You are in: eMedicine Specialties > Otolaryngology and Facial Plastic Surgery > HEAD AND NECK ONCOLOGY Parapharyngeal Space TumorsArticle Last Updated: Oct 10, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Christine G Gourin, MD, Associate Professor, Department of Otolaryngology-Head and Neck Surgery, Chief, Division of Head and Neck Surgery, Medical College of Georgia Coauthor(s): Jonas T Johnson, MD, FACS, Professor and Chairman, Department of Otolaryngology, University of Pittsburgh School of Medicine; Professor, Department of Radiation Oncology, Professor, Department of Oral Maxillofacial Surgery, University of Pittsburgh School of Dental Medicine Editors: William M Lydiatt, MD, Associate Professor, Department of Otolaryngology-Head and Neck Surgery, University of Nebraska Medical Center; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Erik Kass, MD, Chief, Department of Clinical Otolaryngology, Associates in Otolaryngology of Northern VA; Christopher L Slack, MD, Otolaryngology-Facial Plastic Surgery, Private Practice, Associated Coastal ENT; Medical Director, Treasure Coast Sleep Disorders; Arlen D Meyers, MD, MBA, Professor, Department of Otolaryngology-Head and Neck Surgery, University of Colorado School of Medicine Author and Editor Disclosure Synonyms and related keywords: parapharyngeal space tumors, PPS, PPS tumor, upper pharynx, salivary gland neoplasm, prestyloid PPS, PPS lesion, PPS mass, prestyloid PPS lesion, pleomorphic adenoma, neurogenic lesion, paraganglioma, neurilemoma, schwannoma, tumor of the PPS, Schwann cells, neurofibroma, lymphoreticular lesion, poststyloid PPS lesion, poststyloid PPS INTRODUCTIONSection 2 of 12
  The parapharyngeal space (PPS) is a potential space lateral to the upper pharynx. EtiologyTumors of the PPS are uncommon, comprising less than 1% of all head and neck neoplasms. Both benign and malignant tumors may arise from any of the structures contained within the PPS. Of PPS tumors, 70-80% are benign, and 20-30% are malignant. Most PPS tumors are of salivary or neurogenic origin, although metastatic lesions; lymphoreticular lesions; and a variety of uncommon, miscellaneous lesions may arise in this location. Salivary gland neoplasms Neoplasms of salivary gland origin are located in the prestyloid PPS and account for 40-50% of PPS lesions. Salivary neoplasms may arise from the deep lobe of the parotid gland, ectopic salivary rests, or minor salivary glands of the lateral pharyngeal wall. The prevalence of neoplasms that arise within the deep lobe of the parotid gland is identical to that of those that arise in the superficial lobe. The most common prestyloid PPS lesion is pleomorphic adenoma, which represents 80-90% of salivary neoplasms in the PPS. Other benign salivary lesions, including Warthin tumors and oncocytomas, develop in the prestyloid PPS, as do malignant salivary lesions. Carcinoma ex pleomorphic adenoma and adenoid cystic carcinoma are the most frequently reported salivary malignancies of the PPS. Approximately 20% of all salivary lesions in the PPS are malignant. Common benign neoplasms include pleomorphic adenomas, monomorphic adenomas, and oncocytomas. Malignant neoplasms include adenoid cystic carcinomas, mucoepidermoid carcinomas, adenocarcinomas, and acinic cell carcinomas. Neurogenic lesions Neurogenic lesions are the most common tumors of the poststyloid PPS and account for 25-30% of PPS lesions. Neurilemomas are the most commonly encountered lesions, followed in frequency by paragangliomas and neurofibromas. Benign neurogenic lesions include neurilemoma (schwannoma), paraganglioma, neurofibroma, and ganglioneuroma. Malignant neurogenic lesions include malignant paraganglioma, neurofibrosarcoma, schwannosarcoma, and sympathicoblastoma. Neurilemomas, or schwannomas, are the most common neurogenic tumors and arise from any nerve surrounded by Schwann cells. In the PPS, the most common sites of origin are the vagus nerve and the sympathetic chain. Neurilemomas are slow growing and rarely cause palsy of the nerve of origin. They are encapsulated and histologically distinct from the nerve itself. Treatment is by enucleation, and preservation of the nerve of origin is usually possible; however, every patient should be cautioned about the possibility of postoperative paralysis. Neurofibromas, in contrast, are unencapsulated and intimately involved with the nerve of origin. Neurofibromas are often multiple. They may occur as a manifestation of the neurofibromatosis-1 (NF-1) syndrome, and, in these patients, the incidence of malignant transformation is increased. The nerve of origin usually has to be sacrificed during excision to ensure complete removal of the neoplasm. Paragangliomas are benign vascular neoplasms that arise from the paraganglia or extra-adrenal neural crest tissue. Paraganglia function as chemoreceptors and are associated with the carotid body, the jugular bulb, and the vagus nerve in the poststyloid PPS. Carotid body tumors, glomus jugulare, and glomus vagale are slow-growing paragangliomas that may not produce symptoms but do cause cranial nerve (CN) deficits, bone