- Email: [email protected]
Neurilemoma of the medial plantar nerve: A case report
Neurilemoma of the Medial Plantar Nerve: A Case Report Gregory P. Still, DPM, C Ped The incidence of neurilemoma in the foot is uncommon. Neurilemoma of the medial plantar nerve distal to the tarsal tunnel, with symptoms isolated to the foot, is rare. A case presentation of neurilemoma arising from the distal portion of the medial plantar nerve that was identified and excised is presented with a 19-month follow-up. (The Journal of Foot & Ankle Surgery 40(4):236-239,2001)
Key words: foot, medial plantar nerve, neurilemoma, peripheral nerve sheath tumor
Stout and Carson first introduced the term "neurilemoma" in 1935 for a particular type of benign nerve sheath tumor (1). The lesion was accurately described histologically by Verocay in 1908 and named "neurinoma" by him in 1910 (1). Since that time, there have been several names used for this particular lesion, making terminology confusing. Some of the terms that have been used are peripheral glioma, perineurial fibroblastoma, schwannoma, neurinoma, and neurilemoma (1, 2). The two most common designations utilized today are neurilemoma and schwannoma. Because this neoplasm arises from nerve sheath cells, the term neurilemoma is preferred (1) and will be the only term used in this discussion. Although neurilemoma is the most common type of peripheral nerve sheath tumor (3), it is still uncommonly found in the foot (4-7). Most literature reports no predilection for sex or a particular age group. Neurilemomas can arise either on the trunk or extremities. However, there is a strong preponderance for them to arise on flexor aspects of the extremities due to the presence of larger peripheral nerve trunks (1-4, 6-8). Two of the more frequently involved nerves are the ulnar and peroneal (2, 9). It is well known that there is a higher incidence of neurilemomas in Von Recklinghausen's disease (1, 9, 10). However, in Von Recklingahausen's disease neurofibromas are a more common lesion than neurilemoma and multiple lesions are usually present (3). Malignant transformation is rare (2, 7 -9, 11-13).
Neurilemomas arising in the leg or ankle are more frequently seen than in the foot (5, 6, 11, 12, 14). There are several reports of neurilemomas arising Address correspondence to: Gregory P. Still, DPM, C Ped, 517 Big Thompson Ave. #120, Estes Park, CO 80517. Received for publication March 22, 2000; accepted in revised form for publication April l l , 200 I. The Journal of Foot & Ankle Surgery 1067-2516/01/4004-0236$4.00/0 Copyright © 200 I by the American College of Foot and Ankle Surgeons
236
THE JOURNAL OF FOOT & ANKLE SURGERY
from the posterior tibial nerve causing a tarsal tunnel syndrome (14-17). In addition, previously reported cases of neurilemoma arising from the medial plantar nerve were reported to cause a tarsal tunnel syndrome (11, 12). In one of those reports, the authors' description and intraoperative photographs reveal the lesion to be posterior to the medial malleolus in the tarsal tunnel (11). One report of neurilemoma of the medial plantar nerve is very similar to the case presented by the author (5). Most commonly, the patient will present with a complaint of a painful palpable mass. Often a history of a progressively enlarging mass that has been present from a few months to several years is elicited. Usually a single lesion is identified (1-4, 8, 9, 18), and the pain most often corresponds to the distribution of the affected nerve (1, 2, 4, 7, 8, 19). Clinical symptoms include paresthesias, hypesthesia, and, less frequently, hypoesthesia (1, 2, 4, 8). Although rare, motor weakness is possible (1). Physical examination often reveals a palpable mass that is mobile in a plane that is transverse to the