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Neuroradiology Case of the Week

Case 203

Devang Butani, MD

Clinical Presentation: Patient is a 56-year-old man presenting with low back pain for two weeks.

Radiological Findings: There is heterogeneous low signal diffusely throughout the lumbar spine, including the posterior column, on T1WI (Fig. 1), with heterogeneous high signal on T2WI (Fig. 2). There is heterogeneous contrast enhancement of these lesions (Fig. 3). There are varying degrees of degenerative changes. There is a compression deformity of L1. Alignment is normal.

Diagnosis: Multiple myeloma

DDX: Metastatic disease (e.g. prostate), multiple myeloma, diffuse osteoporosis, hyperplastic bone marrow.

Discussion: MR findings in multiple myeloma range from normal to variegated to diffuse involvement. Conversion of diffuse to variegated or focal pattern is also reported. MRI is useful in imaging multiple myeloma because of it's superior soft tissue resolution. The typical appearance of a myeloma deposit is a round low signal intensity (relative to muscle) focus on T1-weighted images, which becomes high in signal intensity on T2-weighted sequences. Myeloma lesions tend to enhance with gadolinium administration. Diffuse areas of replacement of the normal fatty marrow may result in regions of low T1-weighted signal.
     Nearly all metastasis deposits to the spine have the same signal intensity profile and enhancement pattern as myeloma. MRI, while sensitive to the presence of disease, is not disease specific. Other etiologies for a similar MRI appearance include osteoporosis and marrow replacement.
     Clinical history and work-up, including detection of monoclonal gammopathy, should be used to aid diagnosis. Coexistent pathologies cause MRI to understage or overstage patients with myeloma.
     Alternative modalities include PET for metabolically active lesion (sensitivity 84-92%, specificity 83-100%). It can also be used to monitor response to treatment.
      MRI may be useful in patients with extraosseous lesions to define the degree of involvement and to evaluate for cord compression.

References:

1. Ross JS, Brant-Zawadski M, Moor KR, et al. Diagnostic Imaging Spine. Amirsys 2004. IV-I, 66-69.
2. Schirrmeister H, Bommer M, Buck AK, Muller S, Messer P, Bunjes D, Dohner H, Bergmann L, Reske SN: Initial results in the assessment of multiple myeloma using 18F-FDG PET. Eur J Nucl Med Mol Imaging. 2002 Mar;29(3):361-6. [Medline]
3. www.learningradiology.com
4. Weissleder R, Rieumont MJ, Wittenberg J. Primer of Diagnostic Imaging. 3rd ed. C.V. Mosby, 2002: 552.