- Department of Surgery, University of Chicago, 5841 S. Maryland Ave, MC3026, J341, Chicago, IL, USA
- Department of Neurosurgery, University of Pittsburgh, 4401 Penn Ave, Pittsburgh, PA, USA
- Department of Pathology, University of Pittsburgh, 4401 Penn Ave, Pittsburgh, PA, USA
Department of Neurosurgery, University of Pittsburgh, 4401 Penn Ave, Pittsburgh, PA, USA
DOI:10.4103/2152-7806.106266Copyright: © 2013 Lam S This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Lam S, Grandhi R, Wong R, Hamilton R, Greene S. Neuromuscular hamartoma of the sciatic nerve: Case report and review of the literature. Surg Neurol Int 18-Jan-2013;4:8
How to cite this URL: Lam S, Grandhi R, Wong R, Hamilton R, Greene S. Neuromuscular hamartoma of the sciatic nerve: Case report and review of the literature. Surg Neurol Int 18-Jan-2013;4:8. Available from: http://sni.wpengine.com/surgicalint_articles/neuromuscular-hamartoma-of-the-sciatic-nerve-case-report-and-review-of-the-literature/
Background:Neuromuscular hamartomas are rare benign tumors with mature skeletal elements mixed with mature neural elements. They present typically as solitary lesions in childhood and have been reported to be associated with cranial nerves or large peripheral nerves such as the brachial plexus, median nerve, and sciatic nerve. To date, eight cases of sciatic nerve neuromuscular hamartomas have been reported. We present a case along with an outline for the natural history of the disease with a review of the literature of the reported cases dating back to 1895.
Case Description:An 11-year-old boy presented with progressive right lower extremity pain and atrophy. Magnetic resonance imaging revealed a large right sciatic nerve mass, and electromyography demonstrated evidence of ongoing denervation and reinnervation. Initial computed tomography-guided biopsy was unrevealing and subsequent open biopsy was consistent with neuromuscular choristoma.
Conclusion:Neuromuscular choristomas represent a rare disease. Symptoms of foot deformity, leg size discrepancy, and pain merit a complete work-up including spinal and peripheral nerve etiologies.
Keywords: Neuromuscular choristoma, neuromuscular hamartoma, peripheral nerve tumor, sciatic nerve tumor
Neuromuscular hamartomas (also known as neuromuscular choristomas or benign triton tumors) are rare benign tumors with mature skeletal elements mixed with mature neural elements. They typically present as solitary lesions in childhood with no male/female preponderance, and have been reported to be associated with cranial nerves or large peripheral nerves such as the brachial plexus, median nerve, and sciatic nerve.[
This 11-year-old boy presented with a 3-year history of right buttock pain that radiated into his lower back and into his right lateral thigh. The pain was present most of the time regardless of activity such as walking or sitting. An initial workup involving magnetic resonance imaging (MRI) of the lumbar spine was unrevealing. The patient had significant atrophy of the right thigh, calf, and foot with an asymmetry in his shoe size with the right foot being three US shoe sizes smaller than the right. In December 2010, the patient presented to neurosurgical attention with progressive complaints of proximal right lower extremity pain, muscle spasms, and gait difficulty.
The patient's examination revealed a significant asymmetry in size as the measured circumference at the distal thigh was 53.5 cm at the left thigh versus 50.5 cm in the right thigh, 43 cm in the left calf versus 42 cm in the right calf. The length of his foot from the great toe to the heel was 27 cm in the left foot and 24 cm on the right foot. He had normal strength in the left lower extremity. His right lower extremity exhibited 5−/5 strength in the right hip flexor, 4+ in the quadriceps, 4+ in the hamstrings, 4+ in the hip abductor, 4+ in the hip adductor, 5− in the tibialis anterior, 4+ to 5− in the gastrocnemius, 5− in the extensor hallucis longus, 4+ in foot eversion, and 5− in foot inversion. He was unable to perform heel rise or toe rise on his right leg. He had slightly decreased sensation to light touch and pinprick in the posterior and medial portions of his right thigh, lateral aspect of the right leg, lateral right foot, second toe dorsally and fifth toe dorsally. The corresponding toes were noted to have nonpainful dorsal calluses [
In addition, the patient exhibited tenderness to palpation in the infragluteal area in the right hamstring without radiation of pain, along with point tenderness in the region of the right knee lateral to the patella proximal to the head of the fibula. When walking, he complained of posterior thigh pain. The patient had no skin lesions overlying the right posterior thigh or elsewhere on his body, and no stigmata of neurofibromatosis. He had no scoliosis.
MRI studies revealed a lesion at the right sciatic nerve extending 30 cm from the sciatic notch to the distal thigh. The tumor appeared hypointense on T2-weighted images, isointense-to-hypointense signal on the T1-weighted image with mild heterogeneous internal enhancement in a longitudinal orientation after administration of gadolinium contrast [
The patient's electromyography (EMG) showed electrodiagnostic evidence of a right sciatic neuropathy with evidence of ongoing denervation and reinnervation as demonstrated by increased insertional activity, positive sharp waves, and fibrillation potentials in the distribution of muscles innervated by the sciatic nerve.