course of the nerve and immobile in the longitudinal plane (2, 4, 8). It may transilluminate if the neoplasm is located superficially (1, 8). Palpation often produces pain and a positive Tinel's sign is frequently elicited with percussion (2, 10-12, 14, 16, 17). There are no reliable findings on physical examination to distinguish whether a soft-tissue mass is benign or malignant (20). Surgical removal is the treatment of choice (1, 4, 5, 7, 8, 16). The tumors can range in size from a few millimeters to 20 em (2, 7, 8). The smaller tumors are usually round and firm, while larger ones tend to be soft and lobulated (1, 2, 7, 8). The appearance upon excision is a glistening mass that is pearl gray, pink, or yellow in color. Grossly, the mass is fluctuant and encapsulated. After excision, the neoplasm does not have a high incidence of recurrence (1, 2, 4, 8, 18). Although very rare, there are reports of neurilemoma within bone (21, 22). Interestingly, one of the reports (22) involved a tumor
within the first sacral vertebra, left of the midline, that caused symptoms of pain and paresthesias to the left leg and foot. Histologically, neurilemomas grow slowly (1, 2, 8, 18). The neoplasm develops in the epineurium or perineurium and then expands and encapsulates itself. The capsule is derived from the perineurium (1, 8). Characteristically, neurilemomas have two types of cellular tissue in varying amounts upon microscopic examination. Antoni type A tissue forms a relatively orderly arrangement of cells with elongated nuclei. Antoni type B tissue is made up of cells with no orientation or attempt at differentiation of tissue. It is described as a loose myxoid zone (1, 7, 12, 18). Verocay bodies may also be present, which are tight organized formations of Antoni A cells (4, 8). Diagnosis can be aided by various means. Plainfilm radiographs may show increased soft-tissue density (16, 17). Neurilemomas have been identified with magnetic resonance imaging (MRI), high-resolution ultrasound (US), and computerized tomography (CT) (2). Although CT can be used to determine the size, shape, and location of a peripheral nerve tumor (19), it is no longer commonly used due to the superior quality of MRI. Peripheral nerve tumors in the extremities may be detected with US and are most commonly manifested as hypoechoic masses (23). However, US is primarily a screening test and is helpful in localizing the lesion. This is due to the fact that most soft-tissue tumors imaged with US manifest as hypoechoic masses; therefore, diagnosis should be based primarily on clinical findings (23). For cases involving the posterior tibial nerve, nerve conduction velocity studies may be abnormal (12, 24). However, a neurilemoma usually does not interfere with nerve function, so delayed conduction velocities are nonspecific for this lesion (3). On MRI exam, neurilemomas exhibit intermediate to moderately bright signal on TI-weighted images and bright signal on T2-weighted images (2, 18). Proton density images exhibit a moderately bright signal. Images usually show variable degrees of inhomogeneity (2). One particular study (2) showed that 3 of 12 neurilemomas studied exhibited atrophy along the longitudinal axis of the adjacent musculature associated with increased muscle signal. This atrophy was subtle and best appreciated following comparison of the affected extremity. Although MRI cannot determine between malignant and benign nerve sheath tumors, it is useful in defining the extent of the disease and the relationship of the tumor to neurovascular structures and surrounding musculature. The orthopedic goals of imaging include: I) definition of margins of the tumor, 2) relationship of the tumor to neurovascular structures, and 3) presence or absence of bone involvement (25).
