis. Laryngoscope, 89:857-865, 1979. 14. Sasaki, C. T., Milmoe, G., Yanagisawa, E., et al.: Surgical closure of the larynx for intractable aspiration. Arch. Otolaryngol., in press. 15. Sasaki, C. T., Suzuki, M., Horiuchi, M., et al.: The effect of tracheostomy on reflex laryngeal closure. Laryngoscope, 87:1428-1433, 1977. 16. Townsend, G., Morimoto, A. M., and Kralemann, H.: Management of sialorrhea by transtympanic neurectomy. Mayo Clin. Proc., 48:776-779, 1973. 17. Tucker, H. M.: Human laryngeal reinnervation. Laryngoscope, 86:769-779, 1976. 18. Woodman, D. G., and Pennington, C.: Bilateral abductor paralysis. Ann. Otol. Rhino!. Laryngol., 85:437-440, 1976.
Department of Surgery Yale University School of Medicine 333 Cedar Street New Haven, Connecticut 06510
Paralysis of the Larynx and Pharynx Clarence T. Sasaki, M.D.*
Lesions of the vagus nerve will produce devastating effects on vital functions related to swallowing, breathing, and phonation. Complications of vagal injury can be catastrophic and life-threatening. An understanding of anatomy and function leads to a practical organization of surgical priorities useful in rehabilitating neurologic disorders of the upper aerodigestive tract.
NORMAL ANATOMY AND FUNCTION Although deglutition is a continuous process, it may be divided into three stages: oral, pharyngeal, and esophageal. During the oral stage, the bolus is stripped backward by the tongue (Fig. lA). As food enters the oropharynx, the soft palate, fauces, and posterior pharyngeal wall (all receiving vagal innervation) actively approximate to seal off the nasopharynx (Fig. IB). As the bolus further enters the pharynx, the larynx is abruptly elevated by reflex contraction of the constrictor muscles innervated by the vagus nerve. The upward movement of the larynx accentuates the shield-like configuration of the epiglottis, directing the bolus laterally into the pyriform sinuses. In so doing, swallowed matter is directed laterally and posteriorly away from the laryngeal aditus into the esophagus (Fig. 1, B to D). Relaxation of the cricopharyngeus muscle must precisely coordinate with the arrival of the bolus in order to allow its entry unimpeded into the upper esophagus. Once entering the esophagus, swallowed matter is propelled by gravity into the stomach (Fig. IE). Thus deglutition consists of three stages: a voluntarily controlled oral stage, a reflexly coordinated pharyngeal stage, and a gravitational or esophageal stage. Because the upper airway traverses the digestive tract in the region of the pharynx, intricate coordination between breathing and swallowing is necessary, rendering the pharyngeal state the most complex and thus most vulnerable stage of deglutition. 15 The degree of reflex coordination required in the second stage of deglutition can be appreciated when one recalls that the entire pharyngeal contribution is normally completed in less than 1 second. During this stage, the larynx, as well as the pharynx, plays a key role. Contrary to common opinion, the primary role of the larynx is not phonatory. Rather, its principal function is sphincteric, protecting the lower airway from the aspiration of swallowed matter. This concept is supported clinically as well as phylogenetically when in lower animals the larynx appears to act as a simple valve protecting the lungs from intrusion of foreign matter. Thus, when swallowing, the
* Associate Professor of Surgery (Otolaryngology), Yale University School of Medicine, New Haven, Connecticut Surgical Clinics of North America-Vol. 60, No. 5, October 1980
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Figure 1. Normal deglutition. A, The bolus is moved posteriorly by the tongue. B, The larynx is reflexly elevated and the nasopharyngeal port closed. C, The bolus is directed laterally around the epiglottis, posteriorly into the pyriform sinuses. D, Approximation of the false and true cords prevents the bolus from entering the trachea. E, The bolus is propelled by gravity into the stomach.
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Superior laryngeal Figure 2. The reflex arc responsible for laryngeal closure consists of the sensory limb of the vagus (superior laryngeal nerve) and the motor limb of the vagus (recurrent laryngeal nerve). Note that a small motor branch of the superior laryngeal nerve innervates the cricothyroid muscle (extrinsic adductor).
