Split cord malformations in adults.

Purpose: Split cord malformations represent a small group among tethered cord syndromes. This paper presents the largest series of adult patients with this disorder reported to date. Neuroradiological features, clinical symptoms, surgical management and data on short- and long-term outcomes are analyzed.

Methods: 94 adults (mean age 54.7 ± 15 years) presented with split cord malformations between 1991 and 2024 and were evaluated (follow-up of 64 ± 84 months). Radiological features, intraoperative findings, and neurological examinations before and after surgery were analyzed. Long-term outcomes were evaluated with Kaplan-Meier statistics.

Results: 35 patients presented with a split cord separated in two dural tubes (type I), 59 patients demonstrated a split cord type II with both hemicords in a single dural sac. 79 patients featured a low positioned conus and 10 patients a dermal sinus. In 31 patients (33%), the malformation was combined with a hamartoma, i.e. lipoma or dermoid, epidermoid, neurenteric or neuroepithelial cyst. The commonest clinical course consisted of radicular pain and slowly progressive neurological deficits. 51 patients underwent 59 operations with untethering the split cord, transection of the filum terminale, and hamartoma removal if applicable. There was no permanent surgical morbidity except for patients requiring a revision in split cords type I combined with a hamartoma. 61% considered their postoperative condition improved. Radicular pain responded best with only marginal neurological changes after surgery. Postoperative progression-free courses for 10 years corresponded to the complexity of the malformation: 83.3% experienced 10 year progression-free outcomes after first operation on any split cord without associated hamartoma. If a hamartoma accompanied the split cord, this figure dropped to 59.3%.

Conclusion: The natural history of split cord malformations in adults is benign with slow neurological progression. Surgery should be reserved for symptomatic patients and provide untethering of all structures involved in the split as well as transection of the filum terminale. Associated dysraphic cysts require complete resection, while lipomas may be resected subtotally. The overall prognosis for patients requiring a revision is considerably reduced. Therefore, referral of these patients to appropriate centers is advisable.