Bilateral symmetrical enhancing brainstem lesions: an unusual presentation of primary CNS lymphoma

We report a patient with a progressive brainstem syndrome, who on magnetic resonance imaging had large bilateral, symmetrical, contrast-enhancing, infratentorial space-occupying lesions. Biopsy of one of the lesions revealed this unusual appearance to be due to a primary central nervous system (CNS) lymphoma of B-cell type. Symmetry of lesions may be a clue to the diagnosis, perhaps reflecting the mechanism by which CNS lymphomas spread.