I．Introduction

Spinal cord and/or a nerve root compression at cervical and thoracic spine usually causes myelopathy and/or radiculopathy. Buttock pain and lower extremity pain are relatively rare symptoms in patients with spinal cord compression. However, cord compression is sometimes known to cause pain referred to areas well below the level of the lesion by irritation of the sensory tracts. Here we report a surgically-treated case of a thoracic dumbbell-shaped spinal tumor with contralateral buttock pain and lower extremity pain.

II．Case Report

A 72-year-old man with a history of fall from stairs was admitted with buttock pain of a right side and right lower extremity pain. He had no past medical history. Routine blood tests were normal. He suffered from shooting pain and numbness of his right back through right posterior thigh（Fig. 1）. Neurological examination demonstrated no motor weakness and no sensory loss of trunk and both lower extremities. Deep tendon reflexes were normal in both upper and lower extremities. Babinski signs were negative bilaterally. Magnetic resonance（MR）images showed a space-occupying lesion in the vertebral canal located on the middle to left side at the Th9 level that showed iso intensity with the spinal cord on T1-weighted images（Fig. 2a）and high and low mixed intensity on T2-weighted images（Fig. 2b）. MR images showed enhancement of the mass after Gd-DTPA injection（Fig. 2c, d）

Although the tumor was causing extensive spinal cord compression, the neurological symptom was atypical for thoracic myelopathy. We investigated other diseases which could show right buttock and lower extremity pain like sciatica. We checked brain MR image for excluding the possibility of intracranial lesion, lumbar MR image for lumbar canal and foraminal stenosis and pelvis MR image for pelvic lesion such as intra-pelvic space occupied lesion and piriformis syndrome. But nothing could be found for explaining his symptom except thoracic spinal tumor. Since the symptom of the patient showed refractory for conservative treatment, excision of thoracic dumbbell tumor was performed on patient compliance. We performed a left osteoplastic laminectomy of Th9 with excising the tumor under microscopy. The tumor was a dumbbell-shaped spinal tumor extending intradural and extradural spaces as shown in the preoperative images. The spinal cord was strongly compressed by the tumor from the left side to the right and the ventral side. The tumor was completely resected and considered to be a schwannoma originaing from the Th9 dorsal root. The pathological diagnosis was schwannoma same as intraoperative findings. MR images after surgery showed no tumor recurrence and adequate decompression of the spinal cord for five years. Follow-up examination found that the symptom disappeared immediately after the excision of the spinal tumor. He had returned to his previous activities of daily living and has been symptom free for five years.

III．Discussion

Generally, the symptom caused by spinal cord compression laterally at cervical or thoracic spine shows the motor deficit at the ipsilateral side of the lesion and sensory disturbance at the contralateral side of the lesion （Brown Sequard syndrome）. A patient may also have the ipsilateral symptoms of radiculopathy at the same level of the lesion. Sensory disturbance caused by the compression of the sensory tract is usually noticed as hypalgesia or hyperalgesia rather than pain. And it is usually diffuse and fails to conform to a radicular or peripheral nerve distribution in a sensory dermatome.

Although the most common cause of buttock pain and lower extremity pain is lumbar nerve root irritation due to lumbar canal and/or foraminal stenosis, it can be elicited by any lesion originating anywhere along the course of any peripheral nerve root of the lower extremity or within the lumbosacral roots^［1］. Buttock and lower extremity pain like sciatica may also be referred from sacroiliac joint and hip joint. Pisiformis syndrome is caused by sciatic nerve irritation between pisiformis muscle and short-rotater muscle of the hip. A definite diagnosis of these diseases is often possible by confirming the patient’s symptom and the image findings supporting the symptom. Lumbar canal stenosis can be confirmed by MR images with stenosis that matches the neurological symptom. A definitive diagnosis can be obtained by confirming the symptom reproducibility and therapeutic effect of selective nerve root block. Sacroiliac joint and hip joint disease is usually detected by symptom and images. Piriformis syndrome is often diagnosed by a symptom-inducing test such as Freiberg test and Pace test. It is also useful to make a diagnosis by block injection into the piriformis itself.

Although rare, it may also be caused by lesions involving the spinal cord or thalamus^［1］. There are some previous reports which presented the cases of buttock and lower extremity pain like sciatica in patients with cervical or thoracic cord compression（Table 1）^［1-8］. The mechanism of buttock and lower extremity pain caused by cervical and thoracic compression still remains a matter of speculation. It probably arises from compression of spinothalamic tract or dorsal column. Yakushiji et al ^［6］. considered that pain at the ipsilateral side was caused by the compression of dorsal column and pain at the contralateral side was caused by the compression of spinothalamic tract in his report. We considered that patient’s symptom was caused by the compression of the left spinothalamic tract at thoracic spine level by the spinal tumor and the symptom was seen in his right side.

Our experience suggests that thoracic cord compression caused by such as spinal tumor should be suspected in patients who have buttock and lower extremity pain like sciatica. Even the lesion is located laterally at the opposite side of the pain, the symptom can occur at the contralateral side.

Contributors

T. Furuya, S. Maki, T. Inada, M. Ota, K. Kamiya and M. Koda contributed to patient management. All authors contributed writing of the report.

Financial support

None.

Conflict of interest

S. Ohtori is a member of the Editorial Board of the Chiba Medical Journal. The other authors declare that they have no conflict of interest, either financial or nonfinancial, with the contents of this article.

Ethical approval

Written consent was obtained from the patient for publication of this case report and accompanying images.

Data availability

All relevant data are available in the manuscript.