Positive Antiganglioside Antibodies in a Patient with Primary Diffuse Large B-cell Lymphoma of the Central Nervous System

Up to one-third of lymphoma cases involve the nervous system. Miller-Fisher syndrome (MFS) associated with lymphoma is extremely rare. We herein report a case of primary central nervous system lymphoma initially mimicking MFS in a 70-year-old man who presented with subacute unsteady gait and diplopia. A neurological examination revealed unilateral ophthalmoplegia, ataxia, and areflexia. The patient tested positive for anti-GQ1b antibodies, so MFS was initially suspected. However, the progression extended over one month. Subsequently, disturbance of consciousness was observed. Cranial magnetic resonance imaging revealed lesions in the periventricular fourth ventricle, and a brain biopsy indicated diffuse large B-cell lymphoma.