I t
Superior laryngeal nerve (motor)
Vagus nerve
Recurrent laryngeal-nerve (motor)
Table 1. Sensory Innervation of Upper Aerodigestive Tract NERVE
V IX X
Trigeminal Glossopharyngeal Vagus Pharyngeal plexus Superior laryngeal Recurrent laryngeal
DISTRIBUTION
Oral cavity (palate, tongue) Base of tongue, tonsil Oro- and hypo-pharynx Supraglottic mucosa Subglottic mucosa
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Table 2. Motor Innervation of Upper Aerodigestive Tract NERVE
V
Trigeminal
VII IX X
Facial Glossopharyngeal Vagus Pharyngeal plexus
DISTRIBUTION
Muscles of mastication and tensor of palate Muscles of facial expression Stylopharyngeus muscle
Superior laryngeal Recurrent laryngeal
Levator of palate and pharyngeal constrictors Cricothyroid (extrinsic adductor) Thyroarytenoid } Interarytenoid (intrinsic adductors) Lateral cricoarytenoid Posterior cricoarytenoid (intrinsic abductor)
larynx is reflexly elevated (see Fig. 1B) and simultaneously closed (see Fig. 1, C and D) by contraction of the intrinsic laryngeal adductor musculature. The concerned reflex pathway involves the sensory limbs of the ninth and tenth (superior laryngeal nerve) cranial nerves transmitting impulses from local pharyngeal receptors to the brain stem. In tum, instantaneous closure of the larynx is mediated by the motor limb of the tenth cranial nerve (recurrent laryngeal nerve) from the medulla (Fig. 2).U During deglutition, respiration is reflexly inhibited, thus functionally, although not anatomically, separating the act of breathing from swallowing. Furthermore, between swallows, the larynx is actively opened during inspiration by contraction of the laryngeal abductors. In fact, phasic respiratory contraction of the abductor muscles (posterior cricoarytenoid) is directly controlled by the medullary respiratory center via the motor component of the vagus nerve (recurrent laryngeal nerve). Needless to say, without coordinated activation of the abductor muscles during inspiration, considerable turbulence will result in audible stridor and possible air-hunger." Phonatory function depends upon the active approximation of the vocal cords during the expulsion of air from the lungs. Active contraction of the laryngeal adductors not only approximates the cords, but also alters their shape. The vagus nerve again plays a key role in both voice production and its modulation. 7 Tables 1 and 2 summarize the innervation of the pharynx and larynx.
Thus, in a brief discussion of function related to the pharynx and larynx, it becomes emphatically apparent that neuromuscular dysfunction produces its most serious consequences on the vital act of deglutition. Lesser consequences are apparent in respiration and in phonation. A recognition of these relative consequences now clearly establishes therapeutic priorities.
LOW VAGAL PARALYSIS Low vagal paralysis (below nodose ganglion) rarely affects deglutition. It may, however, produce noticeable respiratory and phonatory disturbances. Generally speaking, disruption of the vagus nerve below the nodose ganglion is considered less than life-threatening.
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Unilateral Paralysis Low vagal paralysis largely spares the pharynx, its major effect being on the larynx. Thus, a unilateral lesion produces a unilateral cord paralysis involving both ipsilateral adductor and abductor muscles. The effect of sucb a lesion depends heavily upon the duration of paralysis. In early paralysis (less than one year) the involved cord assumes a paramedian position caused by the unopposed contraction of the ipsilateral cricothyroid muscle which, as an extrinsic adductor, receives its vagal innervation via the intact superior laryngeal nerve (see Fig. 2). In unilateral paralysis, neither respiration nor phonation is greatly affected (Fig. 3, A and B). The uninvolved cord abducts on inspiration and compensates across and midline on phonation providing a near-normal voice. Because sphincteric closure of the larynx is unimpaired, aspiration is rarely experienced. However, in late paralysis (greater than one year), the involved cord may move to the abducted or open position as the ipsilateral intrinsic muscles slowly atrophy. Although having no untoward effect on respira-
Figure 3. Indirect (mirror) laryngoscopy. A, In acute low vagal paralysis, the paralyzed left cord assumes a paramedian position while the innervated right cord opens on inspiration allowing air to enter the trachea. B, In acute low vagal paralysis, the innervated right vocal cord comJ!ensates on phonation by crossing the midline to meet the paralyzed left cord. C, In the late stages of low vagal paralysis, the left paralyzed vocal cord will often assume a lateralized position because of muscle atrophy. This lateralized position may also occur in high vagal paralysis when the ipsilateral cricothyroid muscle (extrinsic adductor) is denervated. D, During phonation in the late stages of low vagal paralysis, the atrophied left cord may assume such a lateralized position that the right innervated cord cannot possibly compensate. This configuration may also be seen with high vagal paralysis when the ipsilateral cricothyroid muscle has been denervated.