Case Presentation
A 55-year-old female presented with a 2-year history of a slowly enlarging painful mass on the bottom of her left foot. Symptoms included sharp pain, burning, pins and needles sensation, and occasional numbness to the bottom of the left foot. All symptoms were gradually increasing. She had been evaluated by another physician and treated with over-the-counter orthotic devices, which did not help. Past medical history included moderate obesity and hypertension. Physical examination revealed a palpable mass located on the plantar aspect of the left foot along the distal medial aspect of the longitudinal arch. It was approximately 3.5 x 2.5 cm. Upon palpation the lesion was indurated, immobile, and seemed to be deep to the plantar fascia. Palpation produced paresthesias that radiated distally, especially into the second and third digits. Percussion revealed a positive Tinel's sign to the distribution of the medial plantar nerve. There was no motor weakness and light touch, proprioception, and vibratory sensations were normal. Plain-film radiological examination revealed a subtle increase in softtissue density on the AP view in the area of the proximal first intermetatarsal space. MRI revealed a mass in the plantar aspect of the left foot measuring 3.8 x 2.0 em. The mass was described on MRI as being oval-shaped with a bright signal pattern on T2 images (Fig. 1), and isointense or darker signal on T I and multiecho images. The patient was then scheduled for excisional biopsy of the mass. Operative Technique
A 5-cm curvilinear incision was made on the plantar aspect of the left foot from the proximal medial aspect of the longitudinal arch to the level of the first and second metatarsal shafts. The plantar fascia was encountered and incised longitudinally. A mass appeared to arise from the medial plantar nerve. It was glistening in appearance and pearl gray in color and appeared to be well encapsulated. The mass was then carefully enucleated from the medial plantar nerve. It did not appear to invade the internal substance of the medial plantar nerve but was visibly compressing it. The nerve appeared to be splayed and flattened under the mass. Routine closure was performed. Hemostasis was achieved with a pneumatic ankle tourniquet. Pathological analysis of the neoplasm revealed the following: Grossly, an Il-g 3.8 x 2.3 x 1.2 em firm, elastic gray-tan tissue mass with an intact shiny gray capsule. Microscopically, it was described as an encapsulated neoplasm of variable appearance. It was composed of spindle-shaped cells which interdigitated and focally formed Antoni type A palisades. In other areas, the tissue VOLUME 40, NUMBER 4, JULY/AUGUST 2001
237
FIGURE 1 A, Coronal T2 images show bright signal of the mass. The mass is seen in the medial longitudinal arch area. It is lateral to the abductor hallucis muscle and superficial to the flexor hallucis brevis muscle. B, Axial T2 images show bright signal of the mass, delineating its location lateral to abductor hallucis and superficial to flexor hallucis brevis.
digit. At 12 weeks postoperatively, the patient had begun a regular walking routine for exercise and weight reduction without complaints. At last follow-up, 19 months postoperatively, there was no palpable mass or excess cicatrix formation. The patient was without complaint and had exceeded her preoperative activity level. Summary
FIGURE 2 Photomicrograph of neurilemoma, showing spindleshaped cells that form Antoni type palisades (H&E, x20).
was looser and almost myxoid, forming Antoni type B tissue. In a few areas, Verocay bodies were present (Fig. 2). Postoperatively the patient was kept nonweightbearing in a posterior splint for 17 days. Weightbearing activity was commenced and at 5 weeks postoperative, the patient resumed walking in athletic style shoe gear and prefabricated orthoses. For the first 10 postoperative weeks, the patient complained of mild intermittent pain and paresthesias radiating into the second and third digits. The patient also complained of intermittent numbness to the second 238
THE JOURNAL OF FOOT & ANKLE SURGERY
If a painful mass presents in the foot or ankle and the pain is distributed along the course of a nerve, neurilemoma must be included in the differential diagnosis. Diagnosis should be based on clinical findings and imaging techniques. MRI is the imaging modality of choice and surgical excision is the treatment of choice. Upon excision of this peripheral nerve sheath tumor, it is not necessary to remove nerve segments. Recurrence rates upon excision are low. The presenting complaints of a palpable mass, pain, and paresthesias were similar to most other reports in the literature regarding neurilemoma. Unlike other reports of neurilemoma arising from the medial plantar nerve, a tarsal tunnel syndrome was not present in this case. References 1. Stout, A. P., Carson, W. The peripheral manifestations of the specific nerve sheath tumor (neurilemoma). Am. 1. Cancer.
24:751-789, 1935.
