Spinal ependymomas. Part 2: Ependymomas of the filum terminale
Authors: Klekamp Jörg 
Published: August 2015

OBJECT
Ependymomas of the filum terminale provide specific surgical challenges due to their often enormous size, contact with nerve roots of the cauda equina and conus, and potential for subarachnoid dissemination. This study presents treatment results for these tumors over a 30-year period.

METHODS
Among 1447 patients with tumors of the spinal canal treated between 1980 and 2014, 618 patients presented with extramedullary tumors. Of these, 42 patients (25 males, 17 females) demonstrated a myxopapillary ependymoma in the lumbosacral region. Thirty-four patients underwent 36 operations for 39 such tumors. The mean patient age was 38 ± 14 years (range 11−73 years), with an average clinical history of 37 ± 67 months. Patients were followed through outpatient visits and questionnaires, with a mean follow-up of 10 years (127 ± 100 months). Twenty-seven operations were performed to treat de novo tumors and the remainder were undertaken on recurrent tumors. Short-term results were determined for individual symptoms, and tumor recurrence rates were calculated with Kaplan-Meier statistical analyses.

RESULTS
Subarachnoid dissemination was observed in 11 patients and was related to previous surgery in 9 patients and associated with extensive tumors in 2 patients. Gross-total resections (GTR) were achieved in 28 operations (77.7%) and subtotal resections in the remainder. Subtotal resections were restricted to unencapsulated ependymomas (61.5%). Radiotherapy was employed after 6 operations on unencapsulated tumors, with 5 of these also demonstrating subarachnoid seeding. Permanent surgical morbidity affected 3 patients who experienced permanent worsening of bladder function, while 7 patients showed no postoperative changes, and the remaining 26 operations were followed by improvements. Long-term outcome depended on the amount of resection and the presence of a tumor capsule. Eight of 9 tumor recurrences affected unencapsulated tumors, of which 3 had undergone GTR. The overall recurrence rates were 6.6%, 19.0%, and 37.0% after 1, 10, and 20 years, respectively. For unencapsulated ependymomas, the corresponding rates were 15.6%, 32.5%, and 66.2% after 1, 10, and 20 years, respectively, with significantly lower rates of 9.1% after 10 and 20 years for encapsulated tumors. Postoperative radiotherapy tended to prolong the recurrence-free interval for patients with unencapsulated tumors. Five patient deaths occurred during follow-up, of which 2 deaths were tumor related and occurred at 216 and 287 months after surgery.

CONCLUSION
Extramedullary ependymomas are slow-growing tumors in the lumbosacral region, sometimes with an indolent course for long periods of time. Despite their delicate location and often enormous size, surgical morbidity in experienced hands is low, with good chances for postoperative clinical improvements and very low recurrence rates after GTR for encapsulated tumors. The role of postoperative radiotherapy remains controversial. Radiotherapy may be considered after incomplete resections of unencapsulated tumors and/or for patients with subarachnoid dissemination.