- Email: [email protected]
Intraparotid facial nerve schwannoma: diagnosis and management
Intraparotid facial nerve schwannoma: Diagnosis and management ROBERT J. CAUGHEY,
BS,
MARK MAY,
MD,
and BARRY M. SCHAITKIN,
OBJECTIVE: Facial nerve schwannomas are rare neoplasms that present a challenge in diagnosis and management. We sought to gain insight into the clinical presentation and its implications in management. STUDY DESIGN AND SETTING: A group of patients diagnosed with schwannoma was reviewed, with focus on tumor arising in the intraparotid region of the facial nerve. The patient population consisted of 3722 patients evaluated retrospectively over 38 years at the Shadyside Facial Paralysis Center, a tertiary referral center. From this population, 29 patients (18 women and 11 men) with the diagnosis of schwannoma were selected for review. RESULTS: Twenty-nine patients had facial nerve schwannoma. The average age at diagnosis was 44 years (range, 7 to 78 years). Eight patients had intraparotid involvement, with 5 having a palpable mass in the parotid. The duration of symptoms averaged 8.4 years overall, with intraparotid involvement averaging 10.9 years. The 8 intraparotid schwannomas had a mean House-Brackmann grade of 1.5/6 at initial presentation. Postoperative facial nerve function was only 4.4/6 for resected intraparotid schwannomas. CONCLUSIONS: Intraparotid facial nerve schwannomas are slow growing tumors, which are usually asymptomatic but can be painful. Schwannoma should be suspected if the facial nerve cannot be found intraoperatively or if the tumor is intimately associated with the facial nerve. In cases where schwannoma is suspected, biopsy is recommended, while complete resection is postponed to obtain imaging studies to evaluate the extent of
From the Department of Otolaryngology–Head and Neck Surgery, Shadyside Hospital Facial Paralysis Center. Presented at the Ninth International Facial Nerve Symposium, August 1, 2001, San Francisco, CA. Reprint requests: Barry M. Schaitkin, MD, University of Pittsburgh Medical Center–Shadyside Hospital, 5200 Centre Ave, Suite 211, Pittsburgh, PA 15232; e-mail, [email protected]. 0194-5998/$30.00 Copyright © 2004 by the American Academy of Otolaryngology–Head and Neck Surgery Foundation, Inc. doi:10.1016/j.otohns.2003.12.011 586
MD,
Pittsburgh, Pennsylvania
disease and to discuss possible outcomes with the patient. SIGNIFICANCE: This article provides guidance for the appropriate management of intraparotid facial nerve schwannoma. (Otolaryngol Head Neck Surg 2004;130:586-92.)
S chwannomas
are benign, slow growing neoplasms that arise from the cells that ensheath the axons of the peripheral, cranial, and autonomic nervous systems. These tumors are usually solitary and well encapsulated and tend to splay the nerve of origin.1 Although approximately one third of all of these lesions occur in the head and neck, facial nerve schwannomas are rare.2 Since Schmidt first described a facial neurilemmoma or schwannoma in 1930, facial nerve schwannomas have been well documented in the medical literature, with more than 300 reported cases, including several large series.3-5 Schwannomas have been described in every portion of the facial nerve; however, most of the cases involve the intratemporal portion of the facial nerve, with fewer than 60 intraparotid schwannomas appearing in the literature.6 The classic presentation of intratemporal facial nerve schwannoma has been most frequently characterized as progressive facial weakness or paralysis.4,5 The diagnosis and management of intratemporal lesions have also received much attention in the literature.7,8 Because of the rarity of facial nerve schwannomas arising in the parotid gland, schwannomas in this location have not been well described and few practitioners are versed in their clinical management. Most benign parotid tumors, such as pleomorphic adenoma, present as an asymptomatic mass. Intraparotid facial nerve schwannoma can present in exactly the same manner, and because of the rarity of this tumor, even with extensive experience in parotid gland surgery, a surgeon may not have had experience with a schwannoma in this region. It would therefore be wise to have a plan should a schwannoma be encountered.
