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Sciatica in a patient with unusual peripheral nerve sheath tumors
Surgical Neurology 66 (2006) 634 – 637 www.surgicalneurology-online.com
Neoplasm
Sciatica in a patient with unusual peripheral nerve sheath tumors Francis Kralick, DOa,4, Robert Koenigsberg, DO, FAOCRb a
Departments of Neurosurgery, and bRadiology, Drexel University College of Medicine, Hahnemann University Hospital, PA 19102, USA Received 9 February 2006; accepted 19 May 2006
Abstract
Background: Other causes such as peripheral schwannomas can mimic lumbar disk disease. Case Description: We present an unusual case of multiple nerve sheath tumors in a patient with left radicular leg pain accompanied by a Tinel sign. Initial lumbar MR imaging revealed a mass in the right lumbar plexus, side opposite the patient’s symptoms. Magnetic resonance neurography subsequently revealed a compressive mass of the sciatic nerve proximal to the popliteal fossa, histologically identified as a schwannoma. Conclusion: This case emphasizes the importance of continued investigation when the radiographic findings do not correlate with the patient’s history in the presence of localizing signs on physical examination. D 2006 Elsevier Inc. All rights reserved.
Keywords:
Schwannoma; MR neurography; Tinel sign
1. Introduction Patients presenting for neurosurgical consultation frequently are accompanied by diagnostic imaging studies suggesting the cause the patient’s pain, frequently discogenic disease. Nevertheless, other causes such as peripheral schwannomas can mimic lumbar disk disease and can be an important unrecognized etiology of radicular pain. We present an unusual case of multiple nerve sheath tumors in a patient with left radicular leg pain. We stress the importance of the neurosurgical examination in patients with lumbar radiculopathy to guide appropriate treatment. 2. Case report A 58-year-old man presented to his family physician complaining of left radicular leg pain. Appropriately, the family physician obtained a screening MR evaluation of the lumbar spine prompting neurosurgical consultation. On presentation to neurosurgery, the patient described his pain as beginning 5 months prior on the side of his left foot with cramping of his fifth digit. The cramping began to include the remainder of the toes of the left foot and progressed into Abbreviation: MR, magnetic resonance. 4 Corresponding author. Tel.: +1 215 762 3131; fax: +1 215 762 3132. E-mail address: [email protected] (F. Kralick). 0090-3019/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2006.06.016
his calf. He described the pain as intermittent, sharp, and stabbing, further aggravated by sitting or lying in bed. He denied numbness, parathesias, bowel or bladder dysfunction, or motor weakness. His medical history was otherwise unremarkable; medications include 325 mg of aspirin daily because of a strong family history of coronary artery disease. He lists no other family history. Neurosurgical examination revealed a well-developed man with intact cranial nerves and preservation of higher cognitive functions. He was normoreflexic with down-going toes and no signs of upper motor neuron disease. Motor strength was full to hand resistance with normal gait. Sensation was normal to light touch and pinprick, position sense was within normal limits. A Tinel sign was consistently elicited with palpation of the affected left posterior thigh. He had no evidence of cutaneous abnormalities such as cafe´ au lait spots or freckling. Slit-lamp examination showed no posterior subcapsular cataracts or Lisch iris nodules. The initial lumbar spine MR revealed a normal vertebral central canal with mild disk bulges at the L4/5 and L5/S1 levels and desiccation at the L3/4, L4/5, and L5/S1 levels (Fig. 1). Furthermore, a 3-cm-diameter mass was identified in the right paravertebral musculature, appearing hypointense on T1-weighted images and relatively hyperintense on T2-weighted images (Fig. 2). Although the patient was referred to neurosurgery for mass excision, the lesion could not adequately explain the patient’s symptoms (opposite
F. Kralick, R. Koenigsberg / Surgical Neurology 66 (2006) 634–637
635
Fig. 1. T2-weighted sagittal MR images demonstrating mild disk desiccation at the L3/4, L4/5, and L5/S1 levels. Small disk bulges are also seen at the posterior margins of the L4/5 and L5/S1 disks.
