[Leptomeningeal infiltlation of primary CNS B-cell lymphoma diagnosed by the biopsy of cauda equina: a case report].

A 49-year-old man was admitted to our hospital with progressive gait disturbance. Our examination revealed a low grade fever, weight loss derived muscle weakness, sensory disturbance and loss of deep tendon reflex of the lower extremities. Magnetic resonance imaging (MRI) detected an abnormal intensity and gadolinium enhancement in the cauda equina. Two weeks after admission, disturbance of consciousness and bladder appeared. Cerebrospinal fluid examination showed pleocytosis, elevated protein and soluble IL-2R, but cytological examination was class II negative. We performed a cauda equina biopsy urgently and diagnosed malignant lymphoma, of a diffuse large B-cell type. We selected combined MTX-based chemoradiotherapy and his symptoms significantly improved after a month. He achieved complete remission and remains recurrence-free after 10 months post treatment although he remains with light paraparesis and sensory disturbance of the lower extremities. He has already gone back to a normal life. An examination of cauda equina biopsy led to quick diagnosis and treatment.