Osteochondroma

Osteochondroma is a rare tumor of the cervical spine. The authors present a rare case of osteochondroma narrowing the C^sub 1/2^ foramen and causing occipital neuralgia. Complete removal of the tumor was performed with release of the pain. The literature is reviewed and etiology, diagnosis, treatment and differential diagnosis are discussed. [Neurol Res 2001; 23: 777-779]

Keywords: Osteochondroma; occipital nerve neuralgia; cervical vertebrae; osteochondroma surgery

INTRODUCTION

Although osteochondroma is the most common type of benign bone tumor, it is rarely localized in the cervical spine1,2. The lesion may cause many different symptoms ranging from an incidental X-ray finding to sudden death3. It is usually discovered after spinal cord compression1,4. Patients infrequently present with nerve root irritation. In this paper, we present a case of an adult patient suffering from occipital nerve neuralgia due to an osteochondroma of the cervical spine. To the best of our knowledge, only two cases of osteochondromata in this location causing nerve root irritation have been reported in the literature1,5.

CASE REPORT

A 50-year-old woman presented at admission with an induration at the right side of the upper neck which she had noticed for one and a half years. She felt a tingling pain in the suboccipital area. Moreover, she complained of retroauricular and occipital paresthesia. On palpation, local tenderness was present over the mass. It was nonpulsatile, hard and immobile. Full movement of the neck in all directions was present and there was no relation of the symptoms to flexion of the neck. The neurologic and general examination did not show any other abnormalities. There were no symptoms indicating spinal cord compression.

On plain X-ray films of the craniocervical junction and the cervical spine a fairly well delimited extradural bony lesion could be seen (Figure 1). It was located at the right side of the C^sub 2^ vertebral lamina and the spinous process. Computed tomography revealed a heterogenous bony structure continuous with the lateral mass of the second cervical vertebral body measuring 4 cm in diameter and narrowing the C^sub 1/2^ foramen (Figure 2). Bone scintigraphy, performed with 600 MBq Tc 99mHMDP, showed a marked bone metabolism at the side of the mass. The scan of the skeleton was otherwise unremarkable.

Surgical removal of the bony mass was undertaken by a skin incision reaching from the retroauricular region down to the neck. The surrounding soft tissue and the muscles of the neck were dissected and the greater occipital nerve was exposed and followed to its nerve root. Close to the lamina of C^sub 2^, a bony tumor compressing the nerve could be identified. It had a broad base firmly attached to the C^sub 2^ lateral mass (Figure 3). This process was completely exposed and resected in a piecemeal fashion by the drill. Decompression and preservation of the major occipital nerve could be achieved successfully.

Histologic examination in microscopic sections confirmed the diagnosis of an osteochondroma, revealing the typical aspect of a cartilage-capped bone excrescence with some hematopoetic foci in an otherwise fatty marrow. No histologic evidence of malignant transformation was noted.

Plain films of the cervical spine and computed tomography performed after surgery showed complete removal of the tumor. At discharge, the patient was free of symptoms. In a four-month follow-up, she complained of slight muscular rigidity in the neck, but no longer of symptoms consistent with occipital nerve neuralgia.

DISCUSSION

Osteochondroma is a very common tumor affecting long bones3,6, which is also known as 'osteocartilaginous' or 'benign exostosiS,7. It can either present as a single lesion or be multiple. The multiple form can occur sporadically, but it is most often inherited as an autosomal dominant trait called `hereditary multiple exostosis'5. The solitary as well as the multiple forms are detected in males more frequently than in females with a ratio of 1.8: 1 (multiple) to 3: 1 (solitary)7. The inherited multiple form has been reported to account for 12%7 to 74% of all cases.

Osteochondroma occurs in the metaphyseal region of long bones in 80%, especially in the upper humerus2, the distal end of the femur and in the knee8. Although it makes up about 11% of all benign bone tumors, its localization in the spine is observed in less than 2%-7%1,2. The actual incidence may probably be higher, because it is frequently asymptomatic and the patients are often not identified or not reported1.

Approximately half of all spinal osteochondromas are located in the cervical spine7. This is a significant overrepresentation due to the fact that the cervical spine contains only 23% of all vertebrae. The cervical spine has much greater mobility than any other part of the vertebral column and by this suffers from more microtrauma. This might cause displacement of the epiphysial cartilage which can then stimulate the growth of the tumor.