side). This prompted further imaging workup, which included MR imaging of the left lower extremity due primarily to the unexplained Tinel sign elicited on physical exam. This MR study showed a similar mass to that found in the psoas muscle imbedded within the leg musculature in direct continuity with the sciatic nerve (Fig. 3). This mass measured 3.5 cm, with signal characteristics nearly identical
Fig. 3. A: Contrast-enhanced coronal image of the left thigh demonstrating the lesion with intense capsular enhancement. Notice the central tumor material resembles the central tumor characteristics seen in paraspinal mass (Fig. 2). B: Sagittal contrast-enhanced T1-weighted image demonstrating the left thigh mass in continuity with the sciatic nerve.
to the paraspinal mass. Furthermore, imaging of mass suggested continuity with the sciatic nerve. The patient subsequently underwent surgical removal of the leg mass. With the patient in the prone position, a linear, rostral-caudal incision was made proximal to the popliteal fossa (Fig. 4). A plane was developed between biceps femoris and semitendinosis muscle and the mass identified. The mass was eccentric to the sciatic nerve, which coursed over the top of the mass. The yellow mass was dissected free of the nerve en bloc with adherence to microneurosurgical dissection. There was minimal disruption of the sciatic nerve. The mass was removed en bloc and histologically diagnosed as a schwannoma (Fig. 5). Postoperatively, there were no new neurological deficits. The patient’s leg and foot pain were markedly reduced. Surgical resection of the second asymptomatic mass arising from the right lumbar plexus remains pending. 3. Discussion Fig. 2. A: Axial T2-weighted MR image showing a 3-cm right paravertebral mass. B: Coronal T2-weighted MR image demonstrating that the mass arises along the right L3 lumbar plexus, accompanied by a hyperintense capsule.
Tumors arising from peripheral nerves are usually benign masses. The most common tumors are schwannomas, which arise from the schwann cells of peripheral nerves, in this
636
F. Kralick, R. Koenigsberg / Surgical Neurology 66 (2006) 634–637
case, the sciatic nerve [2,5-7]. Sciatic nerve sheath schwannomas tend to occur in the second to fifth decade and are more common in women [5,22]. They are comprised of densely packed spindle cell as in Antoni type A or more loosely textured stroma as in Antoni type B. Most schwannomas are solitary masses but can be multiple as in this case [4,7]. Multiple schwannomas are found in patients with neurofibromatosis type II, of which bilateral vestibular neuromas are the hallmark [1,18].
Fig. 5. En bloc 3.5-cm excised mass.
Fig. 4. A: Left posterior thigh incision. B: Intraoperative view of the mass with the sciatic nerve coursing over the top of the nerve. C: Sciatic nerve after en bloc excision of schwannoma.