2. Stull, M. A., Moser, R. P., Kransdorf, M. 1., Bogumill, G. P., Nelson, M. C. Magnetic resonance appeara nce of peripheral nerve sheath tumors. Skel. Radiol. 20:9- 14, 1991. 3. Arnold, C. A., Kastrup, 1. 1., Rogers, V. P. Neurilemoma about the knee. Am. J. Sports Med. 27:668- 670, 1999. 4. White, N. B. Neurilemomas of the extremities. 1. Bone Joint Surg. 49-A :1605 -1610,1967. 5. Zuckerman, J. D., Powers, B., Miller, 1. W., Lippert , F. Benign solitary schwannoma of the foot. Clin. Orthop. 228:278- 280, 1988. 6. von Deimlin g, U., Munzenberg, K. J., Fischer, H. P. Multiple benign schwannomas of the foot. Arch. Orthop. Trauma Surg. 115:240 - 242, 1996. 7. Das Gupta, T. K., Brasfield, R. D., Strong, E. W., Hajdu, S. I. Benign solitary schwannomas (neurilemomas). Cancer 24:355 - 366, 1969. 8. Hennessee, M. T., Walter, J. H., Wallace, G., Lemont, H., Quintavalle, P. R. Benign schwannoma. J. Am. Podiatr. Med. Assoc. 75:310 - 314,1985 . 9. Bergmann, A. G. Imaging of musculo skeletal tumors , ch. 20. In Musculoskeletal Disorders of the Low er Extremities , pp. 334 -345, edited by L. M. Oloff, W. B. Saunders, Philadelphia , 1994. 10. Potter, G. K., Ward, K. A. Tumors, Ch. 46. In Comprehens ive Textbook of Foot Su rg ery, 2nd ed., vol. 2, pp. 11 61-11 63, edited by E. D. McGlamry, A. S. Banks, M. S. Downey, Williams & Wilkins, Baltimore, 1992. I I. Menon, J., Dorfman, H. D., Renbaum, J., Friedler, S. Tarsal tunnel syndro me secondary to neurilemoma of the medial plantar nerve. J. Bone Joint Surg. 62-A:30 1-303, 1980. 12. Aydin, A. T., Karaveli, S., Tuzener, S. Tarsal tunnel syndro me secondary to neurile moma of the medial plantar nerve. J. Foot Surg. 30:114 -116,1991.
13. Cohen, L. M., Schwartz, A. M., Rockoff, S. O. Benign schwannomas: pathologic basis for CT inhomogeneities. AJR 147: 141-1 43, 1986. 14. Briestein, R. J. Compression neurop athy secondary to neurilemoma. 1. Am. Podiatr. Med. Assoc . 75:160-1 61, 1985. 15. Levin, A. S., Titchenal, W.O., Clark, J. Tarsal tunnel secondary to neurilemoma. J. Am. Podiatr. Med . Assoc. 67:429-431, 1977. 16. Grossman, M. R, Mandracchia, V. J., Urbas, W. M., Mandracchia, D. M. Neuril emoma of the posterior tibial nerve with an uncommon presentation. J. Foot Surg. 3 1:219-224, 1992. 17. Dowling, G. L., Skaggs, R Neurilemoma (schwannoma) as a cause of tarsal tunnel syndrome. J. Am. Podiatr. Med. Assoc. 72:45 -47, 1982 18. Kerr, R. Tumors and tumorlike lesions of soft tissue and bone, ch. 9. In MRI of the Foo t and Ankle, pp. 239 -240, edited by A. L. Deutsch, J. H. Mink, R. Kerr, Raven Press, New York, 1992. 19. Powers, S. K., Norman, D., Edwards, M. S. B. Computeri zed tomogra phy of periph eral nerve lesions. 1. Neurosurg. 59:131-1 36, 1983 . 20. Chang, A. E., Sondak, V. K. Clinical evaluation and treatment of soft tissue tumors. ch. 2. In Soft Tissue Tumors, pp. 17-21 , edited by F. M. Enzinger, S. W. Weiss, Mosby, St. Louis, 1988. 21. Conley, A. H., Miller, D. S. Neuril emoma of bone. J. Bone Joint Surg. 24:684 -689, 1942. 22. Takata, K., Okuda, K., Ochi, M. Intraosseous neurilemoma of the sternum. Ann. Thorac. Surg. 67:1474-1476, 1999. 23. Foma ge, B. D. Peripheral nerves of the extremities: imaging with US. Radiology 167:179 -1 82, 1988. 24. Smith, W., Amis, J. A. Neurilemoma of the tibial nerve. J. Bone Joint Surg. 74-A:443-444, 1992. 25. Kilcoyne, R. F., Richardson, M. L. , Porter, B. A., Olson, D.O., Greenlee, T. K., Lanzer, W. Magnetic resonance imaging of soft tissue masses. Clin. Orthop. 228: 13- 19, 1988.