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Figure 4. Coronal section of the larynx. A, Muscle atrophy (arrow) has resulted in a flattened lateralized true vocal cord. B, Teflon paste injected into the paralyzed left vocal cord (arrow) reestablishes its midline position.
tion, such a configuration may result in occasional aspiration and gradually progressive hoarseness as the intact cord fails to fully compensate on adduction (Fig. 3, C and D). Effective treatment consists of vocal augmentation by the injection of Teflon paste into the paralyzed abducted cord (Fig. 4, A and B) resulting in ils more midline position. Absorbable Gelfoam paste may be used instead of Teflon if the paralysis is judged to be temporary. Vocal cord augmentation alone may be completely effective in the treatment of glottic incompetence caused by low vagal paralysis. 10
Bilateral Paralysis A bilateral low vagal lesion spares the pharynx, but paralyzes the larynx resulting in the paramedian position of both vocal cords. In such a case, deglutition is rarely impaired, aspiration being prevented by the closed position of the cords. For the same reason, voice quality may be near-normal. Breathing, however, may be turbulent. Treatment, while rarely emergent, may require tracheostomy. With the passage of time (greater than one year) the paralysis may cause sufficient bilateral cordal atrophy to result in less turbulent laryngeal air flow. However, as the atrophic vocal cords assume more lateral positions, vocal quality suffers and occasional aspiration may ensue. The early treatment of bilateral low vagal paralysis is tracheostomy. If the paralysis is considered to be permanent, that is, no functional retum in one year, two options can be pursued. First, unilateral
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Figure 5. Laryngeal reinnervation. A, A nerve-muscle pedicle from the anterior belly of the omohyoid muscle is prepared for laryngeal reinnervation. B, The nerve-muscle pedicle is sutured into the thyroarytenoideus muscle (intrinsic adductor). (From Tucker, H.M.: Human laryngeal reinnervation. Laryngoscope, 86:769-779, 1976, with permission.)
A
B
arytenoidectomy, resulting in the permanent lateralization of one paralyzed cord, will allow restoration of air flow through the larynx so that the tracheostomy tube can be removed. Is The greater the lateralization achieved, the greater the chance for aspiration and the greater the degree of hoarseness. For the same reason, bilateral arytenoidectomy is contraindicated because aspiration can be catastrophic . Second, reinnervation ofthe paralyzed vocal cord may successfully alleviate turbulent inspiration (Fig. 5). 17 By transferrring a nerve-muscle pedicle from the omohyoid muscle to the paralyzed posterior cricoarytenoid, phasic vocal cord abduction may be restored. In this case inspiratory activity of the omohyoid, mediated by the ansa cervicalis, is transferred to the paralyzed laryngeal abductor, the posterior cricoarytenoid muscle.