Given the patient's history and the need for tissue diagnosis to elucidate treatment options, the patient initially underwent an ultrasound-guided biopsy followed by a computed tomography (CT)-guided biopsy of the mass, both of which were unsuccessful at obtaining adequate tissue for histologic diagnosis. The patient underwent an open biopsy through exposure of the sciatic nerve via a posterior gluteus maximus-splitting approach. The whole sciatic nerve appeared involved and was notably hypertrophic, firm, and bulbous [
Pathological examination showed the lesion to be a neuromuscular hamartoma (neuromuscular choristoma). Within the specimen, small nerve bundles and axons were seen intermixed with adjacent mature striated skeletal muscle bundles, surrounded by a dense collagenous matrix [
The specimens were embedded in paraffin and the sections were stained with hematoxylin and eosin and trichrome. A panel of immunohistochemistry stains was also performed. The S-100 and neurofilament stains showed normal nerve bundles. The Epithelial Membrane Antigen (EMA) stain was inconclusive. Desmin highlighted the hamartomatous striated muscle fibers intermingled with nerve bundles, and myogenin stain was negative for immature skeletal muscular elements.
Neuromuscular choristomas reported to date in the literature have involved cranial nerves and large peripheral nerves such as the brachial plexus, median nerve, or sciatic nerve. To our knowledge, this is the ninth reported case of sciatic nerve neuromuscular hamartoma [
A pattern emerges in the progression of this disease by laying out the cases in terms of age of diagnosis and presentation, describing the natural history in this literature review [
The MRI findings previously reported are also consistent with the description in our case, in that the lesion tends to appear with low-to-intermediate signal intensity on T1-weighted sequences with mild patchy enhancement and low signal intensity on T2-weighted imaging.[
Neuromuscular hamartomas of any nerve tend to be intercalated or closely associated with the parent nerve, which limits surgical resection options. Microscopically these lesions are usually composed of fascicles separated by fibrous tissue, with the neural tissue intimately associated with the skeletal muscle in nerve fibers or small nerves, and may be sharing the same perimysial sheath.[
The pathogenesis of this tumor is not clearly understood. Various theories proposed include incorporation of limb mesenchyme within the nerve sheaths of developing nerves undergoing peripheral extension, muscle entrapment in developing nerves, neuroectoderm giving rise to metaplastic mesenchymal components, and neural induction on surrounding mesenchyme into skeletal muscle (as in limb regeneration experiments on the Triton salamander).[
An association between aggressive fibromatosis and neuromuscular hamartomas may exist.[
As neuromuscular hamartoma cases are rare and the natural history is not fully characterized, long-term serial follow-up is indicated. While unilateral foot deformity or limb size discrepancy necessitates workup for a spinal etiology such as diastematomyelia or tethered cord, these reports of neuromuscular hamartoma show that peripheral nerve lesions may also lead to this clinical picture.
1. Awasthi D, Kline DG, Beckman EN. Neuromuscular hamartoma (benign “triton” tumor) of the brachial plexus. Case report. J Neurosurg. 1991. 75: 795-7
2. Bassett GS, Monforte-Munoz H, Mitchell WG, Rowland JM. Cavus deformity of the foot secondary to a neuromuscular choristoma (hamartoma) of the sciatic nerve. A case report. J Bone Joint Surg Am. 1997. 79: 1398-401
3. Boman F, Palau C, Floquet A, Floquet J, Lascombes P. [Neuromuscular hamartoma]. Ann Pathol. 1991. 11: 36-41
4. Bonneau R, Brochu P. Neuromuscular choristoma. A clinicopathologic study of two cases. Am J Surg Pathol. 1983. 7: 521-8
5. Castro DE, Raghuram K, Phillips CD. Benign triton tumor of the trigeminal nerve. AJNR Am J Neuroradiol. 2005. 26: 967-9
6. Chen KT. Neuromuscular hamartoma. J Surg Oncol. 1984. 26: 158-60
7. Hebert-Blouin MN, Scheithauer BW, Amrami KK, Durham SR, Spinner RJ. Fibromatosis: A potential sequela of neuromuscular choristoma. J Neurosurg. 2012. 116: 399-408
8. Louhimo I, Rapola J. Intraneural muscular hamartoma: Report of two cases in small children. J Pediatr Surg. 1972. 7: 696-9
9. Maher CO, Spinner RJ, Giannini C, Scheithauer BW, Crum BA. Neuromuscular choristoma of the sciatic nerve. Case report. J Neurosurg. 2002. 96: 1123-6
10. Markel SF, Enzinger FM. Neuromuscular hamartoma-a benign “triton tumor” composed of mature neural and striated muscle elements. Cancer. 1982. 49: 140-4
11. Mitchell A, Scheithauer BW, Ostertag H, Sepehrnia A, Sav A. Neuromuscular choristoma. Am J Clin Pathol. 1995. 103: 460-5
12. Orlandi E. Sopra un caso di rabdomioma del nervo ischiatico. Arch Sci Med. 1895. 19: 113-37
13. Van Dorpe J, Sciot R, De Vos R, Uyttebroeck A, Stas M, Van Damme B. Neuromuscular choristoma (hamartoma) with smooth and striated muscle component: Case report with immunohistochemical and ultrastructural analysis. Am J Surg Pathol. 1997. 21: 1090-5
14. Zwick DL, Livingston K, Clapp L, Kosnik E, Yates A. Intracranial trigeminal nerve rhabdomyoma/choristoma in a child: A case report and discussion of possible histogenesis. Hum Pathol. 1989. 20: 390-2