VOLUME 40, NUMBER 4, JULY/AUGUST 2001
239
Key words: foot, medial plantar nerve, neurilemoma, peripheral nerve sheath tumor
Stout and Carson first introduced the term "neurilemoma" in 1935 for a particular type of benign nerve sheath tumor (1). The lesion was accurately described histologically by Verocay in 1908 and named "neurinoma" by him in 1910 (1). Since that time, there have been several names used for this particular lesion, making terminology confusing. Some of the terms that have been used are peripheral glioma, perineurial fibroblastoma, schwannoma, neurinoma, and neurilemoma (1, 2). The two most common designations utilized today are neurilemoma and schwannoma. Because this neoplasm arises from nerve sheath cells, the term neurilemoma is preferred (1) and will be the only term used in this discussion. Although neurilemoma is the most common type of peripheral nerve sheath tumor (3), it is still uncommonly found in the foot (4-7). Most literature reports no predilection for sex or a particular age group. Neurilemomas can arise either on the trunk or extremities. However, there is a strong preponderance for them to arise on flexor aspects of the extremities due to the presence of larger peripheral nerve trunks (1-4, 6-8). Two of the more frequently involved nerves are the ulnar and peroneal (2, 9). It is well known that there is a higher incidence of neurilemomas in Von Recklinghausen's disease (1, 9, 10). However, in Von Recklingahausen's disease neurofibromas are a more common lesion than neurilemoma and multiple lesions are usually present (3). Malignant transformation is rare (2, 7 -9, 11-13).
Neurilemomas arising in the leg or ankle are more frequently seen than in the foot (5, 6, 11, 12, 14). There are several reports of neurilemomas arising Address correspondence to: Gregory P. Still, DPM, C Ped, 517 Big Thompson Ave. #120, Estes Park, CO 80517. Received for publication March 22, 2000; accepted in revised form for publication April l l , 200 I. The Journal of Foot & Ankle Surgery 1067-2516/01/4004-0236$4.00/0 Copyright © 200 I by the American College of Foot and Ankle Surgeons
236
THE JOURNAL OF FOOT & ANKLE SURGERY
from the posterior tibial nerve causing a tarsal tunnel syndrome (14-17). In addition, previously reported cases of neurilemoma arising from the medial plantar nerve were reported to cause a tarsal tunnel syndrome (11, 12). In one of those reports, the authors' description and intraoperative photographs reveal the lesion to be posterior to the medial malleolus in the tarsal tunnel (11). One report of neurilemoma of the medial plantar nerve is very similar to the case presented by the author (5). Most commonly, the patient will present with a complaint of a painful palpable mass. Often a history of a progressively enlarging mass that has been present from a few months to several years is elicited. Usually a single lesion is identified (1-4, 8, 9, 18), and the pain most often corresponds to the distribution of the affected nerve (1, 2, 4, 7, 8, 19). Clinical symptoms include paresthesias, hypesthesia, and, less frequently, hypoesthesia (1, 2, 4, 8). Although rare, motor weakness is possible (1). Physical examination often reveals a palpable mass that is mobile in a plane that is transverse to the course of the nerve and immobile in the longitudinal plane (2, 4, 8). It may transilluminate if the neoplasm is located superficially (1, 8). Palpation often produces pain and a positive Tinel's sign is frequently elicited with percussion (2, 10-12, 14, 16, 17). There are no reliable findings on physical examination to distinguish whether a soft-tissue mass is benign or malignant (20). Surgical removal is the treatment of choice (1, 4, 5, 7, 8, 16). The tumors can range in size from a few millimeters to 20 em (2, 7, 8). The smaller tumors are usually round and firm, while larger ones tend to be soft and lobulated (1, 2, 7, 8). The appearance upon excision is a glistening mass that is pearl gray, pink, or yellow in color. Grossly, the mass is fluctuant and encapsulated. After excision, the neoplasm does not have a high incidence of recurrence (1, 2, 4, 8, 18). Although very rare, there are reports of neurilemoma within bone (21, 22). Interestingly, one of the reports (22) involved a tumor
