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Paraganglioma surgery
PARAGANGLIOMAS OF THE HEAD AND NECK
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PARAGANGLIOMA SURGERY Complications and Treatment Joseph C. Sniezek, MD, Alain N. Sabri, MD, and James L. Netterville, MD
The vascular nature of paragangliomas and their intimate anatomic association with the carotid artery, jugular vein, sympathetic chain, and lower cranial nerves (IX-XII)make the surgical extirpation of these lesions challenging. Although paragangliomas usually are benign lesions, they grow by local extension and can surround or invade vital neurovascular structures, leading to preoperative paralysis of the lower cranial nerves and significant involvement of the great vessels. The surgical treatment of paragangliomas often entails the sacrifice of important anatomic structures to achieve a complete excision of the tumor. Unintentional damage to these structures also may occur during the dissection of a vascular and infiltrative tumor. The lower cranial nerves control the function of the upper aerodigestive tract. The loss or injury of these nerves leads to alterations in swallowing, speech, and airway protection. Although most patients compensate for damage to one of the lower cranial nerves, greater difficulties arise when multiple cranial nerves are injured. The elderly have a more difficult time compensating for the loss of multiple cranial nerve^.^ The identification and protection of these vital neurovascular structures during the surgical procedure is important. Successful skull base surgery requires the formation of a skull base surgical team, consisting of a neurotologist, skull base surgeon, vascular surgeon, and neuroradiologist. The postoperative rehabilitation of cranial nerve deficits ensures the patient can breathe, speak, and swallow well after the removal of the paraganglioma. Successful rehabilitation usually requires the assistance of a rehabilitative team with aggressive speech, swallowing, and physical therapy. From the Department of Otolaryngology, Vanderbilt University Medical Center, Nashville, Tennessee
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During paraganglioma surgery, cranial nerves IX through XII, the carotid artery, and the sympathetic chain are at risk (Fig. 1). Because most paragangliomas of the head and neck can damage multiple neurovascular structures, each anatomic entity is discussed individually in this article, and techniques for the identification and preservation of these structures during the dissection of paragangliomas are detailed. The rehabilitation of functional deficits also is stressed. GLOSSOPHARYNGEAL NERVE (IX)
The motor function of the glossopharyngeal nerve is limited because it supplies only the stylopharyngeus muscle, which elevates the pharynx
Figure 1. Anatomy of the skull base.
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during swallowing and speech. The isolated loss, of this muscle has little effect on swallowing but its loss, combined with damage to the vagus nerve, makes swallowing rehabilitation more difficult. The parasympathetic fibers that control the secretion of the parotid gland also travel with the glossopharyngeal nerve. These fibers depart the glossopharyngeal nerve at the pars nervosa of the jugular foramen, and pass through the tympanic plexus in the middle ear on their way to the otic ganglion. Injury to these fibers may decrease parotid salivary flow temporarily, but a significant effect usually is not seen. The sensory component of cranial nerve IX provides afferent feedback from the base of the tongue and lateral pharyngeal wall. Loss of this sensory feedback results in significant alterations in the oropharyngeal phase of swallowing; food is delayed on the involved side. When this defect is combined with the loss of the vagus nerve or hypoglossal nerve, swallowing dysfunction can be severe. Because damage to cranial nerve IX can occur near the jugular foramen during the dissection of skull base paragangliomas, and the nerve often is thinned and ribbon-like at this location, a nerve graft is usually not possible. The glossopharyngeal nerve is also vulnerable during the dissection of parapharyngeal space paragangliomas because the nerve courses on the undersurface of the stylopharyngeus muscle. The only treatment for the loss of cranial nerve IX is aggressive swallowing therapy to direct the passage of food to the contralateral, sensate side of the pharynx. The glossopharyngeal nerve also provides feedback from the carotid body and sinus. The alterations of this feedback loop are discussed later in this article.
VAGUS NERVE (X) The vagus nerve is the most important lower cranial nerve. The isolated loss of this nerve affects the ability to speak, swallow, and protect the airway. When combined with the loss of other cranial nerves, the function of the upper aerodigestive tract usually is impaired significantly. The sensory component of the vagus nerve provides afferent information from the larynx and lateral pharyngeal wall. Two ganglia are found in the vagus nerve. The superior (i.e., jugular) ganglion is found in the jugular foramen, whereas the inferior (i.e., nodose) ganglion is located 1to 2 cm outside the foramen. The sensory fibers from the supraglottic larynx form the superior laryngeal nerve, which passes deep to the external and internal carotid arteries to join the vagus nerve at the level of the inferior ganglion. This nerve is at significant risk during the dissection of carotid body tumors, and is the cranial nerve most likely to be injured during the extirpation of these tumors.6 The isolated loss of the superior laryngeal nerve can cause swallowing difficulties. If the nerve is severed during the dissection of a paraganglioma, an attempt at reanastomosis or nerve grafting is worthwhile. With swallowing therapy, however, compensation almost always occurs for this sensory loss.
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Vagal paragangliomas pose a risk to the vagus nerve. In the authors' seriesof 40 patients with vagal paragangliomas treated by surgical excision, 37 patients required sacrifice of the vagus nerve. The remaining three patients suffered permanent vocal cord paralysis on the side of the lesion. The visceral sensory and motor components of the vagus nerve provide sensory feedback and parasympathetic function to the trachea, esophagus, and abdominal viscera. The most common side effect of the loss of these fibers is a decrease in gastroesophageal motility. This effect is seen more commonly when bilateral vagal injury occurs, but can result after only unilateral damage to the vagus. Gastricemptying may be delayed, and significant gastroesophageal reflux may occur in the early postoperative period. Treatment consists of prokinetic agents, such as metoclopramide HCI (Reglan), along with aggressive antireflux medications, such as H2blockers or proton-pump inhibitors. These symptoms tend to improve gradually with time. The motor component of cranial nerve X provides motor function to the palate, pharynx, and larynx, except for the tensor veli palatini and stylopharyngeus muscles. These fibers leave the vagus nerve in three main branches. The pharyngeal branch departs the vagus at the nodose ganglion, passes between the internal and external carotid arteries, and enters the pharynx at the upper border of the middle constrictor. Damage to this branch causes unilateral palatal and pharyngeal paralysis. Velopharyngeal incompetence results from the palatal paralysis, which causes nasal regurgitation of food and bothersome nasal speech. The authors find that a simple procedure consisting of a unilateral palatal adhesion compensates well for the paralysis and usually causes significantly decreased nasal regurgitation and nasal speech.' This procedure usually is performed several months after the removal of the paraganglioma to allow time for an injured but intact nerve to recover. Preoperative assessmentby flexible nasopharyngoscopy confirms the diagnosis of velopharyngeal incompetenceby demonstrating only unilateral closure of the nasopharynx.8With the patient under general anesthesia, a Dingman mouth gag is placed, and the paralyzed hemipalate and posterior pharyngeal wall at the lower border of the residual adenoid pad are infiltrated with epinephrine. An incision is made in the natural palatal crease on the paralyzed side (Fig. 2). After exposing the posterior pharyngeal wall, an incision is made through the posterior pharyngeal mucosa down to the prevertebral fascia. The nasopharyngeal surface of the palate is sutured to the posterior pharyngeal wall with multiple deep mattress sutures, and the oral surface of the palate is closed primarily (Fig. 3). The patient is placed on a liquid diet postoperatively, and usually is discharged on the first postoperative day. No significant complications have occurred after this procedure. Wound dehiscence occurred in one patient, but it eventually scarred and produced an excellent adhesion with improved velopharyngeal incompetence. As with other palatal flap procedures, postoperative sleep apnea was a theoretic consideration, but no patient has complained of any snoring or sleep apnea after a palatal adhesion procedure." The ideal timing of the
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Figure 2. Incision through soft palate at natural crease.