Clinical presentations of peripheral nerve lesions can be confusing or misdiagnosed [5,6,8-11,14,17,20]. Few other disorders require detailed examination, knowledge of anatomic course, patterns of innervation, and experience to accurately evaluate disorders of peripheral nerves [12]. As in this case, other reports of midthigh sciatic nerve schwannoma have produced foot pain mimicking plantar neuropathy [6]. Ghaly [5] described a posterior tibial nerve schwannoma that was undiagnosed for 10 years and ascribed to psychogenic pain. As part of a routine workup for lumbar radiculapathy, MR lumbar spine imaging is typically the initial diagnostic test obtained by primary clinicians to evaluate discogenic causes of radiculopathy. This study did demonstrate a right paravertebral mass showing characteristic imaging appearance of peripheral schwannoma [21], but it was clinically misleading. Careful correlation of the presence of the right-sided paravertebral mass and the patient’s primarily left-sided complaints of pain necessitated further neurosurgical diagnostic studies. One important feature of this case is the unusual multiplicity of schwannomas and the recognition that the initial abnormality referred for neurosurgical excision was not the lesion responsible for the patient’s symptoms. The Tinel sign, named after the French neurologist Jules Tinel, proved an invaluable physical sign in identifying the level of nerve injury in our patient [12]. Importantly, the (+) Tinel sign led to further imaging studies, which clearly demonstrated the mass responsible for the patient’s pain complaints. The evolution of MR neurography has certainly increased the detection of peripheral nerve abnormalities [3,15,16]. Kuntz et al [13] demonstrated in their series of 5 patients that MR neurography is useful in the preoperative evaluation and planning of surgery for peripheral nerve tumors. Using a 1.5-T MR imaging, they were able to correlate increased signal on T2-weighted fast spin-echo and short tau inversion recovery fast spin-echo pulse sequences with clinical and electophysiologic evidence of nerve injury. Sintzoff et al [19] described a case of simultaneous neurofibroma and schwannoma of the sciatic nerve with differences in enhancement characteristics [18,19]. The masses described in our report appeared to arise from
F. Kralick, R. Koenigsberg / Surgical Neurology 66 (2006) 634–637
peripheral nerves and displayed MR signal characteristics typical for a schwannoma. Furthermore, the imaging technique used in our case provided excellent quality views of the mass for the purposes of surgical planning. Once the muscles of the posterior thigh were separated, the mass was easily palpated, localized, and excised. 4. Conclusion We present an unusual case of multiple peripheral schwannomas. The development of improved imaging such as MR neurography has improved the diagnostic sensitivity of peripheral nerve lesions. This case emphasizes the importance of continued investigation when the radiographic findings do not correlate with the patient’s history in the presence of localizing signs on physical examination. References [1] Enzinger FM, Weiss SW. Benign tumors of peripheral nerves. In: Enzinger FM, Weiss SW, editors. Soft tissue tumors. 2nd ed. St. Louis7 Mosby; 1988. p. 719 - 80. [2] Egelhoff JC, Bates DJ, Ross JS, Rothner AD, Cohen BH. Spinal MR findings in neurofibromatosis types 1 and 2. AJNR Am J Neuroradiol 1992;13:1071 - 7. [3] Filler AG, Kliot M, Howe FA, Hayes CE, Saunders DE, Goodkin R, Bell BA, Winn HR, Griffiths JR, Tsuruda JS. Application of magnetic resonance neurography in the evaluation of patients with peripheral nerve pathology. J Neurosurg 1996;85(2):299 - 309. [4] Geschickler CF. Tumors of peripheral nerves. Am J Cancer 1935;25: 377 - 410. [5] Ghaly RF. A posterior tibial nerve neurilemoma unrecognized for 10 years: case report. Neurosurgery 2001;48:668 - 72. [6] Gominak SC, Ochoa JL. Sciatic schwannoma of the thigh causing foot pain mimicking plantar neuropathy. Muscle Nerve 1998;21:528 - 30. [7] Grant GA, Goodkin R, Kliot M. Evaluation and surgical management of peripheral nerve problems. Neurosurgery 1999;44:825 - 40.
