Skull Findings on X-ray in Multiple Myeloma
Classic Radiographic Appearance
- The characteristic skull finding on X-ray in multiple myeloma is the presence of multiple "punched-out" osteolytic lesions, which appear as well-defined, round radiolucent defects without sclerotic borders, often described as having a "raindrop" or "Swiss cheese" appearance 1, 2, 3
- Osteolytic lesions are the hallmark finding, appearing as discrete, round, sharply demarcated areas of bone destruction without surrounding reactive bone formation 1, 2, 3
Imaging Characteristics and Limitations
- Conventional skeletal survey (including skull X-rays) remains the standard technique for detecting lytic lesions and is used in the CRAB criteria (hypercalcemia, renal insufficiency, anemia, bone lesions) for defining myeloma-requiring treatment 2, 3
- Lytic lesions only become visible on X-ray after more than 50% of trabecular bone has been lost 4
Advanced Imaging Considerations
- Whole-body low-dose CT (WBLD-CT) detects up to 60% more relevant findings compared to conventional skeletal surveys and is now recommended as the novel standard procedure for diagnosis of lytic disease 2, 3
- FDG-PET/CT has 90% sensitivity for detecting various myeloma lesions including focal lesions greater than 5 mm 6
- However, skull and rib lesions are not as well detected by WBLD-CT or MRI compared to conventional skeletal surveys, so focused skull X-rays may still be valuable when these areas are of clinical concern 5