Otolaryngology– Head and Neck Surgery Volume 130 Number 5
The purpose of the following report is to contribute to the medical literature the clinical presentation, management, and outcome of 29 patients with schwannoma of the facial nerve, including 8 involving the intraparotid area. MATERIALS AND METHODS A retrospective chart review was conducted for all patients evaluated for facial nerve disorders during the 38-year period from 1963 to 2001 at the Shadyside Facial Paralysis Center. Of the 3722 patients seen during this time period, all patients diagnosed with schwannoma of the facial nerve were included in the study. A total of 29 patients met the criteria for inclusion in the study, including 28 from the Shadyside Facial Paralysis Center and 1 previously reported case from the Eye and Ear Institute of Pittsburgh.9 All cases had data suitable for analysis. The following information was abstracted, when possible, from the medical record: age, gender, clinical presentation, preoperative testing, management, and length of followup. Further analysis was done specifically looking for the characteristics of symptoms, including time between onset and diagnosis, the intraoperative and pathologic appearance of the schwannoma, the usefulness of preoperative imaging studies, and the facial nerve function before and after surgery. Preoperative investigations were considered useful if the radiology/pathology report included schwannoma as a possible diagnosis of images or biopsy material. Facial nerve function was assessed using the House-Brackmann scale. Postoperative facial nerve function was only determined after at least 1 year of follow-up. REPRESENTATIVE CASE A 55-year-old man presented to an outside otolaryngologist with a 40-year history of a slowly growing, painless mass in his left parotid region. There was no history of facial weakness, and physical examination showed a 3 ⫻ 3-cm mobile mass located superficial to the angle of the left mandible. A preoperative computed tomography scan was obtained and interpreted as a 3-cm left parotid mass with a central area of low density. Fine needle aspiration of the mass described several clusters of serous-type glands admixed with
CAUGHEY et al 587
loose myxomatous cells with poorly defined cell borders, which was interpreted as a pleomorphic adenoma. A superficial parotidectomy was planned. After skin flaps were raised and the normal landmarks were identified, the surgeon was unable to isolate the facial nerve. The capsule of the tumor was then incised with a No. 12 blade, and a firm polypoidtype mass of yellowish consistency was expressed from the capsule in its entirety. The mass was sent for permanent evaluation and no frozen section was sent. In proceeding with the excision of the mass, the facial nerve was never able to be confidently identified. Gross pathologic examine showed that a thinly encapsulated, pale, yellow, fatty tumor measuring 4.5 ⫻ 2.5 ⫻ 1.5 cm was removed. On sectioning, the tissue had a smooth fleshy consistency without evidence of hemorrhage or necrosis. Microscopic description demonstrated cellular Antoni A areas with nuclear palisading admixed with loose myxoid Antoni B areas consistent with schwannoma. Postoperatively, the patient had a total paralysis of his left face both immediately postoperatively and 6 months after his operation. Magnetic resonance imaging (MRI) of the brain and skull base with and without contrast was obtained at an outside hospital and read as normal. The patient presented to the senior author (B.S.) 6 months after resection for reanimation. MRI of the ear now revealed schwannoma involving the facial nerve from the geniculate ganglion to the styloid foramen (Fig 1). RESULTS There were 18 females and 11 males in the subject population. The ages of the patients ranged from 7 to 78 years at diagnosis with an average age of 44 years. The locations of the schwannomas are shown in Table 1. The left side of the face was involved in 7 cases, and the right side, 22 cases. The clinical presentation for all schwannomas in this series is shown (Fig 2). Patients with intraparotid lesions presented most frequently with a mass. More proximal lesions exhibited the sudden onset of facial paralysis as a common presenting symptom. The average duration of symptoms before presenting to a physician was 8.4 years, with the longest duration being 40.5 years. Specifically,
Otolaryngology– Head and Neck Surgery May 2004
588 CAUGHEY et al
Fig 1. Axial and coronal computed tomography scans demonstrating proximal extension of tumor into the temporal bone.
Table 1. Location of facial nerve schwannomas (n ⫽ 29) Location of schwannoma
No. of cases
IC IC ⫹ IT IT IT ⫹ IP IP
1 7 13 7 1
IC, Intracranial; IT, intratemporal; IP, intraparotid.
the average duration of symptoms in patients with parotid involvement was 10.9 years. Twenty of the 29 patients had preoperative imaging, either computed tomography, MRI, or both. The preoperative imaging results are shown (Table 2). Of the 8 patients with intraparotid involvement, 4 had preoperative imaging. In the 2 intraparotid cases where the imaging was helpful, the temporal segment of the tumor provided the radiologic clue rather than the parotid segment. In addition to the preoperative imaging, 1 patient with an intraparotid-intratemporal schwannoma had fine needle aspiration that interpreted the results as a pleomorphic adenoma. Of the 29 patients, 26 underwent surgery, including 24 with resection of the tumor. The other 2 patients had facial nerve decompression and
biopsy of the lesion. All 8 patients with parotid involvement had surgical resection of the schwannoma, including 6 via parotidectomy, 1 via a transmastoid/middle cranial fossa approach, and 1 performed at an outside hospital without details of the specific operation. The intraoperative appearance of the schwannomas was available in 14 cases. The most common color was pink(6 cases), followed by tan (5 cases) and yellow (3 cases). The tumors with parotid involvement had yellow as a component in 3 of 4 described cases. The most frequent description in operative and pathologic reports was lobular, multinodular, nonencapsulated, and adherent. Preoperative facial nerve functioning was measured on the House-Brackmann scale for 27 of 29 patients. The average preoperative level of functioning was 3 of 6 for all tumors and 1.5 of 6 for tumors with parotid involvement. Five patients with intraparotid schwannoma had no facial dysfunction at all. The postoperative level of functioning was obtained in 25 of 26 patients, with 1 patient not having 1 year of follow-up and 3 patients electing to not undergo resection. The group achieved an average postoperative level of functioning of 4.3 of 6 on the House-Brackmann scale with intraparotid tumors averaging 4.4 of 6. The 1 patient lost to follow-up had a parotid tumor
Otolaryngology– Head and Neck Surgery Volume 130 Number 5
CAUGHEY et al 589
Fig 2. Presenting symptoms.