procedure also has been debated. Although the authors performed a palatal adhesion at the time of the initial extirpation of a paraganglioma, they prefer to wait several months because the delay allows time for an injured but intact nerve to recover, and the performance of an additional procedure at the end of an already lengthy extirpative procedure probably is not
Figure 3. Adhesion of soft palate to posterior pharyngeal wall.
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justified, because the early postoperative velopharyngeal incompetence does not hamper swallowing rehabilitation significantly. Unilateral paralysis of the pharyngeal constrictor muscles also occurs when the vagus nerve is injured. As a result, when the food bolus passes into the oropharynx, the paralyzed side of the pharynx dilates laterally and forms a pseudopocket that detains the bolus. Instead of advancing the bolus, the contralateral normal side of the pharynx pushes the bolus into this pseudopocket, and the normal timing of the swallow is interrupted. When the larynx opens, the food bolus is still in the hypopharynx instead of in the esophagus, and aspiration results. The treatment for this deficit is a head-positioningtechnique that physically obliterates the paralyzed side of the pharynx and preferentially directs the food bolus into the normal side of the pharynx. The most important motor function of the vagus nerve is to provide innervation to the intrinsic musculature of the larynx. Paralysis of the true vocal cord results from injury to the vagus during paraganglioma surgery. This paralysis leads to poor voice quality, swallowing difficulties, and the risk for aspiration. Although some investigators recommend a tracheotomy be performed if the vagus nerve has been injured during the extirpation of a paraganglioma, the authors find that this procedure is usually unnecessary? Because the degree of swallowing difficulty and risk for aspiration is generally not predictable and the optimal treatment must be individualized to each patient, it is generally wise to wait until the postoperativeperiod to devise the optimal rehabilitative strategy. If the patient has only mild difficulty with swallowing that is unresponsive to swallowing therapy, or if there is a chance for recovery of vagus nerve function, a temporizing injection of Gelfoam or fat into the vocal fold may be performed. If the vagus nerve has been resected or if the return of function is unlikely, a silastic medialization of the true vocal cord and arytenoid adduction suture probably is necessary. The authors' techniques for silastic medialization and arytenoid adduction have been described!, 7, lo The timing of the medialization procedure is controversial. Although the authors perform many medialization procedures at the time of tumor excision (primary medialization),they find that performing the medialization in a secondary procedure has several advantages. It is difficult to predict how much difficulty each patient will have compensating for a vocal cord paralysis. Some patients compensate well, and achieve a satisfactoryvoice and good airway protection without the need for an adjunctive medialization procedure. Other patients are debilitated severely and suffer from an unsatisfactory voice and severe aspiration when a vocal cord is paralyzed. The authors also find that they can obtain more predictable and satisfactory results when the medialization is performed with the patient awake. If the procedure is performed at the time of the tumor resection, the patient is under general anesthesia. The amount of medialization that is required cannot be predicted preoperatively,nor can the potential need for an arytenoid adduction suture be determined. The authors try to predict the required size of a silastic implant by obtaining a preoperative CT scan of the larynx and performing anatomic measurements. The CT
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scan measurements, however, do not correlate with the true size of the required implant. With the patient awake, the ideal position of the vocal cord and the potential need for an arytenoid adduction suture may be ascertained. The arytenoid adduction suture plays an important role in the rehabilitation of patients with postoperative vocal cord paralysis. When the authors treated patients with postoperative vocal cord paralysis with only silastic medialization before the use of the arytenoid adduction suture, only approximately 40% of the patients developed an acceptable result in terms of voice quality. Most patients improve further with the addition of the arytenoid adduction suture. Similar to the results with silastic medialization, it is not wise to perform an arytenoid adduction suture under general anesthesia. A minor adjustment of the arytenoid creates major changes in the quality of voice and patency of the airway. The subtle nature of this procedure requires an awake and cooperative patient and precludes a general anesthetic. A current treatment regimen for the loss of cranial nerve X during lateral skull base surgery is to administer Gelfoam injections at 2 to 4 days after the procedure with the medialization laryngoplasty-arytenoid adduction to follow in 8 weeks under local anesthesia. It is possible to perform the medialization laryngoplasty-arytenoid adduction in the early postoperative period if the patient can tolerate it and there is only minimal laryngeal edema. The authors perform this early medialization laryngoplasty-arytenoid adduction only in patients not from the United States, who cannot return in 8 weeks for the regularly scheduled procedure. Bilateral vocal cord paralysis should be an unlikely complication of paraganglioma surgery. The patient should be examined carefully preoperatively to rule out a contralateral vocal cord paralysis. If a contralateral vocal cord paralysis exists, extreme care should be taken to protect the ipsilateral vagus nerve during the procedure, and the patient should be counseled that a tracheotomy probably will be necessary if the ipsilateral vagus nerve is injured and bilateral vocal cord paralysis results. Patients with bilateral paragangliomas should be managed to avoid bilateral vocal cord paralysis. Observation, radiotherapy, or staged surgical procedures may be necessary to preclude the complication of bilateral vocal cord paralysis. SPINAL ACCESSORY NERVE (XI) The spinal accessory nerve supplies motor control to the sternocleidomastoid and trapezius muscles. It exits the skull base through the pars nervosa of the jugular foramen, and passes laterally over the internal jugular vein to pierce the sternocleidomastoid on its way to the trapezius muscle. Cranial nerve XI may be injured during the dissection of paragangliomas that involve the skull base near the jugular foramen, such as glomus jugulare or vagal tumors. The loss of sternocleidomastoid function
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usually is not noticed, but denervation of the trapezius muscle causes severe shoulder dysfunction. Shoulder drop and severe pain may occur because of the loss of trapezius muscle function. If the nerve is injured, an attempt at grafting should be made. If grafting is impossible, a rehabilitative program of shoulder-strengthening exercises should be started to strengthen the levator, scalene, and rhomboid muscles. Physical therapy improves shoulder stability and decreases pain.
