Multiple Myeloma Presenting as a Clivus and Brain Stem Plasmacytoma.

Multiple myeloma is the most common hematological malignancy. MM can affect many organ systems; therefore, it may mimic different clinical syndromes at presentation. We report an extremely rare presentation of MM.

CASE REPORT: A 62-year-old man presented with progressive cervical pain for 2 months and double vision for 2 weeks. Physical exam demonstrated a cranial nerve 6 palsy, nuchal rigidity and no other abnormalities. A magnetic resonance image (MRI) of the brain revealed a 5 cm enhancing mass in the clivus which extended into the brain stem, left internal auditory and carotid canal, nasopharynx, sphenoid and cavernous sinuses, without midline shift or hydrocephalus. MRI of the spine showed 2 small enhancing lesions in thoracic vertebrae 4 and 11. Computer tomography of the chest abdomen and pelvis demonstrated a lesion in the sternum and no other abnormalities. Technetium-99 bone scan showed uptake in the skull base mass only. Complete blood count and metabolic profile were normal except for an albumin of 3.2 g/dL. Serum protein electrophoresis with immunofixation revealed hypogammaglobulinemia without a monoclonal protein. 24 hour urine collection demonstrated monoclonal free kappa light chains. Transsphenoidal stereotactic biopsy of the mass showed an atypical plasma cell proliferation with multi-nucleation and mitotic activity, positive for kappa light chain. Bone marrow aspirate revealed 17% of the nucleated cell to be abnormal plasma cells, some with plasmablastic morphology. He improved rapidly with dexamethasone and was referred for radiotherapy.

DISCUSSION: The most common neurologic complications of MM are spinal cord compression due to epidural plasmacytomas or vertebral fractures, and peripheral polyneuropathy due to the presence of antibodies directed against myelin structures or due to amyloid deposits. Brain involvement in MM is uncommon. Furthermore, neurologic symptoms due to plasmacytomas located either in the clivus and brain stem are extremely rare. A MEDLINE search from 1950 until July 2005 revealed only 9 cases of MM or plasmacytoma involving the brain stem. Since there is no published autopsy series on MM patients describing the percentage of patients with brain involvement at death, the denominator is difficult to assess. Clinically, extramedullary involvement from MM bears a poor prognosis, and has been described in cases of plasma cell leukemia. We speculate that the aggressive behavior of the MM in our patient might be consistent with the atypical phenotype of the plasma cells.

CONCLUSION: The unusual presentation of this patient adds to the medical knowledge about the clinical spectrum of multiple myeloma.