Spinal Osteochondroma Causing Cord Compression

SPINAL OSTEOCHONDROMA CAUSING CORD COMPRESSION - A RARE CAUSE OF PARAPARESIS
Pradeep B Bhosale, Vidyanand A Raut, Naushad Hussain
Dept. of Orthopaedics, KEM Hospital, Parel, Mumbai - 400 012.

A 28 year old female was admitted with progressive weakness of lower limbs of 2 months duration. Neurological evaluation revealed dorsal myelopathy with spastic paraparesis (Frankel Grade B) and sensory impairment below D10 dermatome. Plain radiographs and CT scan revealed a bony mass arising from right superior articular facet of D10 vertebra. MRI scan of dorso-lumbar spine showed a right posterolateral extradural bony mass arising from the right D10 superior articular facet. The thecal sac was compressed and displaced anteriorly and to the left, flattened against the D9 vertebral body. Imaging studies favoured the diagnosis of an osteochondroma. Surgical decompression was performed via a posterior approach, with D9-10 hemilaminectomy and mass excision in toto. The cord was found to be flattened against the D9 body. Histopathology of the operative specimen was consistent with the diagnosis of an osteochondroma. Postoperatively the patient showed dramatic neurological recovery and attained ambulatory power in lower limbs within 3 weeks.
INTRODUCTION
Incidence of spinal osteochondroma has never been reported to be more than 2%. Cord compression because of these lesions is extremely rare, and rare still is the occurrence of neurological deficit). [1]

About 80% of osteochondromas arise from lower end of femur, upper end of tibia and proximal humerus. Flat bones such as the scapula, ribs and pelvis are involved in about 12% of cases.

This is a case report of paraparesis due to spinal osteochondroma, which recovered after surgical resection.
CASE REPORT

A 28 year old Indian female presented with progressive lower limb weakness of 2 months duration. She had a myelopathic picture with severe spastic paraparesis (Frankel Grade B) and sensory impairment below D10 dermatome.

Roentgenography demonstrated a bony mass arising from the region of D9-10 articulation on the right side (Fig. 1). The cartilage cap was not seen on plain roentgenograms.

CT Scan confirmed the bony growth to be arising from right superior articular facet of D10 vertebra, with associated sclerosis and hypertrophy of the facet (Fig. 2).

Fig. 1 : Plain roentgenogram of thoracic spine showing a vaguely defined bony mass in the region of D9-10 articulation on the right side. Fig. 2 : CT Scan (Transverse cut) showing bony mass encroaching the neural canal.

MRI scan of dorsolumbar spine showed a right posterolateral bony mass arising from the right D10 superior articular facet, with a focal well defined oval epidural component measuring 1.7 x 1.0 cm (Fig. 3). The mass had a central relatively isointense portion surrounded by an inhomogenous rim of low signal intensity. The thecal sac was compressed and displaced anteriorly and to the left, flattened against the D9 vertebral body (Fig. 4).

Fig. 3 : MRI Scan (Transverce cut) showing the cord to be compressed and flattened against the D9 body. Fig. 4 : MRI Scan (Sagittal cut) shows cord compression from posterior aspect at D9-10 level.

Surgical decompression was performed via a posterior approach, with D9-10 hemilaminectomy and mass excision in toto. During excision the cord had to be protected with a spatula. It was compressed against the D9 vertebral body.

Histopathological examination of the operative specimen conclusively proved it to be an osteochondroma.

Postoperatively there was a dramatic improvement in the neurological status and the patient attained ambulatory power in lower limbs within 3 weeks.

DISCUSSION

Only 97 cases of spinal osteochondroma have been reported to date. The solitary type was the most common 72 of 97 cases. Usually osteochondromas arise from the pedicles or laminae and in rare instances from the articular facets, and can be dealt with en masse excision from posterior approach. If the exostosis arises from the vertebral body, anterior approach is preferred.

Plain roentgenograms are inconclusive. CT Scan better delineates the bony excrescence in bones where radiographs are not particularly helpful, as in pelvis and spine. MRI scan is extremely effective for assessment of the size and extent of the bony stalk, as well as of the cartilagenous cap. T2 weighted images show well defined bone, cartilage and marrow signal intensities. MRI of spinal osteochondroma shows an outer osteochondral layer and an ossified control mass.[2]

Neurological recovery may be expected if decompression has been done early.

In this case, the osteochondroma arose from D10 superior facet and was excised without compromising stability by facetectomy. Additional stabilisation was not required. Rapid neurological recovery was seen post-operatively.

ACKNOWLEDGEMENT
The authors would hereby like to profusely thank the valuable co-operation and guidance of Dr. (Mrs.) PM Pai, Director of Medical Education and Major Hospitals and Dean, Seth GS Medical College and KEM Hospital.

The authors are also extremely grateful to Dr. VJ Laheri, Professor and Head, Department of Orthopaedics, Seth GS Medical College and KEM Hospital, for his support and guidance in the preparation of this case report.
REFERENCES

Moriwaka F, Hozen H, Nakane K, Sasaki H, Tashiro K, Abe H. Myelopathy due to osteochondroma : MR and CT studies. J Comput Assist Tomogr Jan.-Feb., 1990; 14 (1) : 128-30.
Okuyama K, Chiba M, Okada K, et al. Huge solitary osteochondroma at T11 level causing myelopathy : case report. Spinal Cord Nov., 1997; 35 (11) : 773-6.

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Fig. 1 : Plain roentgenogram of thoracic spine showing a vaguely defined bony mass in the region of D9-10 articulation on the right side.	Fig. 2 : CT Scan (Transverse cut) showing bony mass encroaching the neural canal.


Fig. 3 : MRI Scan (Transverce cut) showing the cord to be compressed and flattened against the D9 body.	Fig. 4 : MRI Scan (Sagittal cut) shows cord compression from posterior aspect at D9-10 level.