Multiple Myeloma

Multiple myeloma is a systemic malignant disease. It is the most common primary tumor of bone. In its initial stages, marrow infiltration with plasma cells and increased bone resorption result in radiological appearance identical to that seen in osteoporosis. The disease leads to anemia, increased sedimentation rate, hypercalcemia, accumulation of paraprotein in the serum, and Bence-Jones protein in the urine. The diagnosis can be confirmed by finding abnormal serum and urine electrophoresis. Bone marrow biopsy establishes the diagnosis by demonstrating abundance (over 10%) of malignant plasma cells.

Clinical Presentation

Multiple myeloma is more common in males and usually presents in the fifth or sixth decades. Most patients present with pain. Initially the pain may be mechanical in nature, increasing on weight bearing and disappearing with rest. Soon afterward, the pain intensifies, becomes permanent, and may disturb the patient's sleep. At times, sudden, severe axial pain develops due to a pathological fracture. Vague symptoms such as fatigue, generalized weakness, and weight loss accompany the pain. The disease affects the vertebral bodies as well as the posterior elements. The thoracic and lumbar spine regions are the most commonly affected areas. At times a solitary lytic-multicystic bone lesion is found presenting a solitary myeloma or "plasmacytoma."

Imaging Studies

Bone scan may remain negative in the presence of bone marrow infiltration and the absence of fractures. CT may detect lytic lesions, especially in the trabecular bone of the vertebral bodies even in the presence of normal-looking plain films (Figures 11-10A, 11-10B, and 11-10C). Lytic lesions may involve cortical bone as well. About 1% of the lesions may be sclerotic. Spiral or multidetector CT may be able to provide detailed information on osseous involvement. In advanced stages the CT will show destruction of vertebral bodies and the presence of compression fractures with tumor extending beyond the vertebral boundaries (Figure 11-11).

MRI is the best screening test in multiple myeloma patients who appear to have normal plain films or diffuse osteoporosis. In the initial stages of the disease, however, up to 50% of patients with proven bone marrow infiltration may have a normal-looking MRI.

Three patterns of marrow involvement by the disease are known. The most common type consists of focal, well-demarcated low-signal-intensity lesions on T1WI and high intensity on T2WI. Post-contrast

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