erosion, or intracranial extension as they increase in size. Approximately 2% of head and neck paragangliomas secrete catecholamines and may cause paroxysmal symptoms of catecholamine excess. Ten percent of paragangliomas are multiple and associated with paraganglioma at other locations. Ten percent of paragangliomas are hereditary, associated with a familial paraganglioma syndrome. In patients with hereditary paraganglioma, the prevalence of multicentricity is 35%. Hypertension and flushing are suggestive of either a secreting paraganglioma or an associated pheochromocytoma. If these symptoms are present, obtain urinary catecholamine levels. If the level of catecholamines is elevated, rule out a concomitant pheochromocytoma. Malignant transformation occurs in fewer than 10% of patients and is associated with rapid growth and development of metastatic disease. Lymphoreticular lesions Lymphoreticular lesions comprise 10-15% of PPS lesions. The lymphatics of the PPS may be involved primarily or secondarily by carcinoma, or they may be involved by infectious or inflammatory processes. Lymphoma is the most common malignant lymphoid process, but metastases from thyroid cancer, osteogenic sarcoma, squamous cell carcinoma, renal cell carcinoma, hypernephroma, and meningioma may also appear as PPS masses. The most common lymphoreticular lesions are lymphomas and metastases. Miscellaneous lesions
A variety of more unusual lesions may occur in the PPS, and these lesions comprise 10-15% of PPS masses. While the pathologist usually makes the final determination and diagnosis in such cases, recognizing that vascular lesions, such as hemangiomas, arteriovenous malformations, and internal carotid artery aneurysms, may occur in the PPS is important. Imaging studies of this region must be performed before attempting to obtain a biopsy or to excise the lesion. ClinicalClinical presentations may include the following:
Patients with tumors of the PPS most commonly present with a neck or oropharyngeal mass that does not cause symptoms detectable on physical examination because only the inferior and medial boundaries of the PPS are distensible (see Images 1-2). Tumors must be at least 2 cm in size before the bulge or abnormality is palpable. Often, a PPS lesion is discovered incidentally on routine physical examination. Unilateral eustachian tube dysfunction may result from significant medial extension, causing soft palate and nasopharyngeal swelling. Oropharyngeal bulging from an underlying PPS mass may cause significant displacement of the ipsilateral tonsil and may create the appearance of a primary tonsillar lesion. An ill-fitting denture may be the first symptom of a benign prestyloid lesion. Cranial neuropathies may result from enlargement of PPS lesions with compression of CN IX, X, XI, or XII, resulting in symptoms of hoarseness, dysarthria, and dysphagia. Horner syndrome (ie, ptosis, miosis, anhydrosis) has been described as resulting from pressure on the cervical sympathetic chain. With the exception of glomus vagale tumors, which have been associated in the literature with a high frequency of vagal paresis, most benign lesions of the PPS do not result in cranial nerve dysfunction. Pain is unusual with benign lesions and may be due to compression or hemorrhage into the lesion; however, pain and neurologic dysfunction are more often indicative of malignancy with infiltration of the skull base. Under these circumstances, CN VII may be involved. Trismus results from malignant invasion of the pterygoid musculature or involvement of the coronoid process of the mandible. Physical examination findings may suggest the origin and nature of the tumor. The most common physical finding is a painless oropharyngeal or neck mass. Pay careful attention to the oropharynx, tonsillar area, pharynx, and neck. Lesions arising from the deep lobe of the parotid may often be localized using bimanual palpation. Perform a full cranial nerve evaluation, including laryngoscopy, to test the motor and sensory innervation of the larynx. The vagus nerve is the most commonly involved cranial nerve, and vagal palsy is suggestive of either a paraganglioma or a malignancy. A neck mass that is pulsatile or has a thrill to auscultation suggests a vascular tumor, although carotid pulsations may be transmitted through an overlying mass and may be misleading. Paragangliomas are typically mobile in an anteroposterior direction but not in a vertical direction. Any patient with aural symptoms should undergo thorough audiologic evaluation as well as careful examination of the nasopharynx. INDICATIONSSection 3 of 12
Complete surgical excision is the mainstay of treatment and is recommended for both diagnostic and therapeutic purposes. The choice of surgical approach is dictated by the size of the tumor, its location, its relationship to the great vessels, and the suspicion of malignancy (see Surgical therapy). However, when surgery is contraindicated, alternatives to surgical therapy consist of observation or radiation therapy. RELEVANT ANATOMYSection 4 of 12
