Cauda equina tumor mimicking an intradural disc herniation, with emphasis on differential diagnosis--a case report.

We report a rare case of lumbar disc prolapse with intradural schwannoma at the same level. A 33-year-old man had had moderate right leg pain for about four years, which had worsened suddenly when he lifted heavy baggage. MR imaging revealed lumbar disc prolapse at L4/5. An intradural tumor that was iso-intense on T1-weighted and slightly hyperintense on T2-weighted images was also recognized at the same level. The tumor was homogeneously enhanced on Gadolinium-MRI (Gd-MRI). Intractable back and leg pain necessitated surgical treatment, which yielded a definitive diagnosis of the intradural tumor as schwannoma on histological examination. The intractable pain disappeared immediately after surgery. The patient's intractable and prolonged pain appeared to be due to combined compression by the intradural tumor and disc prolapse. The findings of Gadolinium-MRI were helpful in making the diagnosis.