HIGH VAGAL PARALYSIS Whether unilateral or bilateral, high vagal paralysis (above nodose ganglion) is clearly catastrophic. Not only is the larynx paralyzed, but the
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Figure 6. Barium swallow. A, A lateral view shows characteristic aspiration due to high vagal paralysis. B, In high vagal paralysis, an anteroposterior view shows that the paralyzed vocal cord (small arrow) has assumed an open position. The atonic ballooned pyriform sinus (large glottis.arrow) allows swallowed matter to "spill over" into the trachea across an incompetent
pharyngeal muscles are also dennervated. Because high vagal paralysis involves motor impairment of both the superior and recurrent laryngeal nerves, a slightly abducted paralyzed cord results. The open position of the vocal cord invites aspiration (see Fig. 3, C and D). Meanwhile, simultaneous pharyngeal paralysis produces ballooning of the atonic constrictor muscles resulting in a reservoir of secretions capable of contaminating an incompetent larynx and soiling the lungs (Fig. 6). More importantly, the combined absence of sensory cues from pharynx, larynx, and upper trachea produces total impairment of the pharyngeal stage of deglutition resulting in further life-threatening aspiration pneumonitis (Fig. 7). The paralysis may be caused by a variety of intracranial or extracranial events: inflammatory, vascular, traumatic, or neoplastic. In most clinical situations, it is therefore not uncommon to encounter widespread cranial nerve involvement. Associated paralysis of the fifth, seventh, ninth, and twelfth cranial nerves represents a crippling threat to life.
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Figure 7. A, Massive aspiration pneumonitis may be life-threatening. B, A follow-up chest roentgenogram demonstrates an evolving lung abscess (arrows).
The overriding therapeutic concern is the prevention of aspiration. Treatment must be prompt and effective in order to be life-saving. A trial and error approach to treatment is to be condemned. Patients may be divided into two broad therapeutic categories of unilateral paralysis or bilateral paralysis.
Unilateral Paralysis Prompt treatment consists of the following measures in combination: 1. A cuffed tracheostomy allows a temporary means of averting aspiration while providing adequate pulmonary toilet. Long-term cuffed tracheostomy invites stomal infection, 13 tracheal stenosis, 1 esophageal erosion, 2 and innominate artery fistulization. H For this reason, cuffed tracheostomy alone does not serve a useful long-term solution to this problem. Not infrequently the cuffed tube introduces catastrophic complications of its own. 2. Nasogastric tube feeding provides a temporary solution to impaired deglutition. However, long-term nasogastric feeding is not only uncomfortable but invites nasal, esophageal, and laryngeal injury. 3. Vocal cord augmentation by Teflon injection aids in transforming a lateralized cord into a more median position. 10 By aiding glottic closure during deglutition, gross tracheal contamination is minimized. However, vocal cord injection alone is never completely effective in correcting aspiration caused by high vagal paralysis.
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rynx
Cricopharyngeus muscle
Figure 8. A cricopharyngeal myotomy is performed by dividing the cricopharyngeus muscle extramucosally as close to the midline as possible.
4. To facilitate the passage of swallowed matter from oropharynx into the upper esophagus, a cricopharyngeal myotomy is essential (Fig. 8). 9 More importantly, myotomy minimizes stasis of saliva and secretions within the atonic paralyzed pharynx, secretions that can be aspirated if regurgitated. 5. Salivary production can be reduced by bilateral chorda tympani and tympanic nerve sections (Fig. 9). 16 Neurectomy is accomplished transtympanically under local anesthesia. The control of excessive saliva remains effective for months using this method, which interrupts pre-
Tympanic membrane
tympani nerve
Stapes Figure 9. Tympanic neurectomy. A transcanal tympanotomy allows ready access to the chorda tympani nerve and the tympanic nerve.
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ganglionic parasympathetic innervations to the submandibular (chorda tympani nerve) and parotid (tympanic nerve) salivary glands. Rarely in unilateral high vagal paralysis is any single procedure completely successful in preventing life-threatening respiratory complication owing~ to aspiration. However, when used in combination, sufficient rehabilitation can be expected, allowing one to remove both tracheostomy and nasogastric tubes in the satisfactory rehabilitation of deglutatory function.