Table 2. Imaging results
Location
Total No. of cases
IC IC ⫹ IT IT IT ⫹ IP IP
1 7 13 7 1
Patients in Patients who whom where had CT or MRI imaging was (n) useful (n)
1 7 8 3 1
1 6 5 2 0
CT, Computed tomography; MRI, magnetic resonance imaging; IC, intracranial; IT, intratemporal; IP, intraparotid.
and had total paralysis at 6 months. These results include 17 cases of facial nerve repair, with 6 of 8 parotids having undergone repair. The best result achieved postoperatively by any means was a House-Brackmann in grade III. DISCUSSION Parotid tumors occur frequently, and more than 75% are benign. Because of the unsightly appearance of parotid masses, the potential for malig-
nancy, and the relative ease of resection via superficial parotidectomy, management most commonly consists of excisional biopsy. Facial nerve dysfunction, adherence to the surrounding tissue, or cervical lymphadenopathy on physical examination suggests malignancy, and in this setting preoperative imaging and fine needle aspiration biopsy are more frequently used. Facial nerve schwannomas make up a small portion of parotid tumors. Only 8 cases with parotid involvement were encountered, of 29 total schwannoma cases seen over a 38-year period. The relative rarity of intraparotid schwannoma observed in the study is similar to the frequency reported in the literature, with approximately 400 reported cases of facial nerve schwannoma and less than 70 with parotid involvement.6 Intraparotid schwannoma commonly presents as a painless facial mass. Of the 8 cases of intraparotid schwannoma, 5 presented with a palpable parotid mass (with or without pain), and the other 3 were discovered to have parotid involvement via imaging or at the time of surgery. The presence of
590 CAUGHEY et al
facial nerve dysfunction with this lesion has been reported by Bretlau et al10 to be present in only 20% of all cases. Three of 8 study patients with parotid involvement had some facial nerve dysfunction, and just 1 of 5 with a palpable mass reported twitching and slight weakness. Painful masses have also been reported as a presenting symptom and were seen in 2 of the cases.11 The problem with schwannoma arising as a painless parotid mass is illustrated in the sample case. Specifically, a surgeon performing a superficial parotidectomy is unable to locate the facial nerve. In attempting to resect the tumor, the facial nerve is damaged or severed and must be repaired with resultant decrease in facial nerve function. In addition, the extent of the tumor has not been properly assessed. The challenge is, then, to make the diagnosis preoperatively or intraoperatively so an appropriate plan of action can be implemented. Preoperatively, there is little to differentiate a schwannoma from other parotid tumors. Perhaps the best indication of schwannoma is an excessively long duration of symptoms. Symptoms of schwannomas in the study group were present an average of 8.4 years, with intraparotid tumors being symptomatic for 10.9 years. The sample case had evidence of an enlarged parotid for over 40 years! It should be noted that the absence of a lengthy duration of symptoms does not preclude schwannoma as 2 patients with intraparotid tumors presented for evaluation in under 2 months’ time. Other factors such as age, gender, pain associated with the tumor, and facial nerve dysfunction vary widely with schwannoma and are not helpful. Preoperative imaging remains of limited use in detecting intraparotid schwannomas. Although the efficacy of computed tomography and MRI for diagnosing intratemporal schwannoma has been well documented,12,13 there has been no definitive radiologic finding for intraparotid lesions. Chung et al13 looked at intraparotid schwannomas in 4 patients with 4 different radiologic presentations and were only able to suggest that tumor located on the extratemporal facial nerve course may be suspicious for schwannoma. This is consistent with the cases reviewed as the 1 patient presenting with a parotid mass had nondiagnostic imaging
Otolaryngology– Head and Neck Surgery May 2004
and the other 4 patients presenting with a mass had no imaging at all. Fine needle aspiration has also failed to be a useful diagnostic modality in the evaluation of parotid schwannoma, despite a distinctive microscopic appearance.14 Bretlau et al10 suggests that the firmly attached cells in tumors of neurogenic origin make obtaining positive cytology difficult. With facial nerve schwannomas, there are several reports of fine needle aspiration being nondiagnostic,6,15 or worse, as in our case, a diagnosis of pleomorphic adenoma is given, which makes the surgeon less conscious of the possibility of schwannoma. Because of these limitations, fine needle aspiration does not seem to have a place in the diagnosis of schwannoma. Because preoperative diagnosis is often difficult, intraoperative identification during parotidectomy is essential. The intraoperative gross appearance of the intraparotid schwannomas of the study patients does not differ significantly from that of other benign tumors as many appear yellow and rubbery,14 but the most diagnostic feature of intraparotid facial nerve schwannoma is intraoperative difficulty locating the facial nerve.16,17 In addition, tumors intimately involved with or difficult to dissect from the facial nerve during superficial parotidectomy have been reported.9 Electrical stimulation of the tumor may show facial movement and certainly would trigger an intraoperative nerve monitor. This stimulation is highly suggestive of schwannoma. Proceeding with resection at this point puts the facial nerve at risk for injury. Despite claims that schwannomas can be easily separated from their major nerves,18 this has not been the experience of the senior author, nor is it the experience in the majority of literature cases.4,7,9 Because resection of intraparotid schwannomas puts the facial nerve at risk, a conservative initial course should be taken when there is a high degree of suspicion for this lesion. Proper intraoperative management should involve electrical stimulation of the tumor and at most a small tissue biopsy sample, preferably from a distal nonvital location. Although this in itself may cause a facial nerve paralysis as other authors have noted,3,4 the paralysis is usually temporary. A tissue diagnosis reassures the surgeon and the patient that the correct