HYPOGLOSSAL NERVE (XII) Cranial nerve XI1provides motor control to all the extrinsic and intrinsic muscles of the tongue, except for the palatoglossus. The hypoglossal nerve exits the skull base through the hypoglossalforamen,which is medial to the jugular foramen. As it descends, it contacts the vagus near the nodose ganglion and shares fibers with cranial nerve X. A surgical separation of the nerves may cause paralysis of the vocal cord. The hypoglossal nerve may be affected by glomus tumors that involve the skull base, such as glomus jugulare or high vagal paragangliomas.The hypoglossal is also vulnerable during the dissection of carotid body tumors because it lies just superficia1 to the external carotid artery and often in the fascia overlying the superior aspect of the carotid body tumor (Fig. 4).When excising a carotid body tumor, it generally is advisable to identify the hypoglossal nerve and dissect
\ Figure 4. Relationshipof hypoglossal nerve to carotid body tumor.
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it superiorly to its abutment with the vagus nerve. The ansa hypoglossi must be divided from the twelfth nerve in most cases, but the hypoglossal nerve generally can be dissected off the surface of these tumors and be preserved carefully. To prevent vocal cord paralysis, the junction between the twelfth and tenth nerves should not be disturbed. If the hypoglossal nerve is cut, an attempt at reanastomosis probably is justified. Generally, however, most patients can compensate for unilateral tongue paralysis. At first, patients notice that food becomes lodged under the tongue on the paralyzed side. After rehabilitation with lingual exercises, however, the bolus can be placed onto the nonparalyzed side and the oral and preparatory phases of swallowing can normalize. Although some surgeons have recommended performing a Z-plasty of the dorsal tongue to encourage reinnervation of the paralyzed side by nerve fibers from the nonparalyzed side, no histologic evidence of reinnervation has been documented.
CERVICAL SYMPATHETIC CHAIN The sympathetic innervation to the head and neck originates in the upper thoracic segment of the spinal column, and ascends in the sympathetic chain to exit through one of its four ganglia. The superior cervical ganglion lies just deep to the internal carotid artery, and distributes fibers to the skin, pharyngeal plexus, and the sympathetic plexus that ascends along the internal carotid artery. Damage to this ganglion or the internal carotid artery plexus results in Horner 's syndrome, with ptosis, miosis, and anhidrosis. Although no treatment is necessary, the ptosis may be corrected by performing a levator-shortening procedure or resection of Muller's muscle. An additional complication occurs after damage to the cervical sympathetic chain because of the loss of sympathetic input to the parotid gland. When the cervical sympathetic chain is damaged or resected, often the case with high vagal paragangliomas, patients often complain of pain in the parotid area when they take the first bite of food. The authors have termed this phenomenon first bite syndrome. These patients describe a severe cramping phenomenon or spasm that begins with the first bite of food, especially the first meal of the day, and then generally subsides over the next several bites. The intensity of the pain is increased with strong sialogogues, such as tart or bitter foods. First bite syndrome most likely is caused by denervation supersensitivity of the sympathetic receptors that control the myoepithelial cells in the parotid gland. When oral intake occurs, parasympathetic neurotransmitters are released and crossstimulation of the sympathetic receptors cause a supramaximal response of the myoepithelial cells. This pain generally abates over time. Dietary modification with bland foods or oral carbamazepine (100-200 mg twice daily) may be necessary in the early postoperative period if oral intake is deterred because of the pain.
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BARORECEPTOR DYSFUNCTION
Baroreflexes originate in the great vessels of the neck, and function to prevent excessive fluctuations in blood pressure. The carotid body-sinus complex functions as a chemoreceptor and baroreceptor. The chemoreceptor function is mediated primarily through the carotid body, which is a cluster of paraganglionic tissue located along the medial aspect of the carotid bifurcation. The carotid body is sensitive to changes in Pao2, Paco2,pH, and blood flow.I2It participates in the regulation of ventilation by emitting a continual neutral output of neural regulatory information, which can be altered by changes in these chemical parameters. Ventilatory rate then can be increased or decreased appropriately based on the changed neural message from the carotid body. Baroreceptor functionprimarily is mediated through the carotid sinus, which is a grossly imperceptible structure composed of stretch receptors found in the adventitia of the carotid bulb. The sinus consists of two types of baroreceptors that function somewhat differently. Type I baroreceptors emit a low resting output that rises quickly when a pressure threshold is reached. Type I1baroreceptors demonstrate a continuous subthreshold discharge that changes to a pressure-sensitive discharge in response to a rise in the carotid bulb arterial pres~ure.~ Signals then are transferred through the glossopharyngeal nerve into the tractus solitarius in the medullary area of the brain stem. Secondary signals then inhibit the vasoconstrictorcenter of the medulla and excite the vagal center. The resultant parasympathetic response occurs through vasodilation of the veins and arterioles in the peripheral circulatory system and decreased heart rate and cardiac contractile strength. The net effect of stimulation of the baroreceptors is a decrease in systemic blood pressure. The glossopharyngeal nerve provides the major nerve supply to the carotid body and sinus. The small nerve rootlets of the carotid branch of cranial nerve IX depart from its main trunk about 1.5cm distal to the jugular foramen (Fig. 5). This carotid sinus nerve, also known as Hering’s nerve, receives a minor input from the vagus nerve and the cervical sympathetic trunk on its path to the carotid body and sinus. The nerve then runs deep to the intercarotid neural plexus and sends branches to the carotid body and sinus. The carotid sinus nerve is so small that it usually is not visualized during the dissection of paragangliomas involving this region. Functional deinnervation of the carotid body and sinus occurs with deep dissections in the region of the carotid bulb, necessary for the extirpation of carotid body tumors. Patients usually remain asymptomatic when unilateral damage to the baroreceptor system occurs. When bilateral baroreceptor damage occurs, baroreceptor dysfunction may result. Baroreceptor dysfunction may lead to marked fluctuations in blood pressure and a sustained increase in heart rate postoperatively. In time, some compensation occurs, but it is variable and unpredictable. Compensation occurs by one of two methods. Baroreceptor fibers in the aorta partially may compensate for the loss of carotid sinus function, or an intact but deinnervated carotid sinus
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Figure 5. Anatomy of the carotid body and carotid sinus.
