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Multinodular/plexiform schwannoma of the ulnar nerve A 34-year-old right-handed man, presented with left wrist and hand swelling of 6 months duration. The swelling had gradually increased in size and was associated with occasional numbness over the left little finger. Physical examination revealed a soft tissue swelling along the ulnar border of the distal left forearm and the wrist, and extending along the hypothenar area into the radial border of little finger (Fig. 1). Sensation was reduced over left little finger with positive Tinel’s sign over the ulnar nerve at the wrist. He did not have cutaneous pigmentation or scoliosis on physical examination. Magnetic resonance imaging showed a multilobulated tubular soft tissue mass measuring 2.7 cm (Width) × 1.5 cm (Anteroposterior) × 15.6 cm (Length). The lesion appeared slightly hyperintense to the muscle on T1-weighted images and hyperintense on both T2-weighted and short T1 inversion recovery (STIR) images (Fig. 2). Excision biopsy was performed. Intraoperative finding showed strings of multiple fusiform, yellowish-brown nodules arising from the ulnar nerve (Fig. 3). Several fascicles were affected including the proper palmar digital nerve to the radial border of the little finger. These fascicles were excised. The other sensory branches and the motor branch of the ulnar nerve were unaffected and preserved during dissection. Histopathological examination was consistent with neurilemoma. After the operation, he had numbness over the radial border of little finger with no motor weakness of the ulnar nerve-innervated intrinsic muscles. He returned to work and resumed his daily activities without restriction after 6 weeks. Schwannoma or neurilemoma is one of the most common tumours that occur in the central and peripheral nerves. There are many forms of schwannoma: conventional schwannoma, cellular
schwannoma, plexiform schwannoma and melanotic schwannoma. Plexiform schwannoma is an extremely rare entity. It is characterized by multinodular and plexiform growth patterns both grossly and microscopically. Plexiform schwannoma was first reported in 1970 by Masson1 and was fully characterized as a benign variant of schwannoma by Harkin and colleagues2 in 1978. Hébert-Blouin et al. through their retrospective review found a pattern of schwannomas they termed multinodular/plexiform given its distinctive imaging, operative and gross appearance.3 The tumours differ from conventional schwannomas that grow as a globular mass within a single fascicle of an often multifascicular nerve.3 Instead, they typically appear multinodular and often affect multiple fascicles.3 Magnetic resonance imaging is particularly useful in demonstrating this tumour.4 Besides the morphological features suggestive of multinodular configuration, the mass will also have extremely high signal on T2-weighted images.4 Most tumours of the peripheral nerve sheath with the plexiform growth pattern are neurofibromas. Plexiform neurofibroma is almost always associated with Recklinghausen disease, but plexiform schwannoma is rarely associated with Recklinghausen disease. It is important to differentiate plexiform schwannoma from plexiform neurofibroma, because about 5% of plexiform neurofibromas undergo transformation to malignant peripheral nerve sheath tumours.3
Fig. 1. Physical examination revealed a soft tissue swelling arising from the ulnar border of left distal forearm, involving the wrist, palm and extending into radial border of little finger.
This paper is funded by University Malaya Research Fund Assistance. The abstract has been presented as a poster at the 9th Congress of Asian Pacific Federation of Societies for Surgery of the Hand (APFSSH), 10th– 13th October 2012, Bali, Indonesia.
© 2013 Royal Australasian College of Surgeons
Fig. 2. Magnetic resonance imaging showed multilobulated soft tissue mass. The lesion appeared slightly hyperintense to the muscle on T1-weighted image (a) and hyperintense on T2-weighted image (b and d). The lesion also appeared hyperintense on STIR image (c).
ANZ J Surg 84 (2014) 93–94
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Images for surgeons
with that of multinodular/plexiform schwannoma. The eventual functional outcome after excision of multinodular/plexiform schwannoma is very much dependent on the preservation of unaffected fascicles through careful interfascicular dissection under magnification. In this patient, the sensory radial digital branch to the little finger was involved and had to be excised with the tumour. However, the deep motor branch of the ulnar nerve and sensory fascicles to the ulnar digital nerves of the little and ring fingers were unaffected. The successful preservation of these unaffected motor and sensory fascicles limited the neurological deficit to only sensory deficit on the radial border of little finger and maintained a full function of the hand.
References
Fig. 3. Intraoperative photograph (top) showing the extent of the tumour. The excised fascicles (bottom) exhibit multinodular pattern.
