Monoclonal and polyclonal immunoglobulinemia, including lymphoma, Waldenström's macroglobulinemia and less commonly multiple myeloma (MM), are considered as infrequent causes of ischemic stroke. Hyperviscosity states, as well as procoagulant disturbances, both potentially treatable, have been implicated in its etiopathogenesis. The so-called "hyperviscosity syndrome" is a clinical syndrome consisting of headache, visual, auditory and vestibular disturbances, confusion and decreased level of consciousness, and is caused by extreme hypervolemia with a high degree of erythrocyte aggregation caused by paraproteinemia. However, in addition to this global cerebral ischemia syndrome, increase in blood viscosity (BV) can also be a cause of focal ischemia. We report a case of a patient diagnosed with IgG type MM, who suffered multiple vertebrobasilar transient ischemic attacks and minor ischemic strokes concurrent with a reactivation of his hematological disease. He became completely asymptomatic after specific treatment with dexamethasone of the paraproteinemia associated with MM. We discuss its pathophysiology in this report.