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Multiple Myeloma: An Unusual Presentation 2006

General Spine

Chirstopher J Friend, MD, Non ASSR Member
Robert L Williams, MD, ASSR Member
Melanie B Fukui, MD, Non ASSR Member

Excerpta Extraordinaire

Excerpta

Patient 1

A 53-year-old woman presented to our emergency room with a gait instability, lower extremity numbness and incontinence. She had had a long history of chronic back pain and fibromylagia as well as a two-month history of more severe midback pain refractory to anti-inflammatory agents. Six weeks prior to presentation, pain management had administered epidural injections. Approximately two weeks following the injection, she had an episode of fever and chills that was thought to be due to a UTI. On admission exam, she had decreased pinprick sensation below T8 and decreased rectal sensation and tone. With a history of fever and prior epidural injection, an epidural abscess was the working diagnosis.

Due to the patient's symptoms, an emergent MRI was ordered which showed enhancing extradural soft tissue extending from T1 to L1 with several levels of canal compromise. Additionally, the marrow signal in the vertebral bodies was uniformly low, consistent with diffuse marrow infiltration. A differential diagnosis of lymphoma was given with extramedullary hematopoiesis felt less likely.

The patient was taken to the operating room where a partial T4-T5 laminectomy and biopsy of the epidural mass was performed. Frozen section suggested lymphoma and further exploration was terminated. Final pathologic diagnosis was plasmacytoma. Subsequent bone marrow biopsy showed hypercellular bone marrow with 80% plasma cells consistent with multiple myeloma.

Patient 2

A 74-year-old male presented with bilateral leg weakness, decreased proprioception, and urinary retention. He denied any numbness or paresthesias. Due to his leg weakness, an MRI was ordered which demonstrated a large enhancing extradural soft tissue mass at T5 and T6 with displacement of the thecal sac. The mass extended through the right neural foramen with compression of the superior endplate of T5 and inferior endplate of T6. Evaluation of the bone marrow demonstrated scattered abnormal enhancement throughout the spine with areas of more focal involvement and osseous destruction. A diagnosis of multiple myeloma verse metastatic disease was suggested. Serum electrophoresis showed an IgG kappa monoclonal gammopathy. Urine chemistry showed similar results. A Tc-99 MDP bone scan was negative consistent with the patients presumed diagnosis of multiple myeloma.

Multiple myeloma is caused by a malignant proliferation of plasma cells, which usually affect the bone marrow. Other symptoms can include bone pain, impaired renal function, and hypercalcemia. With the increase in imaging utilization, incidental detection has become more common. Spinal compromise is a well-known complication of MM, which is often caused by vertebral fracture. The cases we present are unusual in that the spinal compromise is being caused by an extensive extradural soft tissue mass. This is a much less common cause of spinal compromise in multiple myeloma.

These cases also demonstrate the differing patterns of vertebral involvement in multiple myeloma. Three different marrow patterns have been described: focal, diffuse, and variegated. The focal pattern consists of multiple lesions on a normal background. The diffuse pattern demonstrates a homogenous decrease in marrow signal on a T1 basis. The variegated pattern shows multiple small foci of low T1 signal that enhance post contrast. A normal pattern has also been defined as biopsy proven marrow infiltration with a normal MRI appearance. The differing patterns may have a correlation with tumor burden. Patient 1 illustrates a diffuse pattern of involvement while Patient 2 illustrates a more focal involvement.

We present these cases illustrate an unusual presentation of multiple myeloma as well as the differing patterns of marrow involvement in multiple myeloma.