within the first sacral vertebra, left of the midline, that caused symptoms of pain and paresthesias to the left leg and foot. Histologically, neurilemomas grow slowly (1, 2, 8, 18). The neoplasm develops in the epineurium or perineurium and then expands and encapsulates itself. The capsule is derived from the perineurium (1, 8). Characteristically, neurilemomas have two types of cellular tissue in varying amounts upon microscopic examination. Antoni type A tissue forms a relatively orderly arrangement of cells with elongated nuclei. Antoni type B tissue is made up of cells with no orientation or attempt at differentiation of tissue. It is described as a loose myxoid zone (1, 7, 12, 18). Verocay bodies may also be present, which are tight organized formations of Antoni A cells (4, 8). Diagnosis can be aided by various means. Plainfilm radiographs may show increased soft-tissue density (16, 17). Neurilemomas have been identified with magnetic resonance imaging (MRI), high-resolution ultrasound (US), and computerized tomography (CT) (2). Although CT can be used to determine the size, shape, and location of a peripheral nerve tumor (19), it is no longer commonly used due to the superior quality of MRI. Peripheral nerve tumors in the extremities may be detected with US and are most commonly manifested as hypoechoic masses (23). However, US is primarily a screening test and is helpful in localizing the lesion. This is due to the fact that most soft-tissue tumors imaged with US manifest as hypoechoic masses; therefore, diagnosis should be based primarily on clinical findings (23). For cases involving the posterior tibial nerve, nerve conduction velocity studies may be abnormal (12, 24). However, a neurilemoma usually does not interfere with nerve function, so delayed conduction velocities are nonspecific for this lesion (3). On MRI exam, neurilemomas exhibit intermediate to moderately bright signal on TI-weighted images and bright signal on T2-weighted images (2, 18). Proton density images exhibit a moderately bright signal. Images usually show variable degrees of inhomogeneity (2). One particular study (2) showed that 3 of 12 neurilemomas studied exhibited atrophy along the longitudinal axis of the adjacent musculature associated with increased muscle signal. This atrophy was subtle and best appreciated following comparison of the affected extremity. Although MRI cannot determine between malignant and benign nerve sheath tumors, it is useful in defining the extent of the disease and the relationship of the tumor to neurovascular structures and surrounding musculature. The orthopedic goals of imaging include: I) definition of margins of the tumor, 2) relationship of the tumor to neurovascular structures, and 3) presence or absence of bone involvement (25).
Case Presentation
A 55-year-old female presented with a 2-year history of a slowly enlarging painful mass on the bottom of her left foot. Symptoms included sharp pain, burning, pins and needles sensation, and occasional numbness to the bottom of the left foot. All symptoms were gradually increasing. She had been evaluated by another physician and treated with over-the-counter orthotic devices, which did not help. Past medical history included moderate obesity and hypertension. Physical examination revealed a palpable mass located on the plantar aspect of the left foot along the distal medial aspect of the longitudinal arch. It was approximately 3.5 x 2.5 cm. Upon palpation the lesion was indurated, immobile, and seemed to be deep to the plantar fascia. Palpation produced paresthesias that radiated distally, especially into the second and third digits. Percussion revealed a positive Tinel's sign to the distribution of the medial plantar nerve. There was no motor weakness and light touch, proprioception, and vibratory sensations were normal. Plain-film radiological examination revealed a subtle increase in softtissue density on the AP view in the area of the proximal first intermetatarsal space. MRI revealed a mass in the plantar aspect of the left foot measuring 3.8 x 2.0 em. The mass was described on MRI as being oval-shaped with a bright signal pattern on T2 images (Fig. 1), and isointense or darker signal on T I and multiecho images. The patient was then scheduled for excisional biopsy of the mass. Operative Technique
