Etiology

MSCC is caused by primary bone or (more commonly) metastatic tumors. Prostate, lung, and breast cancers have been particularly associated with MSCC, but any systemic cancer can metastasize to the spine.[7] One UK retrospective cohort study reported that prostate cancer (20%), lung cancer (20%), breast cancer (17%), and renal cancer (12%) accounted for around 70% of cases.[11] Other cancers associated with MSCC include non-Hodgkin lymphoma and myeloma, particularly in patients in whom MSCC is the presenting symptom of cancer.[12] Neuroblastoma and soft tissue sarcoma have been reported to be the most frequent cause of MSCC in children (under 18 years).[13][14]

Pathophysiology

Spinal tumors can be either primary or secondary to metastatic disease, and can result in spinal cord compression. Tumors affecting the spinal column are often classified by their location as extradural, intradural extramedullary, or intradural intramedullary.[1] Extradural tumors are located outside the dura mater, in vertebral bodies and neural arches. Intradural extramedullary tumors are located within the dura but outside the spinal cord parenchyma, whereas intradural intramedullary tumors are located within the spinal cord parenchyma.[1][8]

Spinal epidural metastases represent tumor growth along the spinal column into the epidural space. Most extradural metastases occur through hematogenous spread.[15][16] Breast, lung, and prostate cancer are commonly implicated.[7][11][17] Direct extension of primary tumors may also lead to metastases in the spinal column. For example, prostate, bladder and colorectal cancers may become locally aggressive and invade the lumbar or sacral epidural space.[18]

Spinal epidural metastases can cause epidural spinal cord compression through mechanical injury to axons and myelin, and spinal cord ischemia/infarction via compression of spinal arteries and the epidural venous plexus.[2]

Spinal cord compression may lead to neurologic damage; the resulting disability (e.g., paraplegia, tetraplegia) depends on the level of the lesion. The effects of MSCC may be reversible if it is of recent onset and there is some preservation of neurologic function.

Spinal epidural metastases may also alter normal bone architecture, resulting in deformity or collapse of the affected vertebral body. Vertebral body collapse may lead to spinal instability by increasing strain on the support elements of the spine column, including muscles, tendons, ligaments, and joint capsules.[18][19][20] It can also result in retropulsion of fractured bone fragments into the epidural space causing spinal cord compression.[21]

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