The PPS is a potential space lateral to the upper pharynx. The PPS is shaped like an inverted pyramid, extending from the skull base superiorly to the greater cornu of the hyoid bone inferiorly. The superior border of the PPS comprises a small area of the temporal and sphenoid bones, including the carotid canal, jugular foramen, and hypoglossal foramen. The PPS is limited anteriorly by the pterygomandibular raphe and pterygoid fascia and posteriorly by the cervical vertebrae and prevertebral muscles. The medial border of the PPS is the pharynx, and the lateral border is comprised of the ramus of the mandible, the medial pterygoid muscle, and the deep lobe of the parotid gland. Below the level of the mandible, the lateral boundary consists of the fascia overlying the posterior belly of the digastric muscle. The fascia from the styloid process to the tensor veli palatini divides the PPS into an anteromedial compartment (ie, prestyloid) and a posterolateral (ie, poststyloid) compartment. The prestyloid compartment contains the retromandibular portion of the deep lobe of the parotid gland, adipose tissue, and lymph nodes associated with the parotid gland. The poststyloid compartment contains the internal carotid artery, the internal jugular vein, CNs IX- XII, the sympathetic chain, and lymph nodes. These lymphatics receive afferent drainage from the oral cavity, oropharynx, paranasal sinuses, and thyroid. The distinction between the prestyloid and poststyloid space is more than just semantic because imaging studies can delineate between the 2 compartments and can assist in reaching the correct diagnosis preoperatively. CONTRAINDICATIONSSection 5 of 12
Surgery may be contraindicated and nonoperative management of PPS lesions considered for patients who are poor surgical candidates because of comorbid disease; those who are elderly; those in whom balloon occlusion fails; those who have unresectable lesions; and those who have benign, slow-growing tumors that would carry a significant risk of sacrifice of multiple cranial nerves if resected. The risks and benefits of surgery must be weighed in every case. WORKUPSection 6 of 12
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TREATMENTSection 7 of 12
Medical therapyNonoperative management of PPS lesions may be considered for patients who are poor surgical candidates because of comorbid disease; those who are elderly; those who fail balloon occlusion; those who have unresectable lesions; and those who have benign, slow-growing tumors that would carry a significant risk of sacrifice of multiple cranial nerves if resected. The risks and benefits of surgery must be weighed in every case. The risk of neurovascular complications, including cranial nerve injury and stroke, is increased in patients with paragangliomas and malignancies. Alternatives to surgical therapy consist of observation or radiation therapy. The risks of observation of benign tumors of the PPS are continued growth and malignant degeneration. Most prestyloid lesions can be removed with minimal morbidity. Observation is an acceptable alternative in patients in whom the risks of surgery are greater than not operating. This group consists of patients who are poor surgical candidates and patients who are elderly who have paragangliomas that do not produce symptoms. The mortality rate of untreated paragangliomas is less than 10% per year. Paragangliomas have a slow growth rate, estimated at 1.0-1.5 mm per year. In young patients who are asymptomatic, resection is recommended to avoid future loss of cranial nerve function as the tumor enlarges and to attempt to preserve the nerve of origin, which is far more likely to be successful with a small tumor than a larger one. Patients with partial cranial nerve deficits may initially be observed for 6-12 months to allow compensation to occur because functional compensation to a gradual loss of function is greater than sudden loss of function. Observation may be appropriate in patients with multiple paragangliomas who have preexisting contralateral cranial nerve deficits resulting from resection of a contralateral paraganglioma. Patients who are elderly do not fare as well following loss of CN function, and the natural course of a paraganglioma that is not producing symptoms may be associated with less morbidity than the morbidity associated with surgical resection. Radiation therapy can be used as a primary treatment modality in patients with paragangliomas who are poor surgical candidates and in the treatment of malignancies of the PPS. Radiation is not used for cure in the management of paragangliomas because the chief cells of paragangliomas are not radiosensitive, but it may be used to arrest or slow the growth of these lesions by causing endarteritis and fibrosis. Radiation therapy may be considered in those patients who are poor surgical candidates but who require treatment. These include symptomatic patients who are elderly, patients with internal carotid artery involvement in whom balloon occlusion fails, and patients with contralateral cranial nerve deficits in whom resection would result in a significant reduction in quality of life. Radiation