A 5-cm curvilinear incision was made on the plantar aspect of the left foot from the proximal medial aspect of the longitudinal arch to the level of the first and second metatarsal shafts. The plantar fascia was encountered and incised longitudinally. A mass appeared to arise from the medial plantar nerve. It was glistening in appearance and pearl gray in color and appeared to be well encapsulated. The mass was then carefully enucleated from the medial plantar nerve. It did not appear to invade the internal substance of the medial plantar nerve but was visibly compressing it. The nerve appeared to be splayed and flattened under the mass. Routine closure was performed. Hemostasis was achieved with a pneumatic ankle tourniquet. Pathological analysis of the neoplasm revealed the following: Grossly, an Il-g 3.8 x 2.3 x 1.2 em firm, elastic gray-tan tissue mass with an intact shiny gray capsule. Microscopically, it was described as an encapsulated neoplasm of variable appearance. It was composed of spindle-shaped cells which interdigitated and focally formed Antoni type A palisades. In other areas, the tissue VOLUME 40, NUMBER 4, JULY/AUGUST 2001
237
FIGURE 1 A, Coronal T2 images show bright signal of the mass. The mass is seen in the medial longitudinal arch area. It is lateral to the abductor hallucis muscle and superficial to the flexor hallucis brevis muscle. B, Axial T2 images show bright signal of the mass, delineating its location lateral to abductor hallucis and superficial to flexor hallucis brevis.
digit. At 12 weeks postoperatively, the patient had begun a regular walking routine for exercise and weight reduction without complaints. At last follow-up, 19 months postoperatively, there was no palpable mass or excess cicatrix formation. The patient was without complaint and had exceeded her preoperative activity level. Summary
FIGURE 2 Photomicrograph of neurilemoma, showing spindleshaped cells that form Antoni type palisades (H&E, x20).
was looser and almost myxoid, forming Antoni type B tissue. In a few areas, Verocay bodies were present (Fig. 2). Postoperatively the patient was kept nonweightbearing in a posterior splint for 17 days. Weightbearing activity was commenced and at 5 weeks postoperative, the patient resumed walking in athletic style shoe gear and prefabricated orthoses. For the first 10 postoperative weeks, the patient complained of mild intermittent pain and paresthesias radiating into the second and third digits. The patient also complained of intermittent numbness to the second 238
THE JOURNAL OF FOOT & ANKLE SURGERY
If a painful mass presents in the foot or ankle and the pain is distributed along the course of a nerve, neurilemoma must be included in the differential diagnosis. Diagnosis should be based on clinical findings and imaging techniques. MRI is the imaging modality of choice and surgical excision is the treatment of choice. Upon excision of this peripheral nerve sheath tumor, it is not necessary to remove nerve segments. Recurrence rates upon excision are low. The presenting complaints of a palpable mass, pain, and paresthesias were similar to most other reports in the literature regarding neurilemoma. Unlike other reports of neurilemoma arising from the medial plantar nerve, a tarsal tunnel syndrome was not present in this case. References 1. Stout, A. P., Carson, W. The peripheral manifestations of the specific nerve sheath tumor (neurilemoma). Am. 1. Cancer.
24:751-789, 1935.