637
[8] Harrison MJ, Leis HT, Johnson BA, MacDonald WD, Goldman CD. Hemangiopericytoma of the sciatic notch presenting as sciatica in a young healthy man: case report. Neurosurgery 1995;37:1208 - 12. [9] Kanamori M, Matsui H, Yudoh K. Solitary T-cell lymphoma of the sciatic nerve: case report. Neurosurgery 1995;36:1203 - 5. [10] Katirji B, Wilbourn AJ. High sciatic lesion mimicking peroneal neuropathy at the fibular head. J Neurol Sci 1994;121:172 - 5. [11] Kelso TB, Ferrari CJ, Frassica FJ. Sciatica caused by a neurilemoma of the intrapelvic portion of the sciatic nerve: a case report. J Bone Joint Surg Am 1993;75A:603 - 5. [12] Kline DG, Hudson AR, Zager E. Selection and preoperative work-up for peripheral nerve surgery. Clin Neurosurg 1992;39:8 - 35. [13] Kuntz IV C, Blake L, Britz G, Filler A, Hayes CE, Goodkin R, Tsuruda J, Maravilla K, Kliot M. Magnetic resonance neurography of peripheral nerve lesions in the lower extremity: technical report. Neurosurgery 1996;39:750 - 7. [14] Laurencin CT, Bain M, Yue JJ, Glick H. Schwannoma of the superficial peroneal nerve presenting as web space pain. J Foot Ankle Surg 1995;34:532 - 3. [15] Maravilla KR, Bowen BC. Imaging of the peripheral nervous system: evaluation of peripheral neuropathy and plexopathy. AJNR Am J Neuroradiol 1998;19:1011 - 23. [16] Moore KR, Tsuruda JS, Dailey AT. The value of MR neurography for evaluating extraspinal neuropathic leg pain: a pictorial essay. AJNR Am J Neuroradiol 2001;22:786 - 94. [17] Riccardi C, Ugo P. Slow and unrecognized progression of schwannoma of the sciatic nerve [in Italian]. Chir Organi Mov 1996;81:79 - 83. [18] Shrier DA, Rubio A, Numaguchi Y, Powers JM. Infarcted spinal schwannoma: an unusual MR finding. AJNR Am J Neuroradiol 1996; 17:1566 - 8. [19] Sintzoff SA, Bank WO, Gevenois PA, Matos C, Noterman J, Flament-Durand J, Struyven J. Simultaneous neurofibroma and schwannoma of the sciatic nerve. AJNR Am J Neuroradiol 1992;13: 1249 - 52. [20] Smith W, Amis JA. Neurilemoma of the tibial nerve: a case report. J Bone Joint Surg Am 1992;74A:443 - 4. [21] Varma DGK, Moulopoulos A, Sara AS. MR imaging of extracranial nerve sheath tumors. J Comput Assist Tomogr 1992;16:448 - 53. [22] Woodruff JM. The pathology and treatment of peripheral nerve tumors and tumor-like conditions. CA Cancer J Clin 1993;43:290 - 308.
Neoplasm
Sciatica in a patient with unusual peripheral nerve sheath tumors Francis Kralick, DOa,4, Robert Koenigsberg, DO, FAOCRb a
Departments of Neurosurgery, and bRadiology, Drexel University College of Medicine, Hahnemann University Hospital, PA 19102, USA Received 9 February 2006; accepted 19 May 2006
Abstract
Background: Other causes such as peripheral schwannomas can mimic lumbar disk disease. Case Description: We present an unusual case of multiple nerve sheath tumors in a patient with left radicular leg pain accompanied by a Tinel sign. Initial lumbar MR imaging revealed a mass in the right lumbar plexus, side opposite the patient’s symptoms. Magnetic resonance neurography subsequently revealed a compressive mass of the sciatic nerve proximal to the popliteal fossa, histologically identified as a schwannoma. Conclusion: This case emphasizes the importance of continued investigation when the radiographic findings do not correlate with the patient’s history in the presence of localizing signs on physical examination. D 2006 Elsevier Inc. All rights reserved.