eventually may experience some neural regrowth. Predicting the outcome or degree of compensation, however, is difficult. Generally, patients with smaller tumors seem to compensate earlier in the postoperative period. Even these patients, however, do not respond to stress normally. It seems logical that with the loss of baroreceptor negative feedback on blood pressure control, any abnormal stimulus would result in a rapid rise in blood pressure. A direct correlation between mild stimuli and blood pressure, however, is difficult to identify. Many episodes of postoperative hypertension in the authors’ patients who experience bilateral baroreceptor dysfunction do not have an inciting event. Generally, however, stress can lead to a hypertensive event, with systolic pressures sometimes rising over 200 mm Hg. Because of the potential for cerebrovascular events, patients who exhibit this dramatic increase in blood pressure after stressful events may benefit from anti-anxiety drugs, such as diazepam. Because bilateral baroreceptor dysfunction causes unopposed sympathetic outflow, selective treatment of baroreceptor dysfunction is targeted at controlling this excessive sympathetic drive. There are two main groups of sympathetic receptors on smooth muscle: a! and /I. When stimulated, a receptors produce an excitatory response, whereas /I receptor stimulation results in an inhibitory response. The a receptors also are divided into al and a2receptors. The stimulation of a1 receptors causes the contraction
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of smooth muscle in vessels and an increased contractility of the heart muscle. The a2 receptor acts as a negative feedback to the effects of al. Stimulation of the azreceptor causes inhibition of norephinephrine release from the presynaptic vesicles into the synaptic cleft. These receptors exist in the membrane of terminal nerve endings, and also are found in the brain, where they are associated with reduced sympathetic output from the CNS. Excessive hypertension is controlled in the early postoperative period with sodium nitroprusside. The main use of this drug is in patients with baroreceptor dysfunction,who have undergone vascular repair during the resection of a carotid body tumor. In the early postoperative period, the repair might not tolerate extreme swings in blood pressure. Within 3 to 4 days, the drug is tapered as the plasma levels of an oral antihypertensive, such as clonidine or phenoxybenzamine, become therapeutic. Clonidine is a selective a2 agonist. The stimulation of az receptors by clonidine causes a decreased release of norephinephrine into synaptic clefts. The central stimulation of a2receptors in the lower brain stem, however, is its major site of action. This stimulation inhibits the central sympathetic outflow, preventing the peripheral release of norepinephrine and stimulates parasympathetic outflow, which contributes to a slowing of the heart rate. Because of the combination of these effects, clonidine is an excellent choice for the treatment of patients with loss of baroreceptor function because it treats episodes of hypertension and the tachycardia that often develops postoperatively. Clonidine is well absorbed orally, and has a useful half-life of 12 hours. Initially, a dosage of 0.1 mg orally twice daily is used. This dosage may be increased until the desired response is obtained. The maximum daily dosage is 2.4 mg daily. Once the patient is stabilized, a transdermal patch delivery system may be used. The major adverse effects of clonidine are dry mouth and sedation. Phenoxybenzamine is an additional oral antihypertensive medication that may be helpful in the management of baroreceptor dysfunction. Phenoxybenzamine is an a-adrenergic antagonist that blocks al and az receptors. The blockage of al receptors on smooth muscles results in a progressive decrease in peripheral resistance and an increase in cardiac output. It has a more rapid onset than clonidine, so it may be used initially for hypertensive control as the levels of clonidine stabilize. CAROTID ARTERY
The identification and control of the carotid artery are critical steps in performing safe and successful paraganglioma surgery. The preoperative determination of the degree of involvement of the carotid artery by a paraganglioma is essential in formulating a surgical plan. Magnetic resonance imaging and MR angiography contribute valuable information regarding the need for vessel sacrifice to excise a paraganglioma completely. The patency of the internal carotid artery and adequacy of collateral
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cerebral circulation are also important issues that must be addressed. If there is the likelihood that the internal carotid artery will be resected during an extirpative procedure, consultations with a neuroradiologist and vascular surgeon are necessary. The ideal preoperative method to determine the ability of the patient to tolerate internal carotid artery resection or replacement is controversial. The most current methods are balloon occlusion and xenon perfusion brain scans.' With glomus jugulare and vagale tumors, the carotid artery generally can be preserved and the tumor carefully can be dissected away from the carotid after proximal and distal control of the artery have been achieved. Carotid body tumors may require alternative management of the artery because of the site of origin of the tumor at the carotid bifurcation. Most carotid body tumors can be dissected away from the carotid system with no damage to the internal or external carotid arteries. Netterville et a16report that in 20 tumors less than 5 cm in diameter, only two patients required venous replacement of the involved artery, whereas one patient required a venous patch graft. Tumors larger than 5 cm in diameter, however, generally require resection or replacement of the internal carotid artery to achieve total tumor extirpation. In the series by Netterville et al, five of nine patients with tumors 5 cm or larger underwent resection of the artery, whereas the other four required replacement of the artery with a venous or synthetic graft. The size of the carotid body tumor indicates whether or not a replacement or resection of the internal carotid artery is required. SUMMARY The surgical excision of paragangliomas of the head and neck is challenging. Paragangliomas are vascular in nature and are surrounded by vital neurovascular structures. The extirpation of these lesions requires careful preoperative evaluation, meticulous surgical technique, and the aid of experienced skull base surgical and rehabilitative teams. When surgery is performed in this way, complications can be minimized, and the function of the upper aerodigestive tract can be protected.
References 1. Brisman MH, Sen C, Catalan0 P: Results of surgery for head and neck tumors that involve the carotid artery at the skull base. J Neurosurg 86:787-792,1997 2. Conley SF, Gosain AK, Marks SM, et al: Identification and assessment of VPI. Am J Otolaryngol18:3846,1997 3. Hosemann W, Wigand ME, Herringer P, et al: Surgical reneurotization of the tongue after unilateral paralysis of the XI1 nerve. Eur Arch Otorhinolaryngol248:95-98,1990 4. Netterville JL, Jackson CG, Civantos FJ: Thyroplasty in the functional rehabilitation of neurotologic skull base surgery patients. Am J Otol14:460464,1993 5. Netterville JL, Jackson CG, Miller FR, et al: Vagal paraganglioma: A review of 46 patients treated during a 20-year period. Arch Otolaryngol Head Neck Surg 124:1133-1140,1998 6. Netterville JL, Reilly KM, Robertson D, et al: Carotid body tumors: A review of 30 patients with 46 tumors. Laryngoscope 105:115-126,1995
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7. Netterville JL, Stone RE, Lukens LS, et al: Silasticmedialization and arytenoid adduction: The Vanderbilt experience: A review of 116 phonosurgical procedures. Ann Otol Rhino1 Laryngol102:413-424,1993 8. Netterville JL, Vrabec JT Unilateral palatal adhesion for paralysis after high vagal injury. Arch Otolaryngol Head Neck Surg 120:21&221,1994 9. Seagard JL, van Brederode JMF, Dean C, et al: Firing characteristics of single-fiber carotid sinus baroreceptors. Circ Res 66:1499-1509,1990 10. Wanamaker JR, Netterville JL, Ossoff RH: Phonosurgery: Silastic medialization for unilateral vocal fold paralysis. Oper Tech Otolaryngol Head Neck Surg 4:207-217,1993 11. Witt PD, Marsh JL, Muntz HR, et al: Acute OSA as a complication of sphincter pharyngoplasty: Cleft palate. Craniofac J 33:183-189,1996 12. Zak FG, Lawson W (eds): The paraganglionic chemoreceptor system, physiology, pathology, and clinical medicine. New York, Springer-Verlag,1982, p 157
Address reprint requests to Joseph C. Sniezek, MD Department of Otolaryngology Tripler Army Medical Center MCHK-DSH 1 Jarrett White Road Honolulu, HI 96859-5000
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PARAGANGLIOMA SURGERY Complications and Treatment Joseph C. Sniezek, MD, Alain N. Sabri, MD, and James L. Netterville, MD