therapy is used as an adjunct to surgery in patients with high-grade malignancies and when an oncologic or adequate resection margin cannot be obtained. Surgical therapySurgery is the mainstay of treatment for tumors of the PPS. The choice of surgical approach is dictated by the size of the tumor, its location, its relationship to the great vessels, and the suspicion of malignancy. Preoperative detailsSurgical morbidity can be minimized, or at least anticipated, with careful attention to preoperative evaluation so that both the surgeon and the patient are adequately prepared. The relationship of the tumor to the great vessels should be clearly delineated by preoperative imaging prior to planning resection, and patients should be counseled accordingly. Injury to the great vessels may result in uncontrollable bleeding, stroke, or death. Consult a vascular surgeon if a possibility of carotid resection requiring interposition grafting exists. Consulting a neurosurgeon may be appropriate for lesions involving the skull base. Counsel patients preoperatively about the possibility of loss of CN function and the effects on speech and swallowing. Injury or sacrifice of the vagus nerve alone may initially be managed expectantly to determine the effect on function and the final position of the vocal cord; this is done before proceeding with vocal cord medialization at a subsequent date because many patients compensate for an isolated deficit to a significant degree. Injury to both the vagus and the hypoglossal nerves can be expected to significantly impair swallowing function. In this circumstance, perform a cricopharyngeal myotomy and tracheostomy along with thyroplasty or Teflon injection concomitant with resection. If multiple CN deficits are anticipated, plans may be made for gastrostomy tube placement concomitant with resection if the patient's underlying status suggests that swallowing rehabilitation will be prolonged. Parotidectomy or mandibulotomy may need to be performed intraoperatively for improved exposure; this, as well as the possibility of tracheostomy if mandibulotomy is required, should be discussed with the patient. Preoperative embolization of vascular lesions may decrease intraoperative blood loss and may facilitate dissection of tumors at the skull base by causing retraction. Embolization is recommended for vascular lesions greater than 3 cm in which obvious feeding vessels can be identified on angiography. The use of embolization of paragangliomas is more controversial. Glomus vagale tumors rarely have a single blood supply, and resection is not associated with excessive blood loss. Carotid body tumors are supplied by the adventitia of the carotid rather than an obvious dominant feeding vessel. Embolization of a carotid body tumor may cause an inflammatory response that may obscure the subadventitial plane in which the tumor is dissected, increasing the risk of inadvertent carotid injury during resection. Embolization carries a risk of possible disruption of the blood supply to cranial nerves. If embolization is performed, it is performed within 24 hours prior to resection. Functioning tumors must be identified prior to resection because manipulation of a catecholamine-secreting tumor may cause intraoperative cardiac arrhythmias and hypertensive crisis. Preoperatively, institute alpha- and beta-adrenergic blockade with phenoxybenzamine and propranolol. Patients with multiple paragangliomas should undergo preoperative CT scanning of the adrenal glands to search for an associated pheochromocytoma. Intraoperative detailsTransoral approach The transoral approach has been described for the removal of small, benign neoplasms that originate in the prestyloid PPS and manifest as an oropharyngeal mass. The limitations of this approach are limited exposure, inability to visualize the great vessels, and an increased risk of facial nerve injury and tumor rupture. This approach is best suited for small, benign salivary tumors arising from minor salivary glands of the lateral pharyngeal wall. The transoral approach may be combined with an external approach to mobilize lesions with a significant oropharyngeal component. This is not the approach of choice for most lesions of the PPS. Transcervical approach Most authors prefer the transcervical approach as the method for removal of most poststyloid PPS tumors. A transverse incision at the level of the hyoid bone, 2 fingerbreadths below the mandible, is performed, and the carotid artery and internal jugular vein are identified. The digastric and stylohyoid muscles are retracted to allow access to the PPS. The submandibular gland can be retracted anteriorly for exposure, or it can be removed if necessary. Transcervical-transparotid approach For tumors arising from the deep lobe of the parotid, the transcervical approach can be combined with a transparotid approach by extending the incision superiorly as for parotidectomy. The facial nerve is identified and dissected, superficial parotidectomy is performed, and the deep lobe portion of the tumor is identified. The cervical incision allows access to