Keywords:
Schwannoma; MR neurography; Tinel sign
1. Introduction Patients presenting for neurosurgical consultation frequently are accompanied by diagnostic imaging studies suggesting the cause the patient’s pain, frequently discogenic disease. Nevertheless, other causes such as peripheral schwannomas can mimic lumbar disk disease and can be an important unrecognized etiology of radicular pain. We present an unusual case of multiple nerve sheath tumors in a patient with left radicular leg pain. We stress the importance of the neurosurgical examination in patients with lumbar radiculopathy to guide appropriate treatment. 2. Case report A 58-year-old man presented to his family physician complaining of left radicular leg pain. Appropriately, the family physician obtained a screening MR evaluation of the lumbar spine prompting neurosurgical consultation. On presentation to neurosurgery, the patient described his pain as beginning 5 months prior on the side of his left foot with cramping of his fifth digit. The cramping began to include the remainder of the toes of the left foot and progressed into Abbreviation: MR, magnetic resonance. 4 Corresponding author. Tel.: +1 215 762 3131; fax: +1 215 762 3132. E-mail address: [email protected] (F. Kralick). 0090-3019/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2006.06.016
his calf. He described the pain as intermittent, sharp, and stabbing, further aggravated by sitting or lying in bed. He denied numbness, parathesias, bowel or bladder dysfunction, or motor weakness. His medical history was otherwise unremarkable; medications include 325 mg of aspirin daily because of a strong family history of coronary artery disease. He lists no other family history. Neurosurgical examination revealed a well-developed man with intact cranial nerves and preservation of higher cognitive functions. He was normoreflexic with down-going toes and no signs of upper motor neuron disease. Motor strength was full to hand resistance with normal gait. Sensation was normal to light touch and pinprick, position sense was within normal limits. A Tinel sign was consistently elicited with palpation of the affected left posterior thigh. He had no evidence of cutaneous abnormalities such as cafe´ au lait spots or freckling. Slit-lamp examination showed no posterior subcapsular cataracts or Lisch iris nodules. The initial lumbar spine MR revealed a normal vertebral central canal with mild disk bulges at the L4/5 and L5/S1 levels and desiccation at the L3/4, L4/5, and L5/S1 levels (Fig. 1). Furthermore, a 3-cm-diameter mass was identified in the right paravertebral musculature, appearing hypointense on T1-weighted images and relatively hyperintense on T2-weighted images (Fig. 2). Although the patient was referred to neurosurgery for mass excision, the lesion could not adequately explain the patient’s symptoms (opposite
F. Kralick, R. Koenigsberg / Surgical Neurology 66 (2006) 634–637
635
Fig. 1. T2-weighted sagittal MR images demonstrating mild disk desiccation at the L3/4, L4/5, and L5/S1 levels. Small disk bulges are also seen at the posterior margins of the L4/5 and L5/S1 disks.
side). This prompted further imaging workup, which included MR imaging of the left lower extremity due primarily to the unexplained Tinel sign elicited on physical exam. This MR study showed a similar mass to that found in the psoas muscle imbedded within the leg musculature in direct continuity with the sciatic nerve (Fig. 3). This mass measured 3.5 cm, with signal characteristics nearly identical
Fig. 3. A: Contrast-enhanced coronal image of the left thigh demonstrating the lesion with intense capsular enhancement. Notice the central tumor material resembles the central tumor characteristics seen in paraspinal mass (Fig. 2). B: Sagittal contrast-enhanced T1-weighted image demonstrating the left thigh mass in continuity with the sciatic nerve.
to the paraspinal mass. Furthermore, imaging of mass suggested continuity with the sciatic nerve. The patient subsequently underwent surgical removal of the leg mass. With the patient in the prone position, a linear, rostral-caudal incision was made proximal to the popliteal fossa (Fig. 4). A plane was developed between biceps femoris and semitendinosis muscle and the mass identified. The mass was eccentric to the sciatic nerve, which coursed over the top of the mass. The yellow mass was dissected free of the nerve en bloc with adherence to microneurosurgical dissection. There was minimal disruption of the sciatic nerve. The mass was removed en bloc and histologically diagnosed as a schwannoma (Fig. 5). Postoperatively, there were no new neurological deficits. The patient’s leg and foot pain were markedly reduced. Surgical resection of the second asymptomatic mass arising from the right lumbar plexus remains pending. 3. Discussion Fig. 2. A: Axial T2-weighted MR image showing a 3-cm right paravertebral mass. B: Coronal T2-weighted MR image demonstrating that the mass arises along the right L3 lumbar plexus, accompanied by a hyperintense capsule.