Bilateral Paralysis Bilateral paralysis is incompatible with life. It is therefore mandatory that the extent of deficit be clearly defined. One cannot assume that measures successful in rehabilitating unilateral paralysis will suffice in averting massive aspiration and death. There is simply no place for vocal augmentation, cricopharyngeal myotomy, or transtympanic neurectomy. Rather, the following definitive surgical steps are urgently required.'1 1. Tracheostomy is performed to support respiration and provide pulmonary toilet. 2. Gastrostomy minimizes aspiration of food or fluid taken by mouth and is better tolerated than nasogastric feeding over long-term recovery. 3. Surgical closure of the larynx represents the single most important step in preventing aspiration in those patients who have suffered progressive loss of sphincteric and phonatory laryngeal control. Surgical closure of the larynx is theoretically reversible should sufficient neuromuscular function retum in any given patient. Numerous surgical techniques have been devised to separate the upper respiratory from digestive tract. Each technique has met with diverse success in the hands of most surgeons. The epiglottic flap operation of Rahal,~ Lindeman's diversion procedure,' and Montgomery's glottic closure 6 procedure have all been successful in the prevention of aspiration when reflex closure of the larynx is severely impaired. A variation of Montgomery's procedure greatly improves the chances of successful surgical closure and for this reason is described below.' 1 TECHNIQUE. A permanent tracheostomy is first performed over an endotracheal tube, after which general anesthesia may be delivered through the tracheostomy cannula for the remainder of the surgical procedure. A permanent tracheostomy ensures a safe airway if the tracheostomy tube is accidentally dislodged after surgical closure of the larynx has been accomplished. The larynx is approached through a horizontal skin incision made over the thyroid cartilage (Fig. lOA). Skin flaps are developed by subcutaneous dissection superficial to the sternohyoid muscle, avoiding, if possible, communication with the tracheostomy. The sternohyoid muscles are separated from each other in the midline, exposing the underlying thyroid notch and cricothyroid membrane. A vertical midline thyrotomy is created, using a No. 15 surgical blade if cartilage is un-ossified. If ossification has occurred, an oscillating saw is used to create the vertical incision through the thyroid cartilage (Fig. lOB). Before the lumen of the larynx is entered, the cricothyroid mem-
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Figure 10. Surgical closure of the larynx. 3 •14 A, A horizontal skin incision is made over the thyroid cartilage. B, The thyroid cartilage is opened vertically (arrows). C, The thyroid alae are retracted laterally to expose the true and false cords as well as the laryngeal ventricles. D, The free edges of the fulse cords are approximated in a first layer of closure. E, A superiorly based stemohyoid muscle pedicle is sutured into the midline posterior commissure (arrows). The free edges of the true vocal cords are then approximated in a third layer of closure. F, The thyroid alae are reapproximated and the skin is closed over a drain. (From Glenn, W.L., Haak, B., Sasaki, C.T., and Kirchner, j.A.: Characteristics in management of respiratory complications accompanying pathologic lesions of the brain stem. Ann. Surg., in press, 1980, with permission.)
brane is opened horizontally for a short distance (1 em) in order to visualize the anterior commissure of the larynx from below as the laryngeal airway is gradually opened sagittally. By using small skin hooks, the thyroid alae may be retracted allowing accurate division of the anterior commissure in the midline under direct vision (Fig. 10C). A self-retaining retractor can be inserted for continued exposure. For purposes of hemostasis, lidocaine 1 per cent with epinephrine 1: 100,000 is infiltrated into both true and false cords. Mucous membrane between the free edges of the false and true cords is resected. Mucous membrane is thereby removed from the glottis circumferentially. Specific attention must be paid to the removal of mucous membrane from both laryngeal ventricles and their superior saccular extensions. The free edges of both false and true cords are undermined, 1 to 2 mm, to facilitate their midline approximation. The glottis is then closed superiorly in a first layer by approximating denuded margins of both false cords with interrupted 4-0 Dexon suture, vertically mattressed (Fig. lOD). A superiorly-based sternohyoid muscle pedicle is then routed through the thyroid notch. It may be necessary to resect a margin of alar cartilage in order to widen the notch for the comfortable insertion of the muscle
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pedicle. The leading edge of the muscle flap is anchored to the interarytenoideus muscle in the midline posterior commissure before the free edges of the true vocal cords are approximated inferiorly with vertically mattressed 4-0 Dexon suture (Fig. lOE). A superiorly-based muscle pedicle avoids disrupting its attachment to the posterior commissure as the thyrohyoid complex repeatedly rises and falls with each swallow. In this regard, the viable muscle flap provides a dual function. On the one hand, it obliterates a large dead space created by the apposition of the ventricular concavities. On the other hand, three rather than two layers of closure are accomplished without tension. The thyroid alae are re-approximated with several absorbable sutures and the wound closed over a drain (Fig. lOF). Surgical closure of the larynx, while theoretically reversible, should be reserved only for those patients in whom aspiration is clearly lifethreatening. Those who suffer bilateral high vagal paralysis clearly fall into this category. Those patients with unilateral high vagal paralysis may require such a procedure if the combination of recommended conservative measures fails to control aspiration. The associated involvement of cranial nerves five, seven, nine, or twelve increases the severity of pharyngeal dysfunction in unilateral high vagal paralysis, thus increasing the likelihood for surgical closure of the larynx.
