Contralateral referred pain in a patient with intramedullary spinal cord metastasis from extraskeletal small cell osteosarcoma

Abstract

Context: Referred pain has been observed in some patients after cordotomy, wherein noxious stimulus applied to a region rendered analgesic by cordotomy produces pain at a spot different from the one where the noxious stimulus is applied. We report a patient who had intramedullary spinal cord metastasis of extraskeletal small cell osteosarcoma, a rare form of metastatic disease, and experienced contralateral referred pain.

Findings: Initially, the patient had a mass in the left posterior neck region and later developed a large extradural mass at the C3-C7 level. The masses were excised, and the histological findings led to a diagnosis of small cell osteosarcoma. He underwent chemotherapy and radiation therapy. He experienced numbness in his left leg; subsequently, the numbness slowly spread up the thigh to the left side of the abdomen. When pinched in the numb area on the left side of the body, he felt as though he had been pinched in both that area and the corresponding area on the right side. A magnetic resonance imaging scan showed an enhancing lesion in the right side of the cord at the C6-C7 level.

Conclusion/clinical relevance: An intramedullary spinal cord metastasis can arise from primary extraskeletal small cell osteosarcoma and cause contralateral referred pain, especially in a mirror-image location. Contralateral referred pain may be caused by a subsidiary pathway comprising ascending chains of short neurons that link the dorsal horn neurons longitudinally and latitudinally.

Figure 1

Coronal T1-weighted post-contrast magnetic resonance images of the cervical spine. Magnetic resonance imaging scan of the cervical spine showing a large enhancing mass (arrow) surrounded by the trapezius, splenius, and levator scapulae muscles (A). Magnetic resonance imaging scan of the cervical spine obtained 1 year later showing a large extradural enhancing lesion (arrow), which is displacing the spinal cord to the right (B).

Figure 2

Histologic findings of the operative specimen. Tumor showing proliferation of undifferentiated small round cells with small amounts of cytoplasm (original magnification, ×400) (A). Formation of metaplastic bone among the tumor cells (original magnification, ×100) (B). The tumor cells are separated by pink matrix (original magnification, ×400) (C).

Figure 3

Magnetic resonance imaging scan of the intramedullary mass causing expansion of the cord and edema over several segments. T2-weighted image showing a spinal cord tumor (arrow) that is surrounded by perifocal edema and has an isointense signal (A). Sagittal (B) and axial (C) T1-weighted post-contrast images showing intense and uniform enhancement of a well-circumscribed intramedullary mass (arrow).