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May 20, 2011 - vertebrae.15,48 We describe a case of spinal cord compres- sion due to an exostosis arising from the T-6 vertebral body in a patient with HME.
J Neurosurg Spine 15:252–257, 2011

Spinal cord compression secondary to a thoracic vertebral osteochondroma Case report Ye Tian, M.D., Wen Yuan, M.D., Huajiang Chen, M.D., and Xiaolong Shen, M.D. Department of Orthopaedics, Chang Zheng Hospital, Shanghai, China The authors describe a case of spinal cord compression due to an osteochondroma arising from the T-6 vertebral body in a patient with hereditary multiple exostoses. This 16-year-old boy presented with spastic paraparesis. Surgical decompression was followed by resolution of the neurological impairments. Osteochondroma is the most common bone tumor. The distribution of osteochondromas greatly favors the extremities and these lesions rarely arise in the vertebral column. Osteochondromas occur in 2 distinct clinical settings—as solitary or multiple tumors, the latter being often associated with hereditary multiple exostoses. Osteochondromas are more commonly found in the posterior elements of the vertebrae. Intraspinal presentation of these tumors is usually limited to the cervical regions, with few tumors reported in the thoracic vertebrae. Based on the presented case and literature review, the authors conclude that osteochondromas of the thoracic spine that cause myelopathy usually arise from the vertebral body and pedicle. Prompt and systematic radiological investigations are important in planning surgical management. Surgical excision usually yields good results. (DOI: 10.3171/2011.4.SPINE10484)

Key Words      •      hereditary multiple exostoses      •      osteochondroma      •      exostosis      •      spinal cord compression      •      myelopathy      •      oncology

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are common benign bone tumors that rarely arise in the vertebral column. Most osteochondromas are solitary, but some are multiple, and these multiple lesions are usually associated with hereditary multiple exostoses (HME).5 Intraspinal presentation of these tumors is usually limited to the cervical region, with few tumors reported in the thoracic vertebrae.15,48 We describe a case of spinal cord compression due to an exostosis arising from the T-6 vertebral body in a patient with HME. We also review the pertinent literature. steochondromas

Case Report History and Presentation. This 16-year-old boy with a family history of HME was admitted to our hospital with complaints of progressive weakness and ascending numbness in the lower limbs. He had been experiencing increasing difficulty walking, and his neurological defiAbbreviation used in this paper: HME = hereditary multiple exostoses.

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cit had worsened over the 4 months before admission to the extent that he had become confined to a wheelchair. Physical examination revealed a well-nourished boy with normal vital signs and multiple palpable exostoses in multiple long bones. Neurological examination disclosed a spastic paraparesis, bilateral hyperactive deep tendon reflexes, and hypesthesia of the lower extremities. A MR imaging study of the thoracic spine revealed an extradural mass extending from the posterosuperior endplate of the T-6 vertebral body, which caused extreme compression of the spinal cord (Fig. 1). There was no evidence of disc space narrowing or disc signal to suggest that the entity was a calcified disc herniation. Despite the marked compression, there was no spinal cord signal abnormality. A CT scan showed a bony mass in the spinal canal (Fig. 2). The lesion was located in the anterior right quadrant of the spinal canal at the T5–6 level. The medulla of the bony mass was also seen to be communicating with that of the superior endplate of T-6. A preoperative chest radiograph revealed an osteochondroma overlying the left fourth rib. On the basis of the imaging studies, it was considered highly likely that the T-6 lesion was an osteochondroma. J Neurosurg: Spine / Volume 15 / September 2011

Thoracic vertebral osteochondroma

Fig. 2.  A CT scan showing the lesion projecting into the spinal canal and causing posterior displacement of the spinal cord to the left.

Discussion

Fig. 1.  Sagittal T-2 weighted MR image showing an osteochondroma arising from the posterosuperior endplate of the T-6 vertebral body.

Operation and Postoperative Course. The patient underwent a posterior thoracic laminectomy. The operative findings showed an atrophic spinal cord that was displaced posterolaterally by the bony lesion arising from posterosuperior endplate of the T-6 vertebral body. Instrumented fusion was performed. Histological examination of the operative specimen confirmed the diagnosis of osteochondroma. The patient had an uneventful postoperative recovery. Within a week, he was experiencing gradual improvement in his paraparesis, his numbness had diminished, and he was able to walk with support. The patient was discharged by the 8th day. At his 1-year follow-up examination, the patient’s lower-extremity weakness was completely resolved. J Neurosurg: Spine / Volume 15 / September 2011