the PPS component of the tumor. Transcervical-transmandibular approach The transcervical approach may be combined with mandibulotomy when better exposure is required. Such situations include very large tumors, vascular tumors with superior PPS extension, malignancies in which better exposure facilitates oncologic resection, and cases in which distal control of the carotid at the skull base is required. Mandibulotomy may be lateral or anterior (midline); an osteotomy anterior to the mental foramen is preferred for preservation of inferior alveolar nerve function. A lip-splitting incision is used to expose the mandible for midline osteotomy. After mandibulotomy, the incision is continued intraorally along the floor of the mouth back to the level of the tonsil pillar, and the mandible is retracted laterally. Tracheostomy is required for airway management in the immediate postoperative period. Infratemporal fossa approach A preauricular infratemporal fossa approach, as described by Fisch, can be used for malignant tumors involving the skull base or jugular foramen. This approach can be combined with frontotemporal craniotomy for removal of tumors with significant intracranial extension. A parotidectomy incision with cervical extension as described above is extended superiorly into a hemicoronal scalp incision. The temporalis muscle is elevated to expose the glenoid fossa, which is removed laterally. The temporomandibular joint can be displaced inferiorly, or the mandible condyle can be transected for improved exposure. Orbitozygomatic osteotomies are performed, and the infratemporal skull base and distal carotid are exposed. The facial nerve and vascular structures in the neck are identified through the cervical and preauricular approaches. Postoperative detailsAlways perform tracheostomy in conjunction with a transmandibular approach because significant upper airway edema may result from surgical manipulation of the oral cavity and oropharynx, causing obstruction. Bleeding may also cause airway obstruction because of the proximity of the PPS to the pharynx. Pay careful attention to hemostasis, and closely monitor all patients in the immediate postoperative period. All patients should be managed with closed suction drains because the dead space resulting from removal of PPS tumors may result in seroma formation. The risk of infection is greater if a transoral approach is used or combined with a cervical approach, and patients with oral contamination should be administered broad-spectrum perioperative antibiotics. Injury to the facial nerve may be temporary, from traction injury, or permanent, if the nerve is inadvertently sacrificed or injured. Eye protection with artificial tears, a moisture chamber, and Lacri-Lube ointment is required in these cases in order to prevent corneal exposure and abrasion. Cranial nerve palsies may result from removal of poststyloid PPS lesions. The vagus nerve is the most commonly injured nerve. An isolated unilateral vagal injury is usually well tolerated in the otherwise healthy patient, but a high vagal injury or a vagal injury combined with injury to CN IX and XII may result in significant problems with swallowing and aspiration. Patients should be carefully evaluated prior to the institution of oral feedings, and an alternate method of feeding (eg, nasogastric tube, gastric tube) should be instituted if necessary. Tracheostomy may be required for airway protection if multiple cranial nerve deficits result from resection. Cerebrospinal fluid leaks may occur after removal of tumors with jugular foramen or intracranial extension and result in meningitis. Pay careful attention to the dural closure after tumor removal. Fascia, fat, or muscle can be used to reinforce the closure if necessary. Lumbar drainage is instituted for small leaks; large leaks or those leaks refractory to lumbar drainage require reoperation. Follow-upAll patients with PPS masses should undergo routine follow-up, regardless of whether treatment is nonoperative or surgical. The frequency of follow-up examinations varies according to the tumor histology. Patients treated nonoperatively should be monitored for tumor growth and development or progression of symptoms. Following surgical excision, patients with benign histology are routinely monitored to rule out recurrence. Patients with malignancies require closer observation and monitoring. Adjunctive radiation therapy is appropriate for high-grade malignancies and in cases in which an adequate resection margin cannot be obtained. COMPLICATIONSSection 8 of 12