The vascular nature of paragangliomas and their intimate anatomic association with the carotid artery, jugular vein, sympathetic chain, and lower cranial nerves (IX-XII)make the surgical extirpation of these lesions challenging. Although paragangliomas usually are benign lesions, they grow by local extension and can surround or invade vital neurovascular structures, leading to preoperative paralysis of the lower cranial nerves and significant involvement of the great vessels. The surgical treatment of paragangliomas often entails the sacrifice of important anatomic structures to achieve a complete excision of the tumor. Unintentional damage to these structures also may occur during the dissection of a vascular and infiltrative tumor. The lower cranial nerves control the function of the upper aerodigestive tract. The loss or injury of these nerves leads to alterations in swallowing, speech, and airway protection. Although most patients compensate for damage to one of the lower cranial nerves, greater difficulties arise when multiple cranial nerves are injured. The elderly have a more difficult time compensating for the loss of multiple cranial nerve^.^ The identification and protection of these vital neurovascular structures during the surgical procedure is important. Successful skull base surgery requires the formation of a skull base surgical team, consisting of a neurotologist, skull base surgeon, vascular surgeon, and neuroradiologist. The postoperative rehabilitation of cranial nerve deficits ensures the patient can breathe, speak, and swallow well after the removal of the paraganglioma. Successful rehabilitation usually requires the assistance of a rehabilitative team with aggressive speech, swallowing, and physical therapy. From the Department of Otolaryngology, Vanderbilt University Medical Center, Nashville, Tennessee
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During paraganglioma surgery, cranial nerves IX through XII, the carotid artery, and the sympathetic chain are at risk (Fig. 1). Because most paragangliomas of the head and neck can damage multiple neurovascular structures, each anatomic entity is discussed individually in this article, and techniques for the identification and preservation of these structures during the dissection of paragangliomas are detailed. The rehabilitation of functional deficits also is stressed. GLOSSOPHARYNGEAL NERVE (IX)
The motor function of the glossopharyngeal nerve is limited because it supplies only the stylopharyngeus muscle, which elevates the pharynx
Figure 1. Anatomy of the skull base.
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during swallowing and speech. The isolated loss, of this muscle has little effect on swallowing but its loss, combined with damage to the vagus nerve, makes swallowing rehabilitation more difficult. The parasympathetic fibers that control the secretion of the parotid gland also travel with the glossopharyngeal nerve. These fibers depart the glossopharyngeal nerve at the pars nervosa of the jugular foramen, and pass through the tympanic plexus in the middle ear on their way to the otic ganglion. Injury to these fibers may decrease parotid salivary flow temporarily, but a significant effect usually is not seen. The sensory component of cranial nerve IX provides afferent feedback from the base of the tongue and lateral pharyngeal wall. Loss of this sensory feedback results in significant alterations in the oropharyngeal phase of swallowing; food is delayed on the involved side. When this defect is combined with the loss of the vagus nerve or hypoglossal nerve, swallowing dysfunction can be severe. Because damage to cranial nerve IX can occur near the jugular foramen during the dissection of skull base paragangliomas, and the nerve often is thinned and ribbon-like at this location, a nerve graft is usually not possible. The glossopharyngeal nerve is also vulnerable during the dissection of parapharyngeal space paragangliomas because the nerve courses on the undersurface of the stylopharyngeus muscle. The only treatment for the loss of cranial nerve IX is aggressive swallowing therapy to direct the passage of food to the contralateral, sensate side of the pharynx. The glossopharyngeal nerve also provides feedback from the carotid body and sinus. The alterations of this feedback loop are discussed later in this article.
VAGUS NERVE (X) The vagus nerve is the most important lower cranial nerve. The isolated loss of this nerve affects the ability to speak, swallow, and protect the airway. When combined with the loss of other cranial nerves, the function of the upper aerodigestive tract usually is impaired significantly. The sensory component of the vagus nerve provides afferent information from the larynx and lateral pharyngeal wall. Two ganglia are found in the vagus nerve. The superior (i.e., jugular) ganglion is found in the jugular foramen, whereas the inferior (i.e., nodose) ganglion is located 1to 2 cm outside the foramen. The sensory fibers from the supraglottic larynx form the superior laryngeal nerve, which passes deep to the external and internal carotid arteries to join the vagus nerve at the level of the inferior ganglion. This nerve is at significant risk during the dissection of carotid body tumors, and is the cranial nerve most likely to be injured during the extirpation of these tumors.6 The isolated loss of the superior laryngeal nerve can cause swallowing difficulties. If the nerve is severed during the dissection of a paraganglioma, an attempt at reanastomosis or nerve grafting is worthwhile. With swallowing therapy, however, compensation almost always occurs for this sensory loss.
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Vagal paragangliomas pose a risk to the vagus nerve. In the authors' seriesof 40 patients with vagal paragangliomas treated by surgical excision, 37 patients required sacrifice of the vagus nerve. The remaining three patients suffered permanent vocal cord paralysis on the side of the lesion. The visceral sensory and motor components of the vagus nerve provide sensory feedback and parasympathetic function to the trachea, esophagus, and abdominal viscera. The most common side effect of the loss of these fibers is a decrease in gastroesophageal motility. This effect is seen more commonly when bilateral vagal injury occurs, but can result after only unilateral damage to the vagus. Gastricemptying may be delayed, and significant gastroesophageal reflux may occur in the early postoperative period. Treatment consists of prokinetic agents, such as metoclopramide HCI (Reglan), along with aggressive antireflux medications, such as H2blockers or proton-pump inhibitors. These symptoms tend to improve gradually with time. The motor component of cranial nerve X provides motor function to the palate, pharynx, and larynx, except for the tensor veli palatini and stylopharyngeus muscles. These fibers leave the vagus nerve in three main branches. The pharyngeal branch departs the vagus at the nodose ganglion, passes between the internal and external carotid arteries, and enters the pharynx at the upper border of the middle constrictor. Damage to this branch causes unilateral palatal and pharyngeal paralysis. Velopharyngeal incompetence results from the palatal paralysis, which causes nasal regurgitation of food and bothersome nasal speech. The authors find that a simple procedure consisting of a unilateral palatal adhesion compensates well for the paralysis and usually causes significantly decreased nasal regurgitation and nasal speech.' This procedure usually is performed several months after the removal of the paraganglioma to allow time for an injured but intact nerve to recover. Preoperative assessmentby flexible nasopharyngoscopy confirms the diagnosis of velopharyngeal incompetenceby demonstrating only unilateral closure of the nasopharynx.8With the patient under general anesthesia, a Dingman mouth gag is placed, and the paralyzed hemipalate and posterior pharyngeal wall at the lower border of the residual adenoid pad are infiltrated with epinephrine. An incision is made in the natural palatal crease on the paralyzed side (Fig. 2). After exposing the posterior pharyngeal wall, an incision is made through the posterior pharyngeal mucosa down to the prevertebral fascia. The nasopharyngeal surface of the palate is sutured to the posterior pharyngeal wall with multiple deep mattress sutures, and the oral surface of the palate is closed primarily (Fig. 3). The patient is placed on a liquid diet postoperatively, and usually is discharged on the first postoperative day. No significant complications have occurred after this procedure. Wound dehiscence occurred in one patient, but it eventually scarred and produced an excellent adhesion with improved velopharyngeal incompetence. As with other palatal flap procedures, postoperative sleep apnea was a theoretic consideration, but no patient has complained of any snoring or sleep apnea after a palatal adhesion procedure." The ideal timing of the
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/-T-
Figure 2. Incision through soft palate at natural crease.