Otolaryngology– Head and Neck Surgery Volume 130 Number 5
diagnosis was made and rules out the possibility of a malignant schwannoma, which can mimic a benign schwannoma.19 After biopsy, the parotidectomy should be abandoned. Stopping the surgery provides an opportunity to obtain imaging to evaluate the extent of the tumor and perhaps alter the approach should future resection be planned. In addition, aborting the operation provides the opportunity to discuss with the patient the almost certain outcome of facial paralysis should resection be pursued. This protects the surgeon against an unexpected and potentially devastating result. A similar approach has been advocated for facial nerve tumors unexpectedly discovered during middle ear surgery.20 Unfortunately, in the majority of the study patients, the diagnosis of schwannoma was made after resection, with facial nerve damage already done, but if the diagnosis is made without injury to the facial nerve, then a question of management arises. The ultimate decision of whether to resect facial nerve schwannomas remains controversial in part because of the benign and slow growing nature of the tumor. Some authors favor resection in nearly all cases.4,21 Other authors have shown that facial nerve decompression or even observation alone can be less-disfiguring alternatives.8 The treatment choice is significantly influenced by the patient’s preference after hearing the risks, options, and benefits and also by the preoperative level of facial nerve function. If the facial nerve is severely affected (ie, House-Brackmann grade 5 or 6), then the choice is tumor removal and nerve grafting if viable facial nerve fibers and musculature remain. With intact facial nerve function, resection, decompression, or observation with appropriate follow-up are all reasonable plans if the patient has been informed about the positive and negative aspects of each choice. In the case of observation, yearly physical examinations that including complete facial nerve testing are indicated. Patients should also undergo yearly CT or MRI studies and electrical testing of the facial nerve. By following the tumor via imaging, it ensures that the tumor does not encroach on sensitive structures before possible intervention can take place. Close monitoring of the facial nerve function allows for the most appropriate
CAUGHEY et al 591
time for resection and nerve grafting, as response to facial nerve grafting has been most favorable before there is 50% loss of function of the facial nerve.22 Close follow-up optimizes the chance for the best result should grafting be necessary. CONCLUSIONS Facial nerve schwannomas arising as parotid tumors are rare. Even the most experienced parotid surgeons may only see 1 in their career. A long duration of symptoms and difficulty locating the facial nerve during parotidectomy may be the only signs that a patient has a schwannoma. When faced with this situation, the surgeon should consider electrical stimulation of the tumor and biopsy of a distal nonvital location to make a diagnosis. With pathologic confirmation, the patient should undergo staging radiography to define the extent of the lesion. At this point, a joint decision can be reached between the surgeon and the patient based on the diagnosis, extent, facial nerve status, and the patient’s desires to obtain a mutually satisfactory outcome. REFERENCES
1. Walter JB, Israel MS. Structure and effects of some common tumors. In: General Pathology, 5th Ed. Edinburgh: Churchill Livingstone; 1979. p. 319-20. 2. Putney FJ, Moran JJ, Thomas GK. Neurogenic tumors of the head and neck. Laryngoscope 1964;74:1037-59. 3. Hajjaj M, Linthicum FH. Facial nerve schwannoma: nerve fibre dissemination. J Laryngol Otol 1996;110: 632-3. 4. O’Donoghue GM, Brackman DE, House JW, et al. Neuromas of the facial nerve. Am J Otol 1989;10:49-54. 5. Lipkin A, Coker N, Jenkins H, et al. Intracranial and intratemporal facial neuroma. Otolaryngol Head Neck Surg 1987;96:71-9. 6. Elahi MM, Audet N, Rochan L, et al. Intraparotid facial nerve schwannoma. J Otolaryngol 1995;24:364-7. 7. Dort JC, Fisch U. Facial nerve schwannomas. Skull Base Surg 1991;1:51-6. 8. Angeli SI, Brackmann DE. Is surgical excision of facial nerve schwannomas always indicated? Otolaryngol Head Neck Surg 1997;117:S144-7. 9. Prasad S, Myers EN, Kamerer DB, et al. Neurilemmoma (schwannoma) of the facial nerve presenting as a parotid mass. Otolaryngol Head Neck Surg 1993;108:76-9. 10. Bretlau P, Melchiors H, Krogdahl A. Intraparotid neurilemmona. Acta Otolaryngol 1983;95:382-4. 11. Shambaugh GE, Arenberg IK, Valrassori GE. Facial neurilemmomas: a study of four diverse cases. Arch Otolaryngol 1969;90:742-55. 12. Chen JM, Moll C, Wishmann W, et al. Magnetic resonance imaging and intraoperative frozen sections in intratemporal facial schwannomas. Am J Otolaryngol 1995;16:68-74.
592 CAUGHEY et al
13. Chung SY, Kim DI, Lee BH, et al. Facial nerve schwannomas: CT and MR findings. Yonsei Med J 1998;39:14853. 14. Barnes L, Peel RL, Verbin RS. Tumors of the nervous system. In: Barnes L, editor. Surgical pathology of the head and neck. New York: Marcel Dekker; 1985. p. 553, 662-3. 15. Chong KW, Chung YFA, Khoo MLC, et al. Management of intraparotid facial nerve schwannoma. Aust N Z J Surg 2000;70:732-4. 16. Hehar SS, Dugar J, Sharp J. The changing faces of a parotid mass. J Laryngol Otol 1999;133:938-41. 17. Avery AP, Sprinkle PM. Benign intraparotid schwannoma. Laryngoscope 1972;82:199-203.
Otolaryngology– Head and Neck Surgery May 2004
18. Katz AD, Passy V, Kaplan L. Neurogenic neoplasms of major nerves of face and neck. Arch Surg 1971;103: 51-6. 19. Larian N, Zohar Y. Malignant neurilemmoma of the parotid gland. J Laryngol Otol 1970;84:1267-71. 20. O’Donoghue GM. Tumors of the facial nerve. In: Jackler RK, Brackmann DE, editors. Neurotology. St Louis: Mosby–Year Book; 1994. p. 1328-9. 21. Pillsbury HC, Price HC, Gardiner LJ. Primary tumors of the facial nerve: diagnosis and management. Laryngoscope 1983;83:1045-8. 22. May M. Nerve repair. In: May M, Schaitkin BM, editors. The facial nerve, May’s 2nd Ed. New York: Theime Medical Publishers; 2000. p. 571-609.
