Diagnostic Imaging of Vertebral Metastases

Abstract

Metastatic diseaseCancer is the second leading cause of death and the incidence of cancer is still rising. Currently available therapy can now cure approximately 50% of cancer patients. The majority of patients die of the effects of metastatic disease. Following lung and liver, the skeletal system is the third most common site of metastasis. Up to 80% of all cancer patients will have skeletal disease at autopsy. Metastatic neoplasms vastly outnumber primary tumors of the skeleton. Excluding multiple myeloma, primary bone tumors account for only 0.3% of all malignancies.The spine is the most common site of bone metastases, irrespective of the primary tumor that is involved.Vertebral metastases have a major clinical significance. It is not only an indicator of poor prognosis, but also a major cause of suffering in patients with cancer by producing severe pain, vertebral instability, and disruption of neural function with loss of urinary or sphincter control or complete paralysis.These facts, coupled with increasing financial pressures to optimize the use of diagnostic resources, have led to scrutinize the use of radiologic procedures and radiologists and oncologists to look systematically at the benefits of a variety of staging procedures. Distribution of bone metastasesThe distribution of metastases throughout the skeleton has been the subject of study of many authors since a long period of time. The distribution of bone metastases as assessed by different authors varies widely. The reasons for this variability are, amongst others, patient selection and the techniques used, e.g. autopsy findings versus radiographic survey versus bone scintigraphy. There is general agreement, however, that metastatic disease predominantly occurs in the axial or central skeleton. This is most probably related to the fact that the axial skeleton contains the majority of the red marrow.The distribution of metastases over the vertebral column is, in order of frequency, lumbar, lower thoracic, upper thoracic, sacral and cervical spine. The lower thoracic and lumbar spine are also the most common sites of myelomatous bone lesions. Clinical symptoms and signs of spinal metastasesPain is usually the initial symptom in patients with vertebral metastases. The pain can be radicular, local or both. The mechanism of pain involves stretching or compression of pain conducting nerve fibers, which are situated in the anterior and posterior spinal ligaments, in the annulus of the intervertebral disk, and in the dura and apophyseal joints.Motor deficit is the second most frequent initial symptom. This can be due to compression of the cord, the cauda or spinal roots. Motor weakness and sensory loss are indicative for medullary or radicular compression. The sensory level is an unreliable indicator of the level of compression of the spinal cord, and usually is recorded as several segments below a myelographically demonstrable subarachnoid block.. R_e~ex changes can be present, as hyperreflexia, d1mm1shed or absent reflexes. Sphincter dysfunc-165