Tumors arising from peripheral nerves are usually benign masses. The most common tumors are schwannomas, which arise from the schwann cells of peripheral nerves, in this
636
F. Kralick, R. Koenigsberg / Surgical Neurology 66 (2006) 634–637
case, the sciatic nerve [2,5-7]. Sciatic nerve sheath schwannomas tend to occur in the second to fifth decade and are more common in women [5,22]. They are comprised of densely packed spindle cell as in Antoni type A or more loosely textured stroma as in Antoni type B. Most schwannomas are solitary masses but can be multiple as in this case [4,7]. Multiple schwannomas are found in patients with neurofibromatosis type II, of which bilateral vestibular neuromas are the hallmark [1,18].
Fig. 5. En bloc 3.5-cm excised mass.
Fig. 4. A: Left posterior thigh incision. B: Intraoperative view of the mass with the sciatic nerve coursing over the top of the nerve. C: Sciatic nerve after en bloc excision of schwannoma.
Clinical presentations of peripheral nerve lesions can be confusing or misdiagnosed [5,6,8-11,14,17,20]. Few other disorders require detailed examination, knowledge of anatomic course, patterns of innervation, and experience to accurately evaluate disorders of peripheral nerves [12]. As in this case, other reports of midthigh sciatic nerve schwannoma have produced foot pain mimicking plantar neuropathy [6]. Ghaly [5] described a posterior tibial nerve schwannoma that was undiagnosed for 10 years and ascribed to psychogenic pain. As part of a routine workup for lumbar radiculapathy, MR lumbar spine imaging is typically the initial diagnostic test obtained by primary clinicians to evaluate discogenic causes of radiculopathy. This study did demonstrate a right paravertebral mass showing characteristic imaging appearance of peripheral schwannoma [21], but it was clinically misleading. Careful correlation of the presence of the right-sided paravertebral mass and the patient’s primarily left-sided complaints of pain necessitated further neurosurgical diagnostic studies. One important feature of this case is the unusual multiplicity of schwannomas and the recognition that the initial abnormality referred for neurosurgical excision was not the lesion responsible for the patient’s symptoms. The Tinel sign, named after the French neurologist Jules Tinel, proved an invaluable physical sign in identifying the level of nerve injury in our patient [12]. Importantly, the (+) Tinel sign led to further imaging studies, which clearly demonstrated the mass responsible for the patient’s pain complaints. The evolution of MR neurography has certainly increased the detection of peripheral nerve abnormalities [3,15,16]. Kuntz et al [13] demonstrated in their series of 5 patients that MR neurography is useful in the preoperative evaluation and planning of surgery for peripheral nerve tumors. Using a 1.5-T MR imaging, they were able to correlate increased signal on T2-weighted fast spin-echo and short tau inversion recovery fast spin-echo pulse sequences with clinical and electophysiologic evidence of nerve injury. Sintzoff et al [19] described a case of simultaneous neurofibroma and schwannoma of the sciatic nerve with differences in enhancement characteristics [18,19]. The masses described in our report appeared to arise from
F. Kralick, R. Koenigsberg / Surgical Neurology 66 (2006) 634–637
peripheral nerves and displayed MR signal characteristics typical for a schwannoma. Furthermore, the imaging technique used in our case provided excellent quality views of the mass for the purposes of surgical planning. Once the muscles of the posterior thigh were separated, the mass was easily palpated, localized, and excised. 4. Conclusion We present an unusual case of multiple peripheral schwannomas. The development of improved imaging such as MR neurography has improved the diagnostic sensitivity of peripheral nerve lesions. This case emphasizes the importance of continued investigation when the radiographic findings do not correlate with the patient’s history in the presence of localizing signs on physical examination. References [1] Enzinger FM, Weiss SW. Benign tumors of peripheral nerves. In: Enzinger FM, Weiss SW, editors. Soft tissue tumors. 2nd ed. St. Louis7 Mosby; 1988. p. 719 - 80. [2] Egelhoff JC, Bates DJ, Ross JS, Rothner AD, Cohen BH. Spinal MR findings in neurofibromatosis types 1 and 2. AJNR Am J Neuroradiol 1992;13:1071 - 7. [3] Filler AG, Kliot M, Howe FA, Hayes CE, Saunders DE, Goodkin R, Bell BA, Winn HR, Griffiths JR, Tsuruda JS. Application of magnetic resonance neurography in the evaluation of patients with peripheral nerve pathology. J Neurosurg 1996;85(2):299 - 309. [4] Geschickler CF. Tumors of peripheral nerves. Am J Cancer 1935;25: 377 - 410. [5] Ghaly RF. A posterior tibial nerve neurilemoma unrecognized for 10 years: case report. Neurosurgery 2001;48:668 - 72. [6] Gominak SC, Ochoa JL. Sciatic schwannoma of the thigh causing foot pain mimicking plantar neuropathy. Muscle Nerve 1998;21:528 - 30. [7] Grant GA, Goodkin R, Kliot M. Evaluation and surgical management of peripheral nerve problems. Neurosurgery 1999;44:825 - 40.
