Osteocondroma in the Lumbar Intraspinal Canal

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Spine

Osteochondroma in the Lumbar Intraspinal Canal Causing Nerve Root Compression.
By Jung Xu, MS; Chao-rui Xu, MS; Hong Wu, MD; Hai-le Pan, MD; Jun Tian, MDORTHOPEDICS 2009; 32:133
February 2009

Abstract
Osteochondromas, which are benign bone tumors that usually develop on long bones, tubular bones, are rarely found in the spine. If they are located in the spinal canal, they may cause nerve root or spinal cord compression, which is a rare but potentially catastrophic manifestation of osteochondromas. In this article, we report a case of a 38-year-old man who presented with low back pain, paresthesia, and weakness of the right lower extremity aggravating gradually for 5 months.

No family history of this disease can be traced. The L4-L5 level computed tomography scan showed an abnormal bony protrusion arising from the right interior wall of L5 right lamina toward the intraspinal canal.
The protrusion compressed the L5 nerve root severely. T2-weighted magnetic resonance imaging (MRI) of the same level revealed that the L5 nerve root and spinal dura mater were notably compressed by the intraspinal extradural exostosis attached to the right lamina of L5.

Considering differential diagnosis, lumbar facet synovial cysts must be excluded as they can also cause myeloradiculopathy with the similar mechanism.
The tumor, approximately 6×7×11 mm, was identified after laminectomy of the L5 laminae. Postoperative histopathologic examination confirmed our hypothesis of benign osteochondroma. Postoperatively, the patient recovered rapidly in neurological function and was free of symptoms.
Surgery is essential to this rare case.
Computed tomography and MRI are helpful for the preoperatively precise indication of tumor extent and its relationships with the adjacent.

Osteochondromas, which are benign bone tumors that usually develop on long bones, tubular bones, are rarely found in the spine, with an incidence of only 2% to 7% of all osteochondromas.
1 The tumors have extradural and extraspinal growth patterns and neurological complications are rare.
2,3 Moreover, osteochondromas within spinal canal have a predilection for the cervical or upper thoracic regions.
4,5 To our knowledge, an osteochondroma in the lumbar intraspinal canal with nerve root compression has not yet been reported in China.
This article describes a compressive case to the right lumbar 5 (L5) nerve root secondary to an osteochondroma arising from the L4-5 intraspinal canal concomitant with nerve lesion.
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Case Report
A 38-year-old man with lumbago, weakness, and paresthesia in right lower limb presented with difficulty in walking unaided and in rising from the squatting position.
Physical examination revealed body temperature, pulse rate, respiration and blood pressure were normal and no palpable deformity on the lumbar surface.
Movement of the spinal column was limited.
Neurological examination of the right femoral rear and surae lateral revealed hypoesthesia, a positive right straight leg raising-test at 30° and grade IV paraparesis in the right lower limb. Bilateral Babinskin’ sign (+). He had no familial inherited disease.

Computed tomography (CT) scan at the L4-5 level showed an abnormal bony protrusion arising from the right lamina of L5 toward the intraspinal canal with a superficial hypodense 'cap'.
The protrusion compressed the L5 nerve root severely (Figure 1).
T2-weighted magnetic resonance imaging (MRI) of the same level revealed that the L5 nerve root and spinal dura mater were notably compressed by the intraspinal extradural exostosis attached to the right lamina of L5 (Figure 2).

Figure 1: CT scan showed a tumor of the right intraspinal canal at L5 with narrowing and causing nerve root compression.
Figure 2: T2-weighted MRI of the spine revealed an intraspinal extradural lesion from the right lamina of L5 level compressed nerve root and spinal dura mater.
Figure 3: The complete tumor was excised approximately 6×7×11 mm. Figure 4: Histopathologic examination confirmed the diagnosis of benign osteochondroma (Hematoxylin-eosin stain, original magnification ×40).

The tumor was identified after laminectomy of the L5 laminae.
The tumor was detected in an area at the intraspinal extradural and right lamina of L5, approximately 6×7×11 mm (Figure 3), and the surface covered by a bluish-white, smooth, undulating cartilage ‘cap’, with an attachment to the facet joint, which compressed the L5 nerve root. The tumor was completely excised.

Histopathologic examination confirmed the diagnosis of benign osteochondroma (Figure 4). Postoperatively, physical examination found a negative right straight leg raising test and grade V in the right lower limb.
The patient recovered rapidly in neurological function and was free of symptoms.
Postoperative CT confirmed complete excision of the tumor.

Discussion
Osteochondromas are among the most frequent of benign bone tumors.
They occur either as solitary lesions or as multiple osteochondromatosis.
6 However, the spine is affected by these tumors in only 2% to 7%.
1 Osteochondromas are commonly seen in the second or the third decade of life.

Spinal osteochondromas present as asymptomatic palpable masses or more unusually, with neurological deficit, because the majority of the lesions grow out of the spinal canal and usually do not cause symptoms.
7 But nerve root compression is an uncommon manifestation of exostosis developed within the intraspinal canal. Neurological compromise is more common in the patient.

The neuroimaging findings of osteochondroma reveal a characteristic well-circumscribed lobulated mass with areas of ring-like chondral mineralization as well as calcifications representing mature trabeculated bone.
Radiographs could not establish the diagnosis in this case, possibly because of overlapping of the vertebral plate as well as soft-tissue shadows.

Preoperative diagnosis was facilitated by three-dimensional reconstruction of CT.
Moreover, by giving a precise indication of tumor extent, as well as of its relationships with the adjacent structures, CT was of great value also with regard to surgical treatment. Magnetic resonance imaging was useful in a suspected case of osteochondroma arising from the spine.

8,9 Magnetic resonance imaging demonstrates the relationship of the tumor, the nerve root, and adjacent soft tissue to each other. However, diagnosis by MRI may be made difficult due to unusual gadolinium enhancement by the tumor.

10 Lumbar facet synovial cysts must be kept in mind in the differential diagnosis. These cysts have intraspinal and extradural location and originate from the facet capsules caused by degeneration of the facet joints.
They can also cause myeloradiculopathy, depending on the level of occurrence due to compression of the nerve roots. On CT scans, a thick, cystic structure in the area with the facet joint, and on MRI, capsule with contrast enhancement are characteristic for synovial cysts.

11 Magnetic resonance imaging typically appears as a sharply marginated epidural mass in which the contents most commonly appear isointense to cerebrospinal fluid on T1-weighted images and hyperintense to cerebrospinal fluid on T2-weighted images.

12 Early diagnosis and therapy would most likely reduce the chance of permanent neurologic deficit from a spinal osteochondroma. Radical excision of the apophysis is the choice of treatment and is almost curative.2,8,10,13,14 Recurrences are rare.2,8,9

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Authors
Mr Xu (Jun) and Drs Pan and Tian are from the Department of Orthopedics, the Second Affiliated Hospital, Harbin Medical University, Mr Xu (Chao-rui) is from the Department of Geriatrics, Heilongjiang Provincial Hospital, and Dr Wu is from the Department of Pharmacology, Mudanjiang Medical College, China.
Messrs Xu (Jun) and Xu (Chao-rui) and Drs Wu, Pan, and Tian have no relevant financial relationships to disclose.
Correspondence should be addressed to: Jun Tian, MD, the Second Affiliated Hospital, Haerbin Medical University, 246 Xuefu Rd, Nangang District, Harbin, Heilongjiang 150081, P. R. of China.