procedure also has been debated. Although the authors performed a palatal adhesion at the time of the initial extirpation of a paraganglioma, they prefer to wait several months because the delay allows time for an injured but intact nerve to recover, and the performance of an additional procedure at the end of an already lengthy extirpative procedure probably is not
Figure 3. Adhesion of soft palate to posterior pharyngeal wall.
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justified, because the early postoperative velopharyngeal incompetence does not hamper swallowing rehabilitation significantly. Unilateral paralysis of the pharyngeal constrictor muscles also occurs when the vagus nerve is injured. As a result, when the food bolus passes into the oropharynx, the paralyzed side of the pharynx dilates laterally and forms a pseudopocket that detains the bolus. Instead of advancing the bolus, the contralateral normal side of the pharynx pushes the bolus into this pseudopocket, and the normal timing of the swallow is interrupted. When the larynx opens, the food bolus is still in the hypopharynx instead of in the esophagus, and aspiration results. The treatment for this deficit is a head-positioningtechnique that physically obliterates the paralyzed side of the pharynx and preferentially directs the food bolus into the normal side of the pharynx. The most important motor function of the vagus nerve is to provide innervation to the intrinsic musculature of the larynx. Paralysis of the true vocal cord results from injury to the vagus during paraganglioma surgery. This paralysis leads to poor voice quality, swallowing difficulties, and the risk for aspiration. Although some investigators recommend a tracheotomy be performed if the vagus nerve has been injured during the extirpation of a paraganglioma, the authors find that this procedure is usually unnecessary? Because the degree of swallowing difficulty and risk for aspiration is generally not predictable and the optimal treatment must be individualized to each patient, it is generally wise to wait until the postoperativeperiod to devise the optimal rehabilitative strategy. If the patient has only mild difficulty with swallowing that is unresponsive to swallowing therapy, or if there is a chance for recovery of vagus nerve function, a temporizing injection of Gelfoam or fat into the vocal fold may be performed. If the vagus nerve has been resected or if the return of function is unlikely, a silastic medialization of the true vocal cord and arytenoid adduction suture probably is necessary. The authors' techniques for silastic medialization and arytenoid adduction have been described!, 7, lo The timing of the medialization procedure is controversial. Although the authors perform many medialization procedures at the time of tumor excision (primary medialization),they find that performing the medialization in a secondary procedure has several advantages. It is difficult to predict how much difficulty each patient will have compensating for a vocal cord paralysis. Some patients compensate well, and achieve a satisfactoryvoice and good airway protection without the need for an adjunctive medialization procedure. Other patients are debilitated severely and suffer from an unsatisfactory voice and severe aspiration when a vocal cord is paralyzed. The authors also find that they can obtain more predictable and satisfactory results when the medialization is performed with the patient awake. If the procedure is performed at the time of the tumor resection, the patient is under general anesthesia. The amount of medialization that is required cannot be predicted preoperatively,nor can the potential need for an arytenoid adduction suture be determined. The authors try to predict the required size of a silastic implant by obtaining a preoperative CT scan of the larynx and performing anatomic measurements. The CT
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scan measurements, however, do not correlate with the true size of the required implant. With the patient awake, the ideal position of the vocal cord and the potential need for an arytenoid adduction suture may be ascertained. The arytenoid adduction suture plays an important role in the rehabilitation of patients with postoperative vocal cord paralysis. When the authors treated patients with postoperative vocal cord paralysis with only silastic medialization before the use of the arytenoid adduction suture, only approximately 40% of the patients developed an acceptable result in terms of voice quality. Most patients improve further with the addition of the arytenoid adduction suture. Similar to the results with silastic medialization, it is not wise to perform an arytenoid adduction suture under general anesthesia. A minor adjustment of the arytenoid creates major changes in the quality of voice and patency of the airway. The subtle nature of this procedure requires an awake and cooperative patient and precludes a general anesthetic. A current treatment regimen for the loss of cranial nerve X during lateral skull base surgery is to administer Gelfoam injections at 2 to 4 days after the procedure with the medialization laryngoplasty-arytenoid adduction to follow in 8 weeks under local anesthesia. It is possible to perform the medialization laryngoplasty-arytenoid adduction in the early postoperative period if the patient can tolerate it and there is only minimal laryngeal edema. The authors perform this early medialization laryngoplasty-arytenoid adduction only in patients not from the United States, who cannot return in 8 weeks for the regularly scheduled procedure. Bilateral vocal cord paralysis should be an unlikely complication of paraganglioma surgery. The patient should be examined carefully preoperatively to rule out a contralateral vocal cord paralysis. If a contralateral vocal cord paralysis exists, extreme care should be taken to protect the ipsilateral vagus nerve during the procedure, and the patient should be counseled that a tracheotomy probably will be necessary if the ipsilateral vagus nerve is injured and bilateral vocal cord paralysis results. Patients with bilateral paragangliomas should be managed to avoid bilateral vocal cord paralysis. Observation, radiotherapy, or staged surgical procedures may be necessary to preclude the complication of bilateral vocal cord paralysis. SPINAL ACCESSORY NERVE (XI) The spinal accessory nerve supplies motor control to the sternocleidomastoid and trapezius muscles. It exits the skull base through the pars nervosa of the jugular foramen, and passes laterally over the internal jugular vein to pierce the sternocleidomastoid on its way to the trapezius muscle. Cranial nerve XI may be injured during the dissection of paragangliomas that involve the skull base near the jugular foramen, such as glomus jugulare or vagal tumors. The loss of sternocleidomastoid function
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usually is not noticed, but denervation of the trapezius muscle causes severe shoulder dysfunction. Shoulder drop and severe pain may occur because of the loss of trapezius muscle function. If the nerve is injured, an attempt at grafting should be made. If grafting is impossible, a rehabilitative program of shoulder-strengthening exercises should be started to strengthen the levator, scalene, and rhomboid muscles. Physical therapy improves shoulder stability and decreases pain.
