Small cauda equina neurinoma detected by MR imaging.

A 56-year-old man whose chief complaint was lumbago came to our outpatient clinic . He had mild muscle tenderness in his lower back ; however, neurologic examinations showed no abnormality . Plain films of the lumbar spine were normal. On MR a small highintensity area was seen in the spinal canal of the fourth lumbar vertebra in spin-echo sequences (1200/60 (TR/TE]) (Fig . 1 A). The mass was isointense compared with CSF in inversion recovery sequences (1400/420 (TR/TI]). The possibility of a spinal tumor was considered, and the patient was admitted. Myelography (Fig . 1 B) and X-ray CT showed a small mass less than 1 cm in diameter in the subarachnoid space of the fourth lumbar vertebral body. The mass was diagnosed as a small tumor of the cauda equina. The patient's lumbago disappeared after bed rest , and we did not think that it was related to the tumor. Surgery revealed a yellowish , elastic, soft mass 8 x 5 x 5 mm that was attached to one of the nerve roots of the cauda equina (Fig . 1 C). Complete removal of the mass was easy. Pathologic examinations showed neurinoma. The patient had no neurologic deficit after the operation.