BS,
MARK MAY,
MD,
and BARRY M. SCHAITKIN,
OBJECTIVE: Facial nerve schwannomas are rare neoplasms that present a challenge in diagnosis and management. We sought to gain insight into the clinical presentation and its implications in management. STUDY DESIGN AND SETTING: A group of patients diagnosed with schwannoma was reviewed, with focus on tumor arising in the intraparotid region of the facial nerve. The patient population consisted of 3722 patients evaluated retrospectively over 38 years at the Shadyside Facial Paralysis Center, a tertiary referral center. From this population, 29 patients (18 women and 11 men) with the diagnosis of schwannoma were selected for review. RESULTS: Twenty-nine patients had facial nerve schwannoma. The average age at diagnosis was 44 years (range, 7 to 78 years). Eight patients had intraparotid involvement, with 5 having a palpable mass in the parotid. The duration of symptoms averaged 8.4 years overall, with intraparotid involvement averaging 10.9 years. The 8 intraparotid schwannomas had a mean House-Brackmann grade of 1.5/6 at initial presentation. Postoperative facial nerve function was only 4.4/6 for resected intraparotid schwannomas. CONCLUSIONS: Intraparotid facial nerve schwannomas are slow growing tumors, which are usually asymptomatic but can be painful. Schwannoma should be suspected if the facial nerve cannot be found intraoperatively or if the tumor is intimately associated with the facial nerve. In cases where schwannoma is suspected, biopsy is recommended, while complete resection is postponed to obtain imaging studies to evaluate the extent of
From the Department of Otolaryngology–Head and Neck Surgery, Shadyside Hospital Facial Paralysis Center. Presented at the Ninth International Facial Nerve Symposium, August 1, 2001, San Francisco, CA. Reprint requests: Barry M. Schaitkin, MD, University of Pittsburgh Medical Center–Shadyside Hospital, 5200 Centre Ave, Suite 211, Pittsburgh, PA 15232; e-mail, [email protected]. 0194-5998/$30.00 Copyright © 2004 by the American Academy of Otolaryngology–Head and Neck Surgery Foundation, Inc. doi:10.1016/j.otohns.2003.12.011 586
MD,
Pittsburgh, Pennsylvania
disease and to discuss possible outcomes with the patient. SIGNIFICANCE: This article provides guidance for the appropriate management of intraparotid facial nerve schwannoma. (Otolaryngol Head Neck Surg 2004;130:586-92.)
S chwannomas
are benign, slow growing neoplasms that arise from the cells that ensheath the axons of the peripheral, cranial, and autonomic nervous systems. These tumors are usually solitary and well encapsulated and tend to splay the nerve of origin.1 Although approximately one third of all of these lesions occur in the head and neck, facial nerve schwannomas are rare.2 Since Schmidt first described a facial neurilemmoma or schwannoma in 1930, facial nerve schwannomas have been well documented in the medical literature, with more than 300 reported cases, including several large series.3-5 Schwannomas have been described in every portion of the facial nerve; however, most of the cases involve the intratemporal portion of the facial nerve, with fewer than 60 intraparotid schwannomas appearing in the literature.6 The classic presentation of intratemporal facial nerve schwannoma has been most frequently characterized as progressive facial weakness or paralysis.4,5 The diagnosis and management of intratemporal lesions have also received much attention in the literature.7,8 Because of the rarity of facial nerve schwannomas arising in the parotid gland, schwannomas in this location have not been well described and few practitioners are versed in their clinical management. Most benign parotid tumors, such as pleomorphic adenoma, present as an asymptomatic mass. Intraparotid facial nerve schwannoma can present in exactly the same manner, and because of the rarity of this tumor, even with extensive experience in parotid gland surgery, a surgeon may not have had experience with a schwannoma in this region. It would therefore be wise to have a plan should a schwannoma be encountered.