Operative findings and clinical outcomes in patients with multinodular/plexiform schwannomas also differ from those of patients with conventional schwannomas. In general, the small fascicle associated with a conventional schwannoma can be sacrificed without consequences, because it usually does not transmit an action potential.5 As might be expected, in cases of multinodular and/or multifascicular tumour involvement, it would be difficult to completely resect the lesions without causing neurological deficit. Since these schwannomas have complex growth and are often, if not invariably associated with multiple fascicles, their complete resection implies the sacrifice of the involved fascicles. One study found that patients with tumours not amenable to enucleation had significantly more post-operative neurological deficits (P < 0.0001), an outcome attributed to resection of multiple fascicles6 and consistent
1. Masson P. Human Tumors: Histology, Diagnosis and Technique, 2nd edn. Detroit: Wayne State University Press, 1970. 2. Harkin JC, Arrington JH, Reed RJ. Benign plexiform schwannoma, a lesion distinct from plexiform neurofibroma. J. Neuropathol. Exp. Neurol. 1978; 37: 622. 3. Hébert-Blouin MN, Amrami KK, Scheithauer BW, Spinner RJ. Multinodular/plexiform (multifascicular) schwannomas of major peripheral nerves: an underrecognized part of the spectrum of schwannomas. J. Neurosurg. 2010; 112: 372–82. 4. Pritchard DJ. Surgical management of common benign soft-tissue tumours. Ch. 40. In: Simon MA, Springfield D (eds). Bone and SoftTissue Tumours. Hagerstown, MD: Lippincott-Raven Publishers, 1998; 530–1. 5. Kim DH, Murovic JA, Tiel RL, Moes G, Kline DG. A series of 397 peripheral neural sheath tumors: 30-year experience at Louisiana State University Health Sciences Center. J. Neurosurg. 2005; 102: 246–55. 6. Sawada T, Sano M, Ogihara H, Omura T, Miura K, Nagano A. The relationship between pre-operative symptoms, operative findings and postoperative complications in schwannomas. J. Hand Surg. [Br] 2006; 31: 629–34.
Chiao Yee Lim, MBBS Tze Hau Low, MS Ruban Sivanoli, MS Kok Kheng Teh, MS Ravindran Thuraisingham, MS Department of Orthopaedic Surgery, University Malaya Medical Centre, National Orthopaedic Centre of Excellence for Research and Learning (NOCERAL), Kuala Lumpur, Malaysia doi: 10.1111/ans.12231
© 2013 Royal Australasian College of Surgeons
Multinodular/plexiform schwannoma of the ulnar nerve A 34-year-old right-handed man, presented with left wrist and hand swelling of 6 months duration. The swelling had gradually increased in size and was associated with occasional numbness over the left little finger. Physical examination revealed a soft tissue swelling along the ulnar border of the distal left forearm and the wrist, and extending along the hypothenar area into the radial border of little finger (Fig. 1). Sensation was reduced over left little finger with positive Tinel’s sign over the ulnar nerve at the wrist. He did not have cutaneous pigmentation or scoliosis on physical examination. Magnetic resonance imaging showed a multilobulated tubular soft tissue mass measuring 2.7 cm (Width) × 1.5 cm (Anteroposterior) × 15.6 cm (Length). The lesion appeared slightly hyperintense to the muscle on T1-weighted images and hyperintense on both T2-weighted and short T1 inversion recovery (STIR) images (Fig. 2). Excision biopsy was performed. Intraoperative finding showed strings of multiple fusiform, yellowish-brown nodules arising from the ulnar nerve (Fig. 3). Several fascicles were affected including the proper palmar digital nerve to the radial border of the little finger. These fascicles were excised. The other sensory branches and the motor branch of the ulnar nerve were unaffected and preserved during dissection. Histopathological examination was consistent with neurilemoma. After the operation, he had numbness over the radial border of little finger with no motor weakness of the ulnar nerve-innervated intrinsic muscles. He returned to work and resumed his daily activities without restriction after 6 weeks. Schwannoma or neurilemoma is one of the most common tumours that occur in the central and peripheral nerves. There are many forms of schwannoma: conventional schwannoma, cellular
schwannoma, plexiform schwannoma and melanotic schwannoma. Plexiform schwannoma is an extremely rare entity. It is characterized by multinodular and plexiform growth patterns both grossly and microscopically. Plexiform schwannoma was first reported in 1970 by Masson1 and was fully characterized as a benign variant of schwannoma by Harkin and colleagues2 in 1978. Hébert-Blouin et al. through their retrospective review found a pattern of schwannomas they termed multinodular/plexiform given its distinctive imaging, operative and gross appearance.3 The tumours differ from conventional schwannomas that grow as a globular mass within a single fascicle of an often multifascicular nerve.3 Instead, they typically appear multinodular and often affect multiple fascicles.3 Magnetic resonance imaging is particularly useful in demonstrating this tumour.4 Besides the morphological features suggestive of multinodular configuration, the mass will also have extremely high signal on T2-weighted images.4 Most tumours of the peripheral nerve sheath with the plexiform growth pattern are neurofibromas. Plexiform neurofibroma is almost always associated with Recklinghausen disease, but plexiform schwannoma is rarely associated with Recklinghausen disease. It is important to differentiate plexiform schwannoma from plexiform neurofibroma, because about 5% of plexiform neurofibromas undergo transformation to malignant peripheral nerve sheath tumours.3
Fig. 1. Physical examination revealed a soft tissue swelling arising from the ulnar border of left distal forearm, involving the wrist, palm and extending into radial border of little finger.