HYPOGLOSSAL NERVE (XII) Cranial nerve XI1provides motor control to all the extrinsic and intrinsic muscles of the tongue, except for the palatoglossus. The hypoglossal nerve exits the skull base through the hypoglossalforamen,which is medial to the jugular foramen. As it descends, it contacts the vagus near the nodose ganglion and shares fibers with cranial nerve X. A surgical separation of the nerves may cause paralysis of the vocal cord. The hypoglossal nerve may be affected by glomus tumors that involve the skull base, such as glomus jugulare or high vagal paragangliomas.The hypoglossal is also vulnerable during the dissection of carotid body tumors because it lies just superficia1 to the external carotid artery and often in the fascia overlying the superior aspect of the carotid body tumor (Fig. 4).When excising a carotid body tumor, it generally is advisable to identify the hypoglossal nerve and dissect
\ Figure 4. Relationshipof hypoglossal nerve to carotid body tumor.
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it superiorly to its abutment with the vagus nerve. The ansa hypoglossi must be divided from the twelfth nerve in most cases, but the hypoglossal nerve generally can be dissected off the surface of these tumors and be preserved carefully. To prevent vocal cord paralysis, the junction between the twelfth and tenth nerves should not be disturbed. If the hypoglossal nerve is cut, an attempt at reanastomosis probably is justified. Generally, however, most patients can compensate for unilateral tongue paralysis. At first, patients notice that food becomes lodged under the tongue on the paralyzed side. After rehabilitation with lingual exercises, however, the bolus can be placed onto the nonparalyzed side and the oral and preparatory phases of swallowing can normalize. Although some surgeons have recommended performing a Z-plasty of the dorsal tongue to encourage reinnervation of the paralyzed side by nerve fibers from the nonparalyzed side, no histologic evidence of reinnervation has been documented.
CERVICAL SYMPATHETIC CHAIN The sympathetic innervation to the head and neck originates in the upper thoracic segment of the spinal column, and ascends in the sympathetic chain to exit through one of its four ganglia. The superior cervical ganglion lies just deep to the internal carotid artery, and distributes fibers to the skin, pharyngeal plexus, and the sympathetic plexus that ascends along the internal carotid artery. Damage to this ganglion or the internal carotid artery plexus results in Horner 's syndrome, with ptosis, miosis, and anhidrosis. Although no treatment is necessary, the ptosis may be corrected by performing a levator-shortening procedure or resection of Muller's muscle. An additional complication occurs after damage to the cervical sympathetic chain because of the loss of sympathetic input to the parotid gland. When the cervical sympathetic chain is damaged or resected, often the case with high vagal paragangliomas, patients often complain of pain in the parotid area when they take the first bite of food. The authors have termed this phenomenon first bite syndrome. These patients describe a severe cramping phenomenon or spasm that begins with the first bite of food, especially the first meal of the day, and then generally subsides over the next several bites. The intensity of the pain is increased with strong sialogogues, such as tart or bitter foods. First bite syndrome most likely is caused by denervation supersensitivity of the sympathetic receptors that control the myoepithelial cells in the parotid gland. When oral intake occurs, parasympathetic neurotransmitters are released and crossstimulation of the sympathetic receptors cause a supramaximal response of the myoepithelial cells. This pain generally abates over time. Dietary modification with bland foods or oral carbamazepine (100-200 mg twice daily) may be necessary in the early postoperative period if oral intake is deterred because of the pain.
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BARORECEPTOR DYSFUNCTION
Baroreflexes originate in the great vessels of the neck, and function to prevent excessive fluctuations in blood pressure. The carotid body-sinus complex functions as a chemoreceptor and baroreceptor. The chemoreceptor function is mediated primarily through the carotid body, which is a cluster of paraganglionic tissue located along the medial aspect of the carotid bifurcation. The carotid body is sensitive to changes in Pao2, Paco2,pH, and blood flow.I2It participates in the regulation of ventilation by emitting a continual neutral output of neural regulatory information, which can be altered by changes in these chemical parameters. Ventilatory rate then can be increased or decreased appropriately based on the changed neural message from the carotid body. Baroreceptor functionprimarily is mediated through the carotid sinus, which is a grossly imperceptible structure composed of stretch receptors found in the adventitia of the carotid bulb. The sinus consists of two types of baroreceptors that function somewhat differently. Type I baroreceptors emit a low resting output that rises quickly when a pressure threshold is reached. Type I1baroreceptors demonstrate a continuous subthreshold discharge that changes to a pressure-sensitive discharge in response to a rise in the carotid bulb arterial pres~ure.~ Signals then are transferred through the glossopharyngeal nerve into the tractus solitarius in the medullary area of the brain stem. Secondary signals then inhibit the vasoconstrictorcenter of the medulla and excite the vagal center. The resultant parasympathetic response occurs through vasodilation of the veins and arterioles in the peripheral circulatory system and decreased heart rate and cardiac contractile strength. The net effect of stimulation of the baroreceptors is a decrease in systemic blood pressure. The glossopharyngeal nerve provides the major nerve supply to the carotid body and sinus. The small nerve rootlets of the carotid branch of cranial nerve IX depart from its main trunk about 1.5cm distal to the jugular foramen (Fig. 5). This carotid sinus nerve, also known as Hering’s nerve, receives a minor input from the vagus nerve and the cervical sympathetic trunk on its path to the carotid body and sinus. The nerve then runs deep to the intercarotid neural plexus and sends branches to the carotid body and sinus. The carotid sinus nerve is so small that it usually is not visualized during the dissection of paragangliomas involving this region. Functional deinnervation of the carotid body and sinus occurs with deep dissections in the region of the carotid bulb, necessary for the extirpation of carotid body tumors. Patients usually remain asymptomatic when unilateral damage to the baroreceptor system occurs. When bilateral baroreceptor damage occurs, baroreceptor dysfunction may result. Baroreceptor dysfunction may lead to marked fluctuations in blood pressure and a sustained increase in heart rate postoperatively. In time, some compensation occurs, but it is variable and unpredictable. Compensation occurs by one of two methods. Baroreceptor fibers in the aorta partially may compensate for the loss of carotid sinus function, or an intact but deinnervated carotid sinus
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Figure 5. Anatomy of the carotid body and carotid sinus.