Osteochondroma increases in size by endochondral ossification of its cartilaginous cap2. Diagnosis is usually made before the age of 20 as the growth of the tumor characteristically parallels the parent bone and the active growth period ends in the second decade of life9. Delayed appearance, as in our case, may rather be caused by degenerative changes in the spine which, in combination with the long-standing turmor, can cause neurological symptoms.

In the majority of the cases, osteochondroma is detected as an asymptomatic mass and does not cause neurological deficits. Symptoms of spinal osteochondroma are either caused by spinal cord compression or by nerve root irritation. In the upper spine (cervical and thoracic), myelopathic symptoms are more common1,4, whereas osteochondroma of the lumbar spine causes nerve root compression symptoms much more often due to its location1. Unusual cases may present with features of Horner's syndrome10, Brown-Sequard syndrome11 and Friedreich's ataxia12. In one case, the spinal cord was subtotally transected by an osteochondroma of the odontoid process and the patient suffered from sudden death3. If located anteriorly to the cervical vertebral bodies, osteochondroma can also appear as a pharyngeal mass13 or even a goiter14 causing symptoms such as hoarseness or dysphagia. The lesion may rarely occlude the vertebral artery1, but usually the slow growth of the tumor allows early vascular compensation.

A cervical osteochondroma in an adult causing occipital nerve neuralgia as reported in our case has so far only been reported twice in the literature1,5.

Radiological evaluation of this kind of tumor should include plain films and a CT scan, MRI, bone scintigraphy, myelography and even angiography may be helpful in special cases. The plain X-ray film can outline the typical sessile bone-like projection of the tumor. Demonstration of continuity between the bony cortex of the exostosis and the host bone is considered distinctive15. Nevertheless, plain radiography fails to reveal the lesion in about 79% of cases7. Computed tomography precisely delineates the tumor matrix and its connection to the surrounding structures such as the spinal cord or the nerve root which it is compressing. It is considered the best radiographic tool by the majority of authors5,7 and can be extremely helpful in planning surgical treatment. MRI did not prove to have any significant advantage in solitary exostosis2. It can be helpful if malignant transformation of the tumor is suspected2. Mylography and CT-myelogram can outline the extent of dural compression by showing a filling defect which is usually larger than the bony projection as the cartilaginous part of the lesion cannot be seen on bone scans. A technetium phosphate bone scintigram can be helpful in screening for similar lesions in other locations8, as approximatley 50% of patients with osteochondroma of the cervical spine will have more than one tumor9. Scintigraphy does not contribute to forming of the differential diagnosis.

Surgical therapy should consist of total removal of the osteochondroma, since incomplete resection, leaving the cartilaginous cap inside, can cause recurrence7. Standard surgical approaches are usually sufficient for the various spinal localizations of these tumors. The main difficulty lies in the hard bony consistence of osteochondroma which sometimes urges the surgeon to use heavy instruments close to delicate structures such as the spinal cord or single nerve roots. According to the literature, most of the operated patients who were symptomatic before surgery showed improvement or total disappearance of symptoms after surgical resection7.

Differential diagnosis of benign spinal column tumors includes giant cell tumors, aneurysmal bone cysts, hemangiomas, osteochondromas and osteoblastomas16. Malignant transformation occurs in about 1% of solitary and 10% of multiple osteochondromas17. This should be considered whenever there is recurrence after macroscopic total resection or a sudden acceleration of growth with worsening of clinical features.

CONCLUSION

Osteochondroma of the cervical spine is a rare entity which most often causes myelopathy or radiculopathy. Its real incidence remains unknown as a large number of asymptomatic lesions are never detected. CT scan is the neuroradiological modality of choice. Complete operative removal is indicated and has proven to be successful in the great majority of patients.

ACKNOWLEDGEMENTS

The authors are grateful to Dr Almuth Brandis for the histological examination of the case and to Mr Klaus Ehrhardt and Mrs Swanhild Fischer for preparing the photographs.

REFERENCES

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Stefanie Baer-Henney, Marcos Tatagiba and Madjid Samii

Department of Neurosurgery, Hannover Medical School, Hannover, Germany

Correspondence and reprint requests to: S. Baer-Henney, MD, Department of Neurosurgery, Hannover Medical School, Carl-- Neuberg-Str. 1, 30625 Hannover, Germany.

[sbaerhenney@hotmail.com] Accepted for publication December 2000.

Copyright Forefront Publishing Group Oct 2001
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