This paper is funded by University Malaya Research Fund Assistance. The abstract has been presented as a poster at the 9th Congress of Asian Pacific Federation of Societies for Surgery of the Hand (APFSSH), 10th– 13th October 2012, Bali, Indonesia.
© 2013 Royal Australasian College of Surgeons
Fig. 2. Magnetic resonance imaging showed multilobulated soft tissue mass. The lesion appeared slightly hyperintense to the muscle on T1-weighted image (a) and hyperintense on T2-weighted image (b and d). The lesion also appeared hyperintense on STIR image (c).
ANZ J Surg 84 (2014) 93–94
94
Images for surgeons
with that of multinodular/plexiform schwannoma. The eventual functional outcome after excision of multinodular/plexiform schwannoma is very much dependent on the preservation of unaffected fascicles through careful interfascicular dissection under magnification. In this patient, the sensory radial digital branch to the little finger was involved and had to be excised with the tumour. However, the deep motor branch of the ulnar nerve and sensory fascicles to the ulnar digital nerves of the little and ring fingers were unaffected. The successful preservation of these unaffected motor and sensory fascicles limited the neurological deficit to only sensory deficit on the radial border of little finger and maintained a full function of the hand.
References
Fig. 3. Intraoperative photograph (top) showing the extent of the tumour. The excised fascicles (bottom) exhibit multinodular pattern.
Operative findings and clinical outcomes in patients with multinodular/plexiform schwannomas also differ from those of patients with conventional schwannomas. In general, the small fascicle associated with a conventional schwannoma can be sacrificed without consequences, because it usually does not transmit an action potential.5 As might be expected, in cases of multinodular and/or multifascicular tumour involvement, it would be difficult to completely resect the lesions without causing neurological deficit. Since these schwannomas have complex growth and are often, if not invariably associated with multiple fascicles, their complete resection implies the sacrifice of the involved fascicles. One study found that patients with tumours not amenable to enucleation had significantly more post-operative neurological deficits (P < 0.0001), an outcome attributed to resection of multiple fascicles6 and consistent
1. Masson P. Human Tumors: Histology, Diagnosis and Technique, 2nd edn. Detroit: Wayne State University Press, 1970. 2. Harkin JC, Arrington JH, Reed RJ. Benign plexiform schwannoma, a lesion distinct from plexiform neurofibroma. J. Neuropathol. Exp. Neurol. 1978; 37: 622. 3. Hébert-Blouin MN, Amrami KK, Scheithauer BW, Spinner RJ. Multinodular/plexiform (multifascicular) schwannomas of major peripheral nerves: an underrecognized part of the spectrum of schwannomas. J. Neurosurg. 2010; 112: 372–82. 4. Pritchard DJ. Surgical management of common benign soft-tissue tumours. Ch. 40. In: Simon MA, Springfield D (eds). Bone and SoftTissue Tumours. Hagerstown, MD: Lippincott-Raven Publishers, 1998; 530–1. 5. Kim DH, Murovic JA, Tiel RL, Moes G, Kline DG. A series of 397 peripheral neural sheath tumors: 30-year experience at Louisiana State University Health Sciences Center. J. Neurosurg. 2005; 102: 246–55. 6. Sawada T, Sano M, Ogihara H, Omura T, Miura K, Nagano A. The relationship between pre-operative symptoms, operative findings and postoperative complications in schwannomas. J. Hand Surg. [Br] 2006; 31: 629–34.
Chiao Yee Lim, MBBS Tze Hau Low, MS Ruban Sivanoli, MS Kok Kheng Teh, MS Ravindran Thuraisingham, MS Department of Orthopaedic Surgery, University Malaya Medical Centre, National Orthopaedic Centre of Excellence for Research and Learning (NOCERAL), Kuala Lumpur, Malaysia doi: 10.1111/ans.12231
© 2013 Royal Australasian College of Surgeons