Osteochondroma is the most common bone tumor, accounting for 36%–40% of all benign bone tumors and approximately 10% of primary bone tumors.19 Osteochondromas occur in 2 distinct clinical settings—as solitary or multiple lesions. Solitary lesions are more common, whereas the multiple variant is often associated with hereditary multiple exostoses (HME). The distribution of osteochondromas greatly favors the extremities, and spinal osteochondromas are uncommon, with only 1.3%–4.1% of solitary osteochondromas arising within the spine.2,51 The syndrome of HME was first described by Boyer in 1814 and is manifested by multiple osteocartilaginous lesions from cortical surfaces of bones derived from cartilage.47,48,55 It is a genetic disorder with an autosomal dominant pattern of inheritance and variable penetrance. Hereditary multiple exostoses is a genetically heterogeneous disorder and is associated with mutations in EXT1 or EXT2 genes, which are both tumor suppressor genes. The prevalence of HME has been estimated to be at least 1 in 50,000 in the general population,62 and penetrance is estimated to be 96%. Most published instances of nonpenetrance have occurred in females,40 although some authors described HME as having no sex predilection. 58,72 Neurological complications are uncommon in HME and most frequently involve the peripheral nervous system when they do occur.45 Involvement of the spinal cord from vertebral exostosis is rare. It is estimated that 9% of patients with multiple osteochondromas have spinal lesions,2 although Roach et al.59 thought the risk may be much higher than previously suspected. Exostoses that affect the vertebral column usually arise from secondary centers of ossification. They are most commonly located near the tips of the spinous processes.55 Osteochondromas are composed of lamellar bone with a cartilaginous cap from which growth occurs. These lesions are known to be continuous with the marrow and cortex of the bone from which they arise.61 Unlike the typical long bone osteochondroma, spinal osteochondromas tend to be sessile rather than pe253

Y. Tian et al. dunculated.58 The most common location is the cervical spine, in particular the atlantoaxial area, followed by the thoracic and the lumbar area.2,12,15,48, 60 The predominance of cervical lesions is hypothesized to be related to the greater mobility of and stress on the cervical spine, with microtrauma leading to displacement and subsequent growth of a small cartilaginous remnant.2 Patients with exostoses associated with HME often present in the 2nd and 3rd decades of life (median age 20 years).35 Osteochondromas are more commonly found in the posterior elements of the vertebrae.15,27 Compressive lesions in patients with HME usually arise from the laminae when they involve the cervical spine and from the laminae or transverse processes in the lumbar spine.20,70 Solitary thoracic osteochondromas causing spinal cord compression mostly arise from the laminae or pedicles.9 As for thoracic osteochondromas associated with HME, only a few case reports were found in the literature. Radiation-induced osteochondromas can occur. Such tumors arise in 12% of patients who received radiation therapy for childhood malignancy,41 and approximately 10%–15% of osteochondromas are associated with radia-

tion therapy.23 Radiation-induced osteochondromas usually occur in or at the field of irradiation, and tend to be solitary rather than multiple.23,26 Computed tomography is useful in the detection of the origin and extent of spinal exostoses, whereas MR imaging is of greater value in demonstrating the relationship of the mass to the spinal cord, nerve roots, and adjacent soft tissue.3 Furthermore, the exact size of the tumor may be underestimated on CT scans because the cartilage cap of the tumor is invisible. Cartilage itself is best shown on MR images; cartilage caps with a thickness of more than 3 mm can be reliably detected on MR images,39,49 leading to an accurate preoperative diagnosis.14 Resection is the mainstay of treatment of these lesions and often leads to improvement of symptoms.61 Complete resection of the tumor is the goal, and removal of the entire cartilaginous cap is recommended to prevent recurrence. A review of the literature revealed 28 cases (Table 1), including our case, of myelopathy resulting from thoracic vertebral exostosis in patients with HME and 33 cases involving patients with solitary thoracic osteochondromas. In the HME group (Table 1), there were 20 male and

TABLE 1: Reported cases of myelopathy resulting from thoracic vertebral exostosis in patients with HME* Authors & Year Cannon, 1954 Gokay & Bucy, 1955 Larson et al., 1957 Goncharova et al., 1965 Adams & Movin, 1966 Decker & Wei, 1969 Thierry et al., 1970 Crowell & Wepsic, 1972 Signargout et al., 1973 Blaauw, 1975 Twersky et al., 1975 Becker & Epstein, 1978 Ho & Lipton, 1979 Old & Triplett, 1979 Buur & Mørch, 1983 Moriwaka et al., 1990 O’Brien et al., 1994 Quirini et al., 1996 Govender & Parbhoo, 1999 Mermer et al., 2002 Nassar et al., 2003 Bess et al., 2005 Ezra et al., 2010 Gunay et al., 2010 Lotfinia et al., 2010 present study

Age (yrs), Sex

Level

Origin

23, F 24, F 33, M 23, M 24, M 15, M 21, M 13, M 18, M 16, F 13, M 48, M 53, M 17, M 44, M 21, F 33, M 9, M 14, F 24, M 14, F 15, M 16, M 11, F 4, M 36, F 31, M 16, M

T-10 T-3 T-3 T-3 T-4 T10–11 T-5 T-2 T-8 T-5 T-1 T-1 T-5 T-2 T-1 T-3 T-4 C7–T1 T-12 T-8 T-8 T-5 T1–2 T-5 C7–T1 T11–12 T-8 T-6

NR lamina CVJ transverse process facet CVJ facet pedicle pedicle pedicle/VB facet CVJ CVJ CVJ lamina CVJ pedicle pedicle/VB pedicle VB lamina/pedicle VB VB VB lamina pedicle facet VB

Family Hx of HME Surgical Treatment Outcome yes yes no yes yes no no yes yes NR NR NR no NR yes yes yes NR NR NR NR yes yes NR yes yes yes yes

yes yes yes yes yes yes yes yes yes yes yes yes yes yes yes yes yes yes yes yes yes yes yes no yes yes yes yes

good good good good good good good good good good good good worsened good not good good good good good good good good good good good good good good

*  CVJ = costovertebral junction; NR = not reported; VB = vertebral body.

