Various presentations of multiple myeloma MRI review: A Case series

We present the MRI findings in four cases of multiple myeloma involving the musculo-skleletal system. The diagnosis is made by combination of imaging and histopathologic findings. Radiologists should be aware of the imaging findings of this condition to ensure early diagnosis and treatment.


Introduction
Multiple myeloma is the most common primary malignant neoplasm of bone. It usually originates from the hematopoietic element of the bone marrow but occasionally arises in extraskeletal sites. Bone deposits have been shown by MRI in about 50% of asymptomatic myeloma patients with normal plain radiographs. The imaging patterns in multiple myeloma can be classified as normal, focal, diffuse and variegated [2].
The focal pattern consists of localised areas of decreased signal intensity on T1-weighted images and increased signal intensity on T2-weighted images [1]. Myelomatous deposits are generally sharply demarcated on a background of an otherwise normal appearing bone marrow. Homogeneous enhancement occurs on T1-weighted images following intravenous contrast injection. [6]

Case reports
The present cases were studied at Assam Medical College, in the department of Radiodiagnosis, Dibrugarh, Assam. All studies were performed using Siemens magnatom avanto 1.5 T whole body MR system. Scanning was done in axial, coronal and sagittal planes. Post contrast fat saturated T1 weighted images were obtained after giving 10ml of IV Gadolinium in all cases. Biopsy confirmation (ultrasound guided/CT guided FNAC, /or direct FNAC by a pathologist) or pathological correlation was done in all cases.

Case 1
A 51 -year old male presented with backache and chest pain since one month. His general condition was fine and was healthy otherwise. Clinician did not suspect anything like multiple myeloma. Plain X-ray of lumbar spine revealed a normal study. Magnetic resonance imaging (MRI) showed involvement of D4-L3 vertebrae ( In phase and opposed phase images ( Figure  2 a,b) showed SIR=1.8 (SIR >0.8). Splenomegaly was present ( figure 1E).
Serum electrophoresis showed a normal pattern, no M-band or spike was detected. Bone marrow biopsy from sternum showed 46% plasma cells few of them showed bi-nucleation. (Figure 3a). A conclusion of non-secretory myeloma was made.

Case 2
A 35 year old female presented with low back ache since one and a half month. It was sudden in onset and was gradually progressing. Pain was radiating to both the lower limbs. Presently she is unable to walk; clinically traumatic paraparesis. There was mild weight loss. Blood picture revealed a normal study. Magnetic resonance imaging (MRI) showed complete collapse of D1 vertebra with posterior vertebral convexity with retropulsion into spinal canal causing marked spinal canal stenosis and In phase and opposed phase sequences showed SIR of 0.9.Histological study from D1 showed multiple myeloma (Fig 6).

Case 3
A 54 year old male presenting with pain in the right upper limb from shoulder since 15 days. He was unable to hold things with the right hand with tingling sensation. Clinically right brachial plexopathy was suspected. The blood picture showed raised ESR (120mmAEFH) and was anaemic; TC was low. He underwent MRI of cervical spine. The lesions were scattered in multiple cervical, lumbar, sacral vertebrae, sternum (figure 7c), ribs. It was hypo to isointense on TIWI (figure 7a), intermediate on T2WI (fig7 b) and homogeneously hyperintense on T2FS(c).

Case 4
A 60 year old female with low back ache since one and a half month. It was sudden in onset. She also had a history of fall. She had pain and swelling of left arm after a very subtle injury which showed pathological fracture of left shaft humerus(9f). Her blood urea was high 42mg/dl. However blood picture did not reveal any abnormality. Partial collapse of D12 with mild posterior vertebral convexity with retropulsion into spinal canal was seen. Abnormal TIWI hypointese

Discussion
Multiple myeloma is a common malignancy of older patients (70% of cases are diagnosed between 50 and 70 years of age) and it is the most common primary malignancy of bone. [6] Our studies too show three cases within this range; only one (case no.2) is of 35 years old. It has a male predilection (M: F 2:1). The exact pathogenesis of multiple myeloma is unknown, but environmental factors such as exposure to herbicides, insecticides, benzene, and ionizing radiation may contribute to its occurrence. [3] On MRI Multiple myeloma typically appears as multiple intramedullary zones with lowintermediate signal on TIWI; and intermediate, slightly high to high signal on T2WI [1] and slightly high to high signal on FST2WI.
FST2WI is important for detecting myeloma because intermediate and high signal heterogeneity on TIWI from red and yellow marrow respectively, can be seen in normal vertebral marrow in elderly patients. Zones of cortical destruction may occur associated with extraosseous soft tissue lesion, as seen in case 3,4 in our series.
Bone deposits have been shown by MRI in about 50% of asymptomatic myeloma patients with normal plain radiographs as seen in cases in this series. Sagittal studies of the spine enable screening of a high proportion of hematopoietic marrow and detection of any potential threat to the spinal cord as depicted in our study. [6] Extraosseous multiple myeloma usually occurs as an extension from intraosseous (as seen in our cases 2,3,4) or less frequently arises from within the soft tissue. Zones of high signal on T2WI peripheral to the Gd-contrast enhancement portion of the lesion may represent zones of tumor invasion or peripheral oedema.
Multiple myeloma results from monoclonal proliferation of malignant plasma cells which produce immunoglobulins (commonly IgG) and infiltrate haemopoietic locations (i.e. red marrow) [1]. Bone marrow containing more than 15% plasma cells (normally no more than 4% of the cells in the bone marrow are plasma cells). Blood serum and/or urine containing an abnormal protein. This was also the basis of our diagnosis. Renal insufficiency is one of the causes of death.
The focal pattern consists of localised areas of decreased signal intensity on T1-weighted images and increased signal intensity on T2-weighted images was also seen in our study. Myelomatous deposits are generally sharply demarcated on a background of an otherwise normal appearing bone marrow. Homogeneous enhancement occurs on T1-weighted images following intravenous contrast injection (Case1 and 2), also detects subtle lesions not seen in pre contrast study (case2).
The diffuse pattern is characterised by a diffuse and homogeneous decrease in marrow signal intensity which becomes identical to or lower than that of adjacent inter-vertebral discs on a T1weighted image and on a T2-weighted image by a diffuse or patchy increase in signal intensity. Marked enhancement is usually seen on T1-weighted images following intravenous contrast (case 3 figure 8 D).
Distribution of multiple myeloma mirrors that of red marrow in the older individual, and thus this is mostly encountered in the axial skeleton and proximal appendicular skeleton.
Extraosseous epidural tumors causing compression myelopathy without evidence of destruction or collapse of vertebral bodies are a b c d IJBR (2015) 6 (07) www.ssjournals.com relatively rare; to our knowledge very few cases exist in the literature.(5)

Conclusion
MRI plays a major role in detecting occult lesions of multiple myeloma. MRI detects myelomatous infiltration early, thus helps in early treatment. Serum electrophoresis is the mainstay of diagnosing multiple myeloma. However its absence does not rule out multiple myeloma especially in non secretory type [3] where bone biopsy is confirmatory. Lack of specificity of the MRI patterns should always be kept in mind. Differentiation between red marrow hyperplasia secondary to anaemia, infection, malignant or treated marrow infiltration can be extremely difficult. MRI is generally more sensitive in detecting multiple lesions compared to the standard plain film skeletal survey [3].
Infiltration and replacement of bone marrow is exquisitely visualised, and newer scanners are able to perform whole body scans for this purpose which has been shown to be superior to both CT and skeletal surveys. [4] The main differential is that of widespread bony metastases, non-hodgkins lymphoma. Contrast study depicts the hidden myelomatous infiltrations.