In addition to the postoperative complications discussed above, injury to the lingual and hypoglossal nerves may result from the transcervical approach when the submandibular triangle is entered. Warn patients preoperatively that injury to any or all branches of the facial nerve may result from nerve resection or traction injury and also that the ramus mandibularis branch is at risk during cervical approaches. Intraoperative transection of the facial nerve is best managed by performing nerve grafting at the time of surgery. Eye protection (as mentioned above) is required in the postoperative period; insertion of a gold weight can be performed at surgery or postoperatively. Facial reanimation procedures may be required for unrecognized facial nerve injury that does not resolve. Injury to CN IX, X, XI, and XII and the cervical sympathetic chain may result from surgery of the PPS. The risk of postoperative cranial nerve deficits ranges from 11-57%, with higher frequencies observed in studies of patients with proportionately greater numbers of malignancies or neurogenic lesions. An isolated nerve injury is usually well tolerated in an otherwise healthy patient. Isolated injury to the hypoglossal nerve does not usually significantly impair swallowing or speech function. Injury to the vagus nerve results in vocal cord paralysis, and if injury occurs above the level of the nodose ganglion, laryngeal sensation is also affected. Thyroplasty or Teflon injection may be performed intraoperatively or at a later date. The advantage to delaying vocal cord medialization procedures is that patients will often compensate, and the extent of medialization required can be better assessed after this has occurred. Patients who are elderly or patients with multiple CN deficits are expected to have greater difficulty with swallowing, and medialization as well as cricopharyngeal myotomy should be performed concomitant with resection. If swallowing rehabilitation is prolonged or unsuccessful, gastrostomy tube placement may be necessary. Patients with difficulty handling oral secretions may require tracheostomy for airway protection. Injury to the spinal accessory nerve results in weakness of the trapezius muscle, winging of the scapula, and adhesive capsulitis from disuse. This can be managed postoperatively by an active range of motion physical therapy program. When recognized intraoperatively, transection of CN XI is best managed by nerve grafting to achieve some recovery of function. Horner syndrome may result from injury to the cervical sympathetic chain. The resulting anhydrosis is managed symptomatically. Vascular complications are more common with removal of neurogenic or vascular lesions. The prevalence of intraoperative vascular injury and of perioperative stroke has been reported at 4% for poststyloid lesions. Morbidity may be reduced by avoidance of undue traction on the carotid artery, which may result in intimal tears. Primary repair or vein grafting should be performed for all vessel lacerations. Complications of mandibulotomy include infection, temporomandibular joint dysfunction, nonunion, plate extrusion, and tooth loss. When the osteotomy site is through dental sockets rather than between them, tooth loss is more common. Malocclusion may occur following mandibulectomy in dentate patients. Complications of radiation therapy, whether used primarily or as an adjunct to surgery, include xerostomia, tissue fibrosis, acceleration of dental caries, and osteoradionecrosis. Osteoradionecrosis is managed by debridement, antibiotics for secondary infection, and hyperbaric oxygen when it is available. Dental caries may be prevented by the use of fluoride trays. Teeth in poor condition should be extracted. Xerostomia is a life-long problem, but it can be alleviated by treatment with pilocarpine (Salagen, 5 mg PO tid) or artificial saliva applications. OUTCOME AND PROGNOSISSection 9 of 12
The recurrence rate of benign PPS neoplasms following surgical extirpation ranges from 0-9%. Paragangliomas recur in approximately 5% of cases, and because 10% are multicentric, the risk of developing a second tumor remains. Patients with a familial paraganglioma syndrome have a 35% risk of multicentricity. In addition, patients with paragangliomas who are being treated nonoperatively must be alerted to the risk of malignant degeneration, which is approximately 10% and usually associated with rapid growth. Thus, patients with paragangliomas require lifetime follow-up. Malignant tumors of the PPS have a much higher rate of recurrence (25-77%), depending on histology, extent of resection, and duration of follow-up. Postoperative radiation therapy for PPS malignancies is recommended to prevent recurrence; however, because of the relative scarcity of these lesions, no large series are available to demonstrate a survival benefit. FUTURE AND CONTROVERSIESSection 10 of 12
In the future, genetic screening of patients at risk for hereditary paragangliomas should be possible. The gene responsible for transmission of hereditary paragangliomas, termed PGL, has been mapped to chromosome 11. In large pedigree analyses, loci at 11q23 (PGL1) have been shown to be most commonly associated with a mutant PGL gene, which is inherited from carrier fathers in an autosomal dominant fashion subject to maternal imprinting. No affected offspring from affected mothers are documented. Genetic manipulation of a mutant PGL gene may prevent or interrupt the development of these tumors. MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
Parapharyngeal Space Tumors excerpt Article Last Updated: Oct 10, 2007 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