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Thoracic vertebral osteochondroma 8 female patients (71% vs 29%), whereas in the solitary lesion group (Table 2), there were 20 male and 13 female patients (61% vs 39%). The mean age was 22 years in the HME group and 30 years in the solitary lesion group. Family history was positive for HME in 54% of patients in the HME group. In the HME group, the T-1 vertebra was the most frequent lesion site, followed by T-5 and T-3. In the solitary lesion group, T-4 was the most commonly involved vertebra (27%). The most common region of involvement was the upper thoracic region (T1–4, 51% in the HME group and 63% in the solitary lesion group). Instead of arising in laminae, the majority of thoracic osteochondromas arise in the vertebral body (30% in the HME group and 33% in the solitary lesion group) and pedicle (30% in the HME group and 30% in the solitary lesion group); in this characteristic, thoracic osteochondromas differ from osteochondromas of the cervical and

lumbar spine.20,70 Surgery was performed in the majority of cases and led to a good outcome in most patients.

Conclusions

Spinal cord compression resulting from osteochondroma is a rare but devastating complication. Based on the presented case and literature review, it seems osteochondromas of the thoracic spine that cause myelopathy usually arise from the vertebral bodies and pedicles. Prompt and systematic radiological investigations are important in planning the management. Surgical excision usually yields good results. Disclosure

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

TABLE 2: Reported cases of myelopathy resulting from solitary thoracic vertebral exostoses* Authors & Year Bradford, 1954 Twersky et al., 1975 Natarajan et al., 1976 Le Goff et al., 1978 Loftus et al., 1980 Palmer & Blum, 1980 Spallone et al., 1981 Karian et al., 1984 Linkowski et al., 1985 Kak et al., 1985 Czorny et al., 1985 Lanzieri et al., 1985 Marchand et al., 1986 Kulali et al., 1991 Prasad et al., 1992 Braunschweig & Rose, 1994 Shuangshoti & Lerdlum, 1997 Sener, 1998 Govender & Parbhoo, 1999 Javadpour et al., 1999 Khosla et al., 1999 Gorospe et al., 2002 Sharma et al., 2002 Blamoutier et al., 2002 Brastianos et al., 2005 Faik et al., 2005 Bess et al., 2005 Song & Lee, 2007 Lotfinia et al. 2010

Age (yrs), Sex

Level

Origin

Op

Outcome

61, F 29, M 12, M 21, M 54, F 28, M 31, F 22, F 24, M 33, M 40, F 22, M 18, F 49, F 9, F 45, M 16, F 51, F 21, M 65, M 33, M 51, F 39, M 5, M 18, M 18, F 13, M 38, M 26, F 19, M 19, M 11, M 55, M

T-9 T-8 T-4 T4–5 T-10 T-4 T-2 T1–2 T-4 T-3 T7–8 T1–4 T11–12 T8–9 T-2 T-6 T-10 T-1 T-1 T-6 C7–T1 T-5 T-1 T-8 T-4 T-12 T-4 T-7 T-12 T4–5 T-11 T-4 T-9

VB VB CVJ CVJ pst arch pedicle/VB pedicle pedicle pedicle/VB lamina/facet lamina VB CVJ VB pst arch/pedicle VB pedicle pedicle VB neural arch/rib pst elements pst arch pst arch pedicle/lamina VB pedicle pedicle NR VB CVJ lamina facet VB

laminectomy laminectomy laminectomy thoracotomy laminectomy laminectomy laminectomy thoracotomy/laminectomy laminectomy laminectomy laminectomy thoracotomy NR laminectomy/facetectomy laminectomy laminectomy laminectomy laminectomy laminectomy laminectomy laminectomy laminectomy laminectomy laminectomy/fusion laminectomy/facetectomy laminectomy laminectomy NR T-12 corpectomy laminectomy laminectomy/fusion laminectomy combined ant & pst approach w/ fusion

worsened worsened good good good good good NR good good good good good good good worsened good good good good good good good good good good good good good good good good good

*  ant = anterior; pst = posterior.

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Manuscript submitted August 10, 2010. Accepted April 5, 2011. Please include this information when citing this paper: published online May 20, 2011; DOI: 10.3171/2011.4.SPINE10484. Address correspondence to: Wen Yuan, M.D., Department of Orthopaedics, Chang Zheng Hospital, 415 Feng Yang Road, Shanghai, People’s Republic of China. email: [email protected].

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