Otolaryngology– Head and Neck Surgery Volume 130 Number 5
The purpose of the following report is to contribute to the medical literature the clinical presentation, management, and outcome of 29 patients with schwannoma of the facial nerve, including 8 involving the intraparotid area. MATERIALS AND METHODS A retrospective chart review was conducted for all patients evaluated for facial nerve disorders during the 38-year period from 1963 to 2001 at the Shadyside Facial Paralysis Center. Of the 3722 patients seen during this time period, all patients diagnosed with schwannoma of the facial nerve were included in the study. A total of 29 patients met the criteria for inclusion in the study, including 28 from the Shadyside Facial Paralysis Center and 1 previously reported case from the Eye and Ear Institute of Pittsburgh.9 All cases had data suitable for analysis. The following information was abstracted, when possible, from the medical record: age, gender, clinical presentation, preoperative testing, management, and length of followup. Further analysis was done specifically looking for the characteristics of symptoms, including time between onset and diagnosis, the intraoperative and pathologic appearance of the schwannoma, the usefulness of preoperative imaging studies, and the facial nerve function before and after surgery. Preoperative investigations were considered useful if the radiology/pathology report included schwannoma as a possible diagnosis of images or biopsy material. Facial nerve function was assessed using the House-Brackmann scale. Postoperative facial nerve function was only determined after at least 1 year of follow-up. REPRESENTATIVE CASE A 55-year-old man presented to an outside otolaryngologist with a 40-year history of a slowly growing, painless mass in his left parotid region. There was no history of facial weakness, and physical examination showed a 3 ⫻ 3-cm mobile mass located superficial to the angle of the left mandible. A preoperative computed tomography scan was obtained and interpreted as a 3-cm left parotid mass with a central area of low density. Fine needle aspiration of the mass described several clusters of serous-type glands admixed with
CAUGHEY et al 587
loose myxomatous cells with poorly defined cell borders, which was interpreted as a pleomorphic adenoma. A superficial parotidectomy was planned. After skin flaps were raised and the normal landmarks were identified, the surgeon was unable to isolate the facial nerve. The capsule of the tumor was then incised with a No. 12 blade, and a firm polypoidtype mass of yellowish consistency was expressed from the capsule in its entirety. The mass was sent for permanent evaluation and no frozen section was sent. In proceeding with the excision of the mass, the facial nerve was never able to be confidently identified. Gross pathologic examine showed that a thinly encapsulated, pale, yellow, fatty tumor measuring 4.5 ⫻ 2.5 ⫻ 1.5 cm was removed. On sectioning, the tissue had a smooth fleshy consistency without evidence of hemorrhage or necrosis. Microscopic description demonstrated cellular Antoni A areas with nuclear palisading admixed with loose myxoid Antoni B areas consistent with schwannoma. Postoperatively, the patient had a total paralysis of his left face both immediately postoperatively and 6 months after his operation. Magnetic resonance imaging (MRI) of the brain and skull base with and without contrast was obtained at an outside hospital and read as normal. The patient presented to the senior author (B.S.) 6 months after resection for reanimation. MRI of the ear now revealed schwannoma involving the facial nerve from the geniculate ganglion to the styloid foramen (Fig 1). RESULTS There were 18 females and 11 males in the subject population. The ages of the patients ranged from 7 to 78 years at diagnosis with an average age of 44 years. The locations of the schwannomas are shown in Table 1. The left side of the face was involved in 7 cases, and the right side, 22 cases. The clinical presentation for all schwannomas in this series is shown (Fig 2). Patients with intraparotid lesions presented most frequently with a mass. More proximal lesions exhibited the sudden onset of facial paralysis as a common presenting symptom. The average duration of symptoms before presenting to a physician was 8.4 years, with the longest duration being 40.5 years. Specifically,
Otolaryngology– Head and Neck Surgery May 2004
588 CAUGHEY et al
Fig 1. Axial and coronal computed tomography scans demonstrating proximal extension of tumor into the temporal bone.
Table 1. Location of facial nerve schwannomas (n ⫽ 29) Location of schwannoma
No. of cases
IC IC ⫹ IT IT IT ⫹ IP IP
1 7 13 7 1
IC, Intracranial; IT, intratemporal; IP, intraparotid.
the average duration of symptoms in patients with parotid involvement was 10.9 years. Twenty of the 29 patients had preoperative imaging, either computed tomography, MRI, or both. The preoperative imaging results are shown (Table 2). Of the 8 patients with intraparotid involvement, 4 had preoperative imaging. In the 2 intraparotid cases where the imaging was helpful, the temporal segment of the tumor provided the radiologic clue rather than the parotid segment. In addition to the preoperative imaging, 1 patient with an intraparotid-intratemporal schwannoma had fine needle aspiration that interpreted the results as a pleomorphic adenoma. Of the 29 patients, 26 underwent surgery, including 24 with resection of the tumor. The other 2 patients had facial nerve decompression and
biopsy of the lesion. All 8 patients with parotid involvement had surgical resection of the schwannoma, including 6 via parotidectomy, 1 via a transmastoid/middle cranial fossa approach, and 1 performed at an outside hospital without details of the specific operation. The intraoperative appearance of the schwannomas was available in 14 cases. The most common color was pink(6 cases), followed by tan (5 cases) and yellow (3 cases). The tumors with parotid involvement had yellow as a component in 3 of 4 described cases. The most frequent description in operative and pathologic reports was lobular, multinodular, nonencapsulated, and adherent. Preoperative facial nerve functioning was measured on the House-Brackmann scale for 27 of 29 patients. The average preoperative level of functioning was 3 of 6 for all tumors and 1.5 of 6 for tumors with parotid involvement. Five patients with intraparotid schwannoma had no facial dysfunction at all. The postoperative level of functioning was obtained in 25 of 26 patients, with 1 patient not having 1 year of follow-up and 3 patients electing to not undergo resection. The group achieved an average postoperative level of functioning of 4.3 of 6 on the House-Brackmann scale with intraparotid tumors averaging 4.4 of 6. The 1 patient lost to follow-up had a parotid tumor
Otolaryngology– Head and Neck Surgery Volume 130 Number 5
CAUGHEY et al 589
Fig 2. Presenting symptoms.
Table 2. Imaging results
Location
Total No. of cases
IC IC ⫹ IT IT IT ⫹ IP IP
1 7 13 7 1
Patients in Patients who whom where had CT or MRI imaging was (n) useful (n)
1 7 8 3 1
1 6 5 2 0
CT, Computed tomography; MRI, magnetic resonance imaging; IC, intracranial; IT, intratemporal; IP, intraparotid.