637
[8] Harrison MJ, Leis HT, Johnson BA, MacDonald WD, Goldman CD. Hemangiopericytoma of the sciatic notch presenting as sciatica in a young healthy man: case report. Neurosurgery 1995;37:1208 - 12. [9] Kanamori M, Matsui H, Yudoh K. Solitary T-cell lymphoma of the sciatic nerve: case report. Neurosurgery 1995;36:1203 - 5. [10] Katirji B, Wilbourn AJ. High sciatic lesion mimicking peroneal neuropathy at the fibular head. J Neurol Sci 1994;121:172 - 5. [11] Kelso TB, Ferrari CJ, Frassica FJ. Sciatica caused by a neurilemoma of the intrapelvic portion of the sciatic nerve: a case report. J Bone Joint Surg Am 1993;75A:603 - 5. [12] Kline DG, Hudson AR, Zager E. Selection and preoperative work-up for peripheral nerve surgery. Clin Neurosurg 1992;39:8 - 35. [13] Kuntz IV C, Blake L, Britz G, Filler A, Hayes CE, Goodkin R, Tsuruda J, Maravilla K, Kliot M. Magnetic resonance neurography of peripheral nerve lesions in the lower extremity: technical report. Neurosurgery 1996;39:750 - 7. [14] Laurencin CT, Bain M, Yue JJ, Glick H. Schwannoma of the superficial peroneal nerve presenting as web space pain. J Foot Ankle Surg 1995;34:532 - 3. [15] Maravilla KR, Bowen BC. Imaging of the peripheral nervous system: evaluation of peripheral neuropathy and plexopathy. AJNR Am J Neuroradiol 1998;19:1011 - 23. [16] Moore KR, Tsuruda JS, Dailey AT. The value of MR neurography for evaluating extraspinal neuropathic leg pain: a pictorial essay. AJNR Am J Neuroradiol 2001;22:786 - 94. [17] Riccardi C, Ugo P. Slow and unrecognized progression of schwannoma of the sciatic nerve [in Italian]. Chir Organi Mov 1996;81:79 - 83. [18] Shrier DA, Rubio A, Numaguchi Y, Powers JM. Infarcted spinal schwannoma: an unusual MR finding. AJNR Am J Neuroradiol 1996; 17:1566 - 8. [19] Sintzoff SA, Bank WO, Gevenois PA, Matos C, Noterman J, Flament-Durand J, Struyven J. Simultaneous neurofibroma and schwannoma of the sciatic nerve. AJNR Am J Neuroradiol 1992;13: 1249 - 52. [20] Smith W, Amis JA. Neurilemoma of the tibial nerve: a case report. J Bone Joint Surg Am 1992;74A:443 - 4. [21] Varma DGK, Moulopoulos A, Sara AS. MR imaging of extracranial nerve sheath tumors. J Comput Assist Tomogr 1992;16:448 - 53. [22] Woodruff JM. The pathology and treatment of peripheral nerve tumors and tumor-like conditions. CA Cancer J Clin 1993;43:290 - 308.