SUMMARY Widespread neurologic dysfunction of the pharynx and larynx is catastrophic. Aspiration pneumonitis, resulting from laryngeal and pharyngeal incompetence, is incompatible with life. In· such cases, surgical intervention plays a key role and may be clearly life-saving. A system of surgical management has evolved based upon an understanding of functional priorities, leading to an organized plan of treatment and rehabilitation.
REFERENCES J., and Pearson, F. G.: Incidence and pathogenesis of tracheal injury following cuffed tube tracheostomy with assisted ventilation: Analysis of a two-year prospective study. Ann. Surg., 173:249-263, 1971. Flege, J, B.: Tracheoesophageal fistula caused by cuffed tracheostomy tube. Ann. Surg., 166:153-156, 1967. Glenn, W. L., Haalk, B., Sasaki, C. T., et al.: Characteristics and management of respiratory complications accompanying pathologic lesions of the brainstem. Ann. Surg., in press. Habal, M. B., and Murray, j. E.: Surgical treatment of life-endangering chronic aspiration pneumonia. j. Plast. Reconstr. Surg., 49:305-311, 1972. Lindeman, R. C.: Diverting the paralyzed larynx: A reversible procedure for intractable aspiration. Laryngoscope, 85:157-180, 1975. Montgomery, W. W.: Surgery to prevent aspiration. Arch. Otolaryngol., 101:679-682, 1975. Negus, V. E.: Comparative Anatomy and Physiology of the Larynx. New York, Hafner Publishing Co., Inc., 1962, pp. 128-154, ch. 10. Reich, M. P., and Rosenkrantz, J, G.: Fistula between innominate artery and trachea. Arch. Surg., 96:401-402, 1968.
1. Andrews, M.
2. 3. 4. 5. 6. 7. 8.
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9. Rontal, M., and Rontal E.: Lesions of the vagus nerve: Diagnosis, treatment, and rehabilitation. Laryngoscope, 87:72-86, 1977. 10. Ron tal, E., Rontal, M., Morse, G., et al.: Vocal cord injection in the treatment of acute and chronic aspiration. Laryngoscope, 86:625-634, 1976. 11. Sasaki, C. T.: Physiology of the larynx. In English, G. (ed.): Otolaryngology. Hagerstown, Maryland, Harper and Row Publishers, Inc., 1977. 12. Sasaki, C. T., Fukuda, H., and Kirchner, J. A.: Laryngeal abductor activity in response to varying ventilatory resistance. Trans. Am. Acad. Ophthalmol. Otolaryngol., 77:403410, 1973. 13. Sasaki, C. T., Horiuchi, M., and Koss, N.: Tracheostomy-related subglottic stenosis: Bacteriologic pathogenesis. Laryngoscope, 89:857-865, 1979. 14. Sasaki, C. T., Milmoe, G., Yanagisawa, E., et al.: Surgical closure of the larynx for intractable aspiration. Arch. Otolaryngol., in press. 15. Sasaki, C. T., Suzuki, M., Horiuchi, M., et al.: The effect of tracheostomy on reflex laryngeal closure. Laryngoscope, 87:1428-1433, 1977. 16. Townsend, G., Morimoto, A. M., and Kralemann, H.: Management of sialorrhea by transtympanic neurectomy. Mayo Clin. Proc., 48:776-779, 1973. 17. Tucker, H. M.: Human laryngeal reinnervation. Laryngoscope, 86:769-779, 1976. 18. Woodman, D. G., and Pennington, C.: Bilateral abductor paralysis. Ann. Otol. Rhino!. Laryngol., 85:437-440, 1976.
Department of Surgery Yale University School of Medicine 333 Cedar Street New Haven, Connecticut 06510