and had total paralysis at 6 months. These results include 17 cases of facial nerve repair, with 6 of 8 parotids having undergone repair. The best result achieved postoperatively by any means was a House-Brackmann in grade III. DISCUSSION Parotid tumors occur frequently, and more than 75% are benign. Because of the unsightly appearance of parotid masses, the potential for malig-
nancy, and the relative ease of resection via superficial parotidectomy, management most commonly consists of excisional biopsy. Facial nerve dysfunction, adherence to the surrounding tissue, or cervical lymphadenopathy on physical examination suggests malignancy, and in this setting preoperative imaging and fine needle aspiration biopsy are more frequently used. Facial nerve schwannomas make up a small portion of parotid tumors. Only 8 cases with parotid involvement were encountered, of 29 total schwannoma cases seen over a 38-year period. The relative rarity of intraparotid schwannoma observed in the study is similar to the frequency reported in the literature, with approximately 400 reported cases of facial nerve schwannoma and less than 70 with parotid involvement.6 Intraparotid schwannoma commonly presents as a painless facial mass. Of the 8 cases of intraparotid schwannoma, 5 presented with a palpable parotid mass (with or without pain), and the other 3 were discovered to have parotid involvement via imaging or at the time of surgery. The presence of
590 CAUGHEY et al
facial nerve dysfunction with this lesion has been reported by Bretlau et al10 to be present in only 20% of all cases. Three of 8 study patients with parotid involvement had some facial nerve dysfunction, and just 1 of 5 with a palpable mass reported twitching and slight weakness. Painful masses have also been reported as a presenting symptom and were seen in 2 of the cases.11 The problem with schwannoma arising as a painless parotid mass is illustrated in the sample case. Specifically, a surgeon performing a superficial parotidectomy is unable to locate the facial nerve. In attempting to resect the tumor, the facial nerve is damaged or severed and must be repaired with resultant decrease in facial nerve function. In addition, the extent of the tumor has not been properly assessed. The challenge is, then, to make the diagnosis preoperatively or intraoperatively so an appropriate plan of action can be implemented. Preoperatively, there is little to differentiate a schwannoma from other parotid tumors. Perhaps the best indication of schwannoma is an excessively long duration of symptoms. Symptoms of schwannomas in the study group were present an average of 8.4 years, with intraparotid tumors being symptomatic for 10.9 years. The sample case had evidence of an enlarged parotid for over 40 years! It should be noted that the absence of a lengthy duration of symptoms does not preclude schwannoma as 2 patients with intraparotid tumors presented for evaluation in under 2 months’ time. Other factors such as age, gender, pain associated with the tumor, and facial nerve dysfunction vary widely with schwannoma and are not helpful. Preoperative imaging remains of limited use in detecting intraparotid schwannomas. Although the efficacy of computed tomography and MRI for diagnosing intratemporal schwannoma has been well documented,12,13 there has been no definitive radiologic finding for intraparotid lesions. Chung et al13 looked at intraparotid schwannomas in 4 patients with 4 different radiologic presentations and were only able to suggest that tumor located on the extratemporal facial nerve course may be suspicious for schwannoma. This is consistent with the cases reviewed as the 1 patient presenting with a parotid mass had nondiagnostic imaging
Otolaryngology– Head and Neck Surgery May 2004
and the other 4 patients presenting with a mass had no imaging at all. Fine needle aspiration has also failed to be a useful diagnostic modality in the evaluation of parotid schwannoma, despite a distinctive microscopic appearance.14 Bretlau et al10 suggests that the firmly attached cells in tumors of neurogenic origin make obtaining positive cytology difficult. With facial nerve schwannomas, there are several reports of fine needle aspiration being nondiagnostic,6,15 or worse, as in our case, a diagnosis of pleomorphic adenoma is given, which makes the surgeon less conscious of the possibility of schwannoma. Because of these limitations, fine needle aspiration does not seem to have a place in the diagnosis of schwannoma. Because preoperative diagnosis is often difficult, intraoperative identification during parotidectomy is essential. The intraoperative gross appearance of the intraparotid schwannomas of the study patients does not differ significantly from that of other benign tumors as many appear yellow and rubbery,14 but the most diagnostic feature of intraparotid facial nerve schwannoma is intraoperative difficulty locating the facial nerve.16,17 In addition, tumors intimately involved with or difficult to dissect from the facial nerve during superficial parotidectomy have been reported.9 Electrical stimulation of the tumor may show facial movement and certainly would trigger an intraoperative nerve monitor. This stimulation is highly suggestive of schwannoma. Proceeding with resection at this point puts the facial nerve at risk for injury. Despite claims that schwannomas can be easily separated from their major nerves,18 this has not been the experience of the senior author, nor is it the experience in the majority of literature cases.4,7,9 Because resection of intraparotid schwannomas puts the facial nerve at risk, a conservative initial course should be taken when there is a high degree of suspicion for this lesion. Proper intraoperative management should involve electrical stimulation of the tumor and at most a small tissue biopsy sample, preferably from a distal nonvital location. Although this in itself may cause a facial nerve paralysis as other authors have noted,3,4 the paralysis is usually temporary. A tissue diagnosis reassures the surgeon and the patient that the correct
Otolaryngology– Head and Neck Surgery Volume 130 Number 5