2. Stull, M. A., Moser, R. P., Kransdorf, M. 1., Bogumill, G. P., Nelson, M. C. Magnetic resonance appeara nce of peripheral nerve sheath tumors. Skel. Radiol. 20:9- 14, 1991. 3. Arnold, C. A., Kastrup, 1. 1., Rogers, V. P. Neurilemoma about the knee. Am. J. Sports Med. 27:668- 670, 1999. 4. White, N. B. Neurilemomas of the extremities. 1. Bone Joint Surg. 49-A :1605 -1610,1967. 5. Zuckerman, J. D., Powers, B., Miller, 1. W., Lippert , F. Benign solitary schwannoma of the foot. Clin. Orthop. 228:278- 280, 1988. 6. von Deimlin g, U., Munzenberg, K. J., Fischer, H. P. Multiple benign schwannomas of the foot. Arch. Orthop. Trauma Surg. 115:240 - 242, 1996. 7. Das Gupta, T. K., Brasfield, R. D., Strong, E. W., Hajdu, S. I. Benign solitary schwannomas (neurilemomas). Cancer 24:355 - 366, 1969. 8. Hennessee, M. T., Walter, J. H., Wallace, G., Lemont, H., Quintavalle, P. R. Benign schwannoma. J. Am. Podiatr. Med. Assoc. 75:310 - 314,1985 . 9. Bergmann, A. G. Imaging of musculo skeletal tumors , ch. 20. In Musculoskeletal Disorders of the Low er Extremities , pp. 334 -345, edited by L. M. Oloff, W. B. Saunders, Philadelphia , 1994. 10. Potter, G. K., Ward, K. A. Tumors, Ch. 46. In Comprehens ive Textbook of Foot Su rg ery, 2nd ed., vol. 2, pp. 11 61-11 63, edited by E. D. McGlamry, A. S. Banks, M. S. Downey, Williams & Wilkins, Baltimore, 1992. I I. Menon, J., Dorfman, H. D., Renbaum, J., Friedler, S. Tarsal tunnel syndro me secondary to neurilemoma of the medial plantar nerve. J. Bone Joint Surg. 62-A:30 1-303, 1980. 12. Aydin, A. T., Karaveli, S., Tuzener, S. Tarsal tunnel syndro me secondary to neurile moma of the medial plantar nerve. J. Foot Surg. 30:114 -116,1991.
13. Cohen, L. M., Schwartz, A. M., Rockoff, S. O. Benign schwannomas: pathologic basis for CT inhomogeneities. AJR 147: 141-1 43, 1986. 14. Briestein, R. J. Compression neurop athy secondary to neurilemoma. 1. Am. Podiatr. Med. Assoc . 75:160-1 61, 1985. 15. Levin, A. S., Titchenal, W.O., Clark, J. Tarsal tunnel secondary to neurilemoma. J. Am. Podiatr. Med . Assoc. 67:429-431, 1977. 16. Grossman, M. R, Mandracchia, V. J., Urbas, W. M., Mandracchia, D. M. Neuril emoma of the posterior tibial nerve with an uncommon presentation. J. Foot Surg. 3 1:219-224, 1992. 17. Dowling, G. L., Skaggs, R Neurilemoma (schwannoma) as a cause of tarsal tunnel syndrome. J. Am. Podiatr. Med. Assoc. 72:45 -47, 1982 18. Kerr, R. Tumors and tumorlike lesions of soft tissue and bone, ch. 9. In MRI of the Foo t and Ankle, pp. 239 -240, edited by A. L. Deutsch, J. H. Mink, R. Kerr, Raven Press, New York, 1992. 19. Powers, S. K., Norman, D., Edwards, M. S. B. Computeri zed tomogra phy of periph eral nerve lesions. 1. Neurosurg. 59:131-1 36, 1983 . 20. Chang, A. E., Sondak, V. K. Clinical evaluation and treatment of soft tissue tumors. ch. 2. In Soft Tissue Tumors, pp. 17-21 , edited by F. M. Enzinger, S. W. Weiss, Mosby, St. Louis, 1988. 21. Conley, A. H., Miller, D. S. Neuril emoma of bone. J. Bone Joint Surg. 24:684 -689, 1942. 22. Takata, K., Okuda, K., Ochi, M. Intraosseous neurilemoma of the sternum. Ann. Thorac. Surg. 67:1474-1476, 1999. 23. Foma ge, B. D. Peripheral nerves of the extremities: imaging with US. Radiology 167:179 -1 82, 1988. 24. Smith, W., Amis, J. A. Neurilemoma of the tibial nerve. J. Bone Joint Surg. 74-A:443-444, 1992. 25. Kilcoyne, R. F., Richardson, M. L. , Porter, B. A., Olson, D.O., Greenlee, T. K., Lanzer, W. Magnetic resonance imaging of soft tissue masses. Clin. Orthop. 228: 13- 19, 1988.
VOLUME 40, NUMBER 4, JULY/AUGUST 2001
239