Neurologic sequelae of bone changes in multiple myeloma and its therapy

Multiple myeloma (MM) is a plasma cell malignancy characterized by infiltration of bone marrow, bone destruction, infiltration of soft tissues with plasma cells, and suppression of normal hematopoiesis. The production of monoclonal immunoglobulins with or without light chains is a major feature of the disease. Full spectrum of plasma cell dyscrasias include monoclonal gammapathy of undetermined significance, smouldering myeloma, indolent multiple myeloma, and fully developed, symptomatic multiple myeloma. The usual presenting features of MM include bone pain, weakness, fatigue, fever and infection. Neurologic symptoms are less common but one must not forget that MM may present with a neurologic disease. Careful neurologic history and examination are mandatory in patients with MM. Neurologic symptoms may be a direct manifestation of MM or may be due to the immune effect of monoclonal proteins directed against different neural structures. Finally, metabolic consequences (uremia, hypercalcemia, hyperviscosity) of MM may produce a broad spectrum of different neurologic symptoms including headache, blurring of vision, drowsiness, precoma, coma, vertigo, ataxia, hemiparesis and epileptiform seizures. The most common location of bone changes in MM is the thoracic spine, where it causes osteolytic changes with consequent compressive fractures. The most disastrous sequel is paraplegia. Multiple vertebral involvement with the evidence of osteolytic changes in other bones is usual, but solitary vertebral myeloma may occur. Myeloma usually involves the bone of the vertebral body and then spreads into the extradural space. However, patients with solitary extradural myeloma have been reported. Skull myeloma is frequently asymptomatic. It may grow externally or, rarely, there is intracranial expansion. Involvement of the cranial nerves is not rare, with II, V, VI, VII and VIII cranial nerves being most often affected. Isolated intracerebral plasmacytomas are extremely rare. Diagnostic approach includes plain X-rays of the skeleton, which was found to be the method of choice for demonstration of osteolytic changes, whereas magnetic resonance with gadolinium enhancement most reliably displays the degree of vertebral involvement and demonstrates any associated soft tissue mass. Current treatment of osteolytic changes in multiple myeloma include chemotherapy, radiotherapy in combination with dexamethasone, monthly infusions of bisphosphonates, surgical decompression, and kyphoplasty. Therapeutic approach is dictated by the presenting symptoms. In case of pain as the predominant symptom, treatment with chemotherapy and radiotherapy may be appropriate. Compressive symptoms are relieved with dexamethasone followed by radiotherapy and chemotherapy. Surgical decompression is used in patients with vertebral collapse and vertebral instability. Kyphoplasty is a new method used in the treatment of osteolytic changes of vertebral bodies. A viscous cement is injected into the cavity by a balloon-like inflatable bone tampon. It has been successfully employed to improve the quality of life, to reduce pain, and to increase overall functioning in patients with vertebral compression fractures by restoring most of the original height of the vertebral body. Bisphosphonates reduce pain associated with osteolytic changes in multiple myeloma, but also significantly reduce skeletal events (pathologic fracture, spinal cord compression, surgery or irradiation of bone) via unknown mechanism. It seems that bisphosphonates, by inhibiting bone resorption, alter the microenvironment in which the MM cells grow.