Multiple myeloma (MM) is one of the most common hematological malignancies involving the spine. Pathological fracture of the vertebral body and neurological deterioration can occur as a form of skeleton related event in patients with MM. Under these conditions, surgical intervention or conservative treatment including radiotherapy have been tried for local control. However, there are still debates on which therapeutic approach is optimal7,10,13,17). In particular, spinal cord compression by epidural myeloma with or without pathological fractures is a grave complication and, in this condition, timely optimal treatment is essential. However, there are also debates on optimal treatment. Here, we present three patients suffering from spinal cord compression caused by an epidural myeloma with different clinical courses and results. By reviewing the related literatures, we discuss the surgical roles for these patients with MM and spinal involvement.

Brief descriptions of the presented patients are summarized in (Table 1).

MM is a hematological multicentric disorder. It comprises 1% of malignant tumors and 10-15% of hematopoietic neoplasms16). However, as MM is a bone-marrow based neoplastic proliferation of plasma cells that secrete a monoclonal immunoglobulin, skeleton related events are not uncommon. Among these skeleton events, the spine is one of the most commonly involved sites and pathological fractures of the spinal column are the most common spinal involvement of MM. Another form of spinal involvement of MM is spinal cord compression. Spinal cord compression is reported to develop in 11-24% of patients with MM17). Most cord-compression lesions occur due to a pathological fracture of the involved vertebral body or extension of a vertebral body myeloma lesion. However, an epidural myeloma could elicit spinal cord compression as a rare form of extraosseous myeloma. Although the exact incidence of spinal cord compression by epidural myeloma has not been reported, extraosseous involvement of MM is an uncommon condition and is found in <5% of patients with MM5). The sites of predilection for an extraosseous myeloma are the submucosal tissue of the upper respiratory tract, the gastrointestinal tract, pleura and the central nervous system3). Among them, spinal cord compression from an epidural myeloma without combined pathological fractures of the vertebral body is a rare condition and has mainly been reported as a case presentations in the literature1,8,10). Radiographs in patients with an epidural myeloma are usually normal and in some cases, multiple compression fractures and osteopenic appearance of the vertebral body could suggest MM. MRI is the best diagnostic modality for detecting spinal cord compression, epidural masses and marrow involvement of MM. All of our patients were previously diagnosed by a hematological specialist and referred to our department for an evaluation of the spine lesions. Although the third case showed an accompanying pathological fracture of T4, the spinal cord compression developed not by the pathological fracture but by the posteriorly located epidural mass. This epidural lesion should be distinguished from several other neoplastic or inflammatory conditions, such as tuberculous infection particularly in endemic areas, metastatic lesion, lymphoma and meningioma. Although other clinical data including laboratory results could be useful to differentiate, a histopathological diagnosis might be required to confirm the diagnosis. Extraosseous epidural myeloma is believed to originate from lymphoid tissue in the epidural or paraspinal lymph node10). However, a signal change in the adjacent spinous process was observed in all of our cases. A directly extension or connection to this posterior marrow lesion could not be ruled out.

In general, extraosseous myeloma involvement at diagnosis or during the course of disease is considered a poor prognosis3). Failure of neurological recovery has been observed in most reported cases with various treatment modalities as our cases showed2,9,11). Because of the limited size of most reports and the differences in the treatment provided, no clear guidelines have been established for spinal cord compression caused by a myeloma. Some authors recommend radiotherapy combined with high-dose steroid therapy as the first choice of treatment because MM is highly sensitive to radiotherapy6,12). In one report, radiotherapy alone was tried for 63 patients with MM. The authors reported that 76% of the patients experienced an improvement in motor function, 2% deteriorated and local control was achieved in 98% in 1 year14). In contrast, surgical decompression was attempted in several reports and early surgical decompression followed by radiotherapy or chemotherapy was recommended4,8,10,15). However, most authors agreed that timely intervention is critical for spinal cord compression by a myeloma. As our cases and other reported cases have shown, neurological recovery beyond the critical point is extremely rare regardless of the radiotherapy or surgery attempted. Although further research to define the optimal treatment for this condition is mandatory, close observation of the neurological status and patient and medical staff awareness of neurological deterioration are also important to prevent neurological deficits and obtain favorable results. Moreover, the involved level by the epidural myeloma is one of the important factors to be considered. If the involved level is the cervical or thoracic level, likely these presented cases, more attentions should be paid to monitor the neurologic status. Surgical intervention prior to non-surgical treatment should be considered in the cases presented with any deterioration of the neurologic status.

Although we could not reach a firm conclusion with theses cases of the limited numbers, we present an algorithm to help the clinical decision-making process and define the role for surgery in the spinal involvement of myeloma from the perspective of spine surgeon (Fig. 4). The mechanical status of the spine and neurological status are two important factors to be assessed. As most surgeons recognize, these local factors are one of the many components used to determine management of the patient with spinal lesions caused by a myeloma.

The spine is the main predilection of MM. It is our obligation as spine surgeons to provide patients with the most reliable and optimal treatment and to alleviate pain and maintain their quality of life.

Optimal therapeutic strategy for epidural myeloma and spinal cord compression as one of devastating complications of multiple myeloma is still under debate. By review of cases with different clinical courses and related literatures, the authors tried to suggest therapeutic strategy for optimal clinical results. Close evaluation for mechanical stability and neurologic status, and multidiscipline approach are important factors leading successful results for this systemic disease.