[Clinical study of 21 cases of sacral cysts containing fila terminale]

To summarize the characteristics of sacral cysts containing fila terminale and to explore the surgical treatment methods.

The clinical features, imaging characteristics and surgical methods of 21 cases of sacral cysts containing fila terminale from July 2010 to March 2017 were reviewed and analyzed. Lumbosacral and perineal pain, weakness of the lower limbs and bladder and bowel dysfunction were the common clinical symptoms. MRI showed that the cysts located in the sacral canal. The lower T1 and higher T2 signals were found on MRI. There were fila terminale within the cysts which tethered the spinal cord. No enhancement was visible within the lesion. The key steps of operation included the resection of the cyst wall, the cutting off of the fila terminale, the release of the tethered cord and the reconstruction of the cisterna terminalis.

The total and subtotal resections of cyst walls were achieved in 14 and 7 cases, respectively. The fila terminales were separated and cut off in all the cases, and the tethered cords were released completely. The reconstructions of the cisterna terminalis were accomplished in all the cases. There was no new-onset dysfunction except for 7 cases of mild numbness around anus postoperatively. Pathological examinations confirmed that the cyst wall was fibrous connective tissue, and hyperplasia of fibrous tissue and/or adipose tissue was found within the thickened fila terminale. The lumbosacral and perineal pain disappeared. The weakness of the lower extremities and the bladder and bowel dysfunction gradually improved. The period of follow-up ranged from 3 months to 7 years (average: 2.25 years). The spinal function of all the patients restored to McCormick grade Ⅰ. Only 1 case encountered recurrence of cyst.

The sacral cysts containing fila terminale are rare. The common symptoms include lumbosacral and perineal pain and symptoms of tethered cord. MRI is helpful to the diagnosis, which shows the signal of cerebrospinal fluid and the fila terminale in the cyst as well as tlow-placed conus medullaris. Microsurgery should remove the cyst wall, cut off the fila terminale, release the tethered cord and reconstruct the cisterna terminalis.