eventually may experience some neural regrowth. Predicting the outcome or degree of compensation, however, is difficult. Generally, patients with smaller tumors seem to compensate earlier in the postoperative period. Even these patients, however, do not respond to stress normally. It seems logical that with the loss of baroreceptor negative feedback on blood pressure control, any abnormal stimulus would result in a rapid rise in blood pressure. A direct correlation between mild stimuli and blood pressure, however, is difficult to identify. Many episodes of postoperative hypertension in the authors’ patients who experience bilateral baroreceptor dysfunction do not have an inciting event. Generally, however, stress can lead to a hypertensive event, with systolic pressures sometimes rising over 200 mm Hg. Because of the potential for cerebrovascular events, patients who exhibit this dramatic increase in blood pressure after stressful events may benefit from anti-anxiety drugs, such as diazepam. Because bilateral baroreceptor dysfunction causes unopposed sympathetic outflow, selective treatment of baroreceptor dysfunction is targeted at controlling this excessive sympathetic drive. There are two main groups of sympathetic receptors on smooth muscle: a! and /I. When stimulated, a receptors produce an excitatory response, whereas /I receptor stimulation results in an inhibitory response. The a receptors also are divided into al and a2receptors. The stimulation of a1 receptors causes the contraction
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of smooth muscle in vessels and an increased contractility of the heart muscle. The a2 receptor acts as a negative feedback to the effects of al. Stimulation of the azreceptor causes inhibition of norephinephrine release from the presynaptic vesicles into the synaptic cleft. These receptors exist in the membrane of terminal nerve endings, and also are found in the brain, where they are associated with reduced sympathetic output from the CNS. Excessive hypertension is controlled in the early postoperative period with sodium nitroprusside. The main use of this drug is in patients with baroreceptor dysfunction,who have undergone vascular repair during the resection of a carotid body tumor. In the early postoperative period, the repair might not tolerate extreme swings in blood pressure. Within 3 to 4 days, the drug is tapered as the plasma levels of an oral antihypertensive, such as clonidine or phenoxybenzamine, become therapeutic. Clonidine is a selective a2 agonist. The stimulation of az receptors by clonidine causes a decreased release of norephinephrine into synaptic clefts. The central stimulation of a2receptors in the lower brain stem, however, is its major site of action. This stimulation inhibits the central sympathetic outflow, preventing the peripheral release of norepinephrine and stimulates parasympathetic outflow, which contributes to a slowing of the heart rate. Because of the combination of these effects, clonidine is an excellent choice for the treatment of patients with loss of baroreceptor function because it treats episodes of hypertension and the tachycardia that often develops postoperatively. Clonidine is well absorbed orally, and has a useful half-life of 12 hours. Initially, a dosage of 0.1 mg orally twice daily is used. This dosage may be increased until the desired response is obtained. The maximum daily dosage is 2.4 mg daily. Once the patient is stabilized, a transdermal patch delivery system may be used. The major adverse effects of clonidine are dry mouth and sedation. Phenoxybenzamine is an additional oral antihypertensive medication that may be helpful in the management of baroreceptor dysfunction. Phenoxybenzamine is an a-adrenergic antagonist that blocks al and az receptors. The blockage of al receptors on smooth muscles results in a progressive decrease in peripheral resistance and an increase in cardiac output. It has a more rapid onset than clonidine, so it may be used initially for hypertensive control as the levels of clonidine stabilize. CAROTID ARTERY
The identification and control of the carotid artery are critical steps in performing safe and successful paraganglioma surgery. The preoperative determination of the degree of involvement of the carotid artery by a paraganglioma is essential in formulating a surgical plan. Magnetic resonance imaging and MR angiography contribute valuable information regarding the need for vessel sacrifice to excise a paraganglioma completely. The patency of the internal carotid artery and adequacy of collateral
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cerebral circulation are also important issues that must be addressed. If there is the likelihood that the internal carotid artery will be resected during an extirpative procedure, consultations with a neuroradiologist and vascular surgeon are necessary. The ideal preoperative method to determine the ability of the patient to tolerate internal carotid artery resection or replacement is controversial. The most current methods are balloon occlusion and xenon perfusion brain scans.' With glomus jugulare and vagale tumors, the carotid artery generally can be preserved and the tumor carefully can be dissected away from the carotid after proximal and distal control of the artery have been achieved. Carotid body tumors may require alternative management of the artery because of the site of origin of the tumor at the carotid bifurcation. Most carotid body tumors can be dissected away from the carotid system with no damage to the internal or external carotid arteries. Netterville et a16report that in 20 tumors less than 5 cm in diameter, only two patients required venous replacement of the involved artery, whereas one patient required a venous patch graft. Tumors larger than 5 cm in diameter, however, generally require resection or replacement of the internal carotid artery to achieve total tumor extirpation. In the series by Netterville et al, five of nine patients with tumors 5 cm or larger underwent resection of the artery, whereas the other four required replacement of the artery with a venous or synthetic graft. The size of the carotid body tumor indicates whether or not a replacement or resection of the internal carotid artery is required. SUMMARY The surgical excision of paragangliomas of the head and neck is challenging. Paragangliomas are vascular in nature and are surrounded by vital neurovascular structures. The extirpation of these lesions requires careful preoperative evaluation, meticulous surgical technique, and the aid of experienced skull base surgical and rehabilitative teams. When surgery is performed in this way, complications can be minimized, and the function of the upper aerodigestive tract can be protected.
References 1. Brisman MH, Sen C, Catalan0 P: Results of surgery for head and neck tumors that involve the carotid artery at the skull base. J Neurosurg 86:787-792,1997 2. Conley SF, Gosain AK, Marks SM, et al: Identification and assessment of VPI. Am J Otolaryngol18:3846,1997 3. Hosemann W, Wigand ME, Herringer P, et al: Surgical reneurotization of the tongue after unilateral paralysis of the XI1 nerve. Eur Arch Otorhinolaryngol248:95-98,1990 4. Netterville JL, Jackson CG, Civantos FJ: Thyroplasty in the functional rehabilitation of neurotologic skull base surgery patients. Am J Otol14:460464,1993 5. Netterville JL, Jackson CG, Miller FR, et al: Vagal paraganglioma: A review of 46 patients treated during a 20-year period. Arch Otolaryngol Head Neck Surg 124:1133-1140,1998 6. Netterville JL, Reilly KM, Robertson D, et al: Carotid body tumors: A review of 30 patients with 46 tumors. Laryngoscope 105:115-126,1995
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7. Netterville JL, Stone RE, Lukens LS, et al: Silasticmedialization and arytenoid adduction: The Vanderbilt experience: A review of 116 phonosurgical procedures. Ann Otol Rhino1 Laryngol102:413-424,1993 8. Netterville JL, Vrabec JT Unilateral palatal adhesion for paralysis after high vagal injury. Arch Otolaryngol Head Neck Surg 120:21&221,1994 9. Seagard JL, van Brederode JMF, Dean C, et al: Firing characteristics of single-fiber carotid sinus baroreceptors. Circ Res 66:1499-1509,1990 10. Wanamaker JR, Netterville JL, Ossoff RH: Phonosurgery: Silastic medialization for unilateral vocal fold paralysis. Oper Tech Otolaryngol Head Neck Surg 4:207-217,1993 11. Witt PD, Marsh JL, Muntz HR, et al: Acute OSA as a complication of sphincter pharyngoplasty: Cleft palate. Craniofac J 33:183-189,1996 12. Zak FG, Lawson W (eds): The paraganglionic chemoreceptor system, physiology, pathology, and clinical medicine. New York, Springer-Verlag,1982, p 157
Address reprint requests to Joseph C. Sniezek, MD Department of Otolaryngology Tripler Army Medical Center MCHK-DSH 1 Jarrett White Road Honolulu, HI 96859-5000