diagnosis was made and rules out the possibility of a malignant schwannoma, which can mimic a benign schwannoma.19 After biopsy, the parotidectomy should be abandoned. Stopping the surgery provides an opportunity to obtain imaging to evaluate the extent of the tumor and perhaps alter the approach should future resection be planned. In addition, aborting the operation provides the opportunity to discuss with the patient the almost certain outcome of facial paralysis should resection be pursued. This protects the surgeon against an unexpected and potentially devastating result. A similar approach has been advocated for facial nerve tumors unexpectedly discovered during middle ear surgery.20 Unfortunately, in the majority of the study patients, the diagnosis of schwannoma was made after resection, with facial nerve damage already done, but if the diagnosis is made without injury to the facial nerve, then a question of management arises. The ultimate decision of whether to resect facial nerve schwannomas remains controversial in part because of the benign and slow growing nature of the tumor. Some authors favor resection in nearly all cases.4,21 Other authors have shown that facial nerve decompression or even observation alone can be less-disfiguring alternatives.8 The treatment choice is significantly influenced by the patient’s preference after hearing the risks, options, and benefits and also by the preoperative level of facial nerve function. If the facial nerve is severely affected (ie, House-Brackmann grade 5 or 6), then the choice is tumor removal and nerve grafting if viable facial nerve fibers and musculature remain. With intact facial nerve function, resection, decompression, or observation with appropriate follow-up are all reasonable plans if the patient has been informed about the positive and negative aspects of each choice. In the case of observation, yearly physical examinations that including complete facial nerve testing are indicated. Patients should also undergo yearly CT or MRI studies and electrical testing of the facial nerve. By following the tumor via imaging, it ensures that the tumor does not encroach on sensitive structures before possible intervention can take place. Close monitoring of the facial nerve function allows for the most appropriate
CAUGHEY et al 591
time for resection and nerve grafting, as response to facial nerve grafting has been most favorable before there is 50% loss of function of the facial nerve.22 Close follow-up optimizes the chance for the best result should grafting be necessary. CONCLUSIONS Facial nerve schwannomas arising as parotid tumors are rare. Even the most experienced parotid surgeons may only see 1 in their career. A long duration of symptoms and difficulty locating the facial nerve during parotidectomy may be the only signs that a patient has a schwannoma. When faced with this situation, the surgeon should consider electrical stimulation of the tumor and biopsy of a distal nonvital location to make a diagnosis. With pathologic confirmation, the patient should undergo staging radiography to define the extent of the lesion. At this point, a joint decision can be reached between the surgeon and the patient based on the diagnosis, extent, facial nerve status, and the patient’s desires to obtain a mutually satisfactory outcome. REFERENCES
1. Walter JB, Israel MS. Structure and effects of some common tumors. In: General Pathology, 5th Ed. Edinburgh: Churchill Livingstone; 1979. p. 319-20. 2. Putney FJ, Moran JJ, Thomas GK. Neurogenic tumors of the head and neck. Laryngoscope 1964;74:1037-59. 3. Hajjaj M, Linthicum FH. Facial nerve schwannoma: nerve fibre dissemination. J Laryngol Otol 1996;110: 632-3. 4. O’Donoghue GM, Brackman DE, House JW, et al. Neuromas of the facial nerve. Am J Otol 1989;10:49-54. 5. Lipkin A, Coker N, Jenkins H, et al. Intracranial and intratemporal facial neuroma. Otolaryngol Head Neck Surg 1987;96:71-9. 6. Elahi MM, Audet N, Rochan L, et al. Intraparotid facial nerve schwannoma. J Otolaryngol 1995;24:364-7. 7. Dort JC, Fisch U. Facial nerve schwannomas. Skull Base Surg 1991;1:51-6. 8. Angeli SI, Brackmann DE. Is surgical excision of facial nerve schwannomas always indicated? Otolaryngol Head Neck Surg 1997;117:S144-7. 9. Prasad S, Myers EN, Kamerer DB, et al. Neurilemmoma (schwannoma) of the facial nerve presenting as a parotid mass. Otolaryngol Head Neck Surg 1993;108:76-9. 10. Bretlau P, Melchiors H, Krogdahl A. Intraparotid neurilemmona. Acta Otolaryngol 1983;95:382-4. 11. Shambaugh GE, Arenberg IK, Valrassori GE. Facial neurilemmomas: a study of four diverse cases. Arch Otolaryngol 1969;90:742-55. 12. Chen JM, Moll C, Wishmann W, et al. Magnetic resonance imaging and intraoperative frozen sections in intratemporal facial schwannomas. Am J Otolaryngol 1995;16:68-74.
592 CAUGHEY et al
13. Chung SY, Kim DI, Lee BH, et al. Facial nerve schwannomas: CT and MR findings. Yonsei Med J 1998;39:14853. 14. Barnes L, Peel RL, Verbin RS. Tumors of the nervous system. In: Barnes L, editor. Surgical pathology of the head and neck. New York: Marcel Dekker; 1985. p. 553, 662-3. 15. Chong KW, Chung YFA, Khoo MLC, et al. Management of intraparotid facial nerve schwannoma. Aust N Z J Surg 2000;70:732-4. 16. Hehar SS, Dugar J, Sharp J. The changing faces of a parotid mass. J Laryngol Otol 1999;133:938-41. 17. Avery AP, Sprinkle PM. Benign intraparotid schwannoma. Laryngoscope 1972;82:199-203.
Otolaryngology– Head and Neck Surgery May 2004
18. Katz AD, Passy V, Kaplan L. Neurogenic neoplasms of major nerves of face and neck. Arch Surg 1971;103: 51-6. 19. Larian N, Zohar Y. Malignant neurilemmoma of the parotid gland. J Laryngol Otol 1970;84:1267-71. 20. O’Donoghue GM. Tumors of the facial nerve. In: Jackler RK, Brackmann DE, editors. Neurotology. St Louis: Mosby–Year Book; 1994. p. 1328-9. 21. Pillsbury HC, Price HC, Gardiner LJ. Primary tumors of the facial nerve: diagnosis and management. Laryngoscope 1983;83:1045-8. 22. May M. Nerve repair. In: May M, Schaitkin BM, editors. The facial nerve, May’s 2nd Ed. New York: Theime Medical Publishers; 2000. p. 571-609.