[Remission of lymphomatosis cerebri induced by corticosteroid and high-doses intravenous methotrexate].

Lymphomatosis cerebri (LC) is a rare form of primary central nervous system lymphoma characterized by subacute progressive dementia and unsteady gait. MRI study of LC typically reveals diffuse leukoencephalopathy without contrast enhancement. The clinical presentation and MRI features of LC can resemble infectious, inflammatory, toxic or vascular leukoencephalopathy. Hence diagnosis of LC is easily mistaken for other, more common diseases. In this report, we present a case of a 55-year-old man presenting with subacute progressive dementia and ataxic gait. Brain MRI showed diffuse hyperintense lesions in the cerebral white matter of both hemispheres, left amygdala, brainstem and cerebellar peduncles on FLAIR image. No contrast-enhanced lesion was observed. Cerebrospinal fluid analysis showed elevated levels of soluble interleukin-2 receptor and β2-microglobulin. Based on MRI findings and 123I-IMP SPECT, stereotactic biopsy targeting white matter of the left medial temporal lobe was performed (day 0). On the day after the brain biopsy, corticosteroid therapy was initiated and improved the patient's cognitive function and gait disturbance. Pathological diagnosis of large B-cell lymphoma was obtained on day 9. High-dose intravenous methotrexate chemotherapy was started on day 14 and led to complete remission by day 52. This case highlighted the importance of brain biopsy for diagnosis of LC. This report raises a possibility that timely and proper treatment leads to a favorable outcome of LC that has